Electromagnetic clatter from millions of manmade sources is drowning out whispers from the heavens and crippling research by radio astronomers who probe distant stars, scientists say.

Marcus Price, a radio astronomer at the University of New Mexico, says the machines of modern America - from car engines, to computers, to automatic garage door openers - are helping to pollute the airwaves with electromagnetic garbage."The radio spectrum is a natural resource and, as with any natural resource, it can get polluted," Price said in an interview while attending an astronomy conference Monday. "It's not like air or water pollution because you can't see it, but it's there."

For that reason, he said, astronomers are anxious that unnecessary uses of radio signals be eliminated. In many cases, gross radio interference sources could be controlled with the use of filters or shields that would add only a dollar or two to manufacturing costs, he said.

"The radio spectrum is a vital part of our everyday life," said Price. "Every time you order a pizza or call for an ambulance, it's probably radio dispatched and there's another signal. That's why we worry about this limited resource being used for frivolous purposes."

Electromagnetic gridlock is only one type of pollution affecting astronomers. At a meeting this week sponsored by the International Astronomical Union, astronomers from around the world said their work also is hampered by manmade light and by debris left in space that reflects sunlight and causes streaks on astronomy photographs.

For radio astronomers, the electromagnetic spectrum can help unlock secrets of star formation millions of light years away. Each type of molecule, when excited by heat, puts out a unique radio signal. By capturing and analyzing these signals, radio astronomers can determine the chemical composition of processes taking place at points in the universe not even visible to optical telescopes.

Price said astronomers recognize that eventually they'll have to leave the Earth and its cacophony of electronic noise, if they are to continue studying the dim electronic voice of the universe. But where would they go?

"The backside of the moon has been designated as a quiet zone," he said. "It would be shielded against the signals from Earth. That's about our only choice."