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The idea, arising from Einstein's general theory of
relativity, is that space can be folded like a piece of paper. A journey
along a flat stretch of this paper, corresponding to a voyage through
ordinary space, could take many years. But fold the paper so that two
points on it are adjacent, and one could go straight through one of these
tiny holes. And tiny they are. Not even a worm could get through them, far
less a spaceship containing humans. These holes are believed to be a mere
billionth of a trillionth of a trillionth of an inch, 33 powers of ten
smaller than a human thumbnail, the smallest size that anything in the
Universe can be.
Furthermore they are constantly appearing and
disappearing like ripples on an ocean. Imagine the difficulties of using
the London Underground if the entrances to stations behaved in this way!
But according to Krasnikov, not all wormholes are like
this. There is nothing in physics to prevent them from being stable and
large enough for spaceships to get through. They would be like the ``stargates''
or ``entry points to hyperspace'' that science fiction writers use to
convey their characters swiftly between distant solar systems.
No one knows if Krasnikov's large and stable wormholes
actually exist, and with current technology there seems to he no way to
find out. All he has done is to calculate with elaborate maths that they
can exist, and there is a principle in physics which says anything that
can happen does happen.
And even if he is right, awkward snags are liable to
occur. There may be no large wormholes in the vicinity of Earth. Perhaps
to reach one we might have to travel to as far away as another star, which
would make the journey to the wormhole pointless. Or we may find that a
wormhole journey would take us backwards in time, so that one could return
to Earth after a trip to Alpha Centauri and find oneself back in the
1950s, able to murder one's parents before they met! Or perhaps
Krasnikov's wormholes are the entrances to an unimaginable labyrinth of
other universes. Once in it, you might never be able to return to where,
or when, you started.
Still, I suspect that the feasibility of instantaneous
space travel, because of its potential importance in opening up the
Universe to Mankind, is going to be one of the biggest scientific
challenges of the 21st century. It could be the equivalent of the search
for longitude two centuries ago.
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