In 1932, a Bell Labs engineer trying to solve mysterious static from transatlantic phone calls that repeated every 23 hours and 56 minutes accidentally discovered radio waves from the center of the Milky Way

In the early 1930s, Bell Telephone Laboratories had a frustrating problem.

Static was interfering with its new transatlantic radio-telephone service, and the company wanted to know where the interference was coming from. The job fell to a young radio engineer named Karl Jansky, who had joined Bell Labs in 1928.

Jansky was not looking for aliens, distant galaxies or some new phenomenon in space.


He was simply trying to fix a telephone problem.

To track down the mysterious hiss, Jansky built an enormous directional antenna roughly 100 feet across and 20 feet high. Mounted on wheels taken from a Ford Model T, the contraption could rotate along a circular track and scan different parts of the sky.

His colleagues reportedly nicknamed it “Jansky's merry-go-round.”

For nearly a year, Jansky used the strange-looking machine to classify sources of radio interference. Much of the static came from familiar sources such as thunderstorms.

But there was another signal he couldn't explain.

A faint hiss kept appearing and disappearing with remarkable regularity.

At first, Jansky considered whether the Sun might be responsible. But as he continued observing it, something extraordinary emerged: the signal followed a cycle of about 23 hours and 56 minutes, rather than the familiar 24-hour solar day.

That four-minute difference was the clue.

A sidereal day is the time Earth takes to rotate once relative to the distant stars. Because Earth moves around the Sun while rotating, the sidereal day is about four minutes shorter than the solar day.

In other words, the signal wasn't behaving like something tied to the Sun or a fixed location on Earth.

It appeared to be coming from a fixed direction in the stars.

By comparing his measurements with astronomical charts, Jansky traced the strongest source toward the constellation Sagittarius, in the direction of the center of the Milky Way.

He had stumbled upon something nobody had deliberately set out to find: radio emission from our galaxy.

In a February 1933 letter to his father, Jansky wrote that the mysterious hiss came “from a direction fixed in space” and described the evidence as “very conclusive” and “very startling.”

The discovery soon attracted public attention. On May 5, 1933, The New York Times reported it on its front page, and the hiss was even broadcast to listeners.

To human ears, the cosmic signal sounded remarkably mundane — like steam escaping from a radiator.

But behind that ordinary hiss was something extraordinary.

Jansky had detected electromagnetic radiation arriving from deep space. The radio emission was associated with energetic processes in the Milky Way, opening a completely new way of studying the universe.

And the irony is almost too good.

The first breakthrough in radio astronomy began as a telephone-company troubleshooting job.

Bell Labs had wanted to eliminate an annoying noise.

Instead, Jansky discovered that the sky itself was broadcasting.

The discovery did not immediately launch the new field into the mainstream. Bell Labs had little commercial reason to fund extensive astronomical observations, and Jansky's request for a larger antenna was not pursued. The work might have remained a fascinating footnote had another radio enthusiast not picked it up.

That person was Grote Reber, an amateur radio operator who became fascinated by Jansky's findings and eventually built his own radio telescope in his backyard.

Reber's work helped turn Jansky's accidental observation into the foundation of radio astronomy.

There is something particularly fitting about the story: Jansky wasn't searching for a cosmic message.

He was searching for a fault.

And while trying to silence an unwanted hiss on a telephone line, he discovered that the Milky Way was making itself heard.