Albert Einstein: Difference between revisions

Albert Einstein
Albert Einstein, 1947
Born	14 March 1879 Ulm, Württemberg, Germany
Died	18 April 1955 Princeton, New Jersey, USA

Albert Einstein, 1921

Albert Einstein (14 March 1879– 18 April 1955) was one of the most famous scientists of the 20th century.

He received the Nobel Prize in Physics in 1921. His theories of special and general relativity are of huge importance to many branches of physics and astronomy. They have been verified by many experiments and observations.

Einstein is famous for his theories about light, matter, gravity, space, and time. His most famous equation is $E=mc^{2}$. It means that energy and mass are different forms of the same thing.

Einstein published more than 300 scientific papers and over 150 non-scientific works. He received honorary doctorate degrees in science, medicine and philosophy from many European and American universities.

He escaped from Nazi Germany in 1933, where he had been a professor at the Berlin Academy of Sciences, and settled in the U.S., becoming a citizen in 1940.

On the eve of World War II, he helped alert President Franklin D. Roosevelt that Germany might be developing an atomic weapon, and recommended that the U.S. begin nuclear research. That research, begun by a newly-established Manhattan Project, resulted in the U.S. becoming the first and only country to possess nuclear weapons during the war. He taught physics at the Institute for Advanced Study at Princeton, New Jersey, until his death in 1955.

His life

Einstein was born at Ulm in Württemberg, Germany on March 18, 1879. His family was Jewish but was not very religious. Albert did not talk until he was about three, which is very unusual. When Albert was around four, his father gave him a magnetic compass. He tried hard to understand how the needle could seem to move itself so that it always pointed north. The needle was in a closed case, so clearly nothing like wind could be pushing the needle around, and yet it moved. So in this way Einstein became interested in studying science and mathematics. His compass inspired him to explore the world. Albert went to a Roman Catholic school. He was not a good student, and many people thought him to not be very smart.

When he became older, he went to a school in Switzerland. After he graduated, he got a job in the patent office there. While he was working there, he wrote the papers that made him famous as a great scientist.

Einstein had two heavily-disabled children with his first wife Mileva His daughter 'Lieserl' (her real name may never be known) was born about a year before their marriage in January 1902. She spent her very short life (believed to be less than 2 years) in the care of Serbian grandparents where it is believed she died from Scarlet Fever. Some believe she may have been born with the disorder called Down syndrome but it has never been proven. Her very existence only became known to the world in 1986 when a shoe-box, containing 54 love letters (mostly from Einstein) exchanged between Mileva and Einstein from late 1897 to September 1903, was discovered by Einstein's grand-daughter in an attic in California. Their son, Eduard, was diagnosed at age 7 with a severe mental illness. He spent decades in hospitals, and died in the Zurich sanatorium in 1965.

There is an indirect connection between brain size and the size of the neopallium especially important for the brain's higher functions. However, Einstein's brain weight was below-average and showed signs of degeneration (e.g. Sylvian fissure).

In 1917, Einstein became very sick with an illness that almost killed him. It was his cousin Elsa Lowenthal who nursed him back to health. After this turn of events, Einstein divorced Mileva, and married Elsa on June 2, 1919.

Just before the start of World War I, he moved back to Germany, and became director of a school there. He lived in Berlin until the Nazi government came to power. The Nazis hated people who were Jewish or who came from Jewish families. They accused Einstein of helping to create "Jewish physics," and German physicists tried to prove that his theories were wrong.

In 1933, under death threats from the Nazis and despised by the Nazi-controlled German Press, Einstein and Elsa moved to the United States to Princeton, New Jersey after feeling the heat of Nazi Germany and in 1940 he became a United States citizen.

During World War II, Einstein and Leó Szilárd wrote to the U.S. president Franklin D. Roosevelt, to say that the United States should invent an atomic bomb before the Nazi government could invent one first. He was not part of the Manhattan project, which was the project to create the atomic bomb. He was the only one that signed the letter.

Einstein died on 18 April 1955 of a burst aorta heart disease. He was still writing about quantum physics hours before he died.

The Theory of Special Relativity

The theory of special relativity was published by Einstein in 1905 on a paper called "On the Electrodynamics of Moving Bodies". It states that both distance measurements and time measurements are altered near the speed of light. This means that as you get closer to the speed of 300,000 kilometres per second, lengths appear to shrink, and clocks tick more slowly. Einstein proposed that Special Relativity is based on two ideas. The first is that the laws of physics are the same for all observers that are not moving in relation to each other. All the people on a jet airplane would not be moving much in relation to each other, but the people in two different jet airplanes that come toward each other would be moving toward each other very fast. The people who are all going in the same direction at the same speed are said to be in an "inertial frame." The second idea is that the speed of light in a vacuum is always the same. A vacuum is a volume without any matter in it.

People who are in the same "frame" (think of them as being in a big box so that they all go places together and at the same speed) will measure how long something takes to happen in the same way. Their clocks will keep the same time. But people moving in another "frame" will look over at them and see that their clocks were moving at a different rate. The reason that this happens is actually quite simple. It is the consequence of two ideas. One idea we have seen already. No matter what you are doing, even if you are moving toward a distant star at half the speed of light, or if you are moving away from it at half the speed of light (or any other speed, it does not matter), if you measure the speed of the light coming from that star it will always be the same number. The other idea goes against our ordinary ideas. The other idea says that who is standing still and who is moving is whoever you say is standing still or moving. How can that be?

Imagine you were all alone in a different universe. That universe has no suns, planets, or anything else. It just has you and your spaceship. Are you moving? Are you standing still? Those questions do not mean anything. Why? Because when we say we are moving we mean that we can measure our distance from something else at one time and measure the distance at another time and the numbers will not be the same. If the numbers get bigger we are moving away. If the numbers get smaller we are moving closer. Suppose a sailor is standing on the edge of a very long boat with a flat top. Her boyfriend is standing on the dock. They are still very close together, so they shout to each other. The boat starts to leave. The sailor runs toward the back of the boat at the same speed that the boat moves forward so she and her boyfriend can keep talking. As far as her boyfriend is concerned, she is not moving. So to have movement you must have at least two things. We do not think about it because when we sit on the earth in a park, which is moving very fast around the sun, we think we are not moving because we do not get any closer or farther away from the trees in the park.

Now imagine that another spaceship appears in this other universe. On your spaceship you say that their spaceship is coming closer to yours. After all, you do not feel yourself moving. On their spaceship they say that your spaceship is coming closer to theirs. They do not feel themselves to be moving either. Somebody on an airplane can be moving at several hundred kilometers per hour, but they say, "I am just sitting here."

Let us try to stretch our minds a bit. Imagine that a basketball player is on a glass airplane on the ground. People outside can see him very easily. He begins to walk from the back of the airplane toward the front of the airplane, bouncing his basketball as he goes. Maybe the distance between the places where his basketball hits the floor of the airplane is about one meter or one yard. If some people are under the airplane they can mark the place directly under the airplane where the ball hits the floor. Those marks are a meter or maybe a yard apart. So everybody agrees that the bounces are about a meter or a yard apart. Later the plane takes off. People still watch it from on the ground. But this time bounce number 5 is over a place in England and bounce number 6 is over a place in Scotland. The distance between bounces is measured in kilometers or miles on the ground, but the people on the plane get the same answers they did while the plane was on the ground.

Now suppose some people are on a big spaceship and they want to make a very accurate clock. So they make a long tunnel between decks from what would be like the top of an airplane to what would be the bottom of an airplane. At one end they put a mirror, and at the other end they put a simple machine. It shoots one short burst of light toward the mirror and then waits. The light hits the mirror and bounces back. When it hits a light detector on the machine, the machine says, "Count = 1," it simultaneously shoots another short burst of light toward the mirror, and when that light comes back the machine says, "Count = 2." Of course since light is very fast the count changes very fast. They decide that a certain number of bounces will be defined as a second, and they make the machine change the seconds counter every time it has detected that number of bounces. Every time it changes the seconds counter it also flashes a light out through a porthole under the machine. So somebody out taking a space walk will see the light flashing every second.

Every grade school child knows the formula d=rt (distance equals rate multiplied by time). We know the speed of light, and we can easily measure the distance between the machine and the mirror and multiple that to give the distance the light travels. So we have both d and r, and we can easily calculate t. The people on the spaceship compare their new "light clock" with their various wrist watches and other clocks, and they are satisfied that they can measure time well using their new light clock.

Now this spaceship happens to be going very fast. It is not coming to earth to visit, but it does happen to fly over the north pole. There is a science station with a telescope at the north pole. They see a flash from the clock on the space ship, and then they see another flash. Only the flashes do not come a second apart. They come at a slower rate. The reason is that the situation is like the basketball player on the airplane. The ball is pushed downward by the player's hand. That is the light in the spaceship's machine firing off a burst toward the mirror. The ball hits the floor and bounces. That is like the light hitting the mirror and being reflected. The ball returns to the player's hand. That is like the light hitting the machine and triggering a new burst of light. Note that the distance between the place on the ground where the basketball is seen to hit the floor and the distance on the ground where the basketball is seen to return to the basketball player's hand is some great distance. Depending on how fast the plane is going, it might be a kilometer or even a mile away.

So the man on the north pole sees the light flash on the side of the spaceship when it is thousands of miles away, and then sees the next flash when the spaceship has gotten thousands of miles closer. The way the north pole man sees it, the light started out, let's say, 100,000 miles away and hit its return point when it was perhaps 90,000 miles away. So instead of just traveling twice the diameter of the space ship (perhaps several hundred meters or yards) the light has traveled 10,000 miles. Light always goes at the same speed, d = rt, and so the time this trip took is going to be much greater --- as seen by the man on the north pole. That is why the clock on the spaceship is not flashing once a second for the earth observer.

Special Relativity also relates energy with mass, in Albert Einstein's E=mc² formula.

Mass-energy equivalence

E=mc², also called the mass-energy equivalence, is one of the things that Einstein is most famous for. It is a famous equation in physics and math that shows what happens when mass changes to energy or energy changes to mass. The "E" in the equation stands for energy. Energy is a number which you give to objects depending on how much they can change other things. For instance, a brick hanging over an egg can put enough energy onto the egg to break it. A feather hanging over an egg does not have enough energy to hurt the egg.

There are three basic forms of energy: Potential Energy, Kinetic Energy, and Rest Energy. Two of these forms of energy can be seen in the examples given above, and in the example of a pendulum.

A cannon ball hangs on a rope from an iron ring. A horse pulls the cannon ball to the right side. When the cannon ball is released it will move back and forth as diagrammed. It would do that forever except that the movement of the rope in the ring and rubbing in other places causes friction, and the friction takes away a little energy all the time. If we ignore the losses due to friction, then the energy provided by the horse is given to the cannon ball as potential energy. (It has energy because it is up high and can fall down.) As the cannon ball swings down it gains more and more speed, so the nearer the bottom it gets the faster it is going and the harder it would hit you if you stood in front of it. Then it slows down as its kinetic energy is changed back into potential energy. "Kinetic energy" just means the energy something has because it is moving. "Potential energy" just means the energy something has because it is in some higher position than something else.

When energy moves from one form to another, the amount of energy always remains the same. It cannot be made or destroyed. This rule is called the "conservation law of energy". For example, when you throw a ball, the energy is transferred from your hand to the ball as you release it. But the energy that was in your hand, and now the energy that is in the ball is the same number. For a long time, people thought that the conservation of energy was all there was to talk about.

When energy transforms into mass, the amount of energy does not remain the same. When mass transforms into energy, the amount of energy also does not remain the same. However, the amount of matter and energy remains the same. Energy turns into mass and mass turns into energy in a way that is defined by Einstein's equation, E = mc².

The "m" in Einstein's equation stands for mass. Mass is the amount of matter there is in some body. If you knew the number of protons and neutrons in a piece of matter such as a brick, then you could calculate its total mass as the sum of the masses of all the protons and of all the neutrons. (Electrons are so small that they are almost negligible.) Masses pull on each other, and a very large mass such as that of the Earth pulls very hard on things nearby. You would weigh much more on Jupiter than on Earth because Jupiter is so huge. You would weigh much less on the moon because it is only about one sixth the mass of Earth. Weight is related to the mass of the brick (or the person) and the mass of whatever is pulling it down on a spring scale — which may be smaller than the smallest moon in the solar system or larger than the Sun.

Mass, not weight, can be transformed into energy. Another way of expressing this idea is to say that matter can be transformed into energy. Units of mass are used to measure the amount of matter in something. The mass or the amount of matter in something determines how much energy that thing could be changed into.

Energy can also be transformed into mass. If you were pushing a baby buggy at a slow walk and found it easy to push, but pushed it at a fast walk and found it harder to move, then you would wonder what was wrong with the baby buggy. Then if you tried to run and found that moving the buggy at any faster speed was like pushing against a brick wall, you would be very surprised. The truth is that when something is moved then its mass is increased. Human beings ordinarily do not notice this increase in mass because at the speed humans ordinarily move the increase in mass in almost nothing.

As speeds get closer to the speed of light, then the changes in mass become impossible not to notice. The basic experience we all share in daily life is that the harder we push something like a car the faster we can get it going. But when something we are pushing is already going at some large part of the speed of light we find that it keeps gaining mass, so it gets harder and harder to get it going faster. It is impossible to make any mass go at the speed of light because to do so would take infinite energy.

Sometimes a mass will change to energy. Common examples of elements that make these changes we call radioactivity are radium and uranium. An atom of uranium can change itself into an alpha particle (the atomic nucleus of helium) and becomes a new element with a lighter nucleus. Then that atom will emit two electrons, but it will not be stable yet. It will emit a series of alpha particles and electrons until it finally becomes the element Pb or what we call lead. By throwing out all these particles that have mass it has made its own mass smaller. It has also produced energy, as anyone who has seen a movie of an atomic bomb exploding can believe.

In most radioactivity, the entire mass of something does not get changed to energy. In an atomic bomb, uranium is transformed into lead. There is a slight difference in the mass of the resulting lead and the mass of the original uranium, but the energy that is released by the change is huge. One way to express this idea is to write Einstein's equation as:

E = (m_uranium - m_lead) c²

The c² in the equation stands for the speed of light squared. To square something means to multiply it by itself, so if you were to square the speed of light, it would be 299,792,458 meters per second, times 299,792,458 meters per second, which is approximately
(3•10⁸)² = (9•10¹⁶ meters²)/seconds²=
90,000,000,000,000,000 meters²/seconds²
So the energy produced by one kilogram would be:
E = 1 kg • 90,000,000,000,000,000 meters²/seconds²
E = 90,000,000,000,000,000 kg meters²/seconds²
or
E = 90,000,000,000,000,000 joules
or
E = 90,000 terajoule

About 60 terajoules were released by the atomic bomb that exploded over Hiroshima. So about two thirds of a gram of the radioactive mass in that atomic bomb must have been transformed into lead.

Momentum

In classical physics, momentum is explained by the equation:
p = mv
where
p represents momentum
m represents mass
v represents velocity (speed)

Einstein made an equation that takes account of the way mass relates to velocity:
E² = (mc²)² + (pc)², where:
E represents the energy of the particle
c represents the speed of light.

There are two special cases of this equation.

In the case of photons, because their mass = 0, then:

E² = 0 + (pc)²
E = pc
p = E/c

The energy of a photon can be computed from its frequency or wavelength. Knowing either frequency or wavelength, you can compute the photon's momentum.

In the case of motionless things with mass, since v = 0, then:
E² = (mc²)² + 0
which is just
E = mc²

A photon has no mass, but it nevertheless has momentum. In classical physics, p = mv, which means that momentum is defined as the product of mass and velocity. But as has been discussed above, an increase in velocity also means an increase in mass, something that the classical definition of momentum did not think about. When Einstein generalized the classical equation to include the increase of mass due to the velocity of the moving matter, he arrived at an equation that predicted energy as the sum of two components. One component involves mass and the other component involves velocity. The equation typically has values greater than zero for both components. A 0 mass photon moving at c still has a positive momentum.

If people took the positive momentum calculated from the relativistic equation and plugged it back into the classical equation, they could falsely conclude that a photon of light has mass. But its momentum comes from its energy and not from its mass. The momentum of a photon can be figured from the frequency of the photon, and the frequency is an aspect of its energy.

---

The famous mass-energy equivalency equation can be figured out from classical physics:

p_photon = E/c

p_box = Mv (M = mass of box, v = speed of box in springing back from the firing of the photon

Δt is the time for the photon to reach the other side of the box. Δx is the distance the box will have moved while photon is in flight.

Speed of box

v = Δx/Δt

There is conservation of momentum, therefore

Mv = E/c or M Δx/Δt = E/c (conservation of momentum equation)

L is the length of the box, so time to reach other side of box =

Δt = L/c

so M Δx/(L/c) = E/c

M Δx = (E/c)(L/c) = EL/c²

If there were some particle being shot, instead of light, the particle would have some mass m.

The center of mass for the box plus the particle would be:

x = (Mx₁ + mx₂) / (M + m)

(${\bar {x}}$ (often read as “x bar”) is the mean (average value of $x_{i}$).)

"We require that the centre of mass of the whole system does not change. Therefore, the centre of mass at the start of the experiment must be the same at the end of the experiment. Mathematically: "--http://www.adamauton.com/warp/emc2.html

(Mx₁ + mx₂)/(M+m) = (M(x₁=Δx) + mL)/(M+m)

Photon starts at the left end of the box, so x₂ = 0

(Mx₁ + 0)/(M+m) = (M(x₁=Δx) + mL)/(M+m)

(Mx₁ )/(M+m) = (M(x₁-Δx) + mL)/(M+m)

(Mx₁ ) = (M(x₁=Δx) + mL)

Mx₁ = Mx₁=MΔx + mL

mL = MΔx

Above we had: M Δx/Δt = E/c

or M Δx = EΔt/c

so

mL = MΔx = E Δt /c

and Δt = L/c

so

mL = EL/c²

Dividing both sides by L

m = E/c²

and rearranging,

E = mc²

Starting with Maxwell's law regarding light having momentum related to its energy, Einstein showed that mass must be convertible to energy.

The General Theory of Relativity

The General Theory of Relativity was published in 1915, ten years after the Special Theory of Relativity was created. According to the General Theory of Relativity, the gravitational attraction between masses results in the masses in space and time, meaning that every object is attracted to each other, and that results in space and time. Einstein's General Relativity also explained spacetime. Spacetime is the fact that we have a four dimensional universe, having three spatial(space) dimensions, and one temporal(time) dimension. All physical objects-us, the moon, the sun, the Milky Way, everything, is located inside these three dimensions. Also, mass causes the shape of spacetime to change, making it curved. All things follow these curves. Black holes are a major source of gravitational waves. A black hole is an object in the universe that has such a strong pull of gravity, that not even light can escape it. They are formed when giant stars, at least three times the size of our sun, dies. This is called a supernova. Also, general relativity explains gravitational lensing, which is where light bends when a massive object comes near it. This was proven during a solar eclipse, when the sun's bending of starlight from distant stars could be measured because of the darkness of the eclipse. General Relativity also set the stage for the theory of the formation of our universe. This theory is called the Big Bang. General Relativity explained singularities, which is what scientists think the universe formed from. This singularity was small, dense, and very hot. All of the matter that we know today came out of this point 15 billion years ago.

Beliefs

Many scientists only care about their work, but Einstein also spoke and wrote often about politics and world peace. He liked the ideas of socialism and of having only one government for the whole world. He also worked for Zionism, the effort to try to create the new country of Israel.

Einstein's family was Jewish, but Einstein never practiced this religion seriously. He liked the ideas of the Jewish philosopher Baruch Spinoza and also thought that Buddhism was a good religion.

Even though Einstein thought of many ideas that helped scientists understand the world much better, he disagreed with many scientific theories that were developed later in his life. Many scientific theories discuss things that we cannot know for certain, but only as probabilities. Einstein did not like these kinds of theories; he thought that it should be possible to understand anything, if we had the correct theory. He once said, "I do not believe that God plays dice with the Universe."

Because Einstein helped science so much, his name is now used for several different things. A unit used in photochemistry was named for him. It is equal to Avogadro's number multiplied by the energy of one photon of light. The chemical element Einsteinium is named after the scientist as well. In slang, we sometimes call a very smart person an "Einstein."

One of his inspiring sayings is "There are two ways to live your life, one is as though nothing is a miracle, the other is as though everything is a miracle."

There is still a strong criticism of Einstein. Ronald William Clark says that Einstein hated Germany and the Germans since his youth. A group in Germany called G.O.Mueller wrote a whole encyclopedia refuting Einstein's relativity. G.O.Mueller, Aristotle, Kant, Leibniz say space and time are categories of perception, not distortable "things", and not joined together.The speed of light could be higher. Paul Dirac and others thought that constants can change over time, too (e.g. gravitation). G.O.Mueller lists about 4000 Einstein-critical works since 1905, rallying worldwide for rethinking relativity.

References

• Einstein, Albert and Infeld, Leopold 1938. The evolution of physics: from early concept to relativity and quanta. Cambridge University Press. A non-mathematical account.

Other websites

• G.O.Mueller
• What Did Albert Einstein Invent?