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Andrew Lange, Ph.D. and
Saul Perlmutter, Ph.D.
2003 California Scientists of the Year

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Dr. Andrew Lange is Marvin L. Goldberger Professor of Physics at the California Institute of Technology in Pasadena, and Dr. Saul Perlmutter is Senior Scientist and Group Leader at the Lawrence Berkeley National Laboratory in Berkeley. Using two very different techniques, Lange and Perlmutter’s experimental efforts have confirmed a remarkable theory of how the universe expanded and evolved after “the big bang.”

According to the most widely held theory of cosmic evolution, the universe went though an inflationary phase where its size rapidly increased and where the universe’s geometrical structure took on a very specific form: parallel lines never meet, the sum of the angles inside an astronomically sized triangle add to 180 degrees. Scientists refer to this particular form of geometry as being mathematically “flat.” According to General Relativity, a mathematically flat universe places constraints on the amount of mass and energy in the universe. Unfortunately, astronomers could not account for the requisite mass and energy. Therefore, either the standard cosmological or “big bang” theory was incorrect and the universe’s geometrical structure was not that of Euclid, or the astronomers were missing something important.

Andrew Lange, Ph.D.

Dr. Lange studies fluctuations in the Cosmic Microwave Background (CMB) radiation, a relic of the primeval “fireball” that filled the early universe. These signals, which are visible today at microwave frequencies, provide a clear “snapshot” of the embryonic universe, at an epoch long before the first stars or galaxies had formed. In general, this radiation reaches the earth uniformly from all directions in the sky. However, at the level of 0.003% there is an intricate pattern of fluctuations in the CMB. Using novel detectors developed at the Jet Propulsion Laboratory and flown on a balloon-borne telescope high above Antarctica, Dr. Lange’s group was able to make the first resolved images of these very faint patterns. The images demonstrate that the radiation fluctuates on an angular scale of one degree, which is exactly what scientists expected from a mathematically flat universe.

Saul Perlmutter, Ph.D.

Since the 1930s, scientists have known that galaxies are all moving away from one another, and there has been a concerted effort to study the rate of this expansion. Prior to Perlmutter’s efforts, almost all astronomers expected that the expansion of the universe was slowing, due to the gravitational attraction of galaxies and other matter. However, Perlmutter’s group found that the universe is actually expanding at an accelerating rate, as if a “negative pressure” was pushing everything apart. This negative pressure may be what scientists call the cosmological constant, first hypothesized by Albert Einstein in an attempt to prescribe a stable universe but later rejected by him. Perlmutter’s estimates of the cosmological constant’s magnitude are consistent with Lange’s observations of a flat universe.

Lange’s work demonstrates that the universe is mathematically flat, and that the standard cosmological theory is correct, while Perlmutter’s work indicates that the source of astronomical energy giving rise to a flat universe comes from a type of negative gravitational pressure or dark energy permeating the universe. The nature of this dark energy remains a mystery.

Dr. Lange's site:
Caltech Observational Cosmology Group

Dr. Perlmutter's site:
Supernova Cosmology Project

 
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