Hyperspace (50 page)

About 2 million light-years from the Milky Way is our nearest galactic neighbor, the great Andromeda galaxy, which is two to three times larger than our own galaxy. The two galaxies are hurtling toward each other at 125 kilometers per second, and should collide within 5 to 10 billion years. As astronomer Lars Hernquist at the University of California at Santa Cruz has said, this collision will be “analogous to a hostile takeover. Our galaxy will be consumed and destroyed.”
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As seen from outer space, the Andromeda galaxy will appear to collide with and then slowly absorb the Milky Way galaxy. Computer simulations of colliding galaxies show that the gravitational pull of the larger galaxy will slowly overwhelm the gravity of the smaller galaxy, and after several rotations the smaller galaxy will be eaten up. But because the stars within the Milky Way galaxy are so widely separated by the vacuum of space, the number of collisions between stars will be quite low, on the order of several collisions per century. So our sun may avoid a direct collision for an extended period of time.

Ultimately, on this time scale of billions of years, we have a much more deadly fate, the death of the universe itself. Clever forms of intelligent life may find ways to build space arks to avoid most natural catastrophes, but how can we avoid the death of the universe, when space itself is our worst enemy?

The Aztecs believed that the end of the world would come when the sun one day falls from the sky. They foretold that this would come “when the Earth has become tired …, when the seed of Earth has ended.” The stars would be shaken from the heavens.

Perhaps they were close to the truth.

One can hope that by the time our sun begins to flicker out, humanity
will have long since left the solar system and reached for the stars. (In fact, in Asimov’s Foundation series, the location of our original star system has been lost for thousands of years.) However, inevitably,
all
the stars in the heavens will flicker out as their nuclear fuel is exhausted. On a scale of tens to hundreds of billions of years, we are facing the death of the universe itself. Either the universe is open, in which case it will expand forever until temperatures gradually reach near absolute zero, or the universe is closed, in which case the expansion will be reversed and the universe will die in a fiery Big Crunch. Even for a Type III civilization, this is a daunting threat to its existence. Can mastery of hyperspace save civilization from its ultimate catastrophe, the death of the universe?

Some say the world will end in fire.
Some say in ice.
From what I’ve tasted of desire
I hold with those who favor fire.

Robert Frost

It ain’t over ’til it’s over.

Yogi Berra

WHETHER a civilization, either on earth or in outer space, can reach a point in its technological development to harness the power of hyperspace depends partly, as we have seen, on negotiating a series of disasters typical of Type 0 civilizations. The danger period is the first several hundred years after the dawn of the nuclear age, when a civilization’s technological development has far outpaced its social and political maturity in handling regional conflicts.

By the time a civilization has attained Type III status, it will have achieved a planetary social structure advanced enough to avoid self-annihilation and a technology powerful enough to avoid an ecological or a natural disaster, such as an ice age or solar collapse. However, even a Type III civilization will have difficulty avoiding the ultimate catastrophe: the death of the universe itself. Even the mightiest and most sophisticated of the Type III civilization’s starships will be unable to escape the final destiny of the universe.

That the universe itself must die was known to nineteenth-century
scientists. Charles Darwin, in his
Autobiography
, wrote of his anguish when he realized this profound but depressing fact: “Believing as I do that man in the distant future will be a far more perfect creature than he now is, it is an intolerable thought that he and all other sentient beings are doomed to complete annihilation after such long-continued slow progress.”
¹

The mathematician and philosopher Bertrand Russell wrote that the ultimate extinction of humanity is a cause of “unyielding despair.” In what must be one of the most depressing passages ever written by a scientist, Russell noted:

That man is the product of causes which had no prevision of the end they were achieving; that his origin, his growth, his hopes and fears, his loves and his beliefs, are but the outcome of accidental collocations of atoms; that no fire, no heroism, no intensity of thought or feeling, can preserve a life beyond the grave; that all the labors of the ages, all the devotion, all the inspiration, all the noonday brightness of human genius, are destined to extinction in the vast death of the solar system; and the whole temple of Man’s achievement must inevitably be buried beneath the debris of a universe in ruins—all these things, if not quite beyond dispute, are yet so nearly certain, that no philosophy which rejects them can hope to stand. Only within the scaffolding of these truths, only on the firm foundation of unyielding despair, can the soul’s habitation be safely built.
²

Russell wrote this passage in 1923, decades before the advent of space travel. The death of the solar system loomed large in his mind, a rigorous conclusion of the laws of physics. Within the confines of the limited technology of his time, this depressing conclusion seemed inescapable. Since that time, we have learned enough about stellar evolution to know that our sun will eventually become a red giant and consume the earth in nuclear fire. However, we also understand the basics of space travel. In Russell’s time, the very thought of large ships capable of placing humans on the moon or the planets was universally considered to be the thinking of a madman. However, with the exponential growth of technology, the prospect of the death of the solar system is not such a fearsome event for humanity, as we have seen. By the time our sun turns into a red giant, humanity either will have long perished into nuclear dust or, hopefully, will have found its rightful place among the stars.

Still, it is a simple matter to generalize Russell’s “unyielding despair” from the death of our solar system to the death of the entire universe. In that event, it appears that no space ark can transport humanity out
of harm’s way. The conclusion seems irrefutable; physics predicts that all intelligent life forms, no matter how advanced, will eventually perish when the universe itself dies.

According to Einstein’s general theory of relativity, the universe either will continue to expand forever in a Cosmic Whimper, in which case the universe reaches near absolute zero temperatures, or will contract into a fiery collapse, the Big Crunch. The universe will die either in “ice,” with an open universe, or in “fire,” with a closed universe. Either way, a Type III civilization is doomed because temperatures will approach either absolute zero or infinity.

To tell which fate awaits us, cosmologists use Einstein’s equations to calculate the total amount of matter-energy in the universe. Because the matter in Einstein’s equation determines the amount of space-time curvature, we must know the average matter density of the universe in order to determine if there is enough matter and energy for gravitation to reverse the cosmic expansion of the original Big Bang.

A critical value for the average matter density determines the ultimate fate of the universe and all intelligent life within it. If the average density of the universe is less than 10
⁻²⁹
gram per cubic centimeter, which amounts to 10 milligrams of matter spread over the volume of the earth, then the universe will continue to expand forever, until it becomes a uniformly cold, lifeless space. However, if the average density is larger than this value, then there is enough matter for the gravitational force of the universe to reverse the Big Bang, and suffer the fiery temperatures of the Big Crunch.

At present, the experimental situation is confused. Astronomers have several ways of measuring the mass of a galaxy, and hence the mass of the universe. The first is to count the number of stars in a galaxy, and multiply that number by the average weight of each star. Calculations performed in this tedious fashion show that the average density is less than the critical amount, and that the universe will continue to expand forever. The problem with this calculation is that it omits matter that is not luminous (for example, dust clouds, black holes, cold dwarf stars).

There is also a second way to perform this calculation, which is to use Newton’s laws. By calculating the time it takes for stars to move around a galaxy, astronomers can use Newton’s laws to estimate the total mass of the galaxy, in the same way that Newton used the time it took for the moon to orbit the earth to estimate the mass of the moon and earth.

The problem is the mismatch between these two calculations. In fact, astronomers know that up to 90% of the mass of a galaxy is in the form
of hidden, undetectable “missing mass” or “dark matter,” which is not luminous but has weight. Even if we include an approximate value for the mass of nonluminous interstellar gas, Newton’s laws predict that the galaxy is far heavier than the value calculated by counting stars.

Until astronomers resolve the question of this missing mass or dark matter, we cannot resolve the question of whether the universe will contract and collapse into a fiery ball or will expand forever.

Assume, for the moment, that the average density of the universe is less than the critical value. Since the matter-energy content determines the curvature of space-time, we find that there is not enough matter-energy to make the universe recollapse. It will then expand limitlessly until its temperature reaches almost absolute zero. This increases
entropy
(which measures the total amount of chaos or randomness in the universe). Eventually, the universe dies in an entropy death.

The English physicist and astronomer Sir James Jeans wrote about the ultimate death of the universe, which he called the “heat death,” as early as the turn of the century: “The second law of thermodynamics predicts that there can be but one end to the universe—a ‘heat death’ in which [the] temperature is so low as to make life impossible.”
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To understand how entropy death occurs, it is important to understand the three laws of thermodynamics, which govern all chemical and nuclear processes on the earth and in the stars. The British scientist and author C. P. Snow had an elegant way of remembering the three laws:

1.
You cannot win
(that is, you cannot get something for nothing, because matter and energy are conserved).

2.
You cannot break even
(you cannot return to the same energy state, because there is always an increase in disorder; entropy always increases).

3.
You cannot get out of the game
(because absolute zero is unattainable).

For the death of the universe, the most important is the Second Law, which states that any process creates a net increase in the amount of disorder (entropy) in the universe. The Second Law is actually an integral part of our everyday lives. For example, consider pouring cream into a cup of coffee. Order (separate cups of cream and coffee) has
naturally changed into disorder (a random mixture of cream and coffee). However, reversing entropy, extracting order from disorder, is exceedingly difficult. “Unmixing” the liquid back into separate cups of cream and coffee is impossible without an elaborate chemistry laboratory. Also, a lighted cigarette can fill an empty room with wisps of smoke, increasing entropy in that room. Order (tobacco and paper) has again turned into disorder (smoke and charcoal). Reversing entropy—that is, forcing the smoke back into the cigarette and turning the charcoal back into unburned tobacco—is impossible even with the finest chemistry laboratory on the planet.

Similarly, everyone knows that it’s easier to destroy than to build. It may take a year to construct a house, but only an hour or so to destroy it in a fire. It took almost 5,000 years to transform roving bands of hunters into the great Aztec civilization, which flourished over Mexico and Central America and built towering monuments to its gods. However, it only took a few months for Cortez and the conquistadors to demolish that civilization.

Entropy is relentlessly increasing in the stars as well as on our planet. Eventually, this means that the stars will exhaust their nuclear fuel and die, turning into dead masses of nuclear matter. The universe will darken as the stars, one by one, cease to twinkle.

Given our understanding of stellar evolution, we can paint a rather dismal picture of how the universe will die. All stars will become black holes, neutron stars, or cold dwarf stars (depending on their mass) within 10
²⁴
years as their nuclear furnaces shut down. Entropy increases as stars slide down the curve of binding energy, until no more energy can be extracted by fusing their nuclear fuel. Within 10
³²
years, all protons and neutrons in the universe will probably decay. According to the GUTs, the protons and neutrons are unstable over that vast time scale. This means that eventually all matter as we know it, including the earth and the solar system, will dissolve into smaller particles, such as electrons and neutrinos. Thus intelligent beings will have to face the unpleasant possibility that the protons and neutrons in their bodies will disintegrate. The bodies of intelligent organisms will no longer be made of the familiar 100 chemical elements, which are unstable over that immense period of time. Intelligent life will have to find ways of creating new bodies made of energy, electrons, and neutrinos.

After a fantastic 10
¹⁰⁰
(a googol) years, the universe’s temperature will reach near absolute zero. Intelligent life in this dismal future will face the prospect of extinction. Unable to huddle next to stars, they will freeze to death. But even in a desolate, cold universe at temperatures
near absolute zero, there is one last remaining flickering source of energy: black holes. According to cosmologist Stephen Hawking, black holes are not completely black, but slowly leak energy into outer space over an extended period of time.