Theory of General Relativity and Beyond
not satisfied with his original theory of relativity and
wanted to extend it to include gravity.
After publishing his Theory of Special Relativity,
Einstein began to garner much respect among physicists. However,
Einstein was not satisfied with his work. He felt it was incomplete
and soon started searching for new theories, first one that would
include the force of gravity, then later one that would explain
all of physics.
Einstein knew that his Special Theory of Relativity
should be expanded to include gravity and in 1907 started to work
on what would be later called his General Theory of Relativity.
While he had a picture in his mind of what such a theory might
look like, he found the mathematics daunting. In 1912 he wrote,
"…One thing is certain: never before in my life have I troubled
myself over anything so much…Compared with this problem, the original
theory of relativity is child's play."
To help him learn the complicated mathematics necessary,
Einstein enlisted an old friend of his, Marcel Grossmann, who
was also teaching at Zurich Polytechnic. They wrote several articles
together, with Grossmann handling the math and Einstein the physics.
In 1913 they published Draft of a Generalized Theory of Relativity
and of a Theory of Gravitation. The paper contained several errors,
but still created a stir in the scientific community. Einstein
was invited to join the prestigious Prussian Academy of Sciences.
He accepted the post and moved to Berlin, Germany, alone. He and
his wife Mileva had drifted apart over the years, and she did
not follow him. They soon divorced.
The Prussian Academy at the heart of the German
Scientific world and Einstein had access to some of the best mathematicians
in Europe. By 1915 he had found his errors in the draft paper
and published a new version. What it said would overturn what
was known about the physical laws of the universe.
General Theory of Relativity
Einstein started his paper by saying that mass is
equivalent to inertia. What this means is that the gravity that
presses you down in your seat is the same force that you feel
when you are pulled forwards in car when the driver hits the breaks.
Your chest presses against the seatbelt for the same reason your
bottom pushes against your chair. Since the time of Isaac Newton,
physicists had always thought of gravity as a force that pulled
things toward an object. The bigger the object, the stronger the
pull. The earth was a big object so it had enough pull to hold
objects - people, cars, buildings, cows - on its surface. A smaller
object, like the moon, also had gravity that pulls objects toward
it, but not as strongly (that's why an astronaut on the moon weights
just one-sixth of what he would on Earth).
What Einstein realized was that this picture was
wrong. Gravity, just as inertia, was not a pulling action but
a pushing action because all matter warps the fabric of space
and curves it. The analogy often used is that of a piece of fabric
stretched tightly across a wooden frame and laid flat like a table
top. Imagine what happens to the fabric when a bowling ball is
placed on it. The bowling ball warps the fabric. Now imagine placing
a marble on the fabric. It rolls toward the bowling ball. Its
movement is not because the bowling ball in any way pulls the
marble to it,. it moves because the bowling ball has created a
slope in the fabric and the marble rolls down the slope. In effect
the fabric is pushing on the marble.
It is the same with objects in space. The fabric
in the illustration above is the fabric of space. The bowling
ball is a planet like the earth. The earth does not really pull
other objects toward it, but it warps the fabric of space so that
objects, like the marble, are pushed toward it.
This change in thinking helped explain Galileo's
observations about falling bodies. Galileo did experiments (supposedly
by dropping objects off the Leaning Tower of Pisa) showing that
no matter how heavy or light an object was, they always fell at
the same speed, allowing for air friction. A hammer falls as fast
as a feather in a vacuum, something dramatically demonstrated
by Apollo astronaut Alan Bean on the moon.
including the Earth, warp space around them. This warping
of space creates gravity.
Einstein showed that this was because all the objects
(no matter what their mass) "rolled down the same slope." The
shape of the slope - and the speed at which the objects fall -
is entirely determined by the large body that they are being pulled
toward, not by their own mass. In our example it does not matter
if the marble is made of light wood or heavy stone, once released
it rolls toward the bowling ball at the same rate.
Several other surprising observations came out of
Einstein's theory. First, the universe is not three-dimensional,
but four dimensional: time is the fourth dimension and it cannot
be separated from space. Also space-time itself does not exist
without matter. If you could magically remove all the matter from
the universe, space and time would disappear too.
the Theory Right
Under Newton's laws, light traveling in a vacuum
goes in a straight line. Einstein said that because the fabric
of space is being bent, however, even a beam of light should curve
under gravity and this phenomenon was used to prove his theory.
According to Einstein, if a star is located behind the sun it
should be visible at the edge because the light rays coming from
the star will be bent by the sun's tremendous gravity. This experiment
can only be performed during a solar eclipse when the sun's own
blinding light is blocked by the moon and an object close to the
disc of the sun can be seen. As early as 1914, a group of German
astronomers had planned to go to Siberia and observe a solar eclipse
to see if Einstein's prediction proved true. World War I interrupted
this expedition and it wasn't until 1919 that a British group
of astronomers led by Sir Arthur Eddington was able to travel
to the island of Principe and observe a solar eclipse. When the
group returned to England and developed their photos, they saw
exactly what Einstein had predicted: The star that was actually
behind the sun could be seen by its edge. The light rays were
being bent. The theory of relativity was proven right.
The reaction to this announcement made Einstein
a celebrity, not only in the scientific world, but among non-scientists
too. To his credit he used his fame not for his own gain, but
to support worthy causes in which he believed. Two of his favorite
causes where pacifism and safety of the Jewish people. He also
helped establish the Hebrew University in Jerusalem. Einstein
became so famous that his vistage, a slightly-rumpled scientist
with unkept hair, has become an icon for science and scientists
The Theory of
Relativity was proven by observing the light of a distant
star bent by the sun's gravity. This could only be seen,
though, during a solar eclipse.
The Nazis that came to power in Germany in the 1930's
did not like Einstein because he was a Jew and a pacifist. In
1933, Einstein left Germany and accepted an invitation to join
the Institute for Advanced Study at Princeton University in New
Jersey. He moved to a comfortable house there with his wife, Elsa,
whom he had married in 1919. Elsa died in 1936, but Einstein would
continue living in Princeton until his death in 1955.
Grand Unified Theory of Everything
Einstein was responsible for the two great theories
of 20th century physics: general relativity and quantum theory.
General Relativity seems to govern the movement of large bodies
like stars and planets and, in fact, anything larger than an atom.
Quantum theory was a separate set of rules that seemed to govern
the world of particles smaller than an atom. Einstein, as well
as other physicists, dreamed of creating one theory that covered
both worlds. This quest for a unified theory would occupy Einstein
for the rest of his life and put him at odds with his scientific
colleagues throughout the world.
Despite having a major role in the founding of quantum
physics, Einstein did not feel at all comfortable with the theory.
Unlike classical physics theories, it could not precisely predict
the movement of an object (like a photon). It could only tell
where a photon might be based on probability. Quantum theory also
had many quirks that seemed to make little sense in the real world.
Even so, the theory satisfied many of Einstein's colleagues who
continued to develop it throughout the rest of the 20th century.
Einstein, however, thought that any good physics theory should
make sense and lead to definite predictions, not probabilities.
He expressed this sentiment in his famous quote, "God does not
play dice with the universe."
Einstein found himself practically alone in the
physics world in opposing quantum theory and he spent quite a
bit of time thinking up objections to it. Ironically, this strengthened
the theory as its proponents, like Neils Bohr, were forced to
think about how to refute his complaints. It is said that when
they met during a conference Einstein would raise his objections
at dinner, and Bohr would refute them the next morning at breakfast
after spending the whole night thinking about them.
chased the the Grand Unified Theory for the rest of his
life (Wikipedia Commons)
The final portion of Einstein's career was spent
chasing the Grand Unified Theory. He wasn't the only scientist
with this vision, but he was almost totally alone in approaching
it from the realm of classical physics. Sadly, he was unable to
find a resolution to the problem before his death. Almost all
other physicists thought that any future Grand Unified Theory
would have quantum physics subsuming general relativity, not the
other way round. In fact, the leading contender as a Grand Unified
Theory of physics today is string theory which comes from quantum
So was Einstein's final quest in vain? Perhaps not.
Some physicists, such as Gerad't Hooft of the University of Utrecht
in the Netherlands, have recently been reviewing his work and
wondering if perhaps he was right after all. Is it possible that
there is a classical physics theory hidden behind Quantum Theory?
We may not know for sure until another genius like Einstein, comes
along and shows us the way.
to Part One
Einstein: A Life, by Dennis Brain, John
Wiley & Sons, 1996.
Einstein: Decoding the Universe, Harry
N. Abrams, Inc. Publishers, 2001.
Einstein's Gift for Simplicity, Thomas
Levenson, Discover, September, 2004.
Was Einstein Right?, George Musser, Scientific
American, September, 2004.
Copyright Lee Krystek
2004. All Rights Reserved.