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View from a telescope: A universe expanding forever
Friday, December 18, 1998 By Byron Spice, Science Editor, Post-Gazette
Early results from a telescope that has spent the past year peering through the cold, dry air of the South Pole at the earliest visible remnants of the Big Bang suggest the universe will expand forever and never collapse.
The observations, which will be reported in Paris today by Carnegie Mellon University astrophysicist Jeff Peterson, also can be interpreted as evidence that the expansion of the universe actually is accelerating, that some unknown phenomenon is causing the galaxies to fly away from each other at ever-increasing speed.
This concept of an accelerating universe was first broached last January based on observations of distant supernovae, or exploding stars, by two international teams of astronomers. Though many scientists remain skeptical, the finding may end up forcing physicists to rethink some fundamental physics.
The implications are so profound that the prestigious journal Science today is naming the accelerating universe as the Breakthrough of the Year.
For his part, Peterson doesn't claim that the findings from the Viper's telescope that was installed at the South Pole last January necessarily prove that the universe's expansion is indeed accelerating because it's not measuring how fast the universe is moving.
Michael Turner, an astronomer at the University of Chicago, said the Viper results nevertheless can be seen as corroborating evidence of an accelerating universe.
"We have a picture that fits together," Turner said. The year 1998 may well turn out to be as important a turning point in cosmology as the year 1964, when cosmic background radiation was discovered.
Cosmic background radiation is microwave radiation emitted by clouds of gas that emerged 300,000 years after the Big Bang that began the universe 15 billion years ago. From these clouds, stars and galaxies ultimately would form.
The six-foot diameter Viper, built at Carnegie Mellon, is designed to capture microwaves from these ancient clouds and to look for variations in their temperatures. Microwaves are readily absorbed by moisture, so the telescope is located at the South Pole, where the extreme cold keeps the air exceedingly dry.
Hot spots detected by Viper are areas of unusually high density, Peterson explained. These are the areas that eventually would evolve into galaxies.
Calculations show these hot spots would be about 326 million light-years across. By measuring their apparent size in the sky, Viper can determine how distant these clouds are in space, which in turn provides evidence of the shape of the universe and the speed of its expansion, Peterson noted.
In the observations thus far, these hot spots on the edge of the universe measure about half a degree on the sky, Peterson will report today in Paris at the annual Texas Symposium on Relativistic Physics. That's exactly the size one would expect if the amount of mass in the universe was just enough to reach escape velocity, he added.
That would mean the universe had just enough mass to continue to expand indefinitely, but at an ever- slower rate. The force of gravity would continue to hold the universe together, but wouldn't be great enough to cause the expansion to reverse and for the universe to collapse.
This does not rule out, however, the possibility that the universe might be accelerating, both Peterson and Turner agree. The Viper observations provide a way to measure all the matter and energy in the universe, but today astronomers can account for only 30 to 40 percent of that mass.
Because Albert Einstein's theory of relativity showed that mass and energy are interchangeable, the "missing" mass of the universe can be thought of as missing energy, Turner explained. That energy, so evenly distributed through the universe as to be undetectable, might account for the propulsive force that is accelerating the expansion.
Saul Perlmutter, the Lawrence Berkeley National Laboratory astronomer who headed one of the groups responsible for the supernovae observations, yesterday called this a "weird property" that is driving the universe's expansion. This may be the "cosmological constant," the cosmic repulsion that Einstein suggested in 1917, but later renounced as his biggest blunder.
In the supernovae experiments, Perlmutter's group and a second team found that distant supernovae were surprisingly dim, suggesting they were actually picking up speed as their distance from Earth increased.
Peterson isn't yet convinced that the universe is accelerating, but finds the idea appealing.
"I hope the supernovae results are right because it throws a monkey wrench in the works," he said. "That's what makes science fun."
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