More Than the Eye Can See
While many astronomers were toiling with photons and the most effective way to capture them, Bell Labs physicist Karl Jansky was working on a seemingly unrelated problem - how to cut down interference on overseas telephone calls. He wound up discovering a new way to map the cosmos when he identified a distinct astronomical radiation source called radio waves. His observations opened our eyes to previously unknown invisible information in our cosmos. Celestial bodies emit energy at all different wavelengths on the electromagnetic spectrum, not just the visible wavelengths we can see.

Radio telescopes such as the Goldstone Apple Valley Radio Telescope -- which is used to train middle and high school students to use radio stronomy -- are used to detect invisible radiowave energy in the universe.

Though you might think that a radio telescope looks for sounds from the cosmos, in fact, it simply receives energy emitted at longer wavelengths than visible light. Because radio waves are capable of transmitting signals through clouds of gas with little distortion, they can be used to map incredibly detailed images of space. These telescopes when used in conjunction with very sensitive spectrometers have led to the discovery of many compounds familiar to us on earth but surprising to find in the universe - water vapor, formaldehyde, carbon dioxide, ammonia and one very important in unraveling the mystery of dark matter, hydrogen.

The radical notion that hydrogen clouds surrounding galaxies -- such as our very own Milky Way - are accelerating around the edges has been supported by research done with radio telescopes. Radio telescopes are able to track the shifting clouds of gas and through calculations involving mass, velocity and the distance from the gravitational center. This gives us the evidence that Dark Matter exists.
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