This is a revolutionary idea. It was long believed
that an infinite universe must be ruled out by Olber's Paradox. Heinrich
Olbers declared in 1826 that the universe must be finite in size because
if it were not, stars would fill every part of the sky, and our nights
would be as bright as our days.
But this is only true if all the stars are close
enough to be seen. If some of them are so far away that their light has
not yet had time to reach us, then Olber's Paradox becomes a useless
guide, and there is no longer proof that the universe has any boundaries
at all. Space, filled with galaxies no different from the ones we can
see, may continue without end.
This raises the most extraordinary possibilities.
Travel far enough, from galaxy to galaxy, and eventually you will find a
planet that is indistinguishable from Earth, with exact duplicates of
you and me!
One would of course have to make a long voyage indeed
to find a planet with such precise characteristics. It would lie at a
tremendously great distance. Ordinary astronomical measuring tools would
be useless to describe it. In fact the closest one is likely to find an
identical twin is an estimated distance in light- years of a number with
a trillion digits.
And the distances at which there might exist,
respectively, a region of space 100 light-years in diameter identical to
the 100 light-years around Earth, and a region identical to our entire
Milky Way, with every atom in the same place, are both gigantic
multiples of the above gigantic number.
Still, in an infinite universe such numbers are
infinitesimal. It must contain an infinite number of parallel Earths and
parallel Milky Ways, scattered at distances unimaginable.
Out there, there are infinite alternate histories.
Everything that can happen does happen, no matter how improbable.
Napoleon won at Waterloo, Albert Gore is President, and Elvis Presley is
still alive. Only the physically impossible is excluded because in this
universe even the remotest worlds must be governed by the same physical
laws that govern ours.
There is no proof that any of this is true, and
perhaps there never will be. But at least it gives new meaning to the
speculation by Cassius in Julius Caesar: ``How many ages hence
shall this our lofty scene be acted o'er, in states unborn, and accents
yet unknown!''
