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March 29

Rendering Equations

I've been trying to lean how to render equations instead of having to ask. Why doesn't this render png? On my browser it appears as html.Bugboy52.4 ¦ =-= 03:34, 29 March 2011 (UTC)

${\text{Work}}=F_{av}\times d={\text{2Wd}}$

How about this:

${\text{Work}}=F_{av}\times d={\text{2Wd}}\,\!$

Courtesy of Help:Math#Forced PNG rendering. DMacks (talk) 03:48, 29 March 2011 (UTC)

What about

Failed to parse (syntax error): {\displaystyle \text {E}=\text {mgh}=0.1\times980\times10^{−2}=0.98\text {erg}}

Its not rendering, what am I doing wrong? Bugboy52.4 ¦ =-= 03:53, 29 March 2011 (UTC)

The minus sign in your "-2" is not an ordinary minus sign, it is some sort of fancy dash. The math mode parser does not know how to handle it. If you use an ordinary minus sign, it will render:

${\text{E}}={\text{mgh}}=0.1\times 980\times 10^{-2}=0.98{\text{erg}}$

Looie496 (talk) 04:22, 29 March 2011 (UTC)

Someone please copy this to WP:VPT so the developers know about it. 99.2.149.161 (talk) 17:30, 29 March 2011 (UTC)

The developers will tell you that the TeX parser is fully compliant - and that this behavior is correct. You have entered invalid syntax that is not a valid equation. Unicode (and therefore MediaWiki and its TeX parser) specifies a different interpretation for − and - though the glyphs look similar in most standard Windows, *nix, and Mac fonts. (Consider reading the characters in a hex editor). Read about character duplication in Unicode, which is slightly technical. Nimur (talk) 19:41, 29 March 2011 (UTC)

A test where E. Coli is not exceeding 3/g ???

Under Australian legislation, ready-to-eat meat products must not have E.coli exceeding "3/g"
But it doesn't specify what the unit of measurement is, 3 what???
3 Colony-forming_units?
3 single Bacterium?
^{I have contacted the Food Authority and they will come back to me within 10 days. I have also contacted laboratories but their sales people don't know.}
220.244.35.181 (talk) 05:02, 29 March 2011 (UTC)

Based on this I think it means 3 single Bacteria (per gram). Ariel. (talk) 07:04, 29 March 2011 (UTC)

Thanks, I did come across that paper, but I'm afraid it's no clearer - it doesn't state what test it uses - the test could use a different scale altogether. I'm not a food scientist (or any scientist for that matter) but it was impression that meat products can have thousands if not millions of bacteria - it seems absurd to me that you'd only find "3" micro-scopic bacteria of E. coli on a single gram. 220.244.35.181 (talk) 09:27, 29 March 2011 (UTC)

Reading this [1] report, it seems it may be common to give the number in log10. So "3" actually means "10^3". That's still not a lot though, maybe it just puts a cap on the required measurement sensitivity. If you had say 20 bacteria per gram, you may have had to incubate them for a long time before you could detect them, while a thousand bacteria per gram can be detected just in time to stop a meat shipment. But this is just my speculations. EverGreg (talk) 12:51, 30 March 2011 (UTC)

What percentage of the atoms in our bodies were born in the hearts of dying stars?

Based on this table detailing the Chemical makeup of the human body, what percentage of our atomic composition (not mass) was created as a result of the death of stars? Flaming Ferrari (talk) 06:03, 29 March 2011 (UTC)

It's almost impossible to speculate. Just about any element lighter than iron can be created by Stellar nucleosynthesis; heavier elements than iron are thought to arise from supernovae. However, given all of the various ways that a star may "die"; even if we just consider supernovae, a large percentage of all elements are likely scattered from them, even small elements like hydrogen, so just about any of the atoms in your body could have come from "dying stars"; and since two atoms of the same element and isotope are literally indistinguishable, there's no telling where they came from. --Jayron32 06:23, 29 March 2011 (UTC)

This sounds like a homework question to me. I'd guess that the instructor means for you to figure that everything but hydrogen "was created as a result of the death of stars". So, that's 90% of the mass of a human, but you can do the math to figure out the "percentage of our atomic composition" (which I assume means by count of atoms). Since hydrogen is the lightest element, the count of hydrogen atoms should be considerably more than 10% of the body. If you want to do the math here, we'll check your work. StuRat (talk) 07:16, 29 March 2011 (UTC)

A homework question where the lecturer refers the students to a Wikipedia table? Things have gone downhill since I left academia five years ago! --TammyMoet (talk) 07:57, 29 March 2011 (UTC)

They may have found that on their own, but don't know how to get the answer to the HW question from it. StuRat (talk) 08:55, 29 March 2011 (UTC)

Wikipedia has come on a lot in five years. We hope. Itsmejudith (talk) 16:16, 29 March 2011 (UTC)

A significant part of the Lithium also originates from BBN. Count Iblis (talk) 14:06, 29 March 2011 (UTC)

True, but lithium (and helium, the other major non-radioactive elemental product of Big Bang nucleosynthesis) have no known biological function, and are present in the body in negligibly trace amounts. TenOfAllTrades(talk) 14:29, 29 March 2011 (UTC)

Maybe you should count everything heavier than (or at least as heavy as) lithium and at least as light as iron, because it is hard to think of a supernova's exploding shell as a heart. But then again, most stellar nucleosynthesis takes place when most people would not say the star is dying, but the supernova does, so maybe you should count everything heavier than iron. But don't supernovae synthesize some proportion of light elements, too? Does anyone have a good idea what that proportion may be? 99.2.149.161 (talk) 17:49, 29 March 2011 (UTC)

There's the issue of when elements are created, and also when they are released. Even if somewhat heavier elements are created before the death of a star, if they languish in the star's core, they aren't available biologically. From my experience with sloppy homework (and test) questions, it wouldn't surprise me a bit if the instructor is conflating those elements created by a star's death with those released by it. Unfortunately, with such sloppy questions, figuring out what the instructor really meant to ask is often the most difficult part of the problem. StuRat (talk) 18:09, 29 March 2011 (UTC)

part 2

A.mohammadzade let me ask this again ,as all know the huge part of our body contains water and the protein which made our meat is made of hydro carbon .Calcium element is about 15 percent and iron is in our blood and so zinc and Natherium ,... The first interstellar cloud which made sun and solar system might had hydrogen and helium so the last effects of dust came from novas and supernovae mixed to this cloud and the nebula had some thermodynamic conditions to made water and chemical matters , hydrocarbons made in earth specially condition which made the life .and first nebula did not be able to produce carbon and oxygen , which made 23percent of earth mass and 21%of air ,and several metals and silicates in earth crust are oxidized .

I want you my friends not to say died star for super novae they made life and they are absent in sky and send pulses and notice: Some body used to say something about the black holes but I prefer to say about super novas , the first one shows death and being mystery the second one is about the life and being alive .it had send oxygen and carbon ,so calcium and iron here to made our life(akbar mohammadzade)

 :--78.38.28.3 (talk) 04:08, 30 March 2011 (UTC)

I moved this from your new post on the same topic. It should all be kept together. StuRat (talk) 04:21, 30 March 2011 (UTC)

gas heat

my furnace is AC ready but has no AC hooked up to it. my repair guy said i have to clean that part too. how do i do that? — Preceding unsigned comment added by Wdk789 (talk • contribs) 07:03, 29 March 2011 (UTC)

When you say AC do you mean Air Conditioning or AC electricity? Ariel. (talk) 07:08, 29 March 2011 (UTC)

Air Conditioning — Preceding unsigned comment added by Wdk789 (talk • contribs) 07:17, 29 March 2011 (UTC)

So you have a point where the A/C unit will tie in to the duct-work of a forced-air gas furnace, and need it cleaned ? If it's a matter of cleaning out a duct, I'd use some kind of a mop in the open end. I'd use it dry to get the dust out. Wear work clothes and a dust mask while you do this, or you may be in for a coughing fit. Also, turn the furnace off shortly before you do this, as the duct-work might be hot where it connects. Note that there are companies that clean ducts, if you don't want to do it yourself. StuRat (talk) 07:22, 29 March 2011 (UTC)

Could you fit a model V12 or W16 onto a motor scooter and make it really work?

See, this is a real-working model V12: http://www.youtube.com/watch?v=0V_2v-ol1EU

And this is a W16, intended to be a 1/5th scale model of the Bugatti Veyron engine: http://www.youtube.com/watch?v=-DijdisWkAE

Are the horsepowers divided by their scales? Therefore, if the W16 has 1001 HP, would the fully-working 1/5th scale model have 200.2 HP? If so, how well would a 200.2 HP engine work on your everyday commuter motor scooter?

Regardless, what kind of ride would you get by putting those miniature versions of the Über engines into a motor scooter? What would your top speed be from there on out, as well as the acceleration, noise and fuel mileage? --70.179.169.115 (talk) 07:54, 29 March 2011 (UTC)

I don't know if the simplistic approach to working out the horsepower is right, but even if it is, since the engine is three-dimensional you'd want the inverse cube, which is 1/5th times 1/5th, making 1/25th the horsepower. Wait, or do I mean 1/5th times 1/5th times 1/5th (1/125). It will be disappointing, anyway. 213.122.57.127 (talk) 08:31, 29 March 2011 (UTC)

It would be the cube of 1/5, since the engine displacement volume is related to horsepower. So that would be 1/125th of 1001 HP, or approximately 8 HP, if it worked. However, internal combustion engines aren't very scalable (unless you change the number of cylinders along with the scale). So, while a 3 cylinder engine with that displacement might work well, a 16 cylinder engine would probably barely run, because all those moving cylinders would increase friction relative to the 3 cylinder engine, but without the displacement needed to overcome it. Of course, there are other things to change, too, such as the compression ratio and revs per minute, to get better performance out of the smaller engine. StuRat (talk) 08:47, 29 March 2011 (UTC)

Neutron star matter, on Earth

So let's say some Star Trek like genius, in the 53rd century AD, creates a technology that can grab neutron star matter without it decaying in any way. So the United Federation of Planets decides to go grab some, and transport it back to Earth.

Once at Earth, the matter is released as-is into the Earth's atmosphere. What would the reaction be? of:

1. The Quark-gluon plasma at the center (density: ~6-8 trillion pounds per teaspoon)
2. The crust (density: ~10 thousand pounds per teaspoon, and ten billion times stronger than steal, at least at the immense pressure on the neutron star itself).

Magog the Ogre (talk) 17:16, 29 March 2011 (UTC)

Some potentially useful discussion along similar lines was discussed not too long ago, though it doesn't address your question directly. --Mr.98 (talk) 19:09, 29 March 2011 (UTC)

Oh, neat. From what I can see, regarding the thickest of the matter:

• If it were to remain in this neat sci-fi vessel we have, and not explode, it would barrel a whole to the center of the earth, sucking massive amounts of matter in its wake, and surely causing earthquakes, volcanic eruptions, and all sorts of other havoc.
• If it were released suddenly into the air, it would be the equivalent of a nasty nuclear bomb; however, given that it would keep exploding for a good time, it quite likely could destroy all life on Earth.

For the less dense stuff: maybe just a really big explosion that could kill a lot of people? Magog the Ogre (talk) 20:47, 29 March 2011 (UTC)

At STP, what is the predicted density of a neutron gas. Does a neutron gas have a theoretical triple point? Plasmic Physics (talk) 03:23, 30 March 2011 (UTC)

There isn't any predicted information like that. Neutronium is a term which was coined, conjecturally, for such standard conditions neutron-based matter, but no known substances exist, and there isn't a lot of reliable prediction for what it would look like if it did. The Wikipedia article actually covers this well, at least in noting that no one seriously considers it a likely form of matter, except in some very exotic conditions. The other type of neutron matter, known as Neutron-degenerate matter literally cannot exist at STP, as it requires the literally astronomical pressures in a neutron star to exist. If that matter were to be brought to STP, it would rapidly convert to normal (proton-electron-neutron) matter of some sort, likely mostly hydrogen, deuterium, and helium. --Jayron32 05:21, 30 March 2011 (UTC)

I don't really know what ot make of your answer - I googled "neutron gas", and one result described a low density neutron gas produced for the purposes of a projectile target for a particle physics experiment. For clarification, I'm not refering to degenerate states of matter, but simply a bulk sample of neutrons in a closed container with movable walls. The result did't answer my questions, if you were going to ask. Plasmic Physics (talk) 12:08, 30 March 2011 (UTC)

While I'm at it, here's another one: since neutrons have no atomic orbitals, is there any substance that can contain such a hypothetical gas of neutrons, wouldn't the gas simply diffuse through the walls of the container within a matter of hours? Plasmic Physics (talk) 12:13, 30 March 2011 (UTC)

Hypothetically, neutrons would not be subject to intermolecular forces, since they are both neutral and extremely hard (i.e. nonpolarizable). In other words, they aren't subject to even London dispersion forces, generally held to be the weakest of the common Van der Waals forces regulating the formation of non-gasseous phases of matter. If we were to consider a bulk gas composed of nothing but neutrons which was also at atmospheric densities, there are literally no forces at all which could act, at any temperature, even infinitessimally close to absolute zero, which could cause the neutrons to form a condensed phase. So, there would literally be no triple point, because there are no forces acting to cause neutrons to attract to one another. Collecting low-temperature neutrons like this to even make such a gas is likely impossible; but even if you could it would never be anything but a gas. --Jayron32 13:02, 30 March 2011 (UTC)

The neutrons are made of quarks, right? Quarks have charges, right? Would that make the neutrons slightly polar? So, if the temperature brought within a picokelvin above absolute zero, wouldn't they form transient atractions to one another? Plasmic Physics (talk) 13:12, 30 March 2011 (UTC)

I was about to say no, but reviewing Neutron#Structure_and_geometry_of_charge_distribution_within_the_neutron, it seems that very recent research suggests that there is a non-uniform charge distribution within a neutron, implying that they would be subject to something akin to London dispersion forces, so perhaps at such tiny temperatures (femtokelvin? attokelvin) there may be some time when induced charge seperation could generate a condensed, low-energy, low-pressure form of neutron matter; akin to a neutron liquid or neutron solid. The problem is, we have no reliable way to predict behavior at that level; at the distances that would be required for such tiny forces to work, the electromagnetic force, which would be responsible for solid or liquid formation, is actually much weaker than the nuclear forces which regulate things like quark interactions and internucleon interactions. In other words, at the distance you would need to bring many neutrons together in order to have them be attracted enough to form anything like a condensed phase of normal atomic matter, the situation is so drastically different than even for the smallest atoms. Consider that Hydrogen has a van Der Waals radius of 120 pm; this is the roughly scale of the minimum interatomic distances present in a condensed phase. The Wikipedia article on the neutron doesn't contain any information on its size, but this document calculates a radius of about 1 femtometer, or roughly 1/100,000 the radius of a hydrogen atom. So your hypothetical neutron solid would, once again, be under the influence of forces other than the electromagnetic force, which is sorta the definition of degenerate matter in the first place. In other words, low-temperature neutronium solid wouldn't be a solid under the normal definition of a solid, insofar as it obeys the odd laws of physics regulating degenerate matter rather than that of normal matter. So, once again, there is no hypothetical "normal matter" condensed phase substance composed of neutrons alone. There may be a neutron gas, but it will not condense to form solids or liquids which resemble, in any meaningful way, a real solid or liquid. --Jayron32 14:02, 30 March 2011 (UTC)

The neutron is "supposed" to have a Neutron electric dipole moment according with theoretical models, but that moment is so small that no experiment has ever been able to detect it. Dauto (talk) 19:21, 30 March 2011 (UTC)

Ok, I believe you, there is only one phase in the classical sense for a neutron gas due to the lack of interaction taking place however, interneucleon forces may or may not cause a condensate like phase to form (degenerate matter). What about my other question, concerning its diffusuability through solids? Plasmic Physics (talk) 23:47, 30 March 2011 (UTC)

There is such a thing as a neutron reflector but their efficiency has limitations. Dauto (talk) 01:01, 31 March 2011 (UTC)

What did the retired US Air Force nuclear missile commanders tell the National Press Club?

What's the most reliable summary of this? Specifically I am looking for something with the number of retired officials confirming the incidents, whether there are any incidents reported that vary substantially from the typical report, and the date ranges for each of the incidents. 99.2.149.161 (talk) 17:36, 29 March 2011 (UTC)

That article describes a book, written by a space alien enthusiast. It seems he read about, or attended, a September 2010 press conference, where a retired Air Force officer did make explicit reference to extra-terrestrial life.

But overall, this is just a space-alien enthusiast, who read about, and then created a mangled and contorted version of, a much more benign press version of reality; and then added several generic, probably totally-fictional stock-descriptions about extra-terrestrial encounters. In the 1940s and 1950s, as the threat of nuclear war became real, military brass set up loads of early warning systems: RADARs and other aerial surveillance systems. The plan, part of the Mutually Assured Destruction strategy, was to monitor the sky for anything that looked like an incoming bomber or missile - and if we saw one, we'd blow away the Soviet Union with a full-scale missile strike. (Obviously, this was a bad idea)..

Now, as anyone who has ever used technology of any kind can tell you, electronics have "glitches" sometimes. RADARs often report false-positives - "glitches" - noise, due to electronics and atmospheric effects. (When a RADAR picks displays an unknown dot, it is an "unidentified flying object", right?) So, as the NORAD and SAC commanders and strategists realized that their RADARs had glitches, they realized that they couldn't sustain a "fire all missiles" response to every little static-noise burst.

Our space-alien enthusiasts gladly pick up on Project Blue Book: the Air Force systematically studied UFOs, and then decided to close all further investigations - well, let's step back and read that one more time. After years of policy that required escalating every static noise burst to the President so he could decide whether to nuke the Russians, the Air Force finally realized that there was such a thing as electronic noise, and that not every RADAR pulse was actually an enemy aircraft or missile (or extraterrestrial space-ship). The presence of "UFOs" required bringing our nuclear response to a reasonable level. Nimur (talk) 14:32, 30 March 2011 (UTC)

Is that a fair characterization of what took place at the National Press Club? Is it true or not that "several" retired USAF officials said that they had personally witnessed nuclear ICBMs deactivating at the same time that UFOs were being reported above ground at the same facilities? If so, exactly how many officials and how many separate incidents were there? Over what time period did these incidents occur? Is it true that such incidents have also been reported by former USSR officials? I am baffled that even UFO enthusiasts do not seem to be following this story as closely as I'd expect them to. I just want a reliable summary. 99.2.149.161 (talk) 21:19, 30 March 2011 (UTC)

Here are some more links of interest: video, Socio-Economics History Blog, VeteransToday.com. And [2] might be excerpts from one of the organizers of the National Press Club event. 99.2.149.161 (talk) 02:03, 31 March 2011 (UTC)

What experimental recreational drug am I thinking of?

Resolved

I remember reading a news article a year or two ago (I think) about a company that was trying to create a recreational drug that would get you high, but without side-effects, and with an antidote that you could take should you need to become sober quickly. Does anyone know what I'm thinking of? A Quest For Knowledge (talk) 17:41, 29 March 2011 (UTC)

Nevermind. I found it.[3] A Quest For Knowledge (talk) 20:03, 29 March 2011 (UTC)

Identify my skull

Could anyone help to identify this skull (assuming it is a skull). It was found in rocky hills in Oman; the absence of obvious front-facing eyes is puzzling; it's very light and has what look like air pockets, so possibly a bird? Thanks for any help! Henry^Flower 18:07, 29 March 2011 (UTC)

• 
  side view
• 
  bottom view
• 
  rear view
• 
  eye socket remnant?
• 
  brain case
• 
  the nose

If it lacks eye holes, are you sure it's a skull, as opposed to some other bone ? StuRat (talk) 18:12, 29 March 2011 (UTC)

Not at all sure, no. :) On the other hand, I have no idea what other bone it could be; it is basically round and hollow, with a hole at the back which looks like a spinal cord would go through it; and there might have been an eye socket in the broken part (though then the eyes would have been looking to the side and slightly backwards. Henry^Flower 18:17, 29 March 2011 (UTC)

Yes, it's a skull (you can see the distinctive suture lines), but we'd need more pictures to be sure of what exactly it came from. Based on the general roundness, size, and the area it was found, I'm thinking it's a species of monkey. Matt Deres (talk) 18:57, 29 March 2011 (UTC)

(EC)I can't help with ID, but I think you're on the wrong track with the "lack of eyes" idea. Keep in mind that your specimen is highly damaged, whatever it is. Look at this raccoon skull:[4], and this gerbil skull [5]. Basically, these animals' eyes are well outside the main brain-case enclosure. It could be that what you have is a similarly shaped skull, and the thin bits of bone arch that surround the eye socket have broken off. It's hard to tell from your pictures, but I think the side view may show remnants of such bones. SemanticMantis (talk) 18:59, 29 March 2011 (UTC)

Yes, it's definitely a skull, and definitely very badly damaged -- you really only have a small part of it. It looks to me to be a mammal skull, from a pretty good-sized mammal. One possibility may be a dog. Looie496 (talk) 19:09, 29 March 2011 (UTC)

If there are any teeth left, a close shot of those might be very helpful. Googlemeister (talk) 19:41, 29 March 2011 (UTC)

The round hole at the front made me think of some sort of anteater, something like this doesn't look too dissimilar, has a similar "lack" of obvious eye holes. Having a quick look it seems like there are anteaters in Oman. Vespine (talk) 23:11, 29 March 2011 (UTC)

Hmm well, ok, i'm wrong about the anteater in Oman, seems like they're only in south america.. How about armadillos ? Vespine (talk) 23:21, 29 March 2011 (UTC)

That's the back, so the hole is for the spinal cord. StuRat (talk) 23:18, 29 March 2011 (UTC)

Aaah! Yes, i was looking at it wrong, sorry... but anyway the links I posted show that lack of "obvious" eye holes are not necessarily a problem. Vespine (talk) 23:22, 29 March 2011 (UTC)

I'm really curious now! I don't think it looks rodent, canine or rabbit, what other "common" animals are there in Oman? Vespine (talk) 23:25, 29 March 2011 (UTC)

It would help to know what kind of soil or rock strata it was found in. then we might have an idea whether we're trying to match with a modern (familiar) animal or something else. Also does it seem to be actual bone or rock,as in fossil?190.148.134.128 (talk) 00:32, 30 March 2011 (UTC)

also what is front or back seems at this point to be conjecture.190.148.134.128 (talk) 00:56, 30 March 2011 (UTC)

It's light and has air pockets, i think it's obviously bone, not a fossil. The main problem I think is the OP has not given a good frontal photo showing the nasal area and the jaw structure on the underside photo is badly out of focus, these areas in particular would probably reveal a lot more unique detail. Vespine (talk) 01:02, 30 March 2011 (UTC)

I'm trying to find fauna local to the region but not much luck. There's an awesome feline called a caracal but the skull looks very different, as does a local wolf, hyena and several antelope or goat like animals. I don't think it's a bird or a a lizard, or a rodent, my guess is some sort of mammal but I'm really stumped without some better photos. Just for clarification, you do mean Oman the country on the Arabian peninsula, not some other town somewhere like Paris Texas or something. Vespine (talk) 01:18, 30 March 2011 (UTC)

The nasal area is missing, as is most of the upper jaw. This is really just the back of the skull, and not even all of that. Looie496 (talk) 03:07, 30 March 2011 (UTC)

Thanks for all the ideas! In answer to a few points:

- SemanticMantis, your point about the eyes seems to be along the right lines - the racoon skull is quite similar. Presumably not an actual racoon here in Oman, though there must be something similar.

- I've added a few more photos showing the (probable) remnants of the eye sockets, inside, and what's left of the front/nasal area.

- For what it's worth, this page has photos of various animals from the author's travels (mostly in Oman).

- It's definitely bone, not a fossil. It was in a rocky desert area, altitude about 500m.

Even if we can't identify it for certain, at least is slightly less of a mystery to me now. :) Henry^Flower 03:24, 30 March 2011 (UTC)

AH, I see now. In the first out of focus photo I actually thought those might be tooth socket remnants but it's obvious that whole upper jaw area is worn away.. I take back what I said about it not being a rabbit or rodent, in fact, if you use your imagination, it could be a rabbit, or maybe more likely a hare, if you look at a picture like this and use your imagination to deteriorate the missing parts, it's not extremely dissimilar. Vespine (talk) 04:54, 30 March 2011 (UTC)

My guess would be a Mustelid but without an indication of size it's very hard to be more specific. If it is clearly too big to be a Mustelid I would change my "vote" to Canid. Roger (talk) 12:51, 30 March 2011 (UTC)

I don't think it's a rabbit: the spinal cord hole in the rabbit skulls I've seen is in the base (the head sitting on top of the body); I imagine a hare is the same. This one has the hole in the rear of the skull, which would seem to imply a more horizontal body posture, which in turn would fit with the idea of a weasel-type thing. The skull (or rather the bit I have) is about 7-8cm, so maybe something a bit bigger than a pine marten. Henry^Flower 16:46, 30 March 2011 (UTC)

If I can get a bit nosy: what in the world were you doing in Oman? I can't think of any reason whatsoever to be a tourist in that country. Unless you live there, which also seems unlikely to me. Magog the Ogre (talk) 17:02, 30 March 2011 (UTC)

See Tourism in Oman. Are you confusing Oman with Yemen perhaps? Looie496 (talk) 17:20, 30 March 2011 (UTC)

Didn't they used to be the same country? Regardless, I can't imagine traveling halfway around the world to a part of the world quite hostile to westerners (of which I am one), to go touring in the middle of the desert. Then again, I live in the US, so maybe that will cause some differences. And to each his own (maybe Oman has a great industry I don't know), but I still don't understand why someone else would do it. Magog the Ogre (talk) 19:54, 30 March 2011 (UTC)

We're way off topic here, but the two are quite different. Oman is a country with 2.7 million inhabitants and a per-capita GDP of about $14,000. Yemen is a country with about 22 million inhabitants and a per-capita GDP of less than $1000 -- i.e., one of the poorest countries on earth. Oman is politically stable and welcoming to westerners. Yemen is a hotbed of turmoil and a dangerous place to visit. Looie496 (talk) 20:50, 30 March 2011 (UTC)

What a strange turn the discussion's taking! Looie of course is entirely right. I'm off for the Muslim weekend now, but will be back on Saturday in case there are more thoughts. Henry^Flower 03:35, 31 March 2011 (UTC)

carbon-dioxide atmosphere

I have a long list of questions for an idea that I've been thinking about. But I will stick with the first because it may negate the rest. I only mention this because this question surely seems nonsensical... Assume that a lot of carbon dioxide was added to the Earth's atmosphere. Along with this, there would be extensive global warming. So, it is safe to assume sulfer dioxide would be be produced in excess. Is there a point at which excessive heavy gasses (ie: carbon dioxide and sulfer dioxide) would settle to the lower elevations on Earth and the lighter atmosphere consisting of oxygen and nitrogen would float above that? Obviously, there would be a mixed area. I'm really asking if oxygen can be pushed up higher than it is now due to heavier gasses in the atmosphere - or, will the oxygen remain where it is and just mix with the heavier gasses? -- kainaw™ 19:51, 29 March 2011 (UTC)

We have many different gases in the atmosphere now, and they generally seem to mix rather than form distinct layers. Yes, the concentrations of the various gases does vary a bit by altitude, but, other than the pressure differences, the air on the top of Everest is basically the same as at sea level, because winds continuously mix them up. I'd suspect that winds would be even stronger on a hotter Earth, since heat differences drive winds, so this "mixing bowl" effect would remain. StuRat (talk) 20:32, 29 March 2011 (UTC)

It's because the atmosphere is clear to a lot of radiation, which is then absorbed by the ground thus bottom heating the atmosphere and preventing stable stratification. If the atmosphere was opaque to most radiation, stable stratification could be a possibility. —Preceding unsigned comment added by 92.20.201.71 (talk) 20:57, 29 March 2011 (UTC)

Well, the atmosphere does show quasi-stable stratification, but the strata are relatively thick: troposphere, stratosphere, ionosphere, etc. Within the troposphere there is very extensive mixing due to the fact that solar radiation heats it from the bottom -- this mixing rapidly undoes any separation that may start to arise from differences in density. Note that there have been epochs of geological history when CO2 concentrations were up to 100 or more times higher than today. Looie496 (talk) 21:26, 29 March 2011 (UTC)

One might consider that even with all the lower level mixing there is a surprising degree of stratification.for example ozone being triatomic oxygen O3 is way up there, in the mesosphere if I remember correctly.and we all know how important that is. I don't know what you're theory is but you might pursue it further.190.148.134.128 (talk) 01:21, 30 March 2011 (UTC)

Hi there, i just fixed up 128's reply, please don't manually indent your replies but instead use : at the start of your contribution (have a look at the other replies to see how it works). A manual indent has a different function in wiki formatting. Vespine (talk) 01:27, 30 March 2011 (UTC)

Thank you "vespine". I must explain that I am a really old guy and the computer is a new tool to me. I have no idea what "manual indent" means because I don't speak computorese. you're probably quite young and can't imagine how this can be possible because you probably have grown up with a computor. It sounds to me that you're saying I must read the other entries and agree with them, but I can't believe that. I'm not trying to be a smart ass. please tell me what I did wrong in plain english.190.148.134.128 (talk) 02:22, 30 March 2011 (UTC)

"Manual indent" means starting a line with spaces. If you want a line to be indented in Wikipedia, you should start it with a series of colons, such as "::::::". (I have fixed your previous line.) Looie496 (talk) 03:02, 30 March 2011 (UTC)

And, just to demonstrate:

                      this is a manual indent.

We do use that, but not when we just want regular text, it's reserved for special things. For example, it's sometimes used to make diagrams. StuRat (talk) 03:19, 30 March 2011 (UTC)

It should be noted that in high enough concentrations, carbon dioxide does settle, see Lake_Nyos#The_1986_disaster for an example of what happens when it does. However, this is quite a different scenario from atmospheric carbon dioxide. Essentially what happened at Lake Nyos was a bubble of pure carbon dioxide was "burped" out of the earth; this CO2 had very little mixing with the atmosphere, and so it suffocated the entire region. Atmospheric CO2 accounts for less than one part per thousand (see Atmosphere_of_Earth#Composition). According to Hypercapnia (the medical term for too much CO2), severe effects on humans don't set in until 10 kPa, or about 10% of the air, though minor effects set it at lower concentrations. Even assuming that some medical problems set in at 1% CO2, that would still require there to be 30X as much CO2 in the atmosphere as there is now. Even at those concentrations, there is sufficient circulation in the troposphere to assure complete mixing, even in the face of gravitational seperation. --Jayron32 03:33, 30 March 2011 (UTC)

According to scale height, each gas has its own scale height above 100 km due to diffusion. Wnt (talk) 03:39, 30 March 2011 (UTC)

Yes, but there is a big difference between what happens way up at 100 km and what happens in the much denser, and much more well mixed, troposphere... --Jayron32 03:45, 30 March 2011 (UTC)

Thanks for the answers. It appears that stratification is inhibited by heat that radiates from the planet surface. So, to get stratification to work well, radiant heat must be limited. Low-level greenhouse gasses will assist in two ways. First, they will reflect much of the solar radiation before it reaches the surface. Then, they will absorb and reflect heat before it reaches very high into the atmosphere. I think that studying temperatures on Venus will help me get a good idea of how well that will work. -- kainaw™ 12:15, 30 March 2011 (UTC)

Superallowed beta decay.

Superallowed transitions seems to be defined as those between members of an isotopic spin multiplet.

How could a beta decay not be between members of an isotopic spin multiplet? Since it is a weak interaction surely the number of quarks and hence total isospin will be conserved? So what is the difference between allowed and superallowed transitions? —Preceding unsigned comment added by 92.20.201.71 (talk) 20:29, 29 March 2011 (UTC)

OP: Is it just that nuclear spin doesn't change? In which case how is a superallowed transition different from a pure fermi transition? —Preceding unsigned comment added by 92.20.201.71 (talk) 20:46, 29 March 2011 (UTC)

You stated "the number of quarks and hence total isospin will be conserved?". That's not true. The total isospin can change. Dauto (talk) 21:00, 29 March 2011 (UTC)

up and down quarks both have I=1/2. I don't understand. —Preceding unsigned comment added by 92.20.201.71 (talk) 21:05, 29 March 2011 (UTC)

What don't you understand? We might be able to explain if you let us know. Dauto (talk) 02:14, 30 March 2011 (UTC)

Ok so my understanding was that nuclear isospin multiplets all had the same I and different values of I₃. And that beta decay acted essentially as the creation/annihilation operator I^±. And that since the operator I^± cant get you out of the spin multiplet, all beta decay must be between isospin multiplet states. This appears to be in contradiction with the above statement I was troubled by about superallowed states, and your statement that I can change. So I'd be glad if you could help me grasp the nature of my misunderstanding. Thanks. —Preceding unsigned comment added by 92.20.201.71 (talk) 02:34, 30 March 2011 (UTC)

Let me state upfront that my specialty is with particle physics, not nuclear physics. Your understanding is approximately correct and that's why beta-decays that violate the principle you describe must pay a penalty and will be less probable than naively expected. You must keep in mind that unlike weak isospin, isospin is not an exact symmetry. Dauto (talk) 04:08, 30 March 2011 (UTC)

What kind of beta decays are the ones that break the symmetry? Is it just beta decay which changes a quantum number other than I₃, such as when the neutrino and beta particle make a spin triplet and nuclear spin changes? Sorry, I may be asking tedious questions as I only started nuclear and particle this year so I do not have a condensed understanding of the subjects. —Preceding unsigned comment added by 92.20.201.71 (talk) 20:05, 30 March 2011 (UTC)

I don't remember the answer to that specific question off the top of my head and solving it right now feels too much like homework. You need to get a good book about nuclear physics. As I said, my specialty is high energy physics. But I can explain to you without going into too many details why superallowed decays are favored. Basically, in a superallowed decay the nucleons in the parent and daughter nuclei have similar wave functions so there is a lot of overlap between their wavefunctions and all that needs to happen is the transition between a proton and a neutron or vice-versa. In a non-superallowed decay the form of the nucleon wavefunctions of the parent and daughter nuclei are different and their overlap may be quite small suppressing these decays. Dauto (talk) 00:56, 31 March 2011 (UTC)

ingesting radiation

I am confused as to the reporting concerning the dangers of the current Japanese Radiation problem.

To my very basic knowledge it will be really bad to ingest any radioactive substance even on a small scale as it will spit out beta,gamma or alpha for a lifetime which would harm the body's cells . Hence absorption into the body is the real danger, this will occur via the food chain or inhalation.

I am not sure if the media reporting is referring to "safe" levels of radiation as "safe if you do not ingest/breath it in" in other words the level is safe "at a distance" outside of the body.

In a similar way you can say that Americium in a smoke detector is at a perfectly safe level but if you ate it it would be very bad for you as you are then having a permanent amount of Americium absorbed into your body. —Preceding unsigned comment added by 2.97.155.22 (talk) 21:32, 29 March 2011 (UTC)

It is important to distinguish between "radiation" and "radioactive substances". Radiation reduces very quickly with distance so the radiation being emitted by the reactors in Japan is only potentially harmful for the people working on them. The big risks are associated with radioactive particles escaping, since they can travel great distances and, as you say, be ingested. The big fears at the moment are with water outside the reactors that has been found to contain radioactive particles. As for the media, they usually don't know what they are talking about. They talk about both radiation and radioactivity, but don't always distinguish between them. --Tango (talk) 21:55, 29 March 2011 (UTC)

EC, See Sievert and Gray (unit). Your understanding comes from the fact that ionising radiation has zero risk when the source is at a sufficient distance. However, a suitably small amount of even a potent alpha source, can still be safely consumed. Basically when the scientists say it is safe, it is safe. —Preceding unsigned comment added by 92.20.201.71 (talk) 22:03, 29 March 2011 (UTC)

What happens to you if a radioactive substance gets into your body depends on a lot of things, not just its nuclear properties but also its chemical and biological ones, and mode of administration. For example a very tiny amount of plutonium in your lung is very likely to give you lung cancer. However it might not harm you if you ate it, because it's poorly absorbed (no warranty on this! I will not be responsible for anything that happens to you). See plutonium#toxicity.

Similarly iodine-131 is extra dangerous because of its tendency to concentrate in the thyroid gland, and strontium-90 because it is chemically similar to calcium and is incorporated into bone. --Trovatore (talk) 22:05, 29 March 2011 (UTC)

You are correct that most descriptions of "safe" radiation are about acute exposure, not chronic. Acute exposure is the kind of radiation that'll give you radiation sickness — it's most of what this chart is about. Unfortunately, for 99% of the people concerned, this is not the kind of radiation hazard they are going to be exposed to, because very high levels of radiation are quite rare and usually quite localized (e.g. right around the reactor). The chronic risks are from elements with long half-lives and corresponding low energy radiation, but when ingested can cause a lot of internal damage over time.

Why is this distinction not usually made? Ignorance, probably. Mixed with that lovely impulse by the scientists and engineers to assert that the general public is worried about nothing. But also because discussing chronic exposure requires a lot more specificity about the particular risks you've got in mind, and frankly even the experts are often very poor at breaking these down into separate issues. As Trovatore points out, it really depends on the substances in question and how they get into you. Some radioactive substances through some pathways flush out of the body with no harm. Some deposit themselves in your bones or thyroid or what have you, and can do a lot of damage.

I would not be comfortable if it was just the media telling me it was safe — it is clear that most journalists do not even begin the know what "safe" and "dangerous" means in the context of radiation. I would parse very closely the statements by officials and engineers — they often will say things like, it is safe for you to be in an area, but don't eat anything that grows there. There are also complicating factors — being exposed to radon gas by itself, for example, will have very little effect on your long term lung cancer risk. But if you smoke a cigarette in an area with high amounts of radon, you end up with all sorts of compounding factors and your risk goes up by a huge amount. --Mr.98 (talk) 22:21, 29 March 2011 (UTC)

March 30

Spreading mineral matters on earth

The general oxidation of earth crust might be after the time once the earth surface was molten ,the outer crust material complex and the location of mines such as aluminum and Ferro and copper in Alp -Himalaya belt shows us that thoroughly it was our earth surface molten for about 800 million years , and when any asteroid with mineral matters hinted our earth it had to be molten and spread on earth surface.(A. mohammadzade ) --78.38.28.3 (talk) 05:15, 30 March 2011 (UTC)

Is there a question here ? StuRat (talk) 05:23, 30 March 2011 (UTC)

Also, let me suggest that you also post in your native language (and tell us what it is), as we might be able to translate it better than you. Your English is barely readable. For example, "Coeur" isn't an English word. It means heart in French, but that seems wrong in this context. Did you mean copper ? StuRat (talk) 05:26, 30 March 2011 (UTC)

I can't find a question, but the OP may find useful information on the cooling of the earth at History of the Earth and Hadean Eon. The asteroid impacts he is talking about occuring during Earth's molten phase happened during the Late Heavy Bombardment period. The ancient cores of continents, believed to date from the Hadean, are called Cratons. The location of ore deposits and how they formed are complex geochemical processes known as Ore genesis. All of the links I provided here should answer any questions the OP may have, given the various statements he made. --Jayron32 05:29, 30 March 2011 (UTC)

the continues spreading shows the question about the subject late heavy bombardment say me about this ,and first earth creation .--78.38.28.3 (talk) 05:36, 30 March 2011 (UTC)a. mohammadzade THANK YOU

Please post your question in your own language as your English, which I suspect is a machine translation, is unintelligible. Roger (talk) 13:19, 30 March 2011 (UTC)

His IP suggests he is from Iran. At any rate my guess is that he wants to know is if meteorite strikes have any relation to current composition of Earth's crust (i.e. have they changed location of minerals and metals in it) ~~Xil (talk) 15:37, 30 March 2011 (UTC)

If so, he might be interested in our article on the Sudbury Basin. Matt Deres (talk) 18:35, 30 March 2011 (UTC)

How do you ask him to post in Farsi, in Farsi? 92.15.1.33 (talk) 16:17, 30 March 2011 (UTC)

I will post a request for assistance at the Language RefDesk. Roger (talk) 16:32, 30 March 2011 (UTC)

با در نظر گرفتن جایگری معادن در رگه هایی که به صورت تقریبا پیوسته مابین قاره ها امتداد یافته اند برای مثال معادن آهن و الومینیوم و مس به صورت تقریبا خطی بر روی کره زمین گسترده شده اند دو نتیجه می توانیم بگیریم .یک اینکه این معادن اقفاقی در یک خط قرار گرفته اند ودوم اینکه زمین در هنگام اختلاط هریک از این معادن با خاکش به صورت مذاب بوده است و هر سنگ اسمانی حاوی این عناصر را ذوب و در یک امتداد مثلا طولی یا عرضی کشیده است و با انشقاق قاره هابه شکل کنونی در امده است . اگر در یک دوره سطح زمین به صورت گسترده مورد بمباران شهاب سنگ ها قرار گرفته و هریک دارای عناصر معدنی بوده با فرض جامد بودن جبه زمین در زمان یاد شده به این نتیجه می رسیم که معادن نباید این گستردگی خطی را داشته باشند این تناقض را چگونه حل می کنید ؟

—Preceding unsigned comment added by 78.38.28.3 (talk) 03:39, 31 March 2011 (UTC)

Here's its translation: knowing that mines are located almost continuously along veins across continents, e.g. iron, aluminium, or copper mines are located almost linearly on the surface of the Earth, we can get two results. First, mines were accidentally located in a line; and second, when earth was mixing with these minerals, it was in a molten state, and it melted every meteorite containing these ingredients and pulled them in a latitudinal or longitudinal line, and present forms appeared when continents took shape by splitting. But if Earth was solid when those meteorites fell, this linearity of mines could not be formed. How do you explain this contradiction? (I myself don't see any contradiction here though! I don't understand him clearly --Omidinist (talk) 05:48, 31 March 2011 (UTC))

Most minerals are found in veins, which are roughly tabular in shape, and therefore appear linear where they intersect the surface. They are mostly located along fault of fracture surfaces, that are generally of one or two distinct orientations in an area, relating to the stress field at the time of formation. Stress fields are often fairly constant in orientation over large areas, meaning that the faults/fracture and their associated veins are sub-parallel. If the stress-state changes, further mineralisation will occur along different lines, an example is the so-called 'cross-courses' in SW England associated with the cornubian batholith granitic intrusion, which run mainly north-south, cutting the earlier west-east main course veins. Mikenorton (talk) 07:37, 31 March 2011 (UTC)

If you are interested in reading about metal deposits that are forming right now and being mined have a look for the one on Lihir Island, "Ladolam", in Papua New Guinea. Sean.hoyland - talk 08:55, 31 March 2011 (UTC)

برای مثال به معادن مس و خاکهای حاوی مس دقت کنید که می توانیم آنها را به صورت رگه باریک از شمال غرب ایران تا جنوب شرق از منطقه سونگون آذربایجان تا سرچشمه کرمان مشاهده کنیم یا معادن آهن از زنگولداک ترکیه تا چغارت ایران در یک باریکه خطی قرار گرفته اند —Preceding unsigned comment added by 78.38.28.3 (talk) 09:26, 31 March 2011 (UTC)

OK 78, if google translate hasn't completely misled me, you are talking specifically about the porphyry copper deposits within the Urumieh-Dokhtar magmatic belt, formed as part of the Kerman arc during the collision between the Arabian Plate and Eurasian Plate. This is linear because it marks the location of a past subduction zone along that convergent boundary. Mikenorton (talk) 09:41, 31 March 2011 (UTC)

Most mineral deposits are formed through hydrological deposition interacting with soil strata. 99.2.149.161 (talk) 04:17, 1 April 2011 (UTC)

Milligram scale

We cannot offer you instructions on compounding pharmaceutical products. Please speak with your doctor or pharmacist if you would like to be able to safely adjust the dosages of your medication. TenOfAllTrades(talk) 22:44, 30 March 2011 (UTC)
The following discussion has been closed. Please do not modify it.
This question is a bit unorthodox, I realize, but: where can I get a scale that will accurately measure within 1mg? I am willing to pay no more than $100, $150 if I get really desperate. I looked on Amazon and found a lot of cheap ones that aren't precise at the 1mg level, which is unacceptable for me. And I see some more expensive ones but they don't have enough reviews for me to tell how well they'll work. I am willing to buy online, although buying locally would be even more ideal. Magog the Ogre (talk) 16:59, 30 March 2011 (UTC) What do you need the top end of the scale to be? Googlemeister (talk) 18:19, 30 March 2011 (UTC) Ugh, it turns out I have misread! I need it to be accurate to .01 mg, which I know is ridiculously precise, and probably not something I could find easily on the market. But to answer your question: no more than a few milligrams. Magog the Ogre (talk) 18:32, 30 March 2011 (UTC) You need an analytical balance. You 'might' be able to get a secondhand one on Ebay. A basic balance is not really going to be good enough though so make sure it has the resolution you need. What are you trying to weigh? There might be an easier way to achieve the end result --Aspro (talk) 19:04, 30 March 2011 (UTC) Ouch. A balance with a 10 microgram resolution is going to be costly, whether new or used. In the price regime you're describing, you just can't get precision equipment unless a) it's in need of major repairs; or b) you're buying it from someone who doesn't have a clue what it's worth. Properly packing and shipping a microgram balance is probably going to eat a good chunk of your budget, on top of whatever you pay for the instrument. Scientific American did run a column describing how to construct your own balance with your desired precision. If you're good with your hands, you can do it with less than fifty dollars in parts: [6]. The addition of a microcontroller allows you to automate the readout and tare funcions, and still can ring in under $100: [7]. TenOfAllTrades(talk) 19:11, 30 March 2011 (UTC) Re: Aspro: I am trying to measure my prescribed medication which I am splitting (the minimum dosage is .25mg, and I am cutting it in fourths, leaving ~.06 mg/dose; if I am off by even about 25%, I suffer undesirable side effects until my next dosage; my body is amazingly sensitive to tiny changes in chemistry... I can get pretty buzzed off just one beer for example). You will note I am not asking for medical advice (I've already talked to my doctor); I am asking about a scale. Magog the Ogre (talk) 19:58, 30 March 2011 (UTC) The cheapest one I can find after a (brief) search is about $1000. I would suggest asking your doctor if he can provide your medication in something like a pill which can be easily cut into quarters by hand. Or perhaps ask your local college/university if they have some old scales they're about to throw out? 50.92.121.76 (talk) 20:15, 30 March 2011 (UTC) I hope you realise that a pill containing .25mg active ingredient actually weighs substantially more than that. The bulk of the tablet consists of sugar, chalk or another non-bioactive carrier. If it was pure active ingredient the tablet would be like a tiny speck of dust. If you are unable to divide it accurately enough you could try disolving the tablet and then dividing the solution by volume - the more water you use the more precisely you can divide it: .25mg active ingredient disolved into 100cc of water would result in 2.5 microgrammes per cc. Syringes or pippetes that can accurately measure 0.1cc are widely available and dirt cheap. Roger (talk) 20:36, 30 March 2011 (UTC) Re: 50.*: a good idea; i have local contacts in a very large university chemistry department. Doesn't mean I'll get it though! Re: Dodger67: that is an extremely good idea which hadn't occurred to me. Unfortunately, according to the local Wikipedia article, "when crushed in water it will not fully dissolve." I may have to ask my chemist friend about the solubility though. Magog the Ogre (talk) 20:59, 30 March 2011 (UTC) Wow. As detailed as Erowid is about this stuff, they give neither the gross weight of the pill nor the composition of the oral solution form in which it is sold. Wnt (talk) 21:49, 30 March 2011 (UTC)

I can't be bothered with the elaborate brown rice recipes.

Is it still worthwhile to eat brown rice when I can't be bothered to cook it for a long time? 12.40.220.253 (talk) 17:21, 30 March 2011 (UTC)

It sounds like you are asking if it's OK to eat raw rice. Dauto (talk) 18:54, 30 March 2011 (UTC)

If you can be bothered to walk round the supermarket you can find it ready cooked – just needs two minutes in the microwave.--Aspro (talk) 18:55, 30 March 2011 (UTC)

Yes it is, the fibre is very good for you. The way I make rice is: add half a cup of rice and a full cup of boiling water to a saucepan. Bring back to the boil, then reduce the heat and simmer for 20-25 minutes (depends on the rice - could be 25mins for wholemeal, but down to only 15 for white or easy-cook rice - follow packet instructions). Check the saucepan from time to time to make sure it is not boiling dry. I use a timer to measure the time, as it is essential to remove the saucepan before it gets too dry and starts to burn. You can add chopped vegetables at the beginning, but this can introduce more moisture which may need draining off five minutes or so before the end. Best to be watching the saucepan for the last 5 minutes so that you can get the rice as dry as you wish, without burning. I prefer moist fairly soft rice. I use an open saucepan lid, so that all the interior is moist but which allows the steam to escape. I think you could alternately make rice with more boiling water and then drain and dry it after cooking. 92.15.1.33 (talk) 20:47, 30 March 2011 (UTC)

I was surprised when I had some Chinese and Malaysian borders at my place a couple of years ago, when they told me that NO ASIANS these days cook rice as described above. They ALL use rice cookers. And when I bought one, I could see why. They cost about nothing (say $20). you just put the rice in, cover it with water by a couple of fingers, put the glass top on, and turn it on. It will cook the rice perfectly, then switch off to "keep warm" mode. There is nothing to do at all, and the rice is ALWAYS perfect! I never use anything else now. No chance for burning or undercooking, and the cooker keeps the rice warm for hours. Try it. All the Asians use it, and they are the canniest buyers I know. Myles325a (talk) 00:12, 31 March 2011 (UTC)

But the rice in Asian cooking is usually sticky white rice. I think that some rice cookers won't work properly with other types of rice, so you should check that before buying. -- BenRG (talk) 04:27, 31 March 2011 (UTC)

And, the other part of the "is it worth it" calculation is based on how good it is for you. Take a look at the nutrition here: [8]. The good points are that lack of fat, saturated fat, cholesterol, sugar, and sodium (unless you need to add those things to make it palatable). It also has a moderate glycemic index (less than white rice). It's a mixed bag as far as vitamins and minerals, having lots of some (like manganese), and very little of others. On the bad side, it's also fairly high in calories (almost all of them from starch), low in protein (although it is almost complete in amino acids), and somewhat inflammatory. StuRat (talk) 04:25, 31 March 2011 (UTC)

You've forgotten the fibre, which most people do not get enough of. It is very much better than filling up on junk food such as "french fries" or pizza. 92.29.119.112 (talk) 10:43, 31 March 2011 (UTC)

I didn't list fiber since it had been previously mentioned. And french fries have a fair amount of fiber: [9]. They are unhealthy, but that's due to the salt and fat, not a lack of fiber. The same is true of pizza: [10]. StuRat (talk) 18:32, 1 April 2011 (UTC)

To cook brown rice in a rice cooker you just put in double the amount of water. It does take longer to cook, but it is almost no more work, so level of water=3xlevel of rice. Graeme Bartlett (talk) 21:43, 1 April 2011 (UTC)

Do you mean that the volume of water is double the volume of rice, or double the volume you normally use (whatever that is)? If you are putting in too much water, then you may be spending a lot of time merely evaporating the excess water for already cooked rice. Thanks 92.15.9.102 (talk) 09:45, 3 April 2011 (UTC)

Protein subunit names vs gene names?

Hi, I had a question about how it is that protein subunits get their names. I was under the impression that if an operon had the structure (for example, in the case of the perchlorate reductase enzyme) pcrABCD, the subunits would be alpha, beta, gamma, and delta (respectively). However, I just noticed that in the case of another enzyme, methane monooxygenase, the pmoCAB operon encodes gamma, beta, and alpha, respectively. So, how is it that biochemists name subunits? Is it not supposed to correlate with the genes (i.e., why is "A" not the alpha subunit?) Thanks for your help. Ccarlst (talk) 22:05, 30 March 2011 (UTC)

The subunits of the methane monooxygenase enzyme were discovered and characterized in the 1970s and 1980s (eg. [11], [12], [13], [14]). The biochemical data and protein sequence data were then used to map and clone the genes encoding the proteins in the late 1980s and early 1990s (eg. [15], [16], [17]). The original nomenclature of the protein components did not match up with the molecular biology, which has often been the case in the history of science, but in order to avoid confusion, we keep the standard biochemical nomenclature and accept a few inconvenient inconsistentcies such as the genes being arranged in a different order than their names would imply. --- Medical geneticist (talk) 13:02, 1 April 2011 (UTC)

So how it is that biochemists decide what is alpha, beta, etc? Also, what are the current standard names (and what is the correlation) between genes pmoCAB and alpha, beta, gamma subunits? Thanks for the help. Ccarlst (talk) 19:44, 1 April 2011 (UTC)

Acceleration and relativity

So using the Newtonian a = F/m it would seem an object could be accelerated to any speed. What is the relativistic equation that is asymptotic at the speed of light?   jorgenev (talk) 22:05, 30 March 2011

Four-force —Preceding unsigned comment added by 92.20.201.71 (talk) 22:51, 30 March 2011 (UTC)

(edit conflict):Our article Mass in special relativity explains that the apparent mass M at speed v is given by $M=m/{\sqrt {1-v^{2}/c^{2}}}$ (though this equation is not the best way to look at the situation). The acceleration is thus $a=F{\sqrt {1-v^{2}/c^{2}}}/m$ and gradually reduces towards zero as the speed approaches that of light. Dbfirs 23:00, 30 March 2011 (UTC)

That is totally wrong, and the article you linked to even includes a quote from einstein about the total vacancy of introducing the quantity $M={\frac {m}{\sqrt {1-v^{2}/c^{2}}}}$. Infact

${\mathbf {f} }={d \over dt}\left(\gamma m{\mathbf {u} }\right)=m\gamma \mathbf {a} +m\gamma ^{3}{\frac {\left(\mathbf {a} \cdot \mathbf {u} \right)}{c^{2}}}\mathbf {u}$ —Preceding unsigned comment added by 92.20.201.71 (talk) 00:31, 31 March 2011 (UTC)

I agree, that's why I said it's not the best way of looking at the situation. I thought that the OP was looking for a simplistic explanation (and first approximation) of why an object cannot accelerate to infinite speed. My equation provides an approximate first improvement on Newton's approximation. Your link provides a better view and your equation is more accurate as v approaches c. Dbfirs 12:47, 31 March 2011 (UTC)

No, for parallel acceleration and velocity you are out by two powers of gamma. Thus even to a first order correction in power series your correction is out by a factor of 3. That is big, that is like me responding to a question "what is pi?" with the answer "3" and claiming I thought they just wanted an approximation. Besides this your answer also does not support your claim that you were merely intending to provide a first approximation (never mind discussion as to in what way this is a first approximation), if you were providing an approximate answer you should have stated this. There is no benefit in proliferating some kind of lie on some assumed and awkward notion that the OP couldn't handle the truth. —Preceding unsigned comment added by 92.20.201.71 (talk) 02:19, 1 April 2011 (UTC)

But gamma is very close to 1 until v gets close to c, and the correction term is divided by c squared (a very big number). The questioner was wondering why Newton's even wilder approximation didn't hold. I do agree with you that it was a mistake on my part to ignore the other term in differentiating (by the product rule) the more general form of Newtons Law: Force = rate of change of momentum, where $p={mv \over {\sqrt {1-{\frac {v^{2}}{c^{2}}}}}}\!$ (and another mistake not to use vector differentiation). I apologise for proliferating the misunderstanding. I ought to know better! (In my defence, I would comment that this was the explanation in the text-book from which I learnt about relativity many years ago.) Dbfirs 06:50, 1 April 2011 (UTC)

Antimatter, antigravity, spacetime, retrocausality, and antispace

Warning: Risk of cosmological brain spasms or nonexistent headaches

Hi. Does antimatter have positive or negative mass? Assuming it has negative mass, we could depict its effect on the curvature of spacetime as a flat sheet as an object causing an upward dent in this fabric from antigravity, rather than a downward dent produced by normal matter. Using this representation, could we conclude that the collision of a piece of matter and antimatter represents the overlapping of a positive and a negative dent, therby causing the two warping areas to collide and annihilate? Would this be similar to standing waves cancelling out each other, in this case each respective object's mass/antimass, and would this send out gravitational waves? Or, would the idea of each having the other object's respective antigravity cause some kind of gravitational repulsion?

Since spacetime is the modern interpretation for interwoven space and time, would antimatter cause negative time to occur in addition to causing a negative gravitational "space-dent"? Could antimatter fuel thus have the capacity for time travel alongside massive propulsion? Also, considering that antimatter produces antigravity as an assumption, would the graviton theory apply to "negative gravitons" or regular gravitons going inward? If a negative and positive graviton were to intersect, what would ensue?

Creating negative time from antimatter would enable backward flow of time, and in fact there is some preliminary laboratory evidence of retrocausality. In this scenario, do the occurence of future events cause past events, or do the un-occurrence of future events un-cause past events to un-materialize? When a forward-time-flowing mass of matter and a negative-time-flowing negative mass of antimatter collide, do their respective time reflections cause the collision to un-occur, or does time stop before each object collides into the other?

From the relativistic view of one object, it would take an infinite amount of time for the other object to approach whereas it takes very little time to an outside observer. Would this be similar to the theory that time stops for objects entering black holes, which is also proposed by the varying speed of light hypothesis? Or, would this mean that in a quantum mechanics sense, the objects have both simultaneously annihilated and stopped their annhilation but neither outcome has taken place due to the lack of an observer? Does that mean that black holes are the unity of matter and antimatter confined so that their produced energy are converted to mass as time stops the explosive reaction and release of rest energy from taking place? Similarly, could this explain the paradox of an object entering a black hole and coming out in the past in a different trajectory as to knock the original object away from the black hole's path so that the original event could never have taken place, by realizing the past post-entrance object as one quantum half of the original object so that they merge and two digressional paths occur?

Could any event in the universe, even for a fraction of Plank time, cause the black hole-type dent in spacetime to reach so infinitely deep that it comes around on the other side ("around" the ultra-dimensions of the universe, even if flat) and connects into itself like an infinite regression wormhole? Finally, would a "dent" made in space by antimatter cause the object to take up negative space, so that its dimensions are, say, -2 cm in diameter (and would this also cause "in" to be an infinite directional dimension similar to "out", which does not end until the edge of space is reached)? Does this potential for anti-spacetime have any potential implications, or does this hypothetical description reduce relevance to cosmological nonsense? Thanks. ~AH1^(TCU) 23:33, 30 March 2011 (UTC)

Replace "article" with "thread": {{Sub-sections}} Magog the Ogre (talk) 00:16, 31 March 2011 (UTC)

Unfortunately, none of what you said has any bearing on reality, since as noted in the Antiparticle article, antiparticles (the constituents of antimatter) have the same mass as normal particles, not negative mass. Truthforitsownsake (talk) 00:18, 31 March 2011 (UTC)

Negative mass (if it existed) would not cause an upward dent in space. An upward dent is the same as a downward dent, because only the intrinsic shape (curvature) matters. Rather, negative mass would cause there to be less space in the middle, instead of more. If you add material in the middle of a sheet, it bulges (up or down). If you remove material, it "pinches". That would be the negative-mass version of those bulgy GR images.

There is nothing physically "anti" about antimatter. Every kind of particle in nature has a mirror image under a certain symmetry (CPT symmetry), and sometimes one particle of these mirror-image pairs is named "anti-" followed by the name of the other. By analogy, the shapes F and ꟻ are mirror images of each other under ordinary mirror symmetry, and we could call the second one "reversed F" (that is its name in Unicode). But "reversedness" is not a property of the shape itself. It just happens that F is more commonly encountered in everyday life, so it gets the simpler name.

I'm not aware of any relationship between VSL cosmology and the idea that time stops near a black hole. -- BenRG (talk) 03:31, 31 March 2011 (UTC)

Also, there's no preliminary laboratory evidence of retrocausality. -- BenRG (talk) 04:35, 31 March 2011 (UTC)

Hmmm... to be clear, in order for negative mass to be possible, you'd have to be able to draw a line that is straighter than straight? Wnt (talk) 04:55, 31 March 2011 (UTC)

No, there's no such thing as a line that's straighter than straight, but there is such a thing as spacetime curvature corresponding to negative mass.

A way to make a crude model of the usual "bulge" is to take a circle of paper, cut out (and discard) a wedge, tape the cut edges together to get a cone, then tape that cone to another piece of paper with a circular hole cut in it (as shown here, but I wouldn't necessarily believe any of the text on that page). To get a model of negative mass you could do the same thing, but adding a wedge instead of removing it. That is, make a radial cut in the circle, insert the wedge you removed from the other circle, tape it at both sides, then try to tape the edge of that to a circular hole in another piece of paper. This doesn't work nearly as well as the cone, and it's not clear that the concept of negative mass actually makes sense, but I think that those two facts are unrelated.

(It may seem like you're "removing space" when you make the cone and "adding it" when you make the anti-cone, but it's actually the other way around, in the following sense: if you draw a circle on the flat paper around the cone, the area of the paper inside the circle is larger than you'd expect from the circumference; and in the case of the anti-cone it's smaller.) -- BenRG (talk) 08:33, 31 March 2011 (UTC)

The connection between VSL and time stopping at the event horizon in addition to the experimental evidence of retrocausality are both found in Discover magazine. Perhaps an ultra-straight line would be an anti-geodesic? ~AH1^(TCU) 13:07, 31 March 2011 (UTC)

There's no such thing as an ultra-straight line or an anti-geodesic.

The retrocausality article is this one, I guess, which describes some sort of delayed-choice experiment. These are old news, and aren't evidence of retrocausality. The VSL article is this one, I guess, from which I learned that João Magueijo does believe that black holes are frozen stars, so I stand corrected. But João Magueijo is not a reliable source of information about the real world.

Please understand that Discover has to come up with something to entice its readers every single month. When there's no real news about cosmology or quantum mechanics—which there usually isn't—they have to manufacture something. Real evidence for retrocausality or VSL cosmology would change the whole course of theoretical physics. Anything that appears solely in Discover isn't news. -- BenRG (talk) 01:24, 1 April 2011 (UTC)

March 31

Space and matter shortly after the Big Bang

Hi

1. In the early Universe, just after the Big Bang, was there "as much space" as there is now but compressed into a smaller volume, or was there actually "less space"? If there was "as much space" then in what sense was the Universe "smaller"?

2. In the time shortly after the Big Bang, were particles and atoms in some sense actually "smaller" than they are now? Or did the formation of matter have to wait until enough space had been created to contain it?

86.177.108.189 (talk) 00:19, 31 March 2011 (UTC)

1. What's the difference?
2. There were no atoms. Only a subatomic particle soup. Dauto (talk) 00:33, 31 March 2011 (UTC)

If there was "as much space" then "as much stuff" could fit into it (e.g. all the atoms that now exist), yet that stuff would be "smaller" in some sense that I do not understand. If there was "less space" then "less stuff" could fit into it. In the latter case, as we get smaller and smaller, eventually there would be no room for the particles in your soup. Then what? Just energy in some other form? 86.177.108.189 (talk) 00:53, 31 March 2011 (UTC)

(edit conflict) I think I see what you are getting at. There was actually less space; in the sense that the stuff that was not space (matter and energy) was all closer together. The big bang and inflation created the space in which matter and energy organized itself into its current state. See Metric expansion of space and Timeline of the Big Bang and Inflationary epoch and Inflation (cosmology). Your sense is correct; all the "stuff" in the universe was compressed so there was a lot less room, even down to a singularity at the moment of genesis. --Jayron32 03:49, 31 March 2011 (UTC)

In simple terms, yes. The universe was much, much smaller, and all of the mass-energy was compressed into that very small space. I say mass-energy because at that density it's practically impossible for particles as we know them to exist, and it was all pretty much just high-energy photons. After a while, as the universe expanded, the energy density dropped, and particles started to condense out - starting with the really small ones like quarks and leptons. Check out Timeline of the Big Bang for more info. Confusing Manifestation(Say hi!) 03:45, 31 March 2011 (UTC)

Atoms were never smaller. But atoms only exist at low temperatures, because it doesn't take much energy to knock the electrons off, and it doesn't take much more than that to knock the nuclei apart. So physics is effectively different at higher temperatures, though the laws are the same. At even higher temperatures, the Higgs field gets knocked out of its nonzero vacuum state, and concepts like "electron" and "photon" break down, though the laws of physics are still the same. At even higher temperatures, nobody has any idea what happens (but I suppose the laws of physics are the same even then, by definition...)

Generally, things can be smaller at higher temperatures because there are more accessible fermion states. Ordinary matter is hard to compress because all of the low-energy electron states are occupied, and you aren't strong enough to push a substantial fraction of the electrons into higher energy states. But far more compact configurations of matter are physically possible when the energy is available.

I don't agree with ConMan's response. At high enough temperatures you can pair-produce arbitrary Standard Model particles, so all of the particle types are equally represented in the soup. (And, as I said, at even higher energies the low-energy particle types are meaningless.) I'm also unhappy with the idea that small things condense out first. Things condense out when there's insufficient energy to knock them apart.

I think the "Timeline of the Big Bang" article is of rather poor quality right now. The "inflationary epoch" is certainly misplaced; it should have no start time, since (1) A.B.B. times only make sense post-inflation, and (2) nobody has the slightest idea how long inflation lasted, nor what the pre-inflationary state might have been. I don't want to rewrite the article, though, because I don't really know very much about high energy physics. -- BenRG (talk) 05:56, 31 March 2011 (UTC)

• Thanks for the replies. I'm still a little confused about how we actually measure the size of things when space is not constant. In principle, could we take a 30cm ruler back to the time when the Universe was 30cm across and find that the ruler only just fitted (ignoring practical complications such as the conditions being too extreme for the ruler to survive)? Let's assume the answer is "yes". Then, over billions of years, space has expanded, but the ruler has stayed the same size? How does that work? Space must be expanding in all places, right, so why isn't it expanding "inside" the ruler, thereby stretching it? (Imagine the ruler is a drawing on the surface of a balloon. As the balloon inflates -- as space expands -- the ruler gets bigger.) This is what I don't understand. Thank you! 86.179.115.14 (talk) 12:58, 31 March 2011 (UTC)

I will say "yes" to your first question, although most solids vary in size with temperature and no solid can exist at those temperatures. A better answer is that the laws of the Standard Model haven't changed (it's thought) and various length scales can be derived from that. For example, the confinement scale of the strong force is about a femtometer, and that was the same back then. This is how the size of space is defined, essentially—it's the amount of space you'd need now to reproduce similar conditions in the lab. If the physical laws were different, there would be some fuzziness in how much the universe had expanded.

The reason rulers don't lengthen as the universe expands is the same as the reason they don't lengthen in other circumstances. Rulers are bound together by forces that, for complicated reasons, prefer a certain separation between particles and resist attempts to increase or decrease the separation. The laws of physics don't change, so the preferred separation doesn't change. There's nothing special about the recessional motion associated with the expansion of the universe; it is the same as any other recessional motion as far as the laws of physics are concerned.

Self-gravitation does act on rulers; it's constantly squeezing them. They don't collapse into black holes because the forces binding the ruler resist compression with a force that roughly follows Hooke's law (everything is like a spring under small enough deformations). Self-gravitation compresses the ruler until the opposing force matches the compression force, and the ruler remains permanently in that equilibrium state. It's slightly smaller than it would be without gravity, but it doesn't get smaller over time. If the cosmological constant is real then it also acts on rulers, trying to pull them apart, but because rulers resist pulling also, the effect is again just a slight change in the equilibrium size (much smaller than the effect of self-gravitation, which is already very small). If there were a pushing/pulling force directly associated with the expansion of the universe (which, I want to stress, there is not—Aristotle was wrong about that), it also would simply change the equilibrium size. -- BenRG (talk) 18:38, 31 March 2011 (UTC)

Ben, thank you for your very helpful answer. If I could prevail upon you again: At the time when the 30cm ruler only just fitted into the Universe, did it only just fit because it hit a boundary, or "edge", of available space? I'm guessing the answer to this is "no", but if there is no boundary or edge stopping the ruler extending further, then what would prevent us placing a longer ruler in the same Universe, thereby contradicting the proposition that the 30cm ruler only just fitted? 86.179.117.213 (talk) 01:04, 1 April 2011 (UTC)

When you hear figures like 30cm being quoted, those are the size of the visible universe at that time. In other words, the matter making up the present-day visible universe fit in a 30cm sphere (I'll take that to be the diameter, but a factor of 2 hardly matters). The universe presumably continues past that point, although we can't see it because the light hasn't reached us yet. We have no idea how large the entire universe is, nor what the nature of the boundary would be, if there is one.

But that doesn't mean your long-ruler question is uninteresting. It's actually quite subtle, and made me realize something I hadn't thought about before, which is that a quasi-rigid ruler that spanned the visible universe back then would actually be larger than 30cm now. The reason is that if all points on the ruler are at relative rest, then back then both ends of the ruler were moving rapidly inwards with respect to the Hubble flow, and therefore were Lorentz contracted with respect to cosmological coordinates (which take the Hubble flow as the local standard of rest). So if the coordinate length of the ruler then was 30cm, its proper length (which we would measure now) would have to be larger. Also, you run into difficulties with what it even means for a large solid object to exist at that time, because of synchronization issues. The time since the big bang is the same for all particles moving with the Hubble flow, but it would be different for different parts of the ruler.

So it's really necessary to measure the diameter with smaller rulers. 30 rulers of a centimeter each, maybe, which are moving with the Hubble flow. At the moment in question they all line up end-to-end and span the visible universe; a moment earlier they overlap and a moment later there are gaps between them. If you could gather them up today and arrange them end to end, they would total 30cm. -- BenRG (talk) 04:44, 1 April 2011 (UTC)

Thank you very much, that's very helpful. 86.179.115.50 (talk) 13:18, 1 April 2011 (UTC)

Shrinking Sun

According to the article Formation and evolution of the Solar System and Future of the Earth, the Sun is getting warmer and brighter by around 10% every 1 billion years because of the helium build-up at its core (nearly half the hydrogen has been consumed). This will wipe out Earth's life even before the time of the Red Giant. Now what the young-earth creationist use as evidence for their young Earth is the proof that the Sun is shrinking at 5 feet/hour. Try googling shrinking Sun. Is it really true? The two statements above seem contradictory. Please tell me which one is right. Aquitania (talk) 00:35, 31 March 2011 (UTC)

The evidence that the sun is shrinking is not very good, but I think the idea is that the sun is contacting, and therefore getting warmer in its core (since the extra density causes fusion to happen faster). Although like you I would have expected a warmer sun means a bigger sun, I think that's impossible: A bigger core (of the same mass) means lower energy production, so the core can't be any bigger than it is now. (In a red giant the core is small, but the outer layers are large.) Ariel. (talk) 01:11, 31 March 2011 (UTC)

Each Helium nuclei has half the electric charge and a quarter of the particles of the four protons it replaces. Therefore Sol has less volume (and higher density) and very slightly less mass. Hcobb (talk) 01:34, 31 March 2011 (UTC)

"...half the electric charge..." yes, but only because you have ignored the 2 positrons released when each of two proton pairs fuses into a deuterium nucleus - there is no overall loss of charge (obviously). "... a quarter of the particles ..." - I don't follow this at all - there are 4 nucleons both before and after fusion. Gandalf61 (talk) 09:24, 31 March 2011 (UTC)

Gandalf, Hcobb is talking about reducing the number of nuclei which is the number that appears at the ideal gas law PV=nRT, that governs pressure in non-degenerate matter. Dauto (talk) 12:28, 31 March 2011 (UTC)

And does the core of a star behave like an ideal gas ? As it is a plasma, I would have thought its equation of state would be much more complex. Gandalf61 (talk) 13:02, 31 March 2011 (UTC)

Yes, the core of a main sequence star does behave like an ideal gas. $P=\rho R^{*}T\,$ where $R^{*}\,$ is proportional to the number of particles per molecular weight $R^{*}\sim (2X+0.75Y+0.5Z)\,$. The quantities $X\,$, $Y\,$, and $Z\,$ are the hydrogen, helium, and metalicity mass fraction respectively. So hydrogen contributes two particles (a proton and an electron) per nuclei (which has a molecular mass equal to one): $2/1=2\,$, helium contributes three particles (a nucleus and two electrons) per nuclei (which has a molecular mass equal to 4): $3/4=0.75\,$, and metals contribute (n+1) particles (a nucleus and n electrons) per nuclei (which has a molecular mass equal to 2n): $(n+1)/2n\approx 0.5\,$. Dauto (talk) 15:17, 31 March 2011 (UTC)

When was the last time young earth creationist were right about anything? Dauto (talk) 03:27, 31 March 2011 (UTC)

The problem with that arguement, is that young earth creationists assume that that trend can be extended indefinitely backwards in time. This kind of error is sadly not uncommon. Plasmic Physics (talk) 07:32, 31 March 2011 (UTC)

It is physics 101 or an entry level astronomy class where you learn about the physics of a star, how stars exist by a balance between their mass and the laws of gasses. Gas particles repel eachother. The gravity of a body holds them back. If the mass of the star decreases, the gas particles are allowed to expand away from eachother. If too much of the gas turns into heavier elements thus no longer being a gas, the star ends up having less gas to fight the star's gravity and the star collapses under it's own weight. —Preceding unsigned comment added by 108.67.181.74 (talk) 04:11, 2 April 2011 (UTC)

Size of the universe

How big is the universe? — Preceding unsigned comment added by JoshuaDonald (talk • contribs) 04:36, 31 March 2011 (UTC)

We don't know. It could be infinitely large, or perhaps has finite limits but which the laws of physics do not allow us to probe. See Universe#Size.2C_age.2C_contents.2C_structure.2C_and_laws and Shape of the universe and Observable universe for some extended content on this matter. --Jayron32 04:39, 31 March 2011 (UTC)

There is an interesting concept explaining the big bang and the form of the universe: http://www.teach-nology.com/forum/showthread.php?p=46964 108.67.181.74 (talk) 04:21, 2 April 2011 (UTC)

Would I be able to donate extra skin and fat cells for $?

As I was in Germany as a toddler, I can't donate blood. _{(After over 20 years of not being in Europe, I clearly don't have CJD, but it'll take a lot to get that through the FDA's thick heads.)}

As I'm 11-13 lbs. overweight, and aware of how organs are sold for money, what about donating my extra skin and fat cells to anyone who may need it? Where do I go to get this to happen, and how much $ would I earn per lb.?

Other than that, what CAN I donate (that will replenish/regenerate, so no kidneys, for example) that will still net me some funds? --70.179.169.115 (talk) 11:26, 31 March 2011 (UTC)

I think you're out of luck. Dauto (talk) 12:24, 31 March 2011 (UTC)

Doesn't somebody need skin grafts at any point in time? Also, if fat tissue has been burned, that would need replacement too, right? --70.179.169.115 (talk) 13:18, 31 March 2011 (UTC)

For your second question you might be able to sell blood plasma and gametes (the second is easier for males then females). Googlemeister (talk) 13:15, 31 March 2011 (UTC)

Gametes? Okay then, where is the closest gamete donation center to 66502, please? --70.179.169.115 (talk) 13:18, 31 March 2011 (UTC)

As an aside, I will note that the latent period of CJD infection can run into multiple decades, with some speculation that it may take up to 50 years for symptoms to appear. TenOfAllTrades(talk) 15:13, 31 March 2011 (UTC)

The restrictions on donors with vCJD are borderline paranoia, given that the number of total cases is vanishingly small and the impending epidemic never happened. The restrictions on blood donation are restrictive because people are still paranoid about disease risks, and it leads them to refuse life-saving treatments. Better to deal with their fears ahead of time. I'm not aware of adipose tissue donation. Skin donation is almost entirely either autografts (i.e. from one spot on the patient to another) or from cadavers, and has the same restriction on European residence anyway. Semen/oocyte donation, as of 2005, now has the same restriction unlesss you're giving for someone that knows you and they're notified of the potential risk up front. You can't donate a kidney for money in the US anyway. There's a blood test for vCJD which has been proven on paper, but it'll probably be at least several years before it's commercially available, since getting it to work is one thing, nailing down specificity and sensitivity to a decent level is another entirely. For the record, routine blood donors are not paid (again, volunteers are felt to be safer). Plasma donation is paid in the US, even though the World Health Organization frowns on that practice. SDY (talk) 16:52, 31 March 2011 (UTC)

Out of interest here are the precautions taken in the UK against transmission of CJD in donated blood. A far worse disaster in the UK was the use of blood imported from US prisons in the 1980s. Alansplodge (talk) 18:32, 31 March 2011 (UTC)

We have an article on that topic, though it looks like the UK-specific article is yet to be written. People got scared for a reason. What's sad is that some of this same issue was repeated in China, but there it was shared needles resulting in something like a quarter of a million HIV infections (again, shortcuts for economic reasons). There it was the donors, haven't heard anything about the recipients. Modern processing techniques are fairly thorough, but I wouldn't be surprised if some slipped through. SDY (talk) 19:18, 31 March 2011 (UTC)

Obsolete or speculative physical theories

Are speculative physical theories that don't make any predictions that can easily be tested still considered to be "scientific"? Are obsolete physical theories considered to be unscientific? I ask because in this thread an editor is convinced that Einstein-Cartan theory is some combination of "wildly speculative", "not science", and "pseudoscience". In the end, he says it's mathematics, not physics. To me, that doesn't seem fair to established speculative physical theories (e.g., Brans-Dicke theory, string theory, quantum gravity). But I'm a mathematician, not an empirical scientist. I'd like a broader view on this question. Sławomir Biały (talk) 12:25, 31 March 2011 (UTC)

It is relevant to point out that our definition of hypothesis says "For a hypothesis to be put forward as a scientific hypothesis, the scientific method requires that one can test it." Even our article on theory says "Such theories are preferably described in such a way that any scientist in the field is in a position to understand, verify, and challenge (or "falsify") it." Keep in mind these are fairly narrow definitions, and alternate formulations end up being more about philosophy of science than about science per se.

The work of applied mathematicians, theoretical physicists and their ilk often falls through the cracks of easy-to-formulate definitions of science. Certainly marking string theory as 'pseudoscience' would be perverse. Though I am not that familiar with this notion of Torsion field physics, some of the views at the talk page constitute extremely hard-line bias towards empiricism as the only valid form of science. Consider this: lack of obvious testable predictions does not mean a proposition or theory is not falsifiable. If a case can be made for falsifiability, then you have a good claim that the theory is scientific under the Popperian scheme of science. SemanticMantis (talk) 15:22, 31 March 2011 (UTC)

Slightly off-topic, but: In general relativity you can think of continuous mass distributions (the stuff that appears in the stress-energy tensor) as a continuum limit of a bunch of tiny nonrotating black holes in vacuum. If they're rotating, the continuum limit has torsion. So it's easy to argue that Einstein–Cartan theory is more natural than general relativity, since it doesn't impose an arbitrary constraint on black holes in the continuum limit. The difference between Einstein–Cartan theory and GR is too small to be tested, but neither theory is to blame for that. If you wanted to discard one theory, it would have to be on the basis of Occam's razor. GR has simpler math, but E–C appears to me to have fewer arbitrary assumptions. Newtonian gravity has simpler math than GR, but GR has fewer arbitrary assumptions. So this argument would seem to favor E–C gravity. I suppose the broader point is that the testability of a theory depends somewhat on what alternatives are available. Every theory makes many predictions that aren't testable (because we don't have any labs on distant planets, for example). That doesn't matter until a rival theory comes along that predicts the same result in a lab on Earth but a different result on another planet. Suddenly the untestability of the distant-planet prediction becomes a problem. It's not fair to blame the new theory for that just because it was invented later. -- BenRG (talk) 23:20, 31 March 2011 (UTC)

Very interesting posts. Thanks! Sławomir Biały (talk) 12:55, 2 April 2011 (UTC)

Temperature induced nuclear fission

How do I calculate the theoretical ratio of free nucleons to nuclei in a nuclear plasma, as a function of temperature, pressure, and muclear binding energy? Plasmic Physics (talk) 12:56, 31 March 2011 (UTC)

I don't understand your question. could you elaborate? Dauto (talk) 00:49, 1 April 2011 (UTC)

At the temperature increases for a electromagnetic plasma gas, a new type of plasma develops. I say plasma gas, because a plasma is not a distinct phase like a solid or liquid, as a table salt is considered a solid example of a plasma. This plasma is a nuclear plasma gas - in a nuclear plasma gas, nuclear fission of normally stable nuclei is induced. In this process, the binding energy is overcome by the thermal energy. Since temperature is equivalent to the average thermal energy of a bulk sample, not all nuclei would have energies over the threshold required for nulear fission to be induced. In addition to this, there is a continueum of discrete fission products ranging from no fission, to individual nucleons. So, it is fair to say that across a change in temperature, a gradient of proportion should exist for a specific fission product. Plasmic Physics (talk) 01:37, 1 April 2011 (UTC)

Anyone? Plasmic Physics (talk) 23:29, 1 April 2011 (UTC)

If I understand you correctly you want to know how to calculate the concentration of free nucleons given temperature, pressure and assuming thermodynamic equilibrium. That is done the same way that the concentration of chemical species is calculated for a given reaction. You must calculate the Gibbs energy for the system and minimize it. Read Chemical equilibrium You will also find useful the article thermodynamic potential. specially the section Thermodynamic potential#The equations of state. Dauto (talk) 04:35, 2 April 2011 (UTC)

Helpful, how sure are you that it exists in a state of equilibrium? Plasmic Physics (talk) 07:20, 2 April 2011 (UTC)

Isn't there an anti-hunger pill anywhere?

This question has been removed. Per the reference desk guidelines, the reference desk is not an appropriate place to request medical, legal or other professional advice, including any kind of medical diagnosis or prognosis, or treatment recommendations. For such advice, please see a qualified professional. If you don't believe this is such a request, please explain what you meant to ask, either here or on the talk page discussion (if a link has been provided). --TenOfAllTrades(talk) 01:03, 1 April 2011 (UTC)

I had an anti-hunger pill just the other day. It's called the Big Mac. :) ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:36, 2 April 2011 (UTC)

Green Laser

I have one 20mW green laser pointer. It does not burn matches (as I daydreamed) yet gives a slight sensation of heat on skin. It works on 3 AAA batteries (alkaline). My question is that if I add more voltage will it increase in power, say burn paper etc.  Jon Ascton  (talk) 14:10, 31 March 2011 (UTC)

No. Excessive voltage will simply destroy the laser diode. Roger (talk) 17:00, 31 March 2011 (UTC)

You are probably right. But I have heard that using a typical 3.7 volt Li-ion (rechargeable) battery will make it more powerful. What do you say to that...

What is the voltage of the current battery? A higher voltage will increase power output up to the rated maximum a further increase in voltage will destroy it. However it is most probably already operating at, or very close to, its maximum anyway. Roger (talk) 08:25, 1 April 2011 (UTC)

The current voltage, as I have stated above, is 4.5 volts (3 AAA batteries), yet a 3.7 volt is said to make it more powerful.

That is completely illogical - reducing the voltage while leaving everything else unchanged will reduce the power. Power = Voltage x Current. Roger (talk) 12:37, 2 April 2011 (UTC)

Not something that personally interests me but since it's something I've seen in sites I visit I believe red lasers tend to be far more cost effective if you just want something that will light matches. I believe you can get random Chinese laser of indeterminate power that will nevertheless light matches for around US$30 presuming it can get thru customs. While you can get green and other colour lasers that will do the job, their primary advantage to the hobbyist would be for looks. I presume you're already aware such a laser as yours is very dangerous (probably (3B) and could easily blind anyone who views the light directly and already have appropriate safety goggles. Nil Einne (talk) 17:24, 31 March 2011 (UTC)

Avoid using Class III and Class IV lasers in your home! Your basic assumptions about safety are Just Not Good Enough! Powerful lasers can scintillate, reflect obliquely, and behave in nonintuitive ways. A proper optical laboratory will take much more precaution far beyond just "don't look into the laser beam." You need the laser to be firmly mounted on an optical bench where it can not shine anywhere unexpected. You need the work area (and the rest of the room) to be totally nonreflective; avoid specular reflective surfaces, avoid certain materials in the furniture and walls, and so forth. Even diffuse reflection of powerful laser light can cause permanent eye damage. By definition, Class III and Class IV lasers can cause you physical harm - and most can cause permanent damage faster than it takes you to blink or avert your eyes. Playing with lasers is like juggling knives - fun for a while, but your first "minor accident" will cause permanent and irreparable injury/damage. If you like powerful lasers, get involved with an optical research laboratory and learn the safety procedures, just like the experts do. Nimur (talk) 20:56, 31 March 2011 (UTC)

You can also use a laser from a DVD burner. Instructions here. — DanielLC 20:27, 31 March 2011 (UTC)

Identifying an old timey flying machine

I'm trying to find the identity or history of what I believe is a (failed) pre-Wright flying machine. It's well known to pop culture because it appears as stock footage in many, many movies and television shows, but I know nothing about it so I can only describe it visually.

It appears as though someone has taken an old car and attached a giant parasol to a vertical shaft through the center of the car. There's some sort of engine 'pumping' the parasol up and down. Apparently the principle is that air will be pushed to the sides during the up-stroke but downwards during the down-stroke.

Of course, in the familiar stock footage, the car does not fly. It just sort of bounces up and down on its shocks. I don't think its wheels even leave the ground.

Thanks APL (talk) 16:53, 31 March 2011 (UTC)

Was it the Flugan? --Jayron32 17:21, 31 March 2011 (UTC)

Or is it the first machine in this clip? Alansplodge (talk) 17:44, 31 March 2011 (UTC)

Here is some video of the machine in question. It is called the "John Pitts Skycar". This is the patent for its unique form of "flight". --Sean 17:43, 31 March 2011 (UTC)

Well done sir! A different movie clip of the same beast (with sound) here. On the upstroke the 60 vanes making up the "parasol" opened and on the downstroke they closed, hopefully creating downforce. Not enough apparently. It appears on our List of aircraft (P-Q) but there is no article yet. Alansplodge (talk) 17:45, 31 March 2011 (UTC)

Wow. Thank you. That's exactly what I was looking for.

I didn't even realize that the parasol "propeller" actually rotated as well as oscillated up and down. APL (talk) 18:16, 31 March 2011 (UTC)

That's a big engine under the thing. If they'd just hit on the standard helicopter rotor, I wonder if it could have taken off. (no comment on what would come afterward...) Wnt (talk) 20:01, 31 March 2011 (UTC)

That device probably had a poor power to weight ratio. I wonder if a modern engine could get that contraption to work? Googlemeister (talk) 21:11, 31 March 2011 (UTC)

It looks a bit like an early attempt at the eventually-successful craft called the Autogyro. ←Baseball Bugs ^{What's up, Doc?} carrots→ 08:34, 2 April 2011 (UTC)

What is fertilising the blossoming shrubs in England?

I have not seen any bees around, or any other insects for that matter, at this time of year. So what is fertilizing all the blossoms please? Thanks 92.29.127.125 (talk) 19:21, 31 March 2011 (UTC)

Just because you haven't noticed any bees or other insects doesn't mean they aren't around. Also, just because there are blossoms doesn't mean anything has been fertilised. The blossoms attract the insects to fertilise them so the plant can produce seeds. It's seeds that are proof of fertilisation, not blossoms (and even then some plants can produce seeds without being fertilised by insects). --Tango (talk) 19:28, 31 March 2011 (UTC)

Surely bees pollinate, not fertilize? APL (talk) 20:21, 31 March 2011 (UTC)

The terminology is fine: fertilisation "is the fusion of gametes to produce a new organism." Bees are the vector of fertilization for many plants. "Fertilizing" in the sense of supplying nutrients to a plant is the spurious usage. SemanticMantis (talk) 20:26, 31 March 2011 (UTC)

Plenty of bumblebees up here in Edinburgh. I assume if it's warm enough for them in Scotland, it's warm enough in England. 86.135.222.99 (talk) 21:59, 31 March 2011 (UTC)

We have an article on Pollination which explains quite a bit. There are some plants which don't even require other organisms to pollinate them, but also many other creatures other then bees can pollinate, including butterflies, moths, wasps, flies and beetles, even ants. Vespine (talk) 22:17, 31 March 2011 (UTC)

Although plants which wind-pollinate don't go to the bother of producing blossom with petals, nectar et al - they're purely for the benefit of insect-pollinators. Oak trees for instance have a rather dreary green catkin effort with which to spread their DNA about. Alansplodge (talk) 14:18, 1 April 2011 (UTC)

Though I suspect there are at least a few pollinators around, I'll point out that a match-up between the timing of flowers blooming and pollinators emerging is not guaranteed. The phenology of plants and insects has co-evolved for a long time, and both have something to profit by matching up for this mutualism. However, different species may be attuned to different cues (e.g. photoperiod vs. temperature), and these can get mis-matched, especially when we consider climate change. There is much ongoing research into the consequences of these matchings getting fouled up, see e.g. [18]. SemanticMantis (talk) 13:59, 1 April 2011 (UTC)

I saw my first bumble bee in Hertfordshire at the end of February and since then I've seen several species including the big white-tailed ones and little black ones that I don't know the name of. I've also seen lots of hoverflies and one Large White butterfly. Alansplodge (talk) 14:25, 1 April 2011 (UTC)

April 1

milk

will putting milk thru a coffee filter remove radioactive iodine — Preceding unsigned comment added by Wdk789 (talk • contribs) 00:59, 1 April 2011 (UTC)

No. --Tagishsimon (talk) 01:04, 1 April 2011 (UTC)

why not — Preceding unsigned comment added by Wdk789 (talk • contribs) 01:29, 1 April 2011 (UTC)

Because iodine in milk doesn't form into large particles the size of coffee grounds. StuRat (talk) 01:36, 1 April 2011 (UTC)

The idea is that you can't separate radioactive iodine from normal iodine whithout the use of some very expensive equipment. Secondly, iodine is removed by chemical means which essentialy ruins the milk, rendering it undrinkable in any case. Plasmic Physics (talk) 01:41, 1 April 2011 (UTC)

what about a laboratory filter? — Preceding unsigned comment added by Wdk789 (talk • contribs) 01:45, 1 April 2011 (UTC)

I asked this here, and apparently it's hard to filter iodine. You could freeze the milk for about 2 months and 99.5% of the radioactive iodine will be gone by then. 70% will be gone after 2 weeks. Ariel. (talk) 01:54, 1 April 2011 (UTC)

To give an idea, as I've just added to the article, coffee filters pass particles under about 10 to 15 micrometers. Now by comparison iodine has a Van der Waals radius of 198 picometers (1.98 Angstroms). 1 micrometer = 1000 nanometers = 1 000 000 picometers, so the holes in a coffee filter are about 76,000 times larger than an iodine atom. Wnt (talk) 02:04, 1 April 2011 (UTC)

As stewed rat says, the iodine in milk is not present as crystals that can be filtered, it is dissolved. Similiarly, you can't filter table salt out of solution. Be carefull with your understanding of what filtration is. Plasmic Physics (talk) 02:13, 1 April 2011 (UTC)

Perhaps I should offer a bit more background for clarity. It's very common in research to encounter a .22 micron (220 nanometer) filter, which is still 1000 times larger than the iodine atom. By that point it gets quite hard to pass large amounts of fluid (depending of course on the amount of sediment). At smaller sizes molecular sieves are used, but generally in a different way - because it's no longer practical to wait for everything to pass through, instead they delay the molecules that can pass through them as they're dripped through in chromatography. When you get down to that scale, you generally rate them by the size of the molecule that can go through, such as 1000 daltons. Iodine is smaller than even that! Animals are equipped with gap junctions that work more like traditional filters though, because the cells with them are only 4 nm apart, the time delay isn't a big deal. (There are also tight junctions between cells that work like filters with a size that sometimes can be regulated).

But when you get down the the size of atoms, materials made out of atoms are weird to filter with. You can see ion channels set to pass specific sizes, but which won't pass anything larger or smaller than what they're set for. There's even a specific iodide channel in the thyroid,^[19] but alas we don't have an article for it. And if you go smaller than that - well, a filter that passes half of one of the smaller atoms won't pass anything; besides, any two surfaces half an atom apart are either going to spread out and accept solvent between them, or stick together and be held by Van der Waals forces.

The talk of biological channels suggests a possible practical solution, though I don't know if it works: live kelp and other seaweeds absorb iodide into themselves with great avidity, and one could hope that they might suck up radioactive iodide if left in milk for some time (before, presumably, dying) ... unfortunately you have to have a source of clean, live seaweed to start with! Wnt (talk) 02:50, 1 April 2011 (UTC)

Would you still be inclined to drink the milk following this method? Plasmic Physics (talk) 03:55, 1 April 2011 (UTC)

Well, it depends how desperately I want "cold" milk. And it's a proposal for an experiment, not a guarantee of success. ;) Wnt (talk) 05:24, 1 April 2011 (UTC)

In honor of the day, could the iodine in milk be reacted with ammonia to form nitrogen tri-iodide crystals, which might be more readily filtered out of the milk? Edison (talk) 04:00, 1 April 2011 (UTC)

I like the taste of ammonia even less than kelp. Plasmic Physics (talk) 04:10, 1 April 2011 (UTC)

a old civil defense movie said radioactive fallout was the size of table salt, why couldn't i filter it? would a activated charcoal filter work? what about this filter http://www.parowanprophet.com/Nuclear_War_Comes/water_filter_instructions.htm — Preceding unsigned comment added by Wdk789 (talk • contribs) 06:07, 1 April 2011 (UTC)

That movie is obviously... wrong. Fallout can be any size, fallout includes material of any size material, light enough to be carried by the wind. Is the iodine present in the milk as a result of fallout or a contaminated food cycle? Plasmic Physics (talk) 07:39, 1 April 2011 (UTC)

Think! If it was the size of table salt, how would it get into your milk at all, staying that size? 95.112.203.81 (talk) 10:53, 1 April 2011 (UTC)

fallout, i think — Preceding unsigned comment added by Wdk789 (talk • contribs) 08:00, 1 April 2011 (UTC)

It's not fallout. A normal reactor makes iodine as it runs. If containment is breached (and the fuel melts) the iodine basically just evaporates into the air, so the particles are the size of atoms. In a bomb with fallout, sand and debris get irradiated and then the dust goes everywhere, it's different. Ariel. (talk) 10:43, 1 April 2011 (UTC)

With milk, I should be worried more about Strontium-90 because biologically it behaves like Calcium and has a much longer half life time. But I don't see how it should be distributed in larger amounts through the air. It is more likely to be washed away into the sea. 95.112.203.81 (talk) 11:09, 1 April 2011 (UTC)

Also, it should be noted, both iodine and coffee are brown. Coffee filters are designed specifically to pass brown liquids. As a test, take cream directly from the fridge; you will see that most of it won't pass through the coffee filter. Good <ahem> day. 71.95.147.208 (talk) 21:15, 1 April 2011 (UTC)

so would this work http://www.parowanprophet.com/Nuclear_War_Comes/water_filter_instructions.htm — Preceding unsigned comment added by Wdk789 (talk • contribs) 03:08, 2 April 2011 (UTC)

No, but that's not the whole of the truth. It surely won't work with milk. The instructions make up a very crude kind of ion exchange device. If there was heavy fallout from a nuclear bomb and you have no other water than freshly contaminated surface water then this might be a last resort. If you have access to water from a well then this has already been done naturally as the water seeps through the ground until it appears in the well. 77.3.139.229 (talk) 08:43, 2 April 2011 (UTC)

Our nearest neighbouring solar system

What is the nearest solar system to our own, and based on present technologies, how long would it take for us to send astronauts there? Flaming Ferrari (talk) 01:13, 1 April 2011 (UTC)

About 40,000 years with our currently fastest spaceships, if I recall correctly. --Belchman (talk) 01:32, 1 April 2011 (UTC)

According to this 2006 article, Epsilon Eridani is the next stop for the most intrepid real estate agent, a mere 10.5 light years away. However, our article states that the planet is "unconfirmed". Clarityfiend (talk) 01:31, 1 April 2011 (UTC)

The Proxima Centauri system is closest, but we have no way, with our current technology, to send astronauts there (alive). Also, we don't know if planets are present there. StuRat (talk) 01:34, 1 April 2011 (UTC)

I'm not an expert, but doesn't a solar system require a system of orbiting bodies, not just a star(s). Ergo, does a triple star with no suspected planets (Proxima Centauri) qualify? Plasmic Physics (talk) 01:45, 1 April 2011 (UTC)

I don't think we would be able to detect small planets. And how about asteroids, comets, etc ? What precisely is required to be a solar system ? StuRat (talk) 03:26, 1 April 2011 (UTC)

We can now detect planets that are pretty small, but only if they pass directly between the star and us (thereby dimming its light slightly). That's a low-probability occurrence. Looie496 (talk) 04:12, 1 April 2011 (UTC)

And saying 40,000 years with our fastest spaceships is misleading. We could design spacecraft that could get there faster (at a significant cost), but since we would still be talking about much longer then a human lifespan, we never bothered making something like that. Think about it like this. Our furthest mission we sent out was aimed at Pluto (5 light hours away). The nearest star is more then 7000x further. If the furthest you had to travel in your life was 1 mile, you wouldn't need to bother with a car or plane, you could make do with a bicycle and a wheelbarrow (which are far cheaper assuming you don't get one of those $5,000+ racing bikes). If you wanted to go 7000 miles away, then you might want to look into building some faster transportation. I would imagine 1% c would be possible with current technology if cost was not an issue. Googlemeister (talk) 13:09, 1 April 2011 (UTC)

You also need to taked development time into account. Even with unlimited funds, I don't think 0.01c would be possible in less than a few years. --Tango (talk) 18:23, 1 April 2011 (UTC)

And another problem is, if you designed, built and launched such a ship on it's multi-century journey, it would surely be passed by later, faster ships. This rather takes away any incentive to build the initial slow ship. StuRat (talk) 18:27, 1 April 2011 (UTC)

There have been good short stories about explorers heading out to a nearby star system in "cold sleep" only to wake up and find a prosperous centuries old colony. APL (talk) 01:05, 2 April 2011 (UTC)

Jacob Barnett: amount of carbon created in the early universe

There's a 12-year-old prodigy who's got doubts about an aspect of big bang theory (check Google news today). Can anybody suggest what he means by this? (particularly the last two paragraphs -- the first grafs are fairly common):

"There are two different types of when stars end. When the little stars die, it's just like a small poof. They just turn into a planetary nebula. But the big ones, above 1.4 solar masses, blow up in one giant explosion, a supernova," Jake said. "What it does, is, in larger stars there is a larger mass, and it can fuse higher elements because it's more dense."

"So you get all the elements, all the different materials, from those bigger stars. The little stars, they just make hydrogen and helium, and when they blow up, all the carbon that remains in them is just in the white dwarf; it never really comes off.

"So, um, in the big-bang theory, what they do is, there is this big explosion and there is all this temperature going off and the temperature decreases really rapidly because it's really big. The other day I calculated, they have this period where they suppose the hydrogen and helium were created, and, um, I don't care about the hydrogen and helium, but I thought, wouldn't there have to be some sort of carbon?"

"Otherwise, the carbon would have to be coming out of the stars and hence the Earth, made mostly of carbon, we wouldn't be here. So I calculated, the time it would take to create 2 percent of the carbon in the universe, it would actually have to be several micro-seconds. Or a couple of nano-seconds, or something like that. An extremely small period of time. Like faster than a snap. That isn't gonna happen."

"Because of that," he continued, "that means that the world would have never been created because none of the carbon would have been given 7 billion years to fuse together. We'd have to be 21 billion years old . . . and that would just screw everything up."63.17.54.2 (talk) 03:33, 1 April 2011 (UTC)

I'll add to my own question. He seems to be saying that the earliest epoch of supernovae isn't early enough to have produced enough carbon to create planets by the time the earth was created, OR that the earliest epochS (plural) of supernovae wouldn't have cumulatively produced enough carbon.63.17.54.2 (talk) 03:41, 1 April 2011 (UTC)

Well, "earth made mostly of carbon" is his first mistake, it's only the 15th most abundant element. Looks like boy genius still has a thing or two to learn ;) lol.. (j/k) Vespine (talk) 03:58, 1 April 2011 (UTC)

I'm embarrassed that I didn't notice this big red flag -- obviously, the earth is "iron-centric" (so to speak) not carbon. But maybe the reporter transcribed him wrong or something -- maybe he's saying there aren't enough heavy elements in the big bang chronology? Otherwise, this is just embarrassing for him that he got quoted with such a huge error. This kid is phenomenally good at math ... he's very impressive. It's weird he could get wrong a basic fact like "amount of carbon in early planet formation." (Note: This is NOT an April Fool's Day joke -- you can look this up on Google.)63.17.54.2 (talk) 04:11, 1 April 2011 (UTC)

No i know, i did read about this kid, he did calculus by the time he was 8, sounds like a very clever kid, but i think the story is way over hyped. Carbon IS the 4th most abundant element in the universe, after H, He and O, but i'm not aware that this is a "problem". We have articles on Formation and evolution of the Solar System, Big Bang nucleosynthesis and Abundance of the chemical elements, I don't see anyone saying there's a discrepancy between what's observed and what's expected. Maybe there is, but I'll need more then a tabloid news story to convince me, whether the claim is made by a 12 year old or not. Vespine (talk) 04:17, 1 April 2011 (UTC)

Here is a Youtube video of the child in question: "Jacob Barnett talk about Einstein... And eats lunch". Now, with due respect (I mean, he is twelve) - the guy's not exactly out-doing Einstein. Really, he's just mumbling regurgitated jibberish that sounds like he just finished reading Chapter 3 of a Generic Pop-sci Cosmology book. Yes, it's fantastic that a guy this young is thinking about physics - but he's not exactly "innovating" cosmology as much as "misunderstanding" it. We get this sort of thing on the reference desk a lot. Loads of people are thinking about relativity and the formal mathematics that describe it; and loads of people find it to be a conundrum. And a few think they've resolved the conundrums by disproving modern theoretical physics. (See our RefDesk archives for innumerable examples). But this doesn't mean that all these enthusiasts are actually "smarter than Einstein." It's disappointing to see major media outlets like Time Magazine reporting that this is the new discovery that's going to shatter physics. Such reporting over-inflates a novice physicist's accomplishments. The kid's got a lot to learn - he may well develop a formal theory - but what we have right now is jibberish. Mr. Barnett has neither the necessary experience nor the access to the astrophysical data that would qualify him to make such sweeping assertions about the composition of stellar supernovae. If we were to subject his assertions to the proper scientific channels - that is, peer review in journals, and rigorous experimental and observational testing of his claims - the entire story would collapse. But, the media loves to take "boring" science topics and turn them into juicy human interest stories... Nimur (talk) 05:38, 1 April 2011 (UTC)

The kid is clearly confused. What's not clear is what is he confused about? He seems to be aware that larger stars release heavier elements when they explode but for some mysterious reason he is concerned about carbon's abundance. Dauto (talk) 06:32, 1 April 2011 (UTC)

I'm not sure exactly what he is trying to say is the problem, but he is clearly referring to the carbon creation bottleneck in big bang nucleosynthesis. Because there are no stable nuclei of mass 8, carbon-12 was not significantly created during the big bang. As a result, we assume that essentially all carbon in the universe had to come from supernova. He is correct that if the big bang were somehow slower, such that nucleosynthesis could last longer, then you could create appreciable carbon during the big bang. As far as I know though, there is no evidence of that (and at least some evidence against it). Dragons flight (talk) 07:06, 1 April 2011 (UTC)

Commenters elsewhere have suggested he's been coached by Creationists -- Creationists who (according to the commenters) include in their quiver of ignorance a "not enough carbon" arrow. His wikipedia page (!?) makes reference to a connection to a Christian school ... AND he's been celebrated on TV by one Glenn Beck. So maybe he's being exploited by "young-earth" morons.63.17.37.103 (talk) 02:16, 2 April 2011 (UTC)

Also, his family lives in Indianapolis -- a hotbed of ignorant fundamentalist Christians, as anyone can verify by going to lots of public places there and reading the inscriptions on the white trash's t-shirts.63.17.39.192 (talk) 07:55, 2 April 2011 (UTC)

See Jacob Barnett.63.17.37.103 (talk) 03:31, 2 April 2011 (UTC)

I did the prodigy thing long ago (sort of) - don't be fooled. The thing about mathematics is that it is quite easy to learn it quickly up to about the calculus level, provided you get good instruction to help you over the hiccups in understanding - to provide the step-by-step help of how actually to use the notation and work it to get a result. The way that kids usually learn it is simply inefficient - you just barely get into the swing of it in an hour, then you have half a week to forget what you learned, then you muddle through it the wrong way the next session and so on. I wish that schools would consider teaching groups of children the entire year's math class in a few weeks devoted entirely to that one subject, to improve efficiency. But standard instruction practices aren't so inefficient for learning about the real physical world, so those topics are more difficult for a prodigy to excel with. (the difference is that mathematical facts are connected, so if you learn 1, 2, 3, 4, and 5 in a day and practice working problems 1->2->3->4->5, you drill them all into your head at once; but physical facts are almost unrelated to one another) Moreover, to the degree that prodigies are good at devouring a book and regurgitating its contents, they are vulnerable to believe just pure balderdash when they read it - there's a lack of reasoned adult discrimination and skepticism about what sources to trust and which to recognize as obvious scams. Wnt (talk) 06:45, 2 April 2011 (UTC)

The question is "Can anybody suggest what he means by this?", NOT "Is he a genius?" or "What is your personal experience of having been (sort of) a math prodigy?" 63.17.37.103 (talk) 06:59, 2 April 2011 (UTC)

I think what he's saying^[20] is that he still hasn't read about Population III stars. So he thinks it would have taken an extra 7 billion years for the carbon to form to produce planets like ours (some hedging there; as quoted he is wrong about the Earth being made out of carbon, etc.; more likely something was left out).

From WP re Population III stars: "Their existence is proposed to account for the fact that heavy elements, which could not have been created in the Big Bang, are observed in quasar emission spectra, as well as the existence of faint blue galaxies." WHAT does this have to do with whether there was enough carbon 7 billion years ago to form the earth? Face it: The kid is being coached by "young-earth" Christian fundamentalists to spout a supposed contradiction in big bang theory. 63.17.39.192 (talk) 08:04, 2 April 2011 (UTC)

He was saying that the Big Bang was 21 billion years ago rather than 15 billion years ago (hmmm, that's not exactly 7...). Is that "young earth creationism"?? Wnt (talk) 11:35, 2 April 2011 (UTC)

P.S. Jacob Barnett is up for deletion, if anyone has an opinion. Wnt (talk) 07:25, 2 April 2011 (UTC)

3D for one-eyed Jacks

Is there any 3D TV technology which would work for somebody with vision in only one eye ? StuRat (talk) 04:56, 1 April 2011 (UTC)

No. Is this an April Fool's joke? No current technology can synthesize depth perception in humans who only have one eye. We do not speculate about hypothetical technology on the Reference Desk. Nimur (talk) 05:29, 1 April 2011 (UTC)

As there are numerous monocular cues to depth perception, the question is quite reasonable, and your dismissal of it seems rather abrupt. -- ToE^T 11:04, 1 April 2011 (UTC)

Wiggle stereoscopy is one possibility, but it would probably yield headaches quicker than 3D glasses. -- ToE^T 11:13, 1 April 2011 (UTC)

Good answer. As an aside, many of the concerns about spending too much time watching 3D video based on binocularity is that current methods only use binocular cues, which trains the brain to ignore the monocular cues, since they don't work properly. SemanticMantis (talk) 13:47, 1 April 2011 (UTC)

You may also be interested in reading our Autostereoscopy article. While it does not specifically mention applicability to monocular 3D, several of the technologies would seem to apply. Has anyone here ever seen a Philips WOWvx screen which uses lenticular lenses? (Unfortunately, our Lenticular printing article gives a "morphing" example and not a "3D" one, but imagine such a thing with an LCD display behind it so that a different perspective is shown when you move your head.). -- ToE^T 14:29, 1 April 2011 (UTC)

Prevost theory of heat exchange

Prevost theory of heat exchange Statement & explanation pls.. —Preceding unsigned comment added by 114.79.154.72 (talk) 07:12, 1 April 2011 (UTC)

Early versions of the caloric theory of heat involved two "fluids" - a caloric fluid that was produced by hot objects, such as a fire, and a frigoric fluid that was produced by cold objects, such as ice. In 1790 Swiss physicist Pierre Prévost argued that there was only a single fluid involved - caloric fluid - and that cold objects cooled their surroundings because they absorbed more caloric fluid than they produced. See here and here for more details. Gandalf61 (talk) 08:30, 1 April 2011 (UTC)

parasite chain

I recently read the news that they discovered virophages, small viruses that can only replicate when they co-infect a cell with another virus. They basically function as parasites to that virus. When reading this I was wondering how long the longest 'parasite chain' we know is. Example: when a human is infected with a tapeworm, which in its turn has bacteria in its bowel, this would be a three-level chain. I know you have plenty of external parasites like lice, but in this case I am specifically referring to endoparasites, life within life.

I've been doing some quick google searches but that didn't turn up with anything, and wikipedia was no help either. Of course, since I am interested in the longest chain of parasites, liberty with the term parasite is warranted. Bacteria and viruses are also allowed. —Preceding unsigned comment added by 131.211.27.97 (talk) 09:07, 1 April 2011 (UTC)

I don't know, but a large parasite like Cymothoa exigua or Emerald cockroach wasp might help add a level to your chain. Ariel. (talk) 10:46, 1 April 2011 (UTC)

The longest chain likely involves Ichneumonid wasps. See a nice story about their lifestyle here: [21]. Note that you will find longer chains with parasitoids, which kill their host, compared to parasites, which do not. A parasitoid that targets parasitoids is known as a hyperparasitoid, so this class by definition has a length 3 chain. Googling /hyper-hyperparasitoid/ returns some hits, but many are from amateur blogs, and don't contain detailed species info. SemanticMantis (talk) 13:43, 1 April 2011 (UTC)

Pressure at the seabed

If you dropped a weighted 1 litre bottle or balloon of air into the sea above the Challenger Deep, by how much would it be compressed by when it eventually reached the seabed? After leaving it down there for a while to cool down, how close would this be to becoming liquid air? Thanks 92.15.8.176 (talk) 11:01, 1 April 2011 (UTC)

What temperature was the air before you dropped it? I have assumed 300K. By my calculations, the density of air at Challenger Deep temp and pressure would be 1208x greater then that on the surface. Assuming your balloon can tolerate this change (a bottle would not), it should be .827 mL at the bottom. I don't know if this would make liquid air since I don't have the appropriate graph handy showing the state of air at the various temps and pressures. Googlemeister (talk) 13:01, 1 April 2011 (UTC)

According to this, nitrogen cannot be liquified at temperatures above 147 degrees C, which is the critical temperature for that gas - as air is a mixture, things will be a little different but it suggests that the contents of the balloon (or squashable plastic bottle) will remain in a gaseous state. Mikenorton (talk) 14:02, 1 April 2011 (UTC)

Typo alert: the critical point for N₂ is minus 147 °C. The critical pressure is about 34 atmospheres, so at 1208 bar it would be a supercritical fluid rather than an ordinary gas (this is a gradual matter, but I doubt it would behave much like an ideal gas). –Henning Makholm (talk) 14:17, 1 April 2011 (UTC)

Thanks for spotting the typo, now fixed. Mikenorton (talk) 15:07, 1 April 2011 (UTC)

1208 bar was used with ideal gas properties. If the air starts to behave as a non-ideal gas at some higher pressure, then my volume is not going to be accurate. Googlemeister (talk) 14:52, 1 April 2011 (UTC)

(EC) The density of liquid air is about 870 kg/m³, which is about 710 times greater than the density of air, which is about 1.225 kg/m³ at sea level. But the article section Challenger Deep#History of depth mapping from the surface mentions a pressure of up to 1099 times the pressure at the surface (which is the same as air pressure at the surface). Boyle's law becomes increasingly inaccurate as the pressure of air approaches that of liquid air, but 1099 is a fair bit greater than 710, so it's fairly safe to say that a balloon full of air that's been pulled down to that depth would indeed turn into liquid air. 1 l of air at the surface would turn into 1/710 l = 1.41 ml of liquid air. Red Act (talk) 15:03, 1 April 2011 (UTC)

As indicated above, the contents under those conditions (the critical pressure for air being just over 37 atmospheres) would be a supercritical fluid, which is not a liquid in any normal meaning of that word. Mikenorton (talk) 15:40, 1 April 2011 (UTC)

I stand corrected. Red Act (talk) 04:26, 2 April 2011 (UTC)

The 1208 or 1099 bar down there makes the roughly 0 bar of space seem mild and harmless. If Red Act is correct, could there be pools of liquid air down there, with water floating above it like oil over water? 92.15.8.176 (talk) 15:15, 1 April 2011 (UTC)

I would expect it to mix into the water and actually be indistinguishable from what is usually described as "gasses disolved in water" at more familiar lower pressures. Roger (talk) 15:37, 1 April 2011 (UTC)

And even if it didn't, it would rise above the water, 870 kg/m³ being less dense than water (1000 kg/m³ at surface pressure, increasing very slightly with pressure). –Henning Makholm (talk) 15:59, 1 April 2011 (UTC)

As pointed out by others above, the ideal gas law will not be a good approximation at such high pressures. Van der Waals equation should work much better. Dauto (talk) 04:43, 2 April 2011 (UTC)

Butterfly effect

Consider going outside, flapping your hands violently and then wait for some months until CNN reports that some tornado has hit some particular town in the US. Then, if one assumes that flapping your hands caused the tornado, you could formulate this assumption as saying: "had you not gone outside and flapped your hands, that particular town would not have been hit by the tornado".

Let's look at this precisely. Consider the exact physical state of the Earth that corresponds to you going outside, flapping your hands, which evolves under time evolution to a final state corresponding to that town being hit by the tornado. Then we can consider an alternative initial state corresponding to you not going outside and flapping your hands, but everything else is left the same. Such a state would then not evolve to the final state where the town is hit by a tornado.

One can then object to this analysis by invoking quantum fluctuations. Both intitial states will actually evolve to some complicated superposition of "classical states". So, in both cases, you end up with a probability distribution over the possible states of the weather, and in both cases there is some probability that the particualr town will be hit by a tornado. Only if the probabilities are significantly different, can we say that flapping your hands outside caused the town to be hit by the tornado.

So, what does a fully fledged analysis from first principles show? Can the effect of flapping your hands be more dominant than the effect of quantum fluctuations as far as long range weather patterns is concerned on some time scale? Obviously, if you take the time scale too long, quantum fluctuations will dominate, take it too small and the effect of the hand flapping won't have led weather patterns to diverge much relative to the counterfactual initial state, so there may be some intermediary time scale on which there is a significant effect...

Count Iblis (talk) 16:03, 1 April 2011 (UTC)

No!190.148.136.60 (talk) 16:58, 1 April 2011 (UTC)

Yea, tornadoes don't form from slight air movements that grow over time. They start from temperature and humidity differences which cause supercells to form. So, while your analysis method seems reasonable, in general, it doesn't apply to this particular example. Perhaps a better example would be if you divert a small stream and wonder if this diversion will cause a new Grand Canyon to develop, or fail to develop. If you diverted the Colorado River too late, the Grand Canyon would have already formed, and, there being a big hole in the ground, water would have found a way into it to continue the erosion, in any case. Had you diverted it too soon, then, over time, as the course of rivers change, it would have likely find it's way back to a location where conditions were suitable for the formation of a Grand Canyon (not necessarily in the exact same spot, though). StuRat (talk) 17:37, 1 April 2011 (UTC)

The formalization of your question is something like the following: "Is the occurrence of a tornado Lyapunov stable with respect to a small perturbation of air caused by waving your hand?" I think most aeronautical engineers, global climate modelers, and complex systems theorists would say a resounding "yes", based on gut intuition (meaning that your hand-waving does not alter the course of the tornado's formation or non-formation); but to derive that gut intuition from first principles is downright impossible. In other words, most scientists will tell you the following: waving your hand had some effect on the weather. However, the effect was so small, that it is unlikely that it affected bulk air mass motion in a significant way; as a single event, your hand-waving activity did not alter the course of the weather. Read our Lyapunov stability article, read about techniques to mathematically model complex systems, and read about bifurcation theory, which formalizes the parameters that cause the outcome of a complex system to split into one of two states (e.g., "tornado happens" vs. "tornado does not happen"). As you can see, "affecting the system" by waving your hand is not synonymous with "causing a tornado." Nimur (talk) 21:28, 1 April 2011 (UTC)

Or read our article on the Butterfly effect, noting that the first paper on the effect was titled Does the flap of a butterfly’s wings in Brazil set off a tornado in Texas?. Our article explains why the answer could easily be yes. In short, I don't think the intuition of scientists who are familiar with chaos theory accords with yours. The basic reason is that atmospheric flow is very turbulent, and turbulence is generally believed to imply dynamical chaos, and therefore sensitive dependence on initial conditions (i.e., lack of Lyapunov stability). Looie496 (talk) 22:00, 1 April 2011 (UTC)

Admittedly, I am not an expert in the dynamic modeling of atmospheric weather phenomena. As Looie496 correctly points out, my intuition should not be interpreted as scientific fact. Nimur (talk) 22:37, 1 April 2011 (UTC)

In the OP's thought experiment, two different degrees of hand flapping are considered as alternative initial states. One can think of "degree of hand flapping as an input variable with a continuous range from "no flapping" which won't cause a tornado, to "super-gigantic hand flapping" which would manage to start a tornado. However the possible degrees of hand flapping are not continuous because they are quantised. Somewhere in the range there is a quantum step that makes the difference between tornado or no tornado. (This argument has to assume that thermal vibrations are deterministic.) Cuddlyable3 (talk) 12:30, 2 April 2011 (UTC)

'Carbonating' a drink with N2O

Could a drink feasibly produced with nitrous oxide dissolved in it rather than carbon dioxide? I figure it wouldn't taste the same, but would the gas even go into solution?

Thanks, Daniel (‽) 17:00, 1 April 2011 (UTC)

Nitrogen is used to serve draught Guinness among other beers. --TammyMoet (talk) 17:24, 1 April 2011 (UTC)

Nitrous oxide is usually regulated. Medical-grade stuff is hard to get a hold of; almost everywhere else you can buy the gas, it will have a small amount of added sulfur to prevent huffing (a stupid, but common, problem). N2O has other hazards, including spontaneous decomposition and ignition. Finally, worth noting that CO2 works to form carbonic acid in solution (adding a sharp "tangy" taste); I don't think N2O will have that effect, but it can and does dissolve in water in small quantities. It is also common to see N2O in food as a whipped-cream propellant - the gas bubbles in and "aerates" the whipped cream. I'm not sure where those food processors and manufacturers get a hold of unadulterated gas - it's probably not easy. Nimur (talk) 17:49, 1 April 2011 (UTC)

Of course, other acids can be added. In the case of citric acid, it's probably better for you than carbonic acid, too. Also, does the N₂O form nitric acid ? StuRat (talk) 18:12, 1 April 2011 (UTC)

Whipped cream is made with Nitrous oxide if it comes from an can (Would not work with sour carbon dioxide). So drink a can of Whipped cream or by a small propellant bottle for a Whipped cream maker which looks ver similar to the ones used for making sparkling water.

.--Stone (talk) 21:17, 1 April 2011 (UTC)

The Henry's Law data for carbon dioxide and nitrous oxide are pretty similar: about 0.034 vs 0.024 for the solubility constant (respectively), and 2400 vs. 2700 for the temperature dependence constant. [22][23] I'm not so sure about the biological effects of having N2O coming out of solution in your stomach, however - it can't be buffered to a bicarbonate salt, and I haven't looked up relative anaesthetic potency. Wnt (talk) 11:47, 2 April 2011 (UTC)

List of nuclear reactors using MOX fuel

Hello, what is the list of nuclear reactors using MOX fuel in Japan? and in the world?--88.160.13.244 (talk) 18:54, 1 April 2011 (UTC)

Japan, as of January 2011: 1. Genkai 3, 2. Ikata 3, 3. Fukushima I 3, 4. Takahama 3 .[24][25] As of January 2011 there were 21 MOX fuel plants in France. I don't have other numbers handy. There are other MOX reactors in Belgium, France, Germany and Switzerland [26], as of 2009, at least. --Mr.98 (talk) 16:25, 2 April 2011 (UTC)

Info needed on Broyer Canyon, Brown County, Nebraska

Other than it's location [27], I can't find any info, such as it's history, and, specifically, who it was named for. Any help would be appreciated. StuRat (talk) 19:08, 1 April 2011 (UTC)

Also, going to the satellite or hybrid view, and zooming in as far as you can without losing the satellite image, there appears a white linear feature to the ENE of the canyon. This feature runs from the SW to the NE and looks to be man-made. It looks to be about 10 meters long. What is it ? StuRat (talk) 19:14, 1 April 2011 (UTC)

How about telephoning the Ainsworth Public Library and asking if their reference librarian can direct you to a book on local history? I've found that many small town libraries have local historians and/or local history book repositories that aren't published/available in the "outside world." As far as your mysterious white linear feature - well, the aerial photo is blurry, so it could be anything: a photographic glitch; a man-made structure; an exposed pipe or power line; a light-colored sand/gravel pit; it's not possible to tell from the aerial photo. Nimur (talk) 20:56, 1 April 2011 (UTC)

Stanless Steel Grades

I've scaned several articals and charts pertaning to the various grades of Stainless Steel and could not find which grades of stainless steel a magnet will not stick to. If you could please E mail a chart that shows this or direct me to where I can view and down load a chart.

Thanks,

Peter Corcoran —Preceding unsigned comment added by 72.164.33.18 (talk) 20:22, 1 April 2011 (UTC)

Most austenitic steels will be non-magnetic, while most ferritic and martensitic steels will be magnetic. --Carnildo (talk) 01:39, 2 April 2011 (UTC)

300 series stainless has a higher iron content and is semi-magnetic. 400 series stainless is very slightly magnetic. To have an unnoticable magnetic characteristics, you would have to get nickel-chrome alloys like inconnel, hastalloy or waspalloy. The high nickel and chrome stainless steels are very expensive, though. They are aerospace materials that are used mostly for aircraft and spacecraft parts —Preceding unsigned comment added by 108.67.181.74 (talk) 04:04, 2 April 2011 (UTC)

April 2

911

is 911 a federal or local number — Preceding unsigned comment added by Wdk789 (talk • contribs) 02:54, 2 April 2011 (UTC)

Neither and both. See 9-1-1 for the history - it's the standard in Canada too. 9-1-1 call centers are locally administered, but the FCC and its Canadian equivalent set the standard. Acroterion (talk) 03:07, 2 April 2011 (UTC)

if u call from a cell phone without e 911 how does it route it to your city call center — Preceding unsigned comment added by Wdk789 (talk • contribs) 03:11, 2 April 2011 (UTC)

The very same article you were directed to above answers that question, if you read doen to the section titled "wireless telephones". --Jayron32 03:36, 2 April 2011 (UTC)

no it dont — Preceding unsigned comment added by Wdk789 (talk • contribs) 04:40, 2 April 2011 (UTC)

It did, but if you need more details, the article Enhanced 9-1-1 has more as well. --Jayron32 05:32, 2 April 2011 (UTC)

just answer me — Preceding unsigned comment added by Wdk789 (talk • contribs) 06:50, 2 April 2011 (UTC)

We did. We're not going to copy and paste the words from the articles here just because you don't wish to click the name... --Jayron32 06:52, 2 April 2011 (UTC)

it dont help i read it — Preceding unsigned comment added by Wdk789 (talk • contribs) 10:46, 2 April 2011 (UTC)

Wikipedia articles are written in the same English that we are speaking here. Some readers find that articles like these [28] [29] are easy to read. Cuddlyable3 (talk) 11:04, 2 April 2011 (UTC)

Energy

A 10 W Fluorescent lamp and a 10 W LED Tube light blows for one hour. Will they use same amount / quantity / level of energy? —Preceding unsigned comment added by 122.172.158.243 (talk) 07:09, 2 April 2011 (UTC)

Yes, but the LED is more efficient - more energy is converted into light. Plasmic Physics (talk) 08:33, 2 April 2011 (UTC)

To clarify. "10 W" is the electric power taken by the lamp. After one hour each lamp has dissipated 10 watt-hours, which is the quantity of energy one pays for. The LED tube gives more light from its energy consumption and has a longer life, but it costs more to buy in the first place. Cuddlyable3 (talk) 10:51, 2 April 2011 (UTC)

You meant "glows" instead of "blows", I assume ? There's also the issue that they don't seem to always count the electricity used in the electrical ballast in the base. So, is that 10W the amount used in the bulb only, or including the ballast ? StuRat (talk) 15:38, 2 April 2011 (UTC)

If the flourescent is a compact fluorescent bulb, then the energy lost in the ballast or electronic circuit should be included. If it is, say a 4 foot 32 watt straight fluorescent tube snapped into a light fixture, I would expect additional energy to be used in the ballast. Edison (talk) 19:41, 2 April 2011 (UTC)

What plant is that?

I noticed this in Budapest, Hungary.

Amongst the branches of a tree there was a very distinct bulb of leaves that seemed to be separate from the tree, an individual plant, different in colour (vividly green, unfortunately not seen on the photos). I don't think it's a birds nest. What could it be?

http://i53.tinypic.com/3586yp1.jpg

http://i52.tinypic.com/25ti6wz.jpg —Preceding unsigned comment added by 109.74.50.52 (talk) 08:27, 2 April 2011 (UTC)

Might be mistletoe. 77.3.139.229 (talk) 08:51, 2 April 2011 (UTC)

I think you've nailed it. Thank you!

109.74.50.52 (talk) —Preceding undated comment added 09:51, 2 April 2011 (UTC).

Eggs and earthquakes

Does an earthquake destroy eggs? Clearly they are in danger being hit by some crashing building or to fall out of the nest and hit the ground, but aside of that, is an earthquake strong enough to shake them so violently that they break? 77.3.139.229 (talk) 11:26, 2 April 2011 (UTC)

If you were asked to predict whether the egg falling from the nest will break, you would need quantitative information on the peak acceleration (deceleration) of the egg, the resilence of the surface that it contacts, and the geometry and material stiffness of the particular species of egg. The same difficult-to-supply information is needed to answer your question. Cuddlyable3 (talk) 12:41, 2 April 2011 (UTC)

I see you are right and it would be better to ask for information about acceleration magnitudes from earthquakes, preferably related to the common scales for earthquakes.Where can I find such information? 77.3.139.229 (talk) 15:32, 2 April 2011 (UTC)

Assuming the egg didn't fall or have something fall on it, it would depend on what surface the egg is in on. If it's on a soft surface, like the container they come in from the grocery store (or, presumably the nest), it should be fine. On a hard table, with a strong enough up-down ground motion, it might crack. A side-to-side motion could knock it off the table, but we already excluded that case. It might also run into something on the table. Again, if it's soft, like a cereal box, it should survive, but hitting a hard object like a cereal bowl might crack it. StuRat (talk) 15:33, 2 April 2011 (UTC)

Ah, I see this splits the question into three different aspects: 1) could the first acceleration damage the egg? 2) (I didn't think of it previously) could a vertical acceleration that lifts the egg without damaging it be strong enough that it cracks on falling back (hitting the same material that sent it off flying)? and 3) is it possible that eggs laying next to each other are accelerated horizontally in a way that they hit each other so that they get damaged? Note that I am not especially interested in eggs, it is just some kind of place-holder for something fragile that everyone has a common experience about. 77.3.139.229 (talk) 16:09, 2 April 2011 (UTC)

I see. Stability also comes into play here, as items in stable positions won't tend to fall. So, things on shelves are more likely to be damaged than things on floors. Of course, the stability of other things which could fall on top also matters. A long item (say a lamp) balanced on it's end will also be less stable than one on it's side. One interesting result of this is that it may make sense to leave everything where it lands after the initial quake (as those positions will tend to be more stable) until the aftershocks subside. You might also move things into more stable positions that survived the first quake (like putting lamps on their sides on the floor). StuRat (talk) 16:29, 2 April 2011 (UTC)

It is the momentary distortion of the"egg shell"shape during impact which causes the structural failure of the shells cohesive integrity. To protect the shell from damage from violent motion it's important to make certain that what ever energy absorbing packing material you use (eg.styrofoam) must make perfect contact with the whole of the shell surface so that kinetic energy induced by motion will be transfered to the packing material evenly at all points of the shell thereby eliminating shell ditortion and breakage. I'm not a mathematition but I'll bet one of our wikipedien freinds here can come up with an equation for that concept.190.56.107.186 (talk) 17:24, 2 April 2011 (UTC)

Double-heading

Having just watched a double-header pass through my home town, I'm curious about the physics of double-heading steam locomotives. Presumably it is important that both engines exert roughly the same force, but how critical is this and how do the two crews arrange it, especially since communication between them is very limited?--Shantavira|^{feed me} 12:52, 2 April 2011 (UTC)

Why would communication be very limited? Wired telephony has existed since the 1800s, and presumably the crews today would have a wireless system, with in-ear receivers and noise cancellation systems in place to allow for ease of communication... --Jayron32 14:45, 2 April 2011 (UTC)

Or even more directly, it's hard to imagine that the operators in one locomotive don't have some more direct way to know what the speed/pressure/whatever is in the other locomotive. That kind of "communication" technology would not have to be very sophisticated, I wouldn't imagine. Though honestly I have no clue about trains. --Mr.98 (talk) 16:29, 2 April 2011 (UTC)

The simple fact is most steam locomotives didnt have wired telephones to other parts of of the train, and that since steam engines in the modern day are run for mostly the sake of nostalgia, they still dont. —Preceding unsigned comment added by 92.20.201.71 (talk) 00:26, 3 April 2011 (UTC)

I've wondered about the physics here, too. Here's how I've come to think about it:

One question is, what does the throttle setting on an engine actually do? Does it control how fast the engine tries to turn (i.e., in revolutions per minute), or how hard the engine is trying to work?

It's pretty clear that, for most engines, the answer is the latter. Think about a car: if you kept the accelerator pedal depressed with your foot to exactly the same position, you'd notice yourself going more slowly up hills, and more quickly down. If you jacked the car off the ground and kept the pedal depressed to the same position (or, more simply, put the transmission in neutral), the engine would rev to a very high speed indeed.

And in fact, typically what an engine's throttle does is control the rate that fuel is used. So by one of the most basic principles of physics there is, conservation of energy, the engine is going to try to do precisely enough work to transfer the amount of energy per unit time as is contained in the amount of fuel it's provided in that unit of time.

(Side note: some engines do have to move at a constant speed, but that's typically achieved by use of a governor, a basic mechanical feedback device which adjusts the engine's throttle so that the engine is always doing just the right amount of work to offset its -- possibly varying -- load, such that the speed stays constant.)

So, anyway, what happens if the two engines don't have their throttles set to precisely the same position, or if the two engines have significantly different power capacities, or for whatever reason aren't providing exactly the same force?

I used to think that the "stronger" engine would do all the work, and that the "weaker" would get a free ride. But no. If at any instant the stronger engine manages to do more work and pull ahead of the weaker one, the weaker one will see less resistance, and will speed up, until it is pushing, too.

The same physics end up applying in other situations. Suppose you've got a car that's stuck, and two of you are trying to push it, but you're not strong enough, and you hail a passerby, who agrees to help, and with the combined strength of three of you, you manage. Was it necessary that all three of you provided equal force? No. The force on the car is the simple algebraic sum of the forces provided by the three pushers. Every little bit helps.

I also wonder about those tag-along trailer bikes for kids. The adult on the bike in the front is clearly doing the lion's share (often all) of the work, but if the kid is actually pushing, would the adult feel the difference, that's he's having to do marginally less work to keep the train going? I think so. (It would also be instructive to interview people who ride ordinary tandem bicycles about their experiences when one rider is significantly stronger or is for whatever reason working harder than the other.)

Finally, I'm reminded of the story of two people who are trying to move a large, heavy piece of furniture through a doorway. They push and strain, but they just can't make it. A third person comes along and tries to help, but even with three people pushing and pulling, this way and that, they still can't get it to budge. Finally the newcomer says, "You know, I don't think we're ever going to get this thing into the room." "Into the room?", the other two exclaim. "We were trying to get it out!" —Steve Summit (talk) 17:24, 2 April 2011 (UTC)

Now, when I said, "the engine is going to try to do precisely enough work to transfer the amount of energy per unit time as is contained in the amount of fuel it's provided", that's a bit of a simplification. It can take a fair amount of engineering to realize a practical engine that can in fact transfer large amounts of power effectively and efficiently, even as the speed varies. It was probably simpler back in the days of steam, although even then, there were abstruse complexities having to do with, say, the cutoff. And the diesel-electric control section in our article on diesel locomotives goes into quite a bit of detail about how complicated the power control can be for a modern locomotive. —Steve Summit (talk) 17:37, 2 April 2011 (UTC)

In the days of the Midland Railway Company (who regularly used double header steam locomotives on the Settle-Carlisle Line where the practice was implicated in two accidents near where I live), the drivers were sufficiently experienced to know what sort of head of steam was required for different sections of the track, but I suspect that they just signaled to each other to approximately match power on setting off. If there was a big difference in power output, then the wheels would slip on the rails because they are linked to the pistons in the locomotive so they are much more likely to slip than those on the carriages. Dbfirs 18:01, 2 April 2011 (UTC)

It occurs to me that a considerably more interesting problem occurs when you have a helper engine at the rear, assisting one or more engines which are pulling conventionally from the front as a long train attempts to ascend a grade.

When two engines are both pushing (or pulling) from the same end, they're more or less rigidly coupled, so their speed stays the same, and the only thing that varies (that can vary) is the amount of force each applies.

But if some are pulling from the front, and some are pushing from the rear, the "slack" of the train comes into play. (The full train is far from rigid.) Some portion of the train will be being wholly pulled from the front, and some portion wholly pushed from the rear. If the rear engine(s) work a little harder than necessary, the demarcation point will move forward through the train (i.e. with more cars being pushed); if it/they slack off; the point will move back. Moreover, the feedback from this -- the point at which there's clanking as some car or another shifts from being pushed or pulled -- is invisible/inaudible to the engineers at both the front and the rear. So that must have taken some skill! —Steve Summit (talk) 20:29, 2 April 2011 (UTC)

Assuming the rear engine is not powerful enough alone to push the train, if he just goes at full throttle, the front engine controls simply adjusts their throttle until the required speed. The same principle occurs to both cases, one engine can just provide a constant force which adds to the force provided by the one which is regulating the speed. —Preceding unsigned comment added by 92.20.201.71 (talk) 00:23, 3 April 2011 (UTC)

Engine braking

When shifting down a gear to aid braking, where does all the cars kinetic energy go bearing in mind that the engine revs cannot increase instantaneously?--92.28.66.20 (talk) 16:11, 2 April 2011 (UTC)

We have an article on engine braking, though it could use some work.

I've always understood that you're essentially running the engine as an air compressor, and compressing air heats it up; therefore the kinetic energy is converted into heated gases that are released, either down the tailpipe or (I now learn from the engine braking article) in the case of a diesel engine, back out the intake manifold. —Steve Summit (talk) 16:23, 2 April 2011 (UTC)

Also if you have a petrol (US=gasoline) car, then the air intake valve will be closed, and the engine is trying to create a high vacuum in the air intake manifold. With a diesel car, there is no air intake valve, so the amount of engine breaking is somewhat less.  Ronhjones  ^(Talk) 20:24, 2 April 2011 (UTC)

We have an article on Regenerative brake (to make good use of the energy). Dbfirs 18:03, 2 April 2011 (UTC)

why electrical arcs don't flow straight

When observing an electrical arc flow from one electrode to another or lightning between cloud and ground, I can't help noticing that (the stream of electrons)the spark does not flow in a streight line. the charge, presumably trying to reach the other node by the most direct route, should,it seems,take a direct streight line. Instead it obviously wiggles around taking many momentary directions, none of which aim directly at the target and constantly overcorrecting untill,like a shark seeking it's prey,it eventually homes in on it's target. I've tried to find an article that explains this but no luck.Can anybody explain why it doesn't travel in a direct streight line.Phalcor (talk) 18:10, 2 April 2011 (UTC)

It doesn't take the staightest line, it takes the path of least resistance. The electric field is a messy, complicated thing and does not exist as a clean, continuous gradient. It is constantly changing and in flux, not the least of which is changes created by the electric arc itself as it propagates. The two ends of the path are, of course, the extremes of the potential difference, but in between the electric field isn't a clean, regular gradient between those extremes. The result is that the electric field itself displays chaotic behavior; the electric spark will take the path of least resistance always, but that path is somewhat random and always changing. Sparks are actually highly fractal in nature, so their shape and behavior is explainable if not predictable. --Jayron32 19:20, 2 April 2011 (UTC)

(EC)With respect to an electrical arc flashing between two electrodes (assuming they are at the same height): the arc is at a temperature of many thousands of degrees, and the air and ionized gasses in and near the arc expand and become lighter than the surrounding air, so they rise in an arch shape (that is where the 'arc" got its name in the early 1800's). As for lightning bolts, much is still not known per the Lightning article. Speculating here: A bolt between cloud and cloud or cloud and ground might move in other than a straight line because it is following higher conductivity paths where there is more moisture in the air, or where ice crystals have caused a separation of charge in the atmosphere, creating an ionized path. There is no reason that the ionized path of lower resistance should be a straight line. Edison (talk) 19:36, 2 April 2011 (UTC)

A Jacob's ladder is an easily made demonstration of an electric arc being carried upwards by air convection. Cuddlyable3 (talk) 21:58, 2 April 2011 (UTC)

Name this garden flower?

In south east England: http://img16.imageshack.us/i/unknownflower.jpg/ The plant is branching, so to look at there is a mass of flowers. The flower is wilting rather. Done on a scanner. What could it be please? Thanks 92.29.121.249 (talk) 18:21, 2 April 2011 (UTC)

Looks like a night-scented stock to me. --TammyMoet (talk) 18:51, 2 April 2011 (UTC)

Aluminum foil

Why is one side shiny and the other side dull? --70.244.234.128 (talk) 19:43, 2 April 2011 (UTC)

Aluminum_foil#Properties: "Aluminium foil has a shiny side and a matte side. The shiny side is produced when the aluminium is rolled during the final pass. It is difficult to produce rollers with a gap fine enough to cope with the foil gauge, therefore, for the final pass, two sheets are rolled at the same time, doubling the thickness of the gauge at entry to the rollers. When the sheets are later separated, the inside surface is dull, and the outside surface is shiny." --Mr.98 (talk) 19:46, 2 April 2011 (UTC)

What has more hydrogen?

I read somewhere that a liter of petroleum (or gasoline can't remember) has more hydrogen in it than a liter of liquid hydrogen. What about water? Does a liter of water have more hydrogen in it than a liter of liquid hydrogen? ScienceApe (talk) 19:48, 2 April 2011 (UTC)

Liquid hydrogen has a density of 67.8 kg·m-3, which means that 1 cubic meter will have 67,800 grams of hydrogen molecules, or 135,600 hydrogen atoms. Petroleum is about 10-14% hydrogen by weight (according to our article). Petroleum is a mixture of a whole bunch of stuff, but according to List of crude oil products they seem to range in API gravity from 25-60, so lets take a nice middle of API gravity of 40, which translates to 141.5/171.5 = 0.82 g/cm3 or 820 kg/m3. 10-14% of 820 = 82.0 - 114.8 kg, which is 82,000 - 114,800 grams of hydrogen atoms per cubic meter. Divide those numbers by 1000 to get the per liter amounts. So no, on average petroleum does not seem to contain more hydrogen than pure liquid hydrogen, but those are large ranges we are working with; the densest (lowest API gravity) petroleum with the highest hydrogen mass (14%) may come close or even exceed the figure; this doesn't seem all that unusual as the types of intermolecular bonding that goes on in each substance is likely to be substantially different, accounting for differing numbers of atoms per unit volume. --Jayron32 20:13, 2 April 2011 (UTC)

Editing my response. The relevent comparisons are 67,800 grams of hydrogen per cubic meter for liquid hydrogen and 82,000 - 114,800 grams of hydrogen per cubic meter for petroleum. My math got confused for a second. So yes, clearly petroleum has mor hydrogen per cubic meter than liquid hydrogen. However, as I noted before this is unsurprising, as most of the hydrogen in petroleum is bonded via covalent bonds in large molecules, while the diatomic hydrogen in liquid hydrogen is in relatively small molecules. The intermolecular distances in a substance are somewhat larger than the intramolecular distances within a molecule; since petroleum has larger molecules, it can pack more hydrogen atoms in a smaller space. While by mass most of petroleum is carbon, by number of atoms it averages a little more than two hydrogens per carbon, so it is mostly hydrogen (by number of atoms), and the larger molecule size means that those hydrogens are, on average, packed closer together than in an equivalent volume of liquid hydrogen. --Jayron32 21:46, 2 April 2011 (UTC)

Hissssss touch bringsssssss... decay!

In the fictional Judge Dredd comics, the touch of the evil Judge Mortis causes a person's body to instantly decay as if the person were already dead, causing said person to immediately die. If we assume such a thing is possible, is there a specific effect of the body decaying that causes immediate death? JIP | Talk 20:21, 2 April 2011 (UTC)

The scenario you mention as context is unscientific, and is therefore not within the scope of this desk. Regarding the specific question of what effects of decay could cause immediate death, this is interesting because it highlights key structures that are actively maintained in vivo. A few examples: (i) loss of integrity of major blood vessels, leading to massive internal bleeding; (ii) widespread loss of endothelial tight junctions, leading to multi-organ failure; (iii) loss of integrity of myelin sheaths on neurons; (iv) depolarization of membranes in crucial tissues like heart and brain. I am sure there are many others. -- Scray (talk) 20:40, 2 April 2011 (UTC)

snowflakes

Why do snowflakes have hexagonal symmetry? I know that it has something to do with the hexagonal arrangement of the water molecules, but could someone be more specific? Thanks. 74.15.137.130 (talk) 20:54, 2 April 2011 (UTC)

The Wikipedia article Snowflake says the flake's six-fold radial symmetry is because the crystalline structure of ice is six-fold, and mentions several possible growth mechanisms whose details remain controversial. Cuddlyable3 (talk) 21:35, 2 April 2011 (UTC)

Relativity paradox

Get a sample of a fissionable material that's just under the critical mass and accelerate it to near the speed of light. While it's moving, try to start a chain reaction. From a stationary view, it should have the critical mass and thus start a chain reaction, but an observer moving with the material would see that it doesn't have enough mass. What happens? --70.244.234.128 (talk) 21:46, 2 April 2011 (UTC)

Even the comoving observer will be able to detect the added energy from the acceleration, this added energy will, from his point of view, be the source of the criticality This isn't a paradox... The two will see the excursion happen at different times, but this is due to the relativity of simultaneity. Now, I am a physics retard, so someone next will come along and explain why my explanation is wrong, but that is how I read this situation. --Jayron32 21:50, 2 April 2011 (UTC)

To the observer who's moving with the sample, its mass will still seem to be less than critical because the relative velocity is zero. --70.244.234.128 (talk) 21:55, 2 April 2011 (UTC)

Yes, but the additional forces due to acceleration will be clearly evident. In accelerating the sample, the forces on the sample will create additional pressures which, to the comoving observer, will be the source of the criticality. If the comoving observer calculates the critical mass in conjunction with the forces introduced due to the acceleration, criticality will become mathamatically explainable. Criticallity is not solely mass-dependant. You can decrease the critical mass of a substance by, for example, placing it under pressure. Accelerating it rapidly can introduce that pressure. In other words, the comoving observer will see the mass remain constant, but will be able to detect a change in density due to forces introduced by acceleration; that change in density will be his reasoning for the criticality. Again, I am a physics retard, so please wait for corrections to my explanation... --Jayron32 22:00, 2 April 2011 (UTC)

If we don't take the acceleration literally, and just consider a lump of fissionable material, rest mass just under critical, moving relative to us with near speed of light, then the answer is: No, it won't go off. It doesn't go off in its rest frame, hence it doesn't go off in our frame. 70.244... is presumably thinking of the increase of "relative mass", a popular but ultimately useless concept, and the scenario proposed here is a fine example why it is useless. Bulk motion has no effect on processes that depend only on mass, i.e. it does not increase the mass. The effective mass of the lump can be increased if internal degrees of freedom are excited (e.g. heating it up), and this may indeed happen when forces due to a real acceleration act on it. --Wrongfilter (talk) 22:29, 2 April 2011 (UTC)

The critical mass is not a Lorentz invariant. Why would you expect it to be the same in any frame? —Preceding unsigned comment added by 92.20.201.71 (talk) 00:14, 3 April 2011 (UTC)

It seems to me that the standing observer and the traveling observer are both totally irrelevant to action of the material. If the mass is increased to criticality it will just do it's thing and get really hot. not neccessarily go bang.Phalcor (talk) 01:40, 3 April 2011 (UTC)