In 1931, a communications engineer working for Bell Laboratories was exploring radio frequency disturbances in the atmosphere that might interfere with a transoceanic telephone. He noticed that he was picking up a noise that didn't come from thunderstorms-_but from somewhere in outer space! He discovered that he was able to pick up radiation from far away in our galaxy; and a new branch of astronomy was born--radio astronomy.
Radio astronomy works in two ways. By using special types of antennae, it picks up radiations sent out by objects in space. Some of these are "thermal" radiations, the radiations that any heated body emits in radio frequency waves. But there is also noise, or "cosmic static", which is picked up from outer space and is not thermal in origin.
Another way radio astronomy works are by sending signals out to such objects as meteors and the moon and obtaining the reflection.
This is the way radar works.
So far radio astronomy has been most useful in the study of meteors, the moon, the sun, and other planets. By bouncing back beams from meteors, we learn much about their orbits. By studying the moon with radio astronomy, we learn something about its surface. For example, even before men landed on the moon, radio astronomy led scientists to believe that its surface layers consisted of powdered rocks Perhaps the most exciting use of radio astronomy is about to begin--the search for messages from other worlds! A radio telescope has been developed that can detect a signal almost 50 trillion miles away. What kind of signal do scientists hope to pick up? They believe that if there is some civilization somewhere in outer space, and it wants to make its presence known, it would probably send out some very simple signal such as a series of numbers. It is also thought that the signals would be of the radio frequency of 1,420 megacycles, the frequency at which natural hydrogen emits radio energy in outer space.
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