Hyperspace (34 page)

Their logic, however, was very compelling. Any object, when heated, gradually emits radiation. This is the reason why iron gets red hot when placed in a furnace. The hotter the iron, the higher the frequency of radiation it emits. A precise mathematical formula, the Stefan-Boltzmann law, relates the frequency of light (or the color, in this case) to the temperature. (In fact, this is how scientists determine the surface temperature of a distant star, by examining its color.) This radiation is called
blackbody radiation
.

When the iron cools, the frequency of the emitted radiation also decreases, until the iron no longer emits in the visible range. The iron returns to its normal color, but it continues to emit invisible infrared radiation. This is how the army’s night glasses operate in the dark. At night, relatively warm objects such as enemy soldiers and tank engines may be concealed in the darkness, but they continue to emit invisible blackbody radiation in the form of infrared radiation, which can be picked up by special infrared goggles. This is also why your sealed car gets hot during the summer. Sunlight penetrates the glass of your car and heats the interior. As it gets hot, it begins to emit blackbody radiation in the form of infrared radiation. However, infrared radiation does not penetrate glass very well, and hence is trapped inside your car, dramatically raising its temperature. (Similarly, blackbody radiation drives the greenhouse effect. Like glass, rising levels of carbon dioxide in the atmosphere, caused by the burning of fossil fuels, can trap the infrared blackbody radiation of the earth and thereby gradually heat the planet.)

Gamow reasoned that the Big Bang was initially quite hot, and hence would be an ideal blackbody emitter of radiation. Although the technology of the 1940s was too primitive to pick up this faint signal from Creation, he could calculate the temperature of this radiation and confidently
predict that one day our instruments would be sensitive enough to detect this “fossil” radiation. The logic behind his thinking was as follows: About 300,000 years after the Big Bang, the universe cooled to the point where atoms could begin to condense; electrons could begin to circle protons and form stable atoms that would no longer be broken up by the intense radiation permeating the universe. Before this time, the universe was so hot that atoms were continually ripped apart by radiation as soon as they were formed. This meant that the universe was opaque, like a thick, absorbing, and impenetrable fog. After 300,000 years, however, the radiation was no longer sufficiently strong to break up the atoms, and hence light could travel long distances without being scattered. In other words, the universe suddenly became black and transparent after 300,000 years. (We are so used to hearing about the “blackness of outer space” that we forget that the early universe was not transparent at all, but filled with turbulent, opaque radiation.)

After 300,000 years, electromagnetic radiation no longer interacted so strongly with matter, and hence became blackbody radiation. Gradually, as the universe cooled, the frequency of this radiation decreased. Gamow and his students calculated that the radiation would be far below the infrared range, into the microwave region. Gamow reasoned that by scanning the heavens for a uniform, isotropic source of microwave radiation, one should be able to detect this microwave radiation and discover the echo of the Big Bang.

Gamow’s prediction was forgotten for many decades, until the microwave background radiation was discovered quite by accident in 1965. Penzias and Wilson found a mysterious background radiation permeating all space when they turned on their new horn reflector antenna in Holmdel, New Jersey. At first, they thought this unwanted radiation was due to electrical static caused by contaminants, such as bird droppings on their antenna. But when they disassembled and cleaned large portions of the antenna, they found that the “static” persisted. At the same time, physicists Robert Dicke and James Peebles at Princeton University were rethinking Gamow’s old calculation. When Penzias and Wilson were finally informed of the Princeton physicists’ work, it was clear that there was a direct relationship between their results. When they realized that this background radiation might be the echo of the original Big Bang, they are said to have exclaimed, “Either we’ve seen a pile of bird s——t, or the creation of the universe!” They discovered that this uniform background radiation was almost exactly what had been predicted years earlier by George Gamow and his collaborators if the Big Bang had left a residual blanket of radiation that had cooled down to 3°K.

Perhaps the most spectacular scientific confirmation of the Big Bang theory came in 1992 with the results of the
COBE (Cosmic Background Explorer)
satellite. On April 23, newspaper headlines across the country heralded the findings of a team of scientists at the University of California at Berkeley, led by George Smoot, who announced the most dramatic, convincing argument for the Big Bang theory. Journalists and columnists, with no background in physics or theology, were suddenly waxing eloquent about the “face of God” in their dispatches.

The
COBE
satellite was able to improve vastly the earlier work of Penzias, Wilson, Peebles, and Dicke by many orders of magnitude, sufficient to rule out all doubt that the fossil radiation emitted by the Big Bang had been conclusively found. Princeton cosmologist Jeremiah P. Ostriker declared, “When fossils were found in the rocks, it made the origin of species absolutely clear-cut. Well,
COBE
found its fossils.”
²
Launched in late 1989, the
COBE
satellite was specifically designed to analyze the microscopic details in the structure of the microwave background radiation first postulated by George Gamow and his colleagues. The mission of
COBE
also had a new task: to resolve an earlier puzzle arising from the background radiation.

The original work of Penzias and Wilson was crude; they could show only that the background radiation was smooth to 10%. When scientists analyzed the background radiation in more detail, they found that it was exceptionally smooth, with no apparent ripples, kinks, or blotches. In fact, it was
too
smooth. The background radiation was like a smooth, invisible fog filling up the universe, so uniform that scientists had difficulty reconciling it with known astronomical data.

In the 1970s, astronomers turned their great telescopes to systematically map enormous collections of galaxies across large portions of the sky. To their surprise, they found that, 1 billion years after the Big Bang, the universe had already exhibited a pattern of condensing into galaxies and even large clusters of galaxies and huge, empty spaces called voids. The clusters were enormous, containing billions of galaxies at a time, and the voids stretched across millions of light-years.

But here lay a cosmic mystery: If the Big Bang was exceptionally smooth and uniform, then 1 billion years was not enough time to develop the dumpiness that we see among the galactic clusters. The gross mismatch between the original smooth Big Bang and the lumpiness of the universe 1 billion years later was a nagging problem that gnawed at every cosmologist. The Big Bang theory itself was never in any
doubt; what was in trouble was our understanding of the post-Big Bang evolution 1 billion years after Creation. But without sensitive satellites that could measure the cosmic background radiation, the problem festered over the years. In fact, by 1990, journalists without a rigorous science background began to write sensational articles saying erroneously that scientists had found a fatal flaw in the Big Bang theory itself. Many journalists wrote that the Big Bang theory was about to be overthrown. Long-discredited alternatives to the Big Bang theory began to resurface in the press. Even the
New York Times
published a major article saying that the Big Bang theory was in serious trouble (which was scientifically incorrect).

This pseudocontroversy surrounding the Big Bang theory made the announcement of the
COBE
data all the more interesting. With unprecedented accuracy, capable of detecting variations as small as one part in 100,000, the
COBE
satellite was able to scan the heavens and radio back the most accurate map of the cosmic background radiation ever constructed. The
COBE
results reconfirmed the Big Bang theory, and more.

COBE’s
data, however, were not easy to analyze. The team led by Smoot had to face enormous problems. For example, they had to subtract carefully the effect of the earth’s motion in the background radiation. The solar system drifts at a velocity of 370 kilometers per second relative to the background radiation. There is also the relative motion of the solar system with respect to the galaxy, and the galaxy’s complex motions with respect to galactic clusters. Nevertheless, after painstaking computer enhancement, several stunning results came out of the analysis. First, the microwave background fit the earlier prediction of George Gamow (adjusted with more accurate experimental numbers) to within 0.1% (
Figure 9.1
). The solid line represents the prediction; the
x’s
mark the data points measured by the
COBE
satellite. When this graph was flashed on the screen for the first time to a meeting of about a thousand astronomers, everyone in the room erupted in a standing ovation. This was perhaps the first time in the history of science that a simple graph received such a thunderous applause from so many distinguished scientists.

Second, Smoot’s team was able to show that tiny, almost microscopic blotches did, in fact, appear in the microwave background. These tiny blotches were precisely what was needed to explain the dumpiness and voids found 1 billion years after the Big Bang. (If these blotches had not been found by
COBE
, then a major revision in the post-Big Bang analysis would have had to be made.)

Third, the results were consistent with, but did not prove, the so-called
inflation theory
. (This theory, proposed by Alan Guth of MIT, states that there was a much more explosive expansion of the universe at the initial instant of Creation than the usual Big Bang scenario; it holds that the visible universe we see with our telescopes is only the tiniest part of a much bigger universe whose boundaries lie beyond our visible horizon.)

Figure 9.1. The solid line represents the prediction made by the Big Bang theory, which predicts that the background cosmic radiation should resemble blackbody radiation in the microwave region. The x’s represent the actual data collected by the
COBE
satellite, giving us one of the most convincing proofs of the Big Bang theory
.

The
COBE
results have given physicists confidence that we understand the origin of the universe to within a fraction of a second after the Big Bang. However, we are still left with the embarrassing questions of what preceded the Big Bang and why it occurred. General relativity, if taken to its limits, ultimately yields nonsensical answers. Einstein, realizing that general relatively simply breaks down at those enormously small distances,
tried to extend general relativity into a more comprehensive theory that could explain these phenomena.

At the instant of the Big Bang, we expect quantum effects to be the dominant force, overwhelming gravity. The key to the origin of the Big Bang, therefore, is a quantum theory of gravity. So far, the only theory that can claim to solve the mystery of what happened before the Big Bang is the ten-dimensional superstring theory. Scientists are just now conjecturing how the ten-dimensional universe split into a four- and a six-dimensional universe. What does our twin universe look like?

One physicist who is struggling with these cosmic questions is Cumrum Vafa, a Harvard professor who has spent several years studying how our ten-dimensional universe may have been torn into two smaller universes. He is, ironically, also a physicist torn between two worlds. Living in Cambridge, Massachusetts, Vafa is originally from Iran, which has been racked by political convulsions for the past decade. On the one hand, he wishes eventually to return to his native Iran, perhaps when the social tumult has calmed down. On the other hand, his research takes him far from that troubled region of the world, all the way to the far reaches of six-dimensional space, long before the tumult in the early universe had a chance to stabilize.

”Imagine a simple video game,” he says. A rocket ship can travel in the video screen, he points out, until it veers too far to the right. Any video-game player knows that the rocket ship then suddenly appears from the left side of the screen, at exactly the same height. Similarly, if the rocket ship wanders too far and falls off the bottom of the screen, it rematerializes at the top of the screen. Thus, Vafa explains, there is an entirely self-contained universe in that video screen. You can never leave the universe defined by that screen. Even so, most teenagers have never asked themselves what that universe is actually shaped like. Vafa points out, surprisingly enough, that the topology of the video screen is that of an inner tube!