Our journey has taken us from the beginning of time to
the very edge of the Universe. The legacy left us by Albert
Einstein describes a reality far more wonderful and mysterious
than anything we could have dreamt up. Time warps, black holes,
parallel universes, a past and a future that coexist with the present,
none of these are the stuff of science fiction. Nor are they the
results of the wilder speculations of a nutty minority on the fringes
of the scientific establishment. All these exotica are the results
of years of slow progress, some of which are now regarded as
facts. For instance, the slowing down of time due to gravity is not
‘just a theory which may turn out to be wrong tomorrow when
something better comes along’, but is shown to be true on a regular
basis in scientific laboratories. Other ideas, while possibilities,
may not stand the test of time or the continued close scrutiny of
scientists. Sometimes a theory is shown to be just plain wrong if
its predictions conflict with the results of an experiment, or it may be replaced with a better theory which explains more phenomena
and gives us a deeper understanding of nature.
We are now reasonably confident that black holes exist. This
is despite the fact that we have never come face to face with one.
The evidence for them is so convincing that we cannot find an
alternative explanation. Not only are black holes an inevitable
consequence of the theory of general relativity but we see their
unmistakable signature through our telescopes.
Wormholes are a completely different matter. They are
also allowed by the equations of general relativity which give
a description of them as theoretical entities. But, unlike black
holes, wormholes remain theoretical curiosities with not a shred of
evidence from astronomy for their existence in the real Universe.
I am sorry to be spoiling all the fun by pouring cold water on
objects that I have not even discussed yet. Maybe this is just my
defence mechanism against accusations from other physicists that
I am sailing close to the edge between science fact and science
fiction. Thus in order to justify this chapter to those cynics who
are more conservative in their views I will quote a short passage
from the beginning of Matt Visser’s book Lorentzian Wormholes:
from Einstein to Hawking with my additions in square brackets:
“Even though wormhole physics is speculative, the fundamental
underlying physical theories, those of general relativity and quantum
[mechanics], are both well tested and generally accepted. [Even] if we
succeed in painting ourselves into a corner surrounded by disastrous
inconsistencies and imponderables, the hope is that the type of disaster
encountered will be interesting and informative.”
Thus it may well be that wormholes do not exist, but at the
very least their study might help us to understand a little better
the way our Universe works. Oh, and in case you are wondering,
they have nothing whatsoever to do with worms.