TIME TRAVEL 221
not be easily dismissed (as Einstein thought). In 1974 Hawking also
proved that black holes are not entirely black, but gradually emit radiation, now known as Hawking radiation, because radiation can tunnel
through the gravity field of even a black hole. This paper was the first
major application of the quantum theory to relativity theory, and it
represents his best known work.
As predicted, ALS slowly led to paralysis of his hands, legs, and
even his vocal cords, but at a much slower rate than the doctors had
originally predicted. As a result, he has passed many of the usual milestones of normal people, fathering three children (he is now a grandfather), divorcing his first wife in 1991, four years later marrying the
wife of the man who created his voice synthesizer, and filing for divorce from his second wife in 2006. In 2007 he made headlines when
he went aboard a jet airplane that sent him into weightlessness, fulfilling a lifelong wish of his. His next goal is to blast off into outer space.
Today he is almost totally paralyzed in his wheelchair, communicating to the outside world via movements of his eyes. Yet even with
this crushing disability, he still cracks jokes, writes papers, gives lectures, and engages in controversy. He is more productive moving his
two eyes than are teams of scientists who have full control over their
bodies. (His colleague at Cambridge University, Sir Martin Rees, who
was appointed Astronomer Royal by the Queen, once confided to me
that Hawking's disability does prevent him from doing the tedious calculations necessary to keep at the top of his game. So instead he concentrates on generating new and fresh ideas rather than cranking out
difficult calculations, which can be done by his students.)
In 1990 Hawking read papers of his colleagues proposing their
version of a time machine, and he was immediately skeptical. His intuition told him that time travel was not possible because there are no
tourists from the future. If time travel were as common as taking a
Sunday picnic in the park, then time travelers from the future should
be pestering us with their cameras, asking us to pose for their picture
albums.
Hawking also raised a challenge to the world of physics. There
ought to be a law, he proclaimed, making time travel impossible. He
not be easily dismissed (as Einstein thought). In 1974 Hawking also
proved that black holes are not entirely black, but gradually emit radiation, now known as Hawking radiation, because radiation can tunnel
through the gravity field of even a black hole. This paper was the first
major application of the quantum theory to relativity theory, and it
represents his best known work.
As predicted, ALS slowly led to paralysis of his hands, legs, and
even his vocal cords, but at a much slower rate than the doctors had
originally predicted. As a result, he has passed many of the usual milestones of normal people, fathering three children (he is now a grandfather), divorcing his first wife in 1991, four years later marrying the
wife of the man who created his voice synthesizer, and filing for divorce from his second wife in 2006. In 2007 he made headlines when
he went aboard a jet airplane that sent him into weightlessness, fulfilling a lifelong wish of his. His next goal is to blast off into outer space.
Today he is almost totally paralyzed in his wheelchair, communicating to the outside world via movements of his eyes. Yet even with
this crushing disability, he still cracks jokes, writes papers, gives lectures, and engages in controversy. He is more productive moving his
two eyes than are teams of scientists who have full control over their
bodies. (His colleague at Cambridge University, Sir Martin Rees, who
was appointed Astronomer Royal by the Queen, once confided to me
that Hawking's disability does prevent him from doing the tedious calculations necessary to keep at the top of his game. So instead he concentrates on generating new and fresh ideas rather than cranking out
difficult calculations, which can be done by his students.)
In 1990 Hawking read papers of his colleagues proposing their
version of a time machine, and he was immediately skeptical. His intuition told him that time travel was not possible because there are no
tourists from the future. If time travel were as common as taking a
Sunday picnic in the park, then time travelers from the future should
be pestering us with their cameras, asking us to pose for their picture
albums.
Hawking also raised a challenge to the world of physics. There
ought to be a law, he proclaimed, making time travel impossible. He