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PHVSICS OF THE IMPOSSIBLE
If we could journey back into the past, history would be impossible to write. As soon as a historian recorded the history of the past,
someone could go back into the past and rewrite it. Not only would
time machines put historians out of business, but they would enable us
to alter the course of time at will. If, for example, we were to go back
to the era of the dinosaurs and accidentally step on a mammal that
happens to be our ancestor, perhaps we would accidentally wipe out
the entire human race. History would become an unending, madcap
Monty Python episode, as tourists from the future trampled over historic events while trying to get the best camera angle.
TIME TRAVEL: PHYSICISTS'
PLAYGROUND
Perhaps the person who has distinguished himself the most on the
dense mathematical equations of black holes and time machines is
cosmologist Stephen Hawking. Unlike other students of relativity who
often distinguish themselves in mathematical physics at an early age,
Hawking was actually not an outstanding student as a youth. He was
obviously extremely bright, but his teachers would often notice that he
was not focused on his studies and never lived up to his full potential.
But a turning point came in 1962, after he graduated from Oxford,
when he first began to notice the symptoms of ALS (amyotrophic lateral sclerosis, or Lou Gehrig's disease). He was rocked by the news
that he was suffering from this incurable motor neuron disease that
would rob him of all motor functions and likely soon kill him. At first
the news was extremely upsetting. What would be the use of getting a
Ph.D.
if he was going to die soon anyway?
But once he got over the initial shock he became focused for the
first time in his life. Realizing that he did not have long to live, he began to ferociously tackle some of the most difficult problems in general
relativity. In the early 1970s he published a landmark series of papers
showing that "singularities" in Einstein's theory (where the gravitational field becomes infinite, like at the center of black holes and at the
instant of the big bang) were an essential feature of relativity and could
PHVSICS OF THE IMPOSSIBLE
If we could journey back into the past, history would be impossible to write. As soon as a historian recorded the history of the past,
someone could go back into the past and rewrite it. Not only would
time machines put historians out of business, but they would enable us
to alter the course of time at will. If, for example, we were to go back
to the era of the dinosaurs and accidentally step on a mammal that
happens to be our ancestor, perhaps we would accidentally wipe out
the entire human race. History would become an unending, madcap
Monty Python episode, as tourists from the future trampled over historic events while trying to get the best camera angle.
TIME TRAVEL: PHYSICISTS'
PLAYGROUND
Perhaps the person who has distinguished himself the most on the
dense mathematical equations of black holes and time machines is
cosmologist Stephen Hawking. Unlike other students of relativity who
often distinguish themselves in mathematical physics at an early age,
Hawking was actually not an outstanding student as a youth. He was
obviously extremely bright, but his teachers would often notice that he
was not focused on his studies and never lived up to his full potential.
But a turning point came in 1962, after he graduated from Oxford,
when he first began to notice the symptoms of ALS (amyotrophic lateral sclerosis, or Lou Gehrig's disease). He was rocked by the news
that he was suffering from this incurable motor neuron disease that
would rob him of all motor functions and likely soon kill him. At first
the news was extremely upsetting. What would be the use of getting a
Ph.D.
if he was going to die soon anyway?
But once he got over the initial shock he became focused for the
first time in his life. Realizing that he did not have long to live, he began to ferociously tackle some of the most difficult problems in general
relativity. In the early 1970s he published a landmark series of papers
showing that "singularities" in Einstein's theory (where the gravitational field becomes infinite, like at the center of black holes and at the
instant of the big bang) were an essential feature of relativity and could