Steven Delaney, age 12, of Monroe, Connecticut, for his question:

What data do radio telescopes gather?

Radio telescopes gather radio waves ranging from about half an inch to 30 yards or more. They also measure such factors as frequency, intensity and polarization and present the analyzed data on readable print outs. In the past 40 years, this far reaching radio astronomy has added a whole new dimension to our concept of the universe. It also has revealed some astounding surprises.

An optical telescope gathers light through a fairly small aperture, or peephole. Light waves are 10,000 times shorter than the shortest radio waves. Hence, radio telescopes need wider apertures to gather the amazing radio energies that reach us from space. They can be turned and tuned to catch sighs from the sun, hisses from the far Milky Way or thunderous rumblings from the giant planet Jupiter.

These celestial radio programs may be amusing but the serious work of radio telescopes is downright amazing. They work because outer space pulses with electro¬magnetic energies, including light and X rays, infrared and ultra violet, plus a wide range of radio. Our atmosphere screens out those radiations if their waves are much longer or shorter than those of visible light. It lets through radio waves that range from about one centimeter to thirty meters.

This opens out to the universe a wider window than the narrow range of light, though light tends to be more precise. Radio telescopes work singly or in co ordinated groups to gather data from wide sweeps across the universe. The data may be pin¬pointed and clarified by optical telescopes.

For example, in the 1960s intense radio signals were captured from afar. They were radiating from sources more than a billion times stronger than an average star. Radio telescopes could plot only their general location. Optical telescopes pounced on the new data     and zeroed in to take visual photos. This teamwork introduced us to the baffling quasars     the brightest and most remote objects so far discovered.

Some radio waves indicate temperatures. For example, radio telescopes gather wave lengths of one meter from the sun's far out corona. This indicates a temperature of a million degrees. Radio waves of ten centimeters near the sun's surface indicate a temperature of 10,000 degrees C. These are but a few of the cosmic secrets that radio telescopes have revealed. Who can guess how much more they can be coaxed to reveal in the next 40 years.

For example, optical telescopes cannot photograph our Galaxy through all the bulky objects in the Milky Way. But radio telescopes can capture the 21 centimer wave lengths of neutral hydrogen. This stuff is widely distributed across the flat, starry cart¬wheel. A complete survey was made and translated onto a chart. The result was the first visual portrait of our Galaxy, complete with its crowded hub and spiralling arms. Radio telescopes were able to scan the hydrogen wave length, right through the obstacles that stopped the wave lengths of light.