Parallel Worlds (49 page)

This is not a
trivial academic exercise. Any civilization about to leave the universe will
necessarily have to compute the conditions on the other side of the universe.
Einstein's equations are notoriously difficult because, to calculate the
curvature of space at any point, you have to know the location of all objects
in the universe, each of which contributes to the bending of space. You also
have to know the quantum corrections to the black hole, which at present are impossible
to calculate. Since this is vastly too difficult for our computers, today
physicists usually approximate a black hole by studying a universe dominated by
a single collapsed star. To arrive at a more realistic understanding of the
dynamics within the event horizon of a black hole or near the mouth of a
wormhole, we necessarily have to know the location and energy content of all
the nearby stars and compute quantum fluctuations. Again, this is prohibitively
difficult. It is hard enough to solve the equations for a single star in an
empty universe, let alone billions of galaxies floating in an inflated
universe.

That is why any
civilization that attempts to make the journey through a wormhole would have to
have computational power far beyond that available to a type 0.7 H civilization
like ours. Perhaps the minimum civilization with the energy and information
content to seriously consider making the jump would be a type III Q.

It is also
conceivable that intelligence may spread beyond the confines of the Kardashev
classification. As Sir Martin Rees says, "It's quite conceivable that,
even if life now exists only here on Earth, it will eventually spread through
the galaxy and beyond. So life may not forever be an unimportant trace
contaminant of the universe, even though it now is. In fact, I find it a rather
appealing view, and I think it could be salutary if it became widely
shared." But he warns us, "If we snuffed ourselves out, we'd be
destroying genuine cosmic potentialities. So even if one believes that life is
unique to the earth now, then that doesn't mean that life is forever going to
be a trivial piece of the universe."

How would an
advanced civilization contemplate leaving their dying universe? It would have
to overcome a series of large obstacles.

STEP ONE: CREATE AND TEST A THEORY OF
EVERYTHING

The first hurdle for a civilization hoping to leave the
universe would be to complete a theory of everything. Whether it is string
theory or not, we must have a way to reliably calculate quantum corrections to
Einstein's equations, or else none of our theories are useful.

Fortunately,
because M-theory is rapidly advancing, with some of the best minds on the
planet working on this question, we shall know if it is truly the theory of
everything or a theory of nothing fairly rapidly, within a few decades or
possibly less.

Once a theory of
everything or a theory of quantum gravity has been found, we have to verify the
consequences of this theory using advanced technology. Several possibilities
exist, including building large atom smashers to create super particles, or
even huge gravity wave detectors based in space or on different moons
throughout the solar system. (Moons are quite stable for long periods of time,
free of erosion and atmospheric disturbances, so a planetary system of gravity
wave detectors should be able to probe the details of the big bang, resolving
any questions we may have about quantum gravity and creating a new universe.)

Once a theory of
quantum gravity is found, and huge atom smashers and gravity wave detectors
have confirmed its correctness, then we can begin to answer some essential
questions concerning Einstein's equations and wormholes:

1.
  
Are wormholes stable?

When passing through a Kerr rotating black hole, the problem
is that your very presence disturbs the black hole; it may collapse before you
make a complete passage through the Einstein-Rosen bridge. This stability
calculation has to be redone in light of quantum corrections, which may change
the calculation entirely.

2.
  
Are there divergences?

If we pass through a transversable wormhole connecting two
time eras, then the buildup of radiation surrounding the wormhole entrance may
become infinite, which would be disastrous. (This is because radiation can
pass through the wormhole, go back in time, and return after many years to
enter the wormhole a second time. This process can be repeated an infinite
number of times, leading to an infinite buildup of radiation. This problem can
be solved, however, if the many-worlds theory holds, so that the universe
splits every time radiation passes through the wormhole, and there is no
infinite buildup of radiation. We need a theory of everything to settle this
delicate question.)

3.
Can we find large quantities of negative energy?
Negative energy,
a key ingredient that can open up and stabilize wormholes, is already known to
exist but only in small quantities. Can we find sufficient quantities of it to
open and stabilize a worm- hole?

Assuming that
the answers to these questions can be found, then an advanced civilization may
begin to seriously contemplate how to leave the universe, or face certain
extinction. Several alternatives exist.

STEP TWO: FIND NATURALLY OCCURRING
WORMHOLES AND WHITE HOLES

Wormholes,
dimensional gateways, and cosmic strings may exist naturally in outer space. At
the instant of the big bang, when there was a huge amount of energy released
into the universe, wormholes and cosmic strings may have formed naturally. The
inflation of the early universe might then have expanded these wormholes to
macroscopic size. In addition, there is the possibility that exotic matter or
negative matter exists naturally in outer space. This would help enormously in
any effort to leave a dying universe. However, there is no guarantee that such
objects exist in nature. No one has ever seen any of these objects, and it is
simply too risky to bet the fate of all intelligent life on this assumption.

Next, there is
the possibility that "white holes" may be found by scanning the
heavens. A white hole is a solution of Einstein's equations in which time is
reversed, so that objects are ejected from a white hole in the same way that
objects are sucked into a black hole. A white hole might be found at the other
end of a black hole, so that matter entering a black hole eventually comes out
the white hole. So far, all astronomical searches have found no evidence of
white holes, but their existence might be confirmed or disproved with the next
generation of space-based detectors.

STEP THREE: SEND PROBES THROUGH A BLACK
HOLE

There are
decided advantages to using such black holes as worm- holes. Black holes, as we
have come to discover, are quite plentiful in the universe; if one can solve
the numerous technical problems, they will have to be seriously considered by
any advanced civilization as an escape hatch from our universe. Also, in
passing through a black hole, we are not bound by the limitation that we cannot
go backward in time to a time before the creation of the time machine. The
worm- hole in the center of the Kerr ring may connect our universe to quite
different universes or different points in the same universe. The only way to
tell would be to experiment with probes and use a supercomputer to calculate
the distribution of masses in the universes and calculate quantum corrections
to Einstein's equations through the wormhole.

Currently, most
physicists believe that a trip through a black hole would be fatal. However,
our understanding of black hole physics is still in its infancy, and this
conjecture has never been tested. Assume, for the sake of argument, that a trip
through a black hole might be possible, especially a rotating Kerr black hole. Then
any advanced civilization would give serious thought to probing the interior
of black holes.

Since a trip
through a black hole would be a one-way trip, and because of the enormous
dangers found near a black hole, an advanced civilization would likely try to
locate a nearby stellar black hole and first send a probe through it. Valuable
information could be sent back from the probe until it finally crossed the
event horizon and all contact was lost. (A trip past the event horizon is
likely to be quite lethal because of the intense radiation field surrounding
it. Light rays falling into a black hole will be blueshifted and thereby will
gain in energy as they get close to the center.) Any probe passing near the
event horizon would have to be properly shielded against this intense barrage
of radiation. In addition, this may destabilize the black hole itself, so that
the event horizon would become a singularity, thereby closing the wormhole.
The probe would determine precisely how much radiation there is near the event
horizon and whether the wormhole could remain stable in spite of all this
energy flux.

The data from
the probe before it entered the event horizon would have to be radioed back to
nearby spaceships, but therein lies another problem. To an observer on one of
those spaceships, the probe would seem to be slowing down in time as it got
closer to the event horizon. At it entered the event horizon, the probe in fact
would seem to be frozen in time. To avoid this problem, probes would have to
radio their data a certain distance away from the event horizon, or else even
the radio signals would be redshifted so badly that the data would be
unrecognizable.

STEP FOUR: CONSTRUCT A BLACK HOLE IN SLOW
MOTION

Once the
characteristics near the event horizon of black holes are carefully ascertained
by probes, the next step might be to actually create a black hole in slow
motion for experimental purposes. A type III civilization might try to
reproduce the results suggested in Einstein's paper—that black holes can never
form from swirling masses of dust and particles. Einstein tried to show that a
collection of revolving particles will not reach the Schwarzschild radius by itself
(and as a result black holes were impossible).

Swirling masses,
by themselves, might not contract to a black hole. But this leaves open the
possibility that one may artificially inject new energy and matter slowly into
the spinning system, forcing the masses to gradually pass within the
Schwarzschild radius. In this way, a civilization could manipulate the
formation of a black hole in a controlled way.

For example, one
can imagine a type III civilization corralling neutron stars, which are about
the size of Manhattan but weigh more than our Sun, and forming a swirling
collection of these dead stars. Gravity would gradually bring these stars
closer together. But they would never hit the Schwarzschild radius, as Einstein
showed. At this point, scientists from this advanced civilization might carefully
inject new neutron stars into the mix. This might be enough to tip the balance,
causing this swirling mass of neutron material to collapse to within the
Schwarzschild radius. As a result, the collection of stars would collapse into
a spinning ring, the Kerr black hole. By controlling the speed and radii of the
various neutron stars, such a civilization would make the Kerr black hole open
up as slowly as it wished.

Or, an advanced
civilization might try to assemble small neutron stars together into a single,
stationary mass, until it reached 3 solar masses in size, which is roughly the
Chandrasekhar limit for neutron stars. Beyond this limit, the star would
implode into a black hole by its own gravity. (An advanced civilization would
have to be careful that the creation of a black hole did not set off a
supernovalike explosion. The contraction to the black hole would have to be
done very gradually and very precisely.)

Of course, for
anyone passing through an event horizon, it is guaranteed to be a one-way trip.
But for an advanced civilization facing the certainty of extinction, a one-way
trip might be the only alternative. Still, there is the problem of radiation
as one passes the event horizon. Light beams that follow us through the event
horizon become more energetic as they increase in frequency. This would likely
cause a rain of radiation that would be deadly to any astronaut who passed
through the event horizon. Any advanced civilization would have to calculate
the precise amount of such radiation and build proper shielding to prevent
being fried.

Last, there is
the stability problem: will the wormhole at the center of the Kerr ring be
sufficiently stable to fall completely through? The mathematics of this
question are not totally clear, since we would have to use a quantum theory of
gravity to do a proper calculation. It may turn out that the Kerr ring is
stable under certain very restrictive conditions as matter falls through the
wormhole. This issue would have to be carefully resolved using the mathematics
of quantum gravity and experiments on the black hole itself.

In summary,
passage through a black hole would doubtless be a very difficult and dangerous
journey. Theoretically, it cannot be ruled out until extensive experimentation
is performed and a proper calculation is made of all quantum corrections.

STEP FIVE: CREATE A BABY UNIVERSE

So far, we have
assumed that it might be possible to pass through a black hole. Now let's
assume the reverse, that black holes are too unstable and too full of lethal
radiation. One might then try an even more difficult path: to create a baby
universe. The concept of an advanced civilization creating an escape hatch to
another universe has intrigued physicists like Alan Guth. Because the
inflationary theory is so crucially dependent on the creation of the false
vacuum, Guth has wondered if some advanced civilization might artificially
create a false vacuum and create a baby universe in the laboratory.