Hyperspace (43 page)

Figure 12.1. In Hawking’s wave function of the universe, the wave function is most likely concentrated around own universe. We live in our universe because it is the most likely, with the largest probability. However, there is a small but non-vanishing probability that the wave function prefers neighboring, parallel universes. Thus transitions between universes may be possible (although with very low probability)
.

Think, for example, of a large collection of soap bubbles, suspended in air. Normally, each soap bubble is like a universe unto itself, except that periodically it bumps into another bubble, forming a larger one, or splits into two smaller bubbles. The difference is that each soap bubble is now an entire ten-dimensional universe. Since space and time can exist only on each bubble, there is no such thing as space and time between the bubbles. Each universe has its own self-contained “time.” It is meaningless to say that time passes at the same rate in all these universes. (We should, however, stress that travel between these universes is not open to us because of our primitive technological level. Furthermore,
we should also stress that large quantum transitions on this scale are extremely rare, probably much larger than the lifetime of our universe.) Most of these universes are dead universes, devoid of any life. On these universes, the laws of physics were different, and hence the physical conditions that made life possible were not satisfied. Perhaps, among the billions of parallel universes, only one (ours) had the right set of physical laws to allow life (
Figure 12.2
).

Figure 12.2. Our universe may be one of an infinite number of parallel universes, each connected to the others by an infinite series of wormholes. Travel between these wormholes is possible but extremely unlikely
.

Hawking’s “baby universe” theory, although not a practical method of transportation, certainly raises philosophical and perhaps even religions questions. Already, it has stimulated two long-simmering debates among cosmologists.

The first debate concerns the
anthropic principle
. Over the centuries, scientists have learned to view the universe largely independent of human bias. We no longer project our human prejudices and whims onto every scientific discovery. Historically, however, early scientists often committed the fallacy of anthropomorphism, which assumes that objects and animals have humanlike qualities. This error is committed by anyone who sees human emotions and feelings being exhibited by their pets. (It is also committed by Hollywood scriptwriters who regularly assume that beings similar to us must populate planets orbiting the stars in the heavens.)

Anthropomorphism is an age-old problem. The Ionian philosopher Xenophanes once lamented, “Men imagine gods to be born, and to have clothes and voices and shapes like theirs.… Yea, the gods of the Ethiopians are black and flat-nosed, and the gods of the Thracians are red-haired and blue-eyed.” Within the past few decades, some cosmologists have been horrified to find anthropomorphism creeping back into science, under the guise of the anthropic principle, some of whose advocates openly declare that they would like to put God back into science.

Actually, there is some scientific merit to this strange debate over the anthropic principle, which revolves around the indisputable fact that if the physical constants of the universe were altered by the smallest amount, life in the universe would be impossible. Is this remarkable fact just a fortunate coincidence, or does it show the work of some Supreme Being?

There are two versions of the anthropic principle. The “weak” version states that the fact that intelligent life (us) exists in the universe
should be taken as an experimental fact that helps us understand the constants of the universe. As Nobel laureate Steven Weinberg explains it, “the world is the way it is, at least in part, because otherwise there would be no one to ask why it is the way it is.”
¹
Stated in this way, the weak version of the anthropic principle is hard to argue with.

To have life in the universe, you need a rare conjunction of many coincidences. Life, which depends on a variety of complex biochemical reactions, can easily be rendered impossible if we change some of the constants of chemistry and physics by a small amount. For example, if the constants that govern nuclear physics were changed even slightly, then nucleosynthesis and the creation of the heavy elements in the stars and supernovae might become impossible. Then atoms might become unstable or impossible to create in supernovae. Life depends on the heavy elements (elements beyond iron) for the creation of DNA and protein molecules. Thus the smallest change in nuclear physics would make the heavy elements of the universe impossible to manufacture in the stars. We are children of the stars; however, if the laws of nuclear physics change in the slightest, then our “parents” are incapable of having “children” (us). As another example, it is safe to say that the creation of life in the early oceans probably took 1 to 2 billion years. However, if we could somehow shrink the lifetime of the proton to several million years, then life would be impossible. There would not be enough time to create life out of random collisions of molecules.

In other words, the very fact that we exist in the universe to ask these questions about it means that a complex sequence of events must necessarily have happened. It means that the physical constants of nature must have a certain range of values, so that the stars lived long enough to create the heavy elements in our bodies, so that protons don’t decay too rapidly before life has a chance to germinate, and so on. In other words, the existence of humans who can ask questions about the universe places a huge number of rigid constraints on the physics of the universe—for example, its age, its chemical composition, its temperature, its size, and its physical processes.

Remarking on these cosmic coincidences, physicist Freeman Dyson once wrote, “As we look out into the Universe and identify the many accidents of physics and astronomy that have worked together to our benefit, it almost seems as if the Universe must in some sense have known that we were coming.” This takes us to the “strong” version of the anthropic principle, which states that all the physical constants of the universe have been precisely chosen (by God or some Supreme Being) so that life is possible in our universe. The strong version, because it
raises questions about a deity, is much more controversial among scientists.

Conceivably, it might have been blind luck if only a few constants of nature were required to assume certain values to make life possible. However, it appears that a large set of physical constants must assume a narrow band of values in order for life to form in our universe. Since accidents of this type are highly improbable, perhaps a divine intelligence (God) precisely chose those values in order to create life.

When scientists first hear of some version of the anthropic principle, they are immediately taken aback. Physicist Heinz Pagels recalled, “Here was a form of reasoning completely foreign to the usual way that theoretical physicists went about their business.”
²

The anthropic argument is a more sophisticated version of the old argument that God located the earth at just the right distance from the sun. If God had placed the earth too close, then it would be too hot to support life. If God had placed the earth too far, then it would be too cold. The fallacy of this argument is that millions of planets in the galaxy probably are sitting at the incorrect distance from their sun, and therefore life on them is impossible. However, some planets will, by pure accident, be at the right distance from their sun. Our planet is one of them, and hence we are here to discuss the question.

Eventually, most scientists become disillusioned with the anthropic principle because it has no predictive power, nor can it be tested. Pagels reluctantly concluded that “unlike the principles of physics, it affords no way to determine whether it is right or wrong; there is no way to test it. Unlike conventional physical principles, the anthropic principle is not subject to experimental falsification—the sure sign that it is not a scientific principle.”
³
Physicist Alan Guth says bluntly, “Emotionally, the anthropic principle kind of rubs me the wrong way.… The anthropic principle is something that people do if they can’t think of anything better to do.”
⁴

To Richard Feynman, the goal of a theoretical physicist is to “prove yourself wrong as fast as possible.”
⁵
However, the anthropic principle is sterile and cannot be disproved. Or, as Weinberg said, “although science is clearly impossible without scientists, it is not clear that the universe is impossible without science.”
⁶

The debate over the anthropic principle (and hence, about God) was dormant for many years, until it was recently revived by Hawking’s wave function of the universe. If Hawking is correct, then indeed there are an infinite number of parallel universes, many with different physical constants. In some of them, perhaps protons decay too rapidly, or stars
cannot manufacture the heavy elements beyond iron, or the Big Crunch takes place too rapidly before life can begin, and so on. In fact, an infinite number of these parallel universes are dead, without the physical laws that can make life as we know it possible.

On one such parallel universe (ours), the laws of physics were compatible with life as we know it. The proof is that we are here today to discuss the matter. If this is true, then perhaps God does not have to be evoked to explain why life, precious as it is, is possible in our universe. However, this reopens the possibility of the weak anthropic principle—that is, that we coexist with many dead universes, and that ours is the only one compatible with life.

The second controversy stimulated by Hawking’s wave function of the universe is much deeper and in fact is still unresolved. It is called the Schrödinger’s cat problem.

Because Hawking’s theory of baby universes and wormholes uses the power of quantum theory, it inevitably reopens the still unresolved debates concerning its foundations. Hawking’s wave function of the universe does not completely solve these paradoxes of quantum theory; it only expresses them in a startling new light.

Quantum theory, we recall, states that for every object there is a wave function that measures the probability of finding that object at a certain point in space and time. Quantum theory also states that you never really know the state of a particle until you have made an observation. Before a measurement is made, the particle can be in one of a variety of states, described by the Schrödinger wave function. Thus before an observation or measurement can be made, you can’t really know the state of the particle. In fact, the particle exists in a nether state, a sum of
all possible states
, until a measurement is made.

When this idea was first proposed by Niels Bohr and Werner Heisenberg, Einstein revolted against this concept. “Does the moon exist just because a mouse looks at it?” he was fond of asking. According to the strict interpretation of quantum theory, the moon, before it is observed, doesn’t really exist as we know it. The moon can be, in fact, in any one of an infinite number of states, including the state of being in the sky, of being blown up, or of not being there at all. It is the measurement process of looking at it that decides that the moon is actually circling the earth.

Einstein had many heated discussions with Niels Bohr challenging this unorthodox world view. (In one exchange, Bohr said to Einstein in exasperation, “You are not thinking. You are merely being logical!”
⁷
) Even Erwin Schrödinger (who initiated the whole discussion with his celebrated wave equation) protested this reinterpretation of his equation. He once lamented, “I don’t like it, and I’m sorry I ever had anything to do with it.”
⁸

To challenge this revisionist interpretation, the critics asked, “Is a cat dead or alive before you look at it?”

To show how absurd this question is, Schro’dinger placed an imaginary cat in a sealed box. The cat faces a gun, which is connected to a Geiger counter, which in turn is connected to a piece of uranium. The uranium atom is unstable and will undergo radioactive decay. If a uranium nucleus disintegrates, it will be picked up by the Geiger counter, which will then trigger the gun, whose bullet will kill the cat.

To decide whether the cat is dead or alive, we must open the box and observe the cat. However, what is the state of the cat before we open the box? According to quantum theory, we can only state that the cat is described by a wave function that describes the sum of a dead cat and a live cat.

To Schrödinger, the idea of thinking about cats that are neither dead nor alive was the height of absurdity, yet nevertheless the experimental confirmation of quantum mechanics forces us to this conclusion. At present, every experiment has verified quantum theory.