In the early 1930′s, Bell Labs, the research division of AT&T, launched a project to use radio “short waves” to transmit telephone calls across the Atlantic. The technology to transmit signals via short waves was reasonably well understood. But engineers also needed to understand sources of noise that might interfere with radio communications signals. So the powers-that-were at Bell Labs tasked a young engineer to find sources of radio static that might interfere with transmissions. During his work, this young engineer, Karl Jansky, made an accidental discovery that revolutionized astronomy.
To search for sources of naturally-produced radio noise, Jansky built an antenna to detect radio waves at a frequency of about 20.5 MHz (a wavelength of 14.5 meters). He mounted the antenna on four Ford Model-T tires so he could rotate his contraption to determine the direction of any radio signal he might find. The antenna was jokingly called “Jansky’s merry-go-round”.
After tweaking his antenna and receiver for several months, Jansky found static from nearby and distant thunderstorms. But he also found a faint steady radio hiss of unknown origin. The intensity of the hiss rose and fell once a day. At first, he thought the unknown static might be radio waves from the Sun.
After a few months of following the signal, the brightest source of radio waves slowly moved away from the Sun. The signal repeated not every 24 hours, but every 23 hours and 56 minutes, the same period in which the stars rise and set.
Jansky eventually figured out the radiation was strongest in the direction of the center of our Milky Way galaxy, towards the constellation of Sagittarius. The discovery of strong radio waves from the center of the galaxy was widely publicized, appearing in the New York Times on May 5, 1933.
This was an astonishing and totally unexpected discovery. But there was no one– no scientist anywhere on Earth– who had the tools or time to study it further. Jansky very much wanted to continue his work and learn more about the galactic radio waves, but he was assigned to another project by Bell Labs managers and never again studied this mysterious radio “hiss” from the Milky Way.
Many scientists were fascinated by Jansky’s discovery. But no one followed up on it for several years until a modest radio engineer from Chicago became the world’s first true radio astronomer.
However, a young ham radio operator and radio engineer from Chicago named Grote Reber read of Jansky’s discovery of “cosmic radio waves” in the newspapers. He was captivated by the discovery and applied to work with Jansky at Bell Labs in Holdmel, New Jersey. But the Great Depression prevented Bell from hiring new staff.
Rebuffed by Bell Labs, Reber worked a day job as an engineer with several radio manufacturers from 1933 to 1947. In his spare time, at his own expense, he built his own 30-foot radio antenna out of sheet metal. Just like an optical telescope, Reber’s construction used a parabolic mirror to focus all wavelengths to a single point. There, 20 feet above the dish, he mounted his radio receiver to amplify the faint cosmic signals by million of times, making them strong enough to record on a strip chart. Reber had constructed the world’s first radio telescope, and for a time, this young man from the Chicago suburbs was the first– and only– radio astronomer.
With his backyard radio telescope, Reber confirmed Jansky’s discovery of radio waves from the Milky Way, and found radio emission from the Sun and mysterious radio sources in the constellations Cassiopeia and Cygnus. In time, scientists discovered that the radio emissions from the center of our galaxy were caused by electrons accelerated in a strong magnetic field near the galactic center.
From 1938 to 1943, Reber made the first surveys of radio waves from the sky and published his results widely. His work ensured radio astronomy became a major field of research following World War II.
When other better funded researchers began covering more and more of the radio spectrum, Reber turned to longer-wavelength radio waves in the 1950′s. Such signals penetrate the Earth’s atmosphere in only a few places, including northern Manitoba in Canada and Tasmania in Australia. Reber chose Tasmania for its relative isolation (and perhaps its better weather) and spent 50 years on the deep-southern island. He died there in 2002 at the age of 90.
Reber’s work was the end of a golden age of astronomy, when an accomplished amateur could make groundbreaking discoveries. This often happens in a new and young science, where professionals, by definition, don’t yet exist.
And despite his efforts as a professional radio engineer to build and use the first radio telescope, Reber was an amateur astronomer. The true revolution in radio astronomy dawned after the Second World War when professional physicists and astronomers began to study the sky with larger and more sophisticated radio telescopes. It was a revolutionary advance in science. In a 1998 article in the New York Times commemorating Jansky’s work, the astronomer Jesse Greenstein said that analysis of radio waves emanating from space provided researchers with ”10,000 times the information” they could get from optical astronomy. ”It led to information that overturned the idea of a rationally developing universe,” he said, ”and replaced it with a relativistic, ultra-high energy cosmos of scary, violent, uncontrollable forces like black holes and quasars. It was a revolution.”
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