Telescopes from the Ground Up
Image of some of the radio telescopes that make up the Very Large Array.

Looking at the sky in a whole new light

In the early 1930s, Bell Telephone Laboratories experimented with using radio waves to make phone calls across the ocean. The company quickly encountered a problem: a strange hissing noise that would interfere with the transmissions.

Karl Jansky, a 26-year-old engineer, was assigned the task of figuring out the source of the static. At the time, he couldn’t have imagined that his job would trigger an entire new way of investigating the stars.

Noise from nowhere

Jansky built a set of wire rectangles that served as antennae, and mounted them on four wheels he’d taken from a Model T Ford. He could rotate the arrangement to focus on radio waves coming from a particular direction. This would allow him to trace the static to its source.

Some of the hissing sources were obvious, like the crackle from the electricity of thunderstorms. One low, steady hiss, however, puzzled Jansky. It never went away, and it seemed to follow the path of the Sun. As he studied it further, he realized it was actually moving with the stars!

In fact, the static was coming from the center of the Milky Way. In 1932, Jansky published his findings and then moved on to another assignment.

Jansky’s discovery launched the new field of radio astronomy. His antenna array could be considered the first crude radio telescope.

Image above: Courtesy NRAO/AUI
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