What a satellite can do, balloons can do cheaper.
- By T. A. Heppenheimer
- Air & Space magazine, January 2002
(Page 7 of 8)
The Big Push
Minute variations in the temperature of the very early cosmos, mapped by Boomerang in 1999, support a theory known as inflation. Inflation theorists assert that in the course of the Big Bang, there was an inconceivably rapid expansion, during which the universe grew from a size a trillion times smaller than a proton to that of a grapefruit in less than 10-32 second.
Astrophysicists find this scenario compelling, for it predicts a universe with features that match observations: among them, uniformity over the universe's vast expanse. In an article about the Boomerang project, investigator Andrew Lange explains: "[T]he microwave background can be the same temperature everywhere because, before the universe inflated, all its parts were in very close contact and would naturally equilibrate to the same temperature."
But even in this uniformity—the temperature of the microwave background over the entire universe is 2.73 degrees Kelvin (about absolute zero)—there is variation on a very small scale. In one patch of sky, the temperature of the microwave background may be 2.7283. Inflation theorists believe that these "hot" and "cold" patches are traces of quantum fluctuations in the pre-inflationary universe and, as such, are also proof of instantaneous expansion.
The laws of quantum mechanics recognize that a small amount of energy is always present, even in empty space. Quantum fluctuations are jiggles in this background energy. (Evidence for the energy's existence was found in laboratory experiments in which closely spaced metal plates were found to be pushed together by quantum force.)
The process by which quantum fluctuations wink in and out of existence occurs at the speed of light and over a distance of 10-33 centimeters, known as the Planck length, for the German physicist who identified it. Had the universe expanded at the speed envisioned in the standard Big Bang theory, the expansion would have been far too slow for any trace of the quantum fluctuations to exist today. But according to the inflation theory, space itself expanded at a rate enormously faster than the speed of light. Inflation acted like stop-action photography, freezing the fluctuations in mid-jiggle, and at the same time, blowing them up from the "Planck length" to a macroscopic scale. At their post-inflationary size the fluctuations were no longer quantum—they now behaved according to the rules of classical physics. They took on the character of seismic waves within a universe filled with plasma, or ionized gas.
For the next 15 billion years, the universe expanded and cooled. Had observers been present when the cosmos was about 500,000 years old, and had they looked back towards is infancy, they would have seen these seismic features in optical wavelengths, and the seismic features appear as the minute temperature variations in the cosmic microwave background.