Stephen J. Hawking
by Rachel Finck
BA in 1962, and Cambridge, where he received his doctorate in theoretical
physics. Stephen Hawking is a brilliant and highly productive researcher, and,
writing, or calculating in a direct and simple way. The bulk of his work, involving
stand as a complete, consistent theory of the physical interactions that would
describe all possible observations. Our attempts at modeling physical reality
the universe. Presently, physicist are still trying to unify two separate theories to
relativity and quantum mechanics.
handedly in 1915. First, in 1905, he developed the special theory of relativity,
regardless of velocity. In 1915, he developed the general theory of relativity.
This theory dealt with the concept of gravity as a distortion of space-time, and not
just a force within it.
Einstein’s original equations predicted that the universe was either
always positive, which is why gravity always attracts bodies toward each other.
theorized that what if matter could curve a region in on itself so much that it could
cut itself off from the rest of the universe. The region would become what is
To get out, the objects would have to move faster than the speed of light, and this
was not allowed by the general theory of relativity. In 1965, Hawking along with
Roger Penrose proved a number of theorems that showed the fact that space-
time was curved in on itself so that there would be singularities where space-time
had a beginning or an end.
“The fact that Einstein’s general theory of relativity turned out to predict
singularities led to a crisis in physics. (Hawking)” The equations of general
relativity cannot be defined as a singularity. This means that general relativity
cannot predict how the universe should begin at the big bang. Thus, it is not a
complete theory. It must be paired with quantum mechanics.
In 1905, the photoelectric effect was written about by Einstein, which he
theorized could be explain if light came not in continuously variable amounts, but
in packets of a certain size. A few years earlier, the idea of energy in quanta had
been introduced by Max Planck.
when Werner Heisenberg pointed out that it made it impossible to measure the
position of a particle exactly. To see where a particle is, you have to shine a light
on it. As Einstein showed, you had to use at least one quanta of light. This
whole packet of light would disturb the particle and cause it to move at some
speed in some direction different than its state before the light was shined. In this
way, it was theorized that the more accurately you want to measure the position
of the particle, the greater the energy packet you would have to use and thus the
more you would disturb the particle. This dilemma is called the Heisenberg
take into account the uncertainty principle. One therefore has to find a new
theory that combines general relativity and the uncertainty principle. In most
is very small. However, the singularity theorems that Hawking proved show that
space-time will become highly curved on very small scales. The effects of the
uncertainty principle will then become very important.
The problems that Einstein had with quantum mechanics is that he used
the commonsense notion that a particle has a definite history. And that a particle
has a definite location. But, it must be taken into account that a particle has an
helps to illustrate this concept. Let’s say that a cat is placed in a sealed box and
a gun is pointed at it. The gun will only go off if a radioactive nucleus decays.
There is exactly a 50% chance of this happening. Later on, before the box is
box is opened, the cat is both alive and dead at the same time. The cat has two
Another way to think of this was put forth by a physicist Richard Feynman.
He contributed that a system didn’t just have a single history in space-time, but it
had every possible history. “Consider, for example, a particle at point A at a
certain time. Normally, one would assume that the particle would move in a
straight line away from A. However, according to the sum over histories, it can
move on any path that starts at A. (Hawking)” It’s like what happens when you
place a drop of ink on blotting paper, and it diffuses along every path away from
its point of origin.
In 1973, Stephen Hawking began investigating what effect the uncertainty
principle would have on a particle in the curved space-time near a black hole. He
found that the black hole would not be completely black. The uncertainty
principle would allow particles to leak out of the black hole at a steady rate.
obvious. The Feynman sum over histories says that particles can take any path
through space-time. Thus it is possible for a particle to travel faster than light.
In 1983, Stephen Hawking proposed that the sum of histories for the
universe should not be taken over histories in real time. Rather, it should be
taken over histories in imaginary time that were closed in on themselves, like the
beginning or end, what happened to them would be determined entirely by the
laws of physics. This means, what happened in imaginary time could be
calculated. “And if you know the history of the universe in imaginary time, you
can calculate how it behaves in real time. In this way, you could hope to get a
complete unified theory, one that would predict everything in the universe.
Imaginary time is a concept that Hawking has made a particular advance
in as a physicist. It seems obvious that the universe has a unique history, yet
since the discovery of quantum mechanics, we have to consider the universe as
having every possible history. To grasp the concept of imaginary time, think of
right. Then think of lines going 90. from the horizontal line of real time. These
lines, which are at right angles to real time, represent imaginary time. The
importance of imaginary time lies in the fact that the universe is curved in on
itself, leading to singularities. At the singularities, the equations of physics cannot
be defines, thus one cannot predict what will happen. But the imaginary time
direction is at right angles to real time. This means that it behaves in a similar
curvature of space can lead to the three directions and the imaginary time
direction meeting up around the back. These would form a closed surface, like
the surface of the earth. Stephen Hawking as a physicist has many much
progress in the use of imaginary time in the way the field of physics thinks.