The Little-Known Legacy of Radio Astronomer Karl Jansky

The Little-Known Legacy of Radio Astronomer Karl Jansky

The Little-Known Legacy of Radio Astronomer Karl Jansky

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By Dr. Gary L. Deel, Ph.D., J.D.
Faculty Director, School of Business, American Military University

In grade school history and science classes, children learn about a variety of central figures in science who helped mankind to understand its place in the cosmos. From Nicholaus Copernicus to Johannes Kepler, to Isaac Newton to Albert Einstein, students read about exciting characters who tamed new frontiers in science and helped to revolutionize our understanding of the universe. Sadly, however, one name they are not likely to learn about is that of Karl Jansky.

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Jansky was an American physicist and radio astronomer of the early 20th century who more or less accidentally gave birth to radio astronomy in 1931. Jansky was an engineer for Bell Labs working on trans-Atlantic radio communications. As part of his pioneering work, he designed and built a 20-foot-tall radio antenna that was intended to receive radio communications from overseas.

However, when he turned it on and observed the results, he noted a background static that appeared to spike once per day. Because of this cycle, Jansky first thought that the source of the radio spike was the Sun. And so he set about trying to adjust and recalibrate his measurements to account for this source of interference.

But after months of steady observation he eventually noticed that the cycles followed the sidereal day of the Earth and not the solar day. (The sidereal day is the time between two consecutive transits of the First Point of Aries. It represents the time taken by the earth to rotate on its axis relative to the stars, and is almost four minutes shorter than the solar day because of the earth’s orbital motion.)

The Radio Spikes Were Coming from the Center of our Milky Way Galaxy.

Instead of the spikes showing correlation with the rise and fall of the Sun each day, the spikes actually correlated more closely with the antenna’s exposure to a point in deep space. From this, Jansky eventually deduced that the radio spikes were coming from the constellation Sagittarius and, more specifically, from the center of our Milky Way galaxy.

Jansky’s work was extremely influential as it was the pioneering of radio astronomy that would later be one of our most powerful tools in understanding the nature of the universe. Through radio astronomy we’ve discovered exotic objects such as pulsars, quasars, and black holes. We’ve even used it to reveal the cosmic microwave background, which is the residual radioactivity in the universe echoing from the Big Bang. Radio astronomy has made huge contributions to our understanding of the cosmos, and we have Jansky to thank for that. So grade school history and science classes would do well to include Karl Jansky in future lessons.

About the Author

Dr. Gary Deel is a Faculty Director with the School of Business at American Military University. He holds a J.D. in Law and a Ph.D. in Hospitality/Business Management. Gary teaches human resources and employment law classes for American Military University, the University of Central Florida, Colorado State University and others.