Albert Einstein(14 March 1879 – 18
April 1955) was a German-borntheoretical physicist who
developed thegeneral theory of
relativity, one of the two pillars of modern physics (alongsidequantum mechanics).[2]
He received theNobel Prize in
Physics in 1921, but not forrelativity.[3] Histheories of specialand general relativity are
of great importance to many branchesof physics andastronomy. They have been given experimental
confirmation by many experimentsand observations.
Einstein is well known for histheories aboutlight, matter,gravity, space, andtime. His most well known equation is . It means that energyand mass are different forms of the same
thing.
Einstein published more than 3 scientific
papers and over 5 non-scientific works. He received honorary doctorate degrees
in science, medicine and philosophy from many European and Americanuniversities.
Near the beginning of World War II, he warned President Franklin D. Roosevelt that
Germany might be developing an atomic weapon, and recommended that the U.S. begin nuclear weapons research.[4] That research, begun by a newly established Manhattan Project,
resulted in the U.S. becoming the first and only country to have nuclear
weapons during the war.
Contents
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1Life
·
4BEC
·
8Beliefs
Einstein was born [at Ulm] in Württemberg, Germany, on 14 March 1879.[5] His family was Jewish, but was not very religious. However, later in life Einstein
became very interested in his Judaism. Einstein did not begin speaking until
after age two. According to his younger sister, Maja, "He had such
difficulty with language that those around him feared he would never
learn".[6] When Einstein 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 of science.
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 first made him famous as a great scientist.
Einstein had two severely 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.[7] She spent her very short life
(believed to be less than 2 years) in the care of Serbiangrandparents where it is believed she
died from scarlet fever.[8] Some believe she may have been
born with the disorder called Down syndrome but it has never been proved. 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 granddaughter in an attic in California.[9] Their son, Eduard, was
diagnosed with schizophrenia. He
spent decades in hospitals, and died in the Zurich sanatorium in 1965.
In 1917, Einstein became very sick with an
illness that almost killed him. His cousin Elsa Lowenthal nursed him back to health.
After this happened, Einstein divorced Mileva, and married Elsa on 2 June 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 Nazigovernment 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 hated by the Nazi-controlled
German press, Einstein and Elsa moved to Princeton, New Jersey in the United States, and in 1940 he became a United
Statescitizen.
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 so that the Nazi government could not beat them to the
punch. He was the only one who signed the letter. He was, however, not part of
the Manhattan Project,
which was the project that
created the atomic bomb.
Einstein, a Jew but not an Israeli
citizen, was offered the presidency in 1952 but turned it down, stating "I
am deeply moved by the offer from our State of Israel, and at once saddened and
ashamed that I cannot accept it."[10] Ehud Olmert was reported to be
considering offering the presidency to another non-Israeli, Elie Wiesel, but he was said to be "very
not interested".[11]
He taught physics at the Institute
for Advanced Study at Princeton, New Jersey until
his death on 18 April 1955 of a burst aortic aneurysm. He was still writing about quantum physics hours before he died. He
was awarded the Nobel Prize in
Physics.
The theory of special
relativity was published by Einstein in 1905, in a paper called
"On the Electrodynamics of Moving Bodies". It says that both distance
measurements and time measurements change near the speed of light. This means that as you get
closer to the speed of light (nearly 300,000 kilometres per second), lengths
appear to get shorter, and clocks tick more slowly. Einstein said that Special
Relativity is based on two ideas. The first is that the laws of physicsare 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 any observer, no matter how fast that observer moves in
relation to us, is always the same. A vacuum is a volume without any matter in
it.
Light from both stars is
measured as having the same speed
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 meananything. 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."
Distance traveled is
relative to different standards of reference
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 Gibraltar and bounce number 6 is over a place in
Spain. 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.
Light clock faster at
rest and slower in motion
Every grade school child learns 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 dand 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.
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 cannonball hangs on a rope from an iron
ring. A horse pulls the cannonball to the right side. When the cannonball 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 cannonball
as potential energy. (It has energy because it is up high and can fall down.)
As the cannonball 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.
A picture of Einstein
after winning his Nobel Prize, 1921
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.
Albert Einstein, 1921
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 radiumand uranium. An atom of uranium can lose an alpha
particle (the atomic nucleus of helium) and become 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.[12]
In most radioactivity, the entire mass of
something does not get changed to energy. In an atomic bomb, uranium is
transformed intokrypton and barium. There is a slight difference in the
mass of the resulting krypton and barium, 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 = (muranium – mkrypton
and barium) 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
(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.[13] So about two-thirds of a gram
of the radioactive mass in that atomic bomb must have been lost (changed into
energy), when the uranium changed into krypton and barium.
The idea of a Bose-Einstein
condensate came out of a collaboration between S. N. Bose and
Prof. Einstein. Einstein himself did not invent it but, instead, refined the
idea and helped it become popular.
The concept of zero-point energy was
developed in Germany by Albert Einstein and Otto Stern in 1913.
Statue of Albert
Einstein in the Israel
Academy of Sciences and Humanities.
In classical physics,momentum is explained by the equation:
p = mv
where
p represents momentum
m represents mass
v represents velocity (speed)
When Einstein generalized classical
physics to include the increase of mass due to the velocity of the moving
matter, he arrived at an equation that predicted energy to be made of two
components. One component involves "rest mass" and the other
component involves momentum, but momentum is not defined in the classical way.
The equation typically has values greater than zero for both components:
E2 = (m0c2)2 +
(pc)2
where
E represents the energy of a particle
m0 represents the mass of
the particle when it is not moving
p represents the momentum of the particle
when it is moving
c represents the speed of light.
There are two special cases of this
equation.
Einstein
in his later years, c. 1950s
A photon has no rest mass, but it has
momentum. (Light reflecting from a mirror pushes the mirror with a force that
can be measured.) In the case of a photon, because its m0= 0, then:
E2 = 0 + (pc)2
E = pc
p = E/c
The energy of a photon can be computed
from its frequency ν or wavelength λ. These are related to each other by Planck's relation, E = hν = hc/λ, where h is
the Planck constant (6.626×10−34 joule-seconds).
Knowing either frequency or wavelength, you can compute the photon's momentum.
In the case of motionless particles with
mass, since p = 0, then:
E02 = (m0c2)2 +
0
which is just
E0 = m0c2
Therefore, the quantity
"m0" used in Einstein's equation is sometimes called the
"rest mass." (The "0" reminds us that we are talking about
the energy and mass when the speed is 0.) This famous "mass-energy
relation" formula (usually written without the "0"s) suggests
that mass has a large amount of energy, so maybe we could convert some mass to
a more useful form of energy. The nuclear power industry is based on that
idea.
Einstein said that it
was not a good idea to use the classical formula relating momentum to velocity,
p = mv, but that if someone wanted to do that, he would have to use a particle
mass m that changes with speed:
mv2 = m02 /
(1 – v2/c2)
In this case, we can say that E = mc2 is
also true for moving particles.
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The General
Theory of Relativity was published in 1915, ten years after thespecial theory
of relativity was created. Einstein's general theory of
relativity uses the idea of spacetime. Spacetime is the fact that we have
a four-dimensional universe, having three spatial (space) dimensions and one
temporal (time) dimension. Any physical event happens at some place inside
these three space dimensions, and at some moment in time. According to the
general theory of relativity, any mass causes spacetime to curve, and any other
mass follows these curves. Bigger mass causes more curving. This was a new way
to explain gravitation (gravity).
General relativity explains gravitational
lensing, which is light bending when it
comes near a massive object. This explanation was proven correct 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 cosmology (theories of the structure of
our universe at large distances and over long
times). Einstein thought that the universe may curve a little bit in both space
and time, so that the universe always had existed and always will exist, and so
that if an object moved through the universe without bumping into anything, it
would return to its starting place, from the other direction, after a very long
time. He even changed his equations to include a "cosmological
constant," in order to allow a mathematical model of
an unchanging universe. The general theory of relativity also allows the
universe to spread out (grow larger and less dense) forever, and most
scientists think that astronomy has
proved that this is what happens. When Einstein realized that good models of
the universe were possible even without the cosmological constant, he called
his use of the cosmological constant his "biggest blunder," and that
constant is often left out of the theory. However, many scientists now believe
that the cosmological constant is needed to fit in all that we now know about
the universe.
A popular theory of cosmology is called
the Big Bang. According to the Big Bang theory,
the universe was formed 15 billion years ago, in what is called a "gravitational
singularity". This singularity was small, dense, and very hot.
According to this theory, all of the matter that we know today came out of this
point.
Einstein himself did not have the idea of
a "black hole", but
later scientists used this name for an object in the universe that bends
spacetime so much that not even light can escape it. They think that these
ultra-dense objects are formed when giant stars, at least three times the size
of our sun, die. This event can follow what is called asupernova. The formation of black holes may be
a major source of gravitational waves, so the search for proof of gravitational
waves has become an important scientific pursuit.
Many scientists only care about their
work, but Einstein also spoke and wrote often about politics and world peace. He liked the ideas ofsocialism and of having only one government for the whole world. He also
worked for Zionism, the effort to try
to create the new country ofIsrael.
Einstein's family was Jewish, but Einstein
never practiced this religionseriously. He
liked the ideas of the Jewish philosopher Baruch Spinozaand also thought that Buddhism was a good religion.[source?]
Even though Einstein thought of many ideas
that helped scientists understand the world much better, he disagreed with some
scientific theories that other scientists liked. The theory of quantum mechanicsdiscusses
things that can happen only with certain probabilities, which cannot be predicted with
better precision no
matter how muchinformation we
might have. This theoretical pursuit is different fromstatistical mechanics,
in which Einstein did important work. Einstein did not like the part of quantum
theory that denied anything more than the probability that something would be
found to be true of something when it was actually measured; he thought that it
should be possible to predict anything, if we had the correct theory and enough
information. 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 onephoton of light. The
chemical element Einsteinium is
named after the scientist as well.[14] In slang, we sometimes call a very smart person
an "Einstein."
Most scientists think that Einstein's
theories of special and general relativity work very well, and they use those
ideas and formulas in their own work. Einstein could not agree that phenomena
in quantum mechanics can
happen out of pure chance. He believed that all natural phonomena have
explanations that do not include pure chance. He spent much of his later life
trying to find a "unified field theory"
that would include his general relativity theory, Maxwell's theory of
electromagnetism, and perhaps a better quantum theory. Most
scientists do not think that he succeeded in that attempt.
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