Parallel Worlds (50 page)

At first, the
idea of creating a universe seems preposterous. After all, as Guth points out,
to create our universe, you would need 10
⁸⁹
photons, 10
⁸⁹
electrons, 10
⁸⁹
positrons, 10
⁸⁹
neutrinos, 10
⁸⁹
antineu- trinos, 10
⁸⁹
protons, and 10
⁸⁹
neutrons. While
this task sounds daunting, Guth reminds us that although the matter/energy
content of a universe is quite large, it is balanced by the negative energy
derived from gravitation. The total net matter/energy may be as little as an
ounce. Guth cautions, "Does this mean that the laws of physics truly
enable us to create a new universe at will? If we tried to carry out this
recipe, unfortunately, we would immediately encounter an annoying snag: since
a sphere of false vacuum 10
^-26
centimeters across has a mass of one
ounce, its density is a phenomenal i0
⁸⁰
grams per cubic centimeter!
... If the mass of the entire observed universe were compressed to false-vacuum
density, it would fit in a volume smaller than an atom!" The false vacuum
would be the tiny region of space-time where an instability arises and a rift
occurs in space- time. It may only take a few ounces of matter within the false
vacuum to create a baby universe, but this tiny amount of matter has to be
compressed down to an astronomically small distance.

There may be
still another way to create a baby universe. One might heat up a small region
of space to i0
²⁹
degrees K, and then rapidly cool it down. At this
temperature, it is conjectured that space- time becomes unstable; tiny
bubble-universes would begin to form, and a false vacuum might be created.
These tiny baby universes, which form all the time but are short-lived, may
become real universes at that temperature. This phenomenon is already familiar
with ordinary electric fields. (For example, if we create a large enough
electric field, the virtual electron-antielectron pairs that constantly pop out
in and out of the vacuum can suddenly become real, allowing these particles to
spring into existence. Thus, concentrated energy in empty space can transform
virtual particles into real ones. Similarly, if we apply enough energy at a
single point, it is theorized that virtual baby universes may spring into
existence, appearing out of nowhere.)

Assuming that
such an unimaginable density or temperature can be achieved, the formation of a
baby universe might look as follows. In our universe, powerful laser beams and
particle beams may be used to compress and heat a tiny amount of matter to
fantastic energies and temperatures. We would never see the baby universe as
it begins to form, since it expands on the "other side" of the
singularity, rather than in our universe. This alternate baby universe would
potentially inflate in hyperspace via its own antigravity force and
"bud" off our universe. We will, therefore, never see a new universe
is forming on the other side of the singularity. But a wormhole would, like an
umbilical cord, connect us with the baby universe.

There is a
certain amount of danger, however, in creating a universe in an oven. The
umbilical cord connecting our universe with the baby universe would eventually
evaporate and create Hawking radiation equivalent to a 500-kiloton nuclear
explosion, roughly twenty-five times the energy of the Hiroshima bomb. So there
would be a price to pay for creating a new universe in an oven.

One last problem
with this scenario of creating a false vacuum is that it would be easy for the
new universe to simply collapse into a black hole, which, we recall, we assumed
would be lethal. The reason for this is Penrose's theorem, which states that, for
a wide variety of scenarios, any large concentration of sufficiently large
mass will inevitably collapse into a black hole. Since Einstein's equations are
time-reversal invariant, that is, they can be run either forward or backward in
time, this means that any matter that falls out of our baby universe can be run
backward in time, resulting in a black hole.

A baby universe could be
artificially created by an advanced civilization in several ways. A few ounces
of matter could be concentrated to enormous densities and energies, or matter
could be heated to near the Planck temperature.

Thus, one would
have to be very careful in constructing the baby universe to avoid the Penrose
theorem.

Penrose's
theorem rests on the assumption that the infalling matter is positive in energy
(like the familiar world we see surrounding us). However, the theorem breaks
down if we have negative energy or negative matter. Thus, even for the
inflationary scenario, we need to obtain negative energy to create a baby universe,
just as we would with the transversable wormhole.

STEP SIX: CREATE HUGE ATOM SMASHERS

How can we build
a machine capable of leaving our universe, given unlimited access to high
technology? At what point can we hope to harness the power of the Planck
energy? By the time a civilization has attained type III status, it already has
the power to manipulate the Planck energy, by definition. Scientists would be
able to play with wormholes and assemble enough energy to open holes in space
and time.

There are
several ways in which this might be done by an advanced civilization. As I
mentioned earlier, our universe may be a membrane with a parallel universe just
a millimeter from ours, floating in hyperspace. If so, then the Large Hadron
Collider may detect it within the next several years. By the time we advance
to a type I civilization, we might even have the technology to explore the
nature of this neighboring universe. So the concept of making contact with a
parallel universe may not be such a farfetched idea.

But let us
assume the worst case, that the energy at which quantum gravitational effects
arise
is
the Planck
energy, which is a quadrillion times greater than the energy of the LHC. To
explore the Planck energy, a type III civilization would have to create an atom
smasher of stellar proportions. In atom smashers, or particle accelerators,
subatomic particles travel down a narrow tube. As energy is injected into the
tubing, the particles are accelerated to high energies. If we use huge magnets
to bend the particles' path into a large circle, then particles can be
accelerated to trillions of electron volts of energy. The greater the radius of
the circle, the greater the energy of the beam. The LHC has a diameter of 27
kilometers, which is pushing the limit of the energy available to a type 0.7
civilization.

But for a type
III civilization, the possibility opens up of making an atom smasher the size
of a solar system or even a star system. It is conceivable that an advanced
civilization might fire a beam of subatomic particles into outer space and
accelerate them to the Planck energy. As we recall, with the new generation of
laser particle accelerators, within a few decades physicists might be able to
create a tabletop accelerator capable of achieving 200 GeV (200 billion
electron volts) over a distance of a meter. By stacking these tabletop
accelerators one after the other, it is conceivable that one could attain
energies at which space-time becomes unstable.

If we assume
that future accelerators can boost particles only by 200 GeV per meter, which
is a conservative assumption, we would need a particle accelerator i0
light-years long to reach the Planck energy. Although this is prohibitively
large for any type I or II civilization, it is well within the ability of a
type III civilization. To build such a gargantuan atom smasher, a type III
civilization might either bend the path of the beam into a circle, thereby
saving considerable space, or leave the path stretched out in a line that extends
well past the nearest star.

One might, for
example, build an atom smasher that fires subatomic particles along a circular
path inside the asteroid belt. You would not need to build an expensive
circular piece of tubing, because the vacuum of outer space is better than any
vacuum we can create on Earth. But you would have to build huge magnets, placed
at regular intervals on distant moons and asteroids in the solar system or in
various star systems, which would periodically bend the beam.

When the beam
comes near a moon or asteroid, huge magnets based on the moon would then yank
the beam, changing its direction very slightly. (The lunar or asteroid
stations would also have to refocus the beam at regular intervals, because the
beam would gradually diverge the farther it traveled.) As the beam traveled by
several moons, it would gradually form the shape of an arc. Eventually, the
beam would travel in the approximate shape of a circle. One could also imagine
two beams, one traveling clockwise around the solar system, the other
counterclockwise. When the two beams collided, the energy released by the
matter/antimatter collision would create energies approaching the Planck
energy. (One can calculate that the magnetic fields necessary to bend such a
powerful beam far exceed the technology of today. However, it is conceivable
that an advanced civilization could use explosives to send a powerful surge of
energy through coils to create a huge magnetic pulse. This titanic burst of
magnetic energy could only be released once, since it would likely destroy the
coils, so the magnets would have to be rapidly replaced before the particle
beam returned for the next pass.)

Besides the
horrendous engineering problems of creating such an atom smasher, there is also
the delicate question of whether there is a limit to the energy of a particle
beam. Any energetic beam of particles would eventually collide with the
photons that make up the 2.7-degree background radiation and hence lose energy.
In theory, this might, in fact, bleed so much energy from the beam that there
would be an ultimate ceiling for the energy one could attain in outer space.
This result still has not been checked experimentally. (In fact, there are
indications that energetic cosmic ray impacts have exceeded this maximum
energy, casting doubt on the whole calculation.) However, if it is true, then
a more expensive modification of the apparatus would be required. First, one
might enclose the entire beam in a vacuum tubing with shielding to keep out the
2.7-degree background radiation. Or, if the experiment is done in the far future,
it is possible that the background radiation will be small enough so that it no
longer matters.

STEP SEVEN: CREATE IMPLOSION MECHANISMS

One could also
imagine a second device, based on laser beams and an implosion mechanism. In
nature, tremendous temperatures and pressures are attained by the implosion
method, as when a dying star collapses suddenly under the force of gravity.
This is possible because gravity is only attractive, not repulsive, and hence
the collapse takes place uniformly, so the star is compressed evenly to
incredible densities.

This implosion
method is very difficult to re-create on planet Earth. Hydrogen bombs, for
example, have to be designed like a Swiss watch so that lithium deuteride, the
active ingredient of a hydrogen bomb, is compressed to tens of millions of
degrees to attain Lawson's criteria, at which the fusion process kicks in.
(This is done by detonating an atomic bomb next to the lithium deuteride, and
then focusing the X-ray radiation evenly on the surface of a piece of lithium
deuteride.) This process, however, can only release energy explosively, not in
a controlled fashion.

On Earth,
attempts to use magnetism to compress hydrogen-rich gas have failed, mainly
because magnetism does not compress gas uniformly. Because we have never seen a
monopole in nature, magnetic fields are dipolar, like Earth's magnetic field.
As a result, they are horribly nonuniform. Using them to squeeze gas is like
trying to squeeze a balloon. Whenever you squeeze one end, the other end of the
balloon bulges out.

Another way of
controlling fusion might be to use a battery of laser beams, arranged along the
surface of a sphere, so that the beams are fired radially onto a tiny pellet of
lithium deuteride at the center. For example, at the Livermore National
Laboratory, there is a powerful laser/fusion device used to simulate nuclear
weapons. It fires a series of laser beams horizontally down a tunnel. Then mirrors
based at the end of the tunnel carefully reflect each beam, so that the beams
are directed radially onto a tiny pellet. The surface of the pellet is
immediately vaporized, causing the pellet to implode and creating huge temperatures.
In this fashion, fusion has actually been seen inside the pellet (although the
machine consumes more energy than it creates and hence is not commercially
viable).

Similarly, one
can envision a type III civilization building large banks of laser beams on
asteroids and moons of various star systems. This battery of lasers would then
fire at once, releasing a series of powerful beams that converge at a single
point, creating temperatures at which space and time become unstable.

In principle,
there is no theoretical limit to the amount of energy that one can place on a
laser beam. However, there are practical problems with creating extremely
high-powered lasers. One of the main problems is the stability of lasing
material, which will often overheat and crack at high energies. (This can be
remedied by driving the laser beam by an explosion that occurs only once, such
as nuclear detonations.)

The purpose of
firing this spherical bank of laser beams is to heat a chamber so that the
false vacuum is created inside, or to implode and compress a set of plates to
create negative energy via the Casimir effect. To create such a negative-energy
device, one would need to compress a set of spherical plates to within the
Planck length, which is i0
^-
33 centimeters. Because the distance
separating atoms is 10
^-8
centimeters, and the distance separating
the protons and neutrons in the nucleus is i0
^-i3
cm, you see that
the compression of these plates must be enormous. Because the total wattage
that one can amass on a laser beam is essentially unlimited, the main problem
is to create an apparatus that is stable enough to survive this enormous compression.
(Since the Casimir effect creates a net attraction between the plates, we will
also have to add charges to the plates to prevent them from collapsing.) In
principle, a wormhole will develop within the spherical shells connecting our
dying universe with a much younger, much hotter universe.