Steve Wallace, age 13, of Gastonia, N.C., for his question:
What is a radio telescope?
The ordinary telescope is a mechanical larger than life eye for viewing the heavens. The radio telescope is a mechanical larger than life ear for hearing the heavens. Space is filled with all kinds of energies and radiations, pulsing from star to star, from hazy nebula to cloud of hydrogen gas. The radio telescope traps the teeming electromagnetic waves of radio. It can gather over a hundred times more information than the telescope's big glass eye.
The first radio telescope was made by accident in 1931. Karl Jansky, then 23 years old, was doing research on static for the Bell Telephone Laboratories in N.J. He built a radio aerial about 100 feet long and mounted it high on a wooden frame. In the center was an engine which turned the instrument to scan the skies once in every 20 minutes.
Jansky sat with earphones and listened to static made by passing planes and distant storms. He also heard a faint hiss which he could not place at all. Most people would have ignored that hiss but not Karl Jansky. F or a year he worked patiently and systematically to track it down.
The strange static seemed to come from first one spot, then another spot in the sky. Throughout the year. Jansky charted its path. The results were astounding. At all times; the strange whisper came from beyond the constellation Sagittarius, the Archer. The constant heavenly message was coming from the very heart of the Milky Way, a distance of 26,000 light years about 1502000 million, million miles. Jansky's instrument had, by accident, acted as the first radio telescope. Bigger and better radio telescopes were to follow.
The lens telescope traps light waves with wave lengths only up to hundred thousandths of an inch. The radio telescope traps radiation with wave lengths almost anywhere from half an inch to 30 feet. These radio radiations start in the turmoil of some distant star or cloud of gas. There, atoms are so agitated that electrons leap from shell to shell. This agitation sets up electromagnetic disturbances in space. The faster the electrons move, the shorter the radio wave length. All this radiation, long waves and short waves, rips across space at about 186, 000 miles a second.
The science of radio astronomy is still a baby, still unable to read whispered and shouted messages that constantly bombard us from the heavens. Also, many of these messages are kept from us by the earth's, atmosphere. For example, wave lengths of half an inch are kept out by vapor in the air. Wave lengths of 30 feet and over are bounced back by the upper atmosphere. These gaps in our heavenly news will be filled when we set up the first radio telescope on the airless moon.