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Mercury, November/December 2004 Table of Contents

Courtesy of P. Pratap

by Preethi Pratap and Madeleine Needles

It is a bright sunny day in Mary Altenhof's astronomy class at Marlborough High School in Massachuestts. Students are clustered in several groups and intently peering at their equipment. One group, near a window, is drawing sunspot positions on a piece of paper using a Sunspotter solar telescope. Another group is setting up a soda-bottle magnetometer to attempt to measure variations in Earth's magnetic field. A third group is in front of a computer screen operating a small radio telescope that is parked in the lot outside the classroom window. But they all have one goal—studying the Sun, our nearest star, the one that has the most effect on our lives.

One of the tools these students are using—a radio telescope—explores an invisible part of the electromagnetic spectrum, radio waves. While radio waves may be invisible to our eyes, their uses permeate our daily lives. To exploit fully the many uses of radio waves, we need to understand them and the mechanisms that produce them.

From listening to music on the radio to talking on our cell phones, radio waves are the means used to get information across large distances. Neil Armstrong used the power of radio waves to let the world know that for the first time a human had set foot on the Moon. The little Voyager spacecraft used radio waves to send back magnificent images of distant planets and the Mars rovers use radio waves to send back pictures of a red, rocky planet. Closer to us, radio waves are used not just for news, music, and television, but also as a way for police and firemen to react quickly to emergencies.

Radio waves also give us information about the Universe complementing information obtained at other wavelengths. Radio astronomers use large antennas to collect radio waves from all over the Universe. These data tell us about the energetic processes happening at the very centers of galaxies, permit us to peer deeply into stellar nurseries where stars of all sizes form, and give us valuable information about the rich chemistry that occurs all over the Milky Way Galaxy. Other than visible light and some infrared light, radio waves are the only other part of the electromagnetic spectrum that Earth's atmosphere will allow to pass! But radio waves from the Universe are very weak, so astronomers have developed many techniques to detect this emission from objects very far away.

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