Cosmology: Whisper from a Bang

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Is the universe limitless, with no beginning and no end in either time or space? Or did it begin with a "Big Bang," the sudden expansion of a monstrous mass of hot hydrogen that spread out to form galaxies still receding from one another? Scientific dispute ranges between those two extremes and swirls around compromises and variations. New evidence seems to support first one theory, then another. Last week it was the Big Bang that got a boost—all because of some faint radio waves filtering gently down from the sky.

Scientists Arno A. Penzias and Robert W. Wilson of Bell Telephone Laboratories were determined to account for all the radio energy that finds its way into the 20-ft. horn antennas at Holmdel, N.J., that Bell built for talking to the Telstar communication satellite. At the microwave frequency the horn was tuned to, 4080 megacycles, radio waves from the stars and galaxies were all but undetectable, and tests with a ground transmitter proved that waves from the earth's surface could be disregarded. Still, signals were coming in. What was their origin?

All Directions. Penzias and Wilson used an extremely sensitive receiver, part of it cooled by liquid helium to eliminate most of the radio noise that is generated internally by electronic gear. They rebuilt the horn meticulously, cleaned and aligned its joints, covered its seams smoothly with aluminum tape to reduce noise coming from imperfections. They made allowance for radio waves from the earth's atmosphere. After all that, the horn continued to catch a steady radio whisper that did not vary by day or night, winter or summer. It seemed to come from all directions with equal intensity.

When word of the whispering waves reached Professor Robert H. Dicke and a group of Princeton physicists, the Bell observations seemed to fit neatly into the predictions of their own sweeping cosmological theory. Big Bang exponents, the Princeton scientists contend that the universe has had not a single bang but an infinite number. At undetermined intervals, they say, the universe contracts to a single mass, dissolving all its galaxies and the life they may carry into hot hydrogen. Then it expands once more.

Weak Wash. Professor Dicke's group is particularly interested in the period when the universe had just begun to expand after its last Big Bang. It was still very hot, containing vast amounts of light and other radiation, but as it expanded the radiation weakened and increased in wave length because of the speed of expansion. This ancient radia tion came to permeate the universe and washed weakly against the galaxies-one of which is the Milky Way to which the solar system belongs. The weakened radiation, says Professor Dicke, may well be what has been detected—7 bil lion years after the bang—as micro waves whispering m the Holmdel horn.