Zero - Charles Seife [79]
In 1965 several astrophysicists at Princeton University were calculating what would have happened right after the big bang. The entire universe must have been incredibly hot and dense; it would have been glowing with bright light. That light would not have disappeared as the balloon universe expanded; it would instead have gotten stretched out as the rubber fabric of space-time stretched. A few calculations later, the Princeton physicists realized that this light had to be in the microwave region of the spectrum, and had to be coming from all directions. This cosmic background radiation was the afterglow of the big bang. It would give physicists the first direct evidence that the big bang was correct and that steady state was wrong.
The Princeton scientists did not have long to wait before their prediction was confirmed. At Bell Labs in nearby Murray Hill, New Jersey, two engineers had been testing out sensitive microwave-detecting equipment. For all their tinkering, they could not get the equipment to work just right. There was a background hiss of microwave noise—like static on a radio program—that they could not get rid of. At first they thought that pigeons defecating in their antenna were to blame, but after chasing away the birds and cleaning out the droppings, the hiss remained. They tried everything they could think of to get rid of the noise, but nothing worked. Then when the engineers heard of the Princeton group’s work, they realized that they had found the cosmic background radiation. The noise wasn’t pigeon droppings. It was the scream of light from the big bang, stretched and distorted into a whisper’s hiss. (For their discovery the engineers, Arno Penzias and Robert Wilson, got the Nobel Prize. The Princeton physicists, notably Bob Dicke and P. J. E. “Jim” Peebles, got nothing—hardly fair in many scientists’ opinions. The Nobel committee tends to reward painstaking and careful experiments more than important theory.)
The big bang had been spotted; the myth of the static universe was dead. As unappealing as the idea of a finite universe was, physicists gradually accepted the big bang and agreed that the universe had a beginning. However, there were still problems with the theory. For one thing, the universe is somewhat lumpy. Knots of dense galaxies are separated by vast voids. At the same time, the universe is not too lumpy; it looks roughly the same in all directions, so all the matter did not wind up in one huge glob. If the universe had come from a singularity, with all probability the energy from the big bang should have covered the entire balloon fairly evenly or wound up in one big lump; the balloon should be evenly shaded or it should have one giant spot, rather than being polka-dotted. Something had to account for that just-right amount of lumpiness. More troubling still, where did the singularity of the big bang come from? Zero holds the secret.
The zero of the vacuum might explain the lumpiness of the universe. Since the vacuum everywhere in the universe is seething with a quantum foam of virtual particles, the fabric of the universe is filled with infinite zero-point energy. Under the right conditions this energy is able to push objects around; in the early universe it might have pushed objects apart.
In the 1980s physicists suggested that the zero-point energy in the early universe was greater than it is today. That extra energy would try to expand in all directions, pushing the fabric of space and time outward with great speed. It would inflate the balloon with a huge burst of power, smoothing out the lumpiness of the universe in the same way a breath of air smooths out the wrinkles of a balloon. This explains why the universe is relatively smooth. But the vacuum of the first few moments is a false vacuum; its zero-point energy is unnaturally large. The higher energy state of the zero-point energy makes it inherently unstable, and very quickly—in less than a millionth of a millionth of a millionth