PREFACE xvi,
The first are what I call Class I impossibilities. These are technologies that are impossible today but that do not violate the known laws
of physics. So they might be possible in this century, or perhaps the
next, in modified form. They include teleportation, antimatter engines,
certain forms of telepathy, psychokinesis, and invisibility.
The second category is what I term Class II impossibilities. These
are technologies that sit at the very edge of our understanding of the
physical world. If they are possible at all, they might be realized on a
scale of millennia to millions of years in the future. They include time
machines, the possibility of hyperspace travel, and travel through
wormholes.
The final category is what I call Class III impossibilities. These are
technologies that violate the known laws of physics. Surprisingly, there
are very few such impossible technologies. If they do turn out to be
possible, they would represent a fundamental shift in our understanding of physics.
This classification is significant, I feel, because so many technologies in science fiction are dismissed by scientists as being totally impossible, when what they actually mean is that they are impossible for a
primitive civilization like ours. Alien visitations, for example, are usually considered impossible because the distances between the stars are
so vast. While interstellar travel for our civilization is clearly impossible, it may be possible for a civilization centuries to thousands or
millions of years ahead of ours. So it is important to rank such "impossibilities." Technologies that are impossible for our current civilization
are not necessarily impossible for other types of civilizations. Statements about what is possible and impossible have to take into account
technologies that are millennia to millions of years ahead of ours.
Carl Sagan once wrote, "What does it mean for a civilization to be
a million years old? We have had radio telescopes and spaceships for a
few decades; our technical civilization is a few hundred years old ...
an advanced civilization millions of years old is as much beyond us as
we are beyond a bush baby or a macaque."
In my own research I focus professionally on trying to complete
Einstein's dream of a "theory of everything." Personally, I find it quite
The first are what I call Class I impossibilities. These are technologies that are impossible today but that do not violate the known laws
of physics. So they might be possible in this century, or perhaps the
next, in modified form. They include teleportation, antimatter engines,
certain forms of telepathy, psychokinesis, and invisibility.
The second category is what I term Class II impossibilities. These
are technologies that sit at the very edge of our understanding of the
physical world. If they are possible at all, they might be realized on a
scale of millennia to millions of years in the future. They include time
machines, the possibility of hyperspace travel, and travel through
wormholes.
The final category is what I call Class III impossibilities. These are
technologies that violate the known laws of physics. Surprisingly, there
are very few such impossible technologies. If they do turn out to be
possible, they would represent a fundamental shift in our understanding of physics.
This classification is significant, I feel, because so many technologies in science fiction are dismissed by scientists as being totally impossible, when what they actually mean is that they are impossible for a
primitive civilization like ours. Alien visitations, for example, are usually considered impossible because the distances between the stars are
so vast. While interstellar travel for our civilization is clearly impossible, it may be possible for a civilization centuries to thousands or
millions of years ahead of ours. So it is important to rank such "impossibilities." Technologies that are impossible for our current civilization
are not necessarily impossible for other types of civilizations. Statements about what is possible and impossible have to take into account
technologies that are millennia to millions of years ahead of ours.
Carl Sagan once wrote, "What does it mean for a civilization to be
a million years old? We have had radio telescopes and spaceships for a
few decades; our technical civilization is a few hundred years old ...
an advanced civilization millions of years old is as much beyond us as
we are beyond a bush baby or a macaque."
In my own research I focus professionally on trying to complete
Einstein's dream of a "theory of everything." Personally, I find it quite