Parallel Worlds (17 page)

PHASES OF THE UNIVERSE

Perhaps the greatest
contribution of the WMAP satellite is that it gives scientists confidence that
they are headed toward a "Standard Model" of cosmology. Although huge
gaps still exist, astrophysicists are beginning to see outlines of a standard
theory emerging from the data. According to the picture we are putting together
now, the evolution of the universe proceeded in distinct stages as it cooled.
The transition from these stages represents the breaking of a symmetry and the
splitting off of a force of nature. Here are the phases and milestones as we
know them today:

1.
  
Before 10
^-43
seconds—Planck era

Almost nothing
is certain about the Planck era. At the Planck energy (i0
¹⁹
billion
electron volts), the gravitational force was as strong as the other quantum
forces. As a consequence, the four forces of the universe were probably unified
into a single "superforce." Perhaps the universe existed in a perfect
phase of "nothingness," or empty higher-dimensional space. The
mysterious symmetry that mixes all four forces, leaving the equations the same,
is most likely "super- symmetry" (for a discussion of supersymmetry,
see chapter 7). For reasons unknown, this mysterious symmetry that unified all
four forces was broken, and a tiny bubble formed, our embryonic universe,
perhaps as the result of a random, quantum fluctuation. This bubble was the
size of the "Planck length," which is 10
^-33
centimeters.

2.
  
10
^-43
seconds—GUT era

Symmetry
breaking occurred, creating a rapidly expanding bubble. As the bubble
inflated, the four fundamental forces rapidly split off from each other.
Gravity was the first force to be split off from the other three, releasing a
shock wave throughout the universe. The original symmetry of the superforce was
broken down to a smaller symmetry, perhaps containing the GUT symmetry SU(5).
The remaining strong, weak, and electromagnetic interactions were still
unified by this GUT symmetry. The universe inflated by an enormous factor,
perhaps i0
⁵⁰
, during this phase, for reasons that are not understood,
causing space to expand astronomically faster than the speed of light. The
temperature was 10
³²
degrees.

3.
   
io
^-34
seconds—end of inflation

The temperature
dropped to i0
²⁷
degrees as the strong force split off from the other
two forces. (The GUT symmetry group broke down into SU(3)
X
SU(2)
X
U(i).) The
inflationary period ended, allowing the universe to coast in a standard
Friedmann expansion. The universe consisted of a hot plasma "soup"
of free quarks, gluons, and leptons. Free quarks condensed into the protons and
neutrons of today. Our universe was still quite small, only the size of the
present solar system. Matter and antimatter were annihilated, but the tiny
excess of matter over antimatter (one part in a billion) left behind the matter
we see around us today. (This is the energy range that we hope will be
duplicated in the next few years by the particle accelerator the Large Hadron
Collider.)

4.
  
3 minutes—nuclei form

Temperatures
dropped sufficiently for nuclei to form without being ripped apart from the
intense heat. Hydrogen fused into helium (creating the current 75 percent
hydrogen/25 percent helium ratio found today). Trace amounts of lithium were
formed, but the fusion of higher elements stopped because nuclei with 5
particles were too unstable. The universe was opaque, with light being
scattered by free electrons. This marks the end of the primeval fireball.

5.
  
380,000 years—atoms are born

The temperature
dropped to 3,000 degrees Kelvin. Atoms formed as electrons settled around
nuclei without being ripped apart by the heat. Photons could now travel freely
without being absorbed. This is the radiation measured by COBE and WMAP. The
universe, once opaque and filled with plasma, now became transparent. The sky,
instead of being white, now became black.

6.
  
1 billion years—stars condense

The temperature
dropped to i8 degrees. Quasars, galaxies, and galactic clusters began to
condense, largely as a by-product of tiny quantum ripples in the original
fireball. Stars began to "cook" the light elements, like carbon,
oxygen, and nitrogen. Exploding stars spewed elements beyond iron into the
heavens. This is the farthest era that can be probed by the Hubble space
telescope.

7.
  
6.5 billion years—de Sitter expansion

The Friedmann
expansion gradually ended, and the universe began to accelerate and enter an
accelerating phase, called the de Sitter expansion, driven by a mysterious
antigravity force that is still not understood.

8. 13.7 billion years—today

The present. The
temperature has dropped to 2.7 degrees. We see the present universe of
galaxies, stars, and planets. The universe is continuing to accelerate in a
runaway mode.

THE FUTURE

Although
inflation is the theory today that has the power to explain such a wide range
of mysteries about the universe, this does not prove that it is correct. (In
addition, rival theories have recently been proposed, as we see in chapter 7.)
The supernova result has to be checked and rechecked, taking into account
factors such as dust and anomalies in the production of supernovae. The
"smoking gun" that would finally verify or disprove the inflationary
scenario are "gravity waves" that were produced at the instant of the
big bang. These gravity waves, like the microwave background, should still be
reverberating throughout the universe and may actually be found by gravity wave
detectors, as we see in chapter 9. Inflation makes specific predictions about
the nature of these gravity waves, and these gravity wave detectors should find
them.

But one of the
most intriguing predictions of inflation cannot be directly tested, and that is
the existence of "baby universes" existing in a multiverse of
universes, each one obeying a slightly different set of physical laws. To
understand the full implications of the multi- verse, it is important to first
understand that inflation takes full advantage of the bizarre consequences of
both Einstein's equations and the quantum theory. In Einstein's theory, we have
the possible existence of multiple universes, and in the quantum theory, we
have the possible means of tunneling between them. And within a new framework
called M-theory, we may have the final theory that can settle these questions
about parallel universes and time travel, once and for all.

Inside every black hole that collapses may lie the seeds of a
new expanding universe.

—Sir Martin Rees

Black holes may be apertures to elsewhen. Were we to plunge
down a black hole, we would re-emerge, it is conjectured, in a different part
of the universe and in another epoch in time . . . Black holes may be
entrances to Wonderlands. But are there Alices or white rabbits?

—Carl Sagan

General relativity
is like a
Trojan horse. On the surface, the theory is magnificent. With a few simple
assumptions, one can obtain the general features of the cosmos, including the
bending of starlight and the big bang itself, all of which have been measured
to astonishing accuracy. Even inflation can be accommodated if we insert a
cosmological constant by hand into the early universe. These solutions give us
the most compelling theory of the birth and death of the universe.

But lurking
inside the horse, we find all sorts of demons and goblins, including black
holes, white holes, wormholes, and even time machines, which defy common sense.
These anomalies were considered so bizarre that even Einstein himself thought
that they would never be found in nature. For years, he fought strenuously
against these strange solutions. Today, we know that these anomalies cannot be
easily dismissed. They are an integral part of general relativity. And in fact,
they may even provide a salvation to any intelligent being confronting the big
freeze.

But perhaps the
strangest of these anomalies is the possibility of parallel universes and
gateways connecting them. If we recall the metaphor introduced by Shakespeare
that all the world is a stage, then general relativity admits the possibility
of trapdoors. But instead of leading to the basement, we find that the
trapdoors lead to parallel stages like the original. Imagine the stage of life
consisting of multistory stages, one on top of the next. On each stage, the
actors read their lines and wander around the set, thinking that their stage is
the only one, oblivious of the possibilities of alternate realities. However,
if one day they accidentally fall into a trapdoor, they find themselves thrust
into an entirely new stage, with new laws, new rules, and a new script.

But if an
infinite number of universes can exist, then is life possible in any of these
universes with different physical laws? It is a question that Isaac Asimov
posed in his classic science fiction tale
The
Gods Themselves,
where he created a parallel universe with a nuclear force
different from our own. New intriguing possibilities arise when the usual laws
of physics are repealed and new ones are introduced.

The story begins
in the year 2070, when a scientist, Frederick Hallam, notices that ordinary
tungsten-186 is strangely being converted into a mysterious plutonium-186,
which has too many protons and should be unstable. Hallam theorizes that this
strange pluto- nium-186 comes from a parallel universe where the nuclear force
is much stronger, so it overcomes the repulsion of the protons. Since this
strange plutonium-186 gives off large amounts of energy in the form of
electrons, it can be harnessed to give fabulous amounts of free energy. This
makes possible the celebrated Hallam electron pump, which solves Earth's energy
crisis, making him a wealthy man. But there is a price to pay. If enough alien
plutonium-186 enters our universe, then the nuclear force in general will increase
in intensity. This means more energy will be released from the fusion process,
and the Sun will brighten and eventually explode, destroying the entire solar
system!

Meanwhile, the
aliens in the parallel universe have a different perspective. Their universe is
dying. The nuclear force is quite strong in their universe, meaning that the
stars have been consuming hydrogen at an enormous rate and will soon die. They
set up the exchange whereby useless plutonium-i86 is sent to our universe in
exchange for valuable tungsten-i86, which allows them to create the positron
pump, which saves their dying world. Although they realize that the nuclear
force will increase in strength in our universe, causing our stars to explode,
they don't care.

Earth, it seems,
is headed for disaster. Humanity has become addicted to Hallam's free energy,
refusing to believe that the Sun will soon explode. Another scientist comes up
with an ingenious solution to this conundrum. He is convinced that other
parallel universes must exist. He successfully modifies a powerful atom smasher
to create a hole in space that connects our universe to many others. Searching
among them, he finally finds one parallel universe that is empty except for a
"cosmic egg" containing unlimited amounts of energy, but with a
weaker nuclear force.

By siphoning
energy from this cosmic egg, he can create a new energy pump and, at the same
time, weaken the nuclear force in our universe, thus preventing the Sun from
exploding. There is, however, a price to be paid: this new parallel universe
will have its nuclear force increased, causing it to explode. But he reasons
that this explosion will merely cause the cosmic egg to "hatch,"
creating a new big bang. In effect, he realizes, he will become a midwife to a
new expanding universe.

Asimov's science
fiction tale is one of the few to actually use the laws of nuclear physics to
spin a tale of greed, intrigue, and salvation. Asimov was correct in assuming
that changing the strength of the forces in our universe would have disastrous
consequences, that the stars in our universe would brighten and then explode if
the nuclear force was increased in strength. This raises the inevitable question:
are parallel universes consistent with the laws of physics? And if so, what
would be required to enter one?