Parallel Worlds (44 page)

Odin, the father of the gods, will assemble his brave
warriors for

the last time in
Valhalla for the final conflict. Eventually, as the gods die one by one, the
evil god Surtur will breathe fire and brimstone, igniting a gigantic inferno
that will engulf both heaven and earth. As the entire universe is plunged into
flames, the earth sinks into the oceans, and time itself stops.

But out of the
great ash, a new beginning stirs. A new earth, unlike the old, gradually rises
out of the sea, as new fruits and exotic plants spring forth copiously from the
fertile soil, giving birth to a new race of humans.

The Viking
legend of a gigantic freeze followed by flames and a final battle presents a
grim tale of the end of the world. In mythologies around the world, similar
themes can be found. The end of the world is accompanied by great climactic
catastrophes, usually a great fire, earthquakes, or a blizzard, followed by the
final battle between good and evil. But there is also a message of hope. Out
of the ashes comes renewal.

Scientists,
facing the cold laws of physics, must now confront similar themes. Hard data,
rather than mythology whispered around campfires, dictates how scientists view
the final end of the universe. But similar themes may prevail in the scientific
world. Among the solutions of Einstein's equations we also see possible futures
involving freezing cold, fire, catastrophe, and an end to the universe. But
will there be a final rebirth?

According to the
picture emerging from the WMAP satellite, a mysterious antigravity force is
accelerating the expansion of the universe. If it continues for billions or
trillions of years, the universe will inevitably reach a big freeze similar to
the blizzard foretelling the twilight of the gods, ending all life as we know
it. This antigravity force pushing the universe apart is proportional to the
volume of the universe. Thus, the larger the universe becomes, the more
antigravity there is to push the galaxies apart, which in turn increases the
volume of the universe. This vicious cycle repeats itself endlessly, until the
universe enters a runaway mode and grows exponentially fast.

Eventually, this
will mean that thirty-six galaxies in the local group of galaxies will make up
the entire visible universe, as billions of neighboring galaxies speed past our
event horizon. With the space between galaxies expanding faster than the speed
of light, the universe will become terribly lonely. Temperatures will plunge,
as the remaining energy is spread thinner and thinner across space. As
temperatures drop to near absolute zero, intelligent species will have to face
their ultimate fate: freezing to death.

THREE LAWS OF THERMODYNAMICS

If all the world
is a stage, as Shakespeare said, then ultimately there must be an act III. In
act i, we had the big bang and the rise of life and consciousness on Earth. In
act 2, perhaps we will live to explore the stars and galaxies. Finally, in act
3, we face the final death of the universe in the big freeze.

Ultimately, we
find that the script must follow the laws of thermodynamics. In the nineteenth
century, physicists formulated the three laws of thermodynamics which govern
the physics of heat and began contemplating the eventual death of the universe.
In 1854, the great German physicist Hermann von Helmholtz realized that the
laws of thermodynamics could be applied to the universe as a whole, meaning
that everything around us, including the stars and galaxies, would eventually
have to run down.

The first law
states that the total amount of matter and energy is conserved. Although energy
and matter may turn into each other (via Einstein's celebrated equation
E =
mc
²
), the total amount of matter and energy can
never be created or destroyed.

The second law
is the most mysterious and most profound. It states that the total amount of
entropy (chaos or disorder) in the universe always increases. In other words,
everything must eventually age and run down. The burning of forests, the
rusting of machines, the fall of empires, and the aging of the human body all
represent the increase of entropy in the universe. It is easy, for example, to
burn a piece of paper. This represents a net increase in total chaos. However,
it is impossible to reassemble the smoke back into paper. (Entropy can be made
to decrease with the addition of mechanical work, as in a refrigerator, but
only in a small local neighborhood; the total entropy for the entire system—the
refrigerator plus all its surroundings—always increases.)

Arthur Eddington
once said about the second law: "The law that entropy always increases—the
Second Law of Thermodynamics— holds, I think, the supreme position among the
laws of Nature ... If your theory is found to be against the Second Law of
Thermodynamics, I can give you no hope; there is nothing for it but to collapse
in deepest humiliation."

(At first, it
seems as if the existence of complex life forms on Earth violates the second
law. It seems remarkable that out of the chaos of the early Earth emerged an
incredible diversity of intricate life forms, even harboring intelligence and
consciousness, lowering the amount of entropy. Some have taken this miracle to
imply the hand of a benevolent creator. But remember that life is driven by the
natural laws of evolution, and that total entropy still increases, because
additional energy fueling life is constantly being added by the Sun. If we
include the Sun and Earth, then the total entropy still increases.)

The third law
states that no refrigerator can reach absolute zero. One may come within a tiny
fraction of a degree above absolute zero, but you can never reach a state of
zero motion. (And if we incorporate the quantum principle, this implies that
molecules will always have a small amount of energy, since zero energy implies
that we know the exact location and velocity of each molecule, which would
violate the uncertainty principle.)

If the second
law is applied to the entire universe, it means that the universe will
eventually run down. The stars will exhaust their nuclear fuel, galaxies will
cease to illuminate the heavens, and the universe will be left as a lifeless
collection of dead dwarf stars, neutron stars, and black holes. The universe
will be plunged in eternal darkness.

Some
cosmologists have tried to evade this "heat death" by appealing to
an oscillating universe. Entropy would increase continually as the universe
expanded and eventually contracted. But after the big crunch, it is not clear
what would become of the entropy in the universe. Some have entertained the
idea that perhaps the universe might simply repeat itself exactly in the next
cycle. More realistic is the possibility that the entropy would be carried
over to the next cycle, which means that the lifetime of the universe would
gradually lengthen for each cycle. But no matter how one looks at the question,
the oscillating universe, like the open and closed universes, will eventually
result in the destruction of all intelligent life.

THE BIG CRUNCH

One of the first
attempts to apply physics to explain the end of the universe was a paper
written in 1969 by Sir Martin Rees entitled, "The Collapse of the
Universe: An Eschatological Study." Back then, the value of Omega was
still largely unknown, so he assumed it was two, meaning that the universe
would eventually stop expanding and die in a big crunch rather than a big
freeze.

He calculated
that the expansion of the universe will eventually grind to a halt, when the
galaxies are twice as far away as they are today, when gravity finally
overcomes the original expansion of the universe. The redshift we see in the
heavens will become a blueshift, as the galaxies begin to race toward us.

In this version,
about 50 billion years from now, catastrophic events will take place, signaling
the final death throes of the universe. One hundred million years before the
final crunch, the galaxies in the universe, including our own Milky Way
galaxy, will begin to collide with each other and eventually merge. Oddly, Rees
discovered that individual stars will dissolve even before they began to collide
with each other, for two reasons. First, the radiation from the other stars in
the heavens will gain energy as the universe contracts; thus, the stars will be
bathed in the blistering blueshifted light of other stars. Second, the
temperature of the background microwave radiation will be vastly increased as
the temperature of the universe skyrockets. The combination of these two
effects will create temperatures that exceed the surface temperature of the
stars, which will absorb heat faster than they can get rid of it. In other
words, the stars will probably disintegrate and disperse into super- hot gas
clouds.

Intelligent
life, under these circumstances, would inevitably perish, seared by the cosmic
heat pouring in from the nearby stars and galaxies. There is no escape. As
Freeman Dyson has written, "Regrettably I have to concur that in this case
we have no escape from frying. No matter how deep we burrow into the Earth to
shield ourselves from blue-shifted background radiation, we can only postpone
by a few million years our miserable end."

If the universe
is headed for a big crunch, then the remaining question is whether the universe
might collapse and then rebound, as in the oscillating universe. This is the
scenario adopted in Poul Anderson's novel
Tau Zero.
If the universe were Newtonian, this might be possible, if
there was sufficient sideways motion as the galaxies were compressed into each
other. In this case, the stars might not be squeezed into a single point but
might miss each other at the point of maximum compression and then rebound,
without colliding with each other.

The universe,
however, is not Newtonian; it obeys Einstein's equations. Roger Penrose and
Stephen Hawking have shown that, under very general circumstances, a collapsing
collection of galaxies will necessarily be squeezed down to a singularity.
(This is because the sideways motion of the galaxies contains energy and hence
interacts with gravity. Thus, the gravitational pull in Einstein's theory is
much greater than that found in Newtonian theory for collapsing universes, and
the universe collapses into a single point.)

FIVE STAGES OF THE UNIVERSE

Recent data from
the WMAP satellite, however, favors the big freeze. To analyze the life history
of the universe, scientists like Fred Adams and Greg Laughlin of the University
of Michigan have tried to divide up the age of the universe into five distinct
states. Since we are discussing truly astronomical time scales, we will adopt
a logarithmic time frame. Thus, i0
²⁰
years will be represented as
20. (This timetable was drawn up before the implications of an accelerating
universe were fully appreciated. But the general breakdown of the stages of the
universe remains the same.)

The question
that haunts us is: can intelligent life use its ingenuity to survive in some
form through these stages, through a series of natural catastrophes and even
the death of the universe?

StagE 1: Primordial Era

In the first
stage (between -50 and 5, or between 10
^-50
and 10
⁵
seconds),
the universe underwent rapid expansion but also rapid cooling. As it cooled,
the various forces, which were once united into a master
"superforce," gradually broke apart, yielding the familiar four
forces of today. Gravity broke off first, then the strong nuclear force, and
finally the weak nuclear force. At first, the universe was opaque and the sky
was white, since light was absorbed soon after it was created. But 380,000
years after the big bang, the universe cooled enough for atoms to form without
being smashed apart by the intense heat. The sky turned black. The microwave
background radiation dates back to this period.

During this era,
primordial hydrogen fused into helium, creating the current mixture of stellar
fuel that has spread throughout the universe. At this stage of the evolution of
the universe, life as we know it was impossible. The heat was too intense; any
DNA or other autocatalytic molecules that were formed would have been burst
apart by random collisions with other atoms, making the stable chemicals of
life impossible.

StagE 2: StEllifErous Era

Today, we live
in stage 2 (between 6 and i4, or between i0
⁶
and i0
ⁱ⁴
seconds),
when hydrogen gas has been compressed and stars have ignited, lighting up the
heavens. In this era, we find hydrogen-rich stars that blaze away for billions
of years until they exhaust their nuclear fuels. The Hubble space telescope has
photographed stars in all their stages of evolution, including young stars
surrounded by a swirling disk of dust and debris, probably the predecessor to
planets and a solar system.

In this stage, the conditions are ideal for the creation of
DNA and life. Given the enormous number of stars in the visible universe,
astronomers have tried to give plausible arguments, based on the known laws of
science, for the rise of intelligent life on other planetary systems. But any
intelligent life form will have to face a number of cosmic hurdles, many of its
own making, such as environmental pollution, global warming, and nuclear
weapons. Assuming that intelligent life has not destroyed itself, then it must
face a daunting series of natural disasters, any one of which may end in
catastrophe.