August 31st: Grote Reber: The First Radio Astronomer

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365daysDate: August 31, 2009

Title: Grote Reber: The First Radio Astronomer

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Podcaster: Destry Saul

Organization: Columbia University Astronomy: http://outreach.astro.columbia.edu

Description: The first detection of radio waves from space was made by Karl Jansky in 1932, but it was an amateur radio enthusiast in a suburb of Chicago that would continue Jansky’s work. His name was Grote Reber, and this is his story.

Bio: Destry Saul is currently a graduate student at Columbia University. He attended UC Berkeley where he earned a B.A. in Astrophysics, Physics, and Theater Performance Studies. His research interests include radio observations of nearby galaxies, masers, and transient astronomy.

Outside of astronomy, Destry enjoys cycling, playing the mandolin, and knitting.

His website is: http://astro.columbia.edu/~destry

Today’s sponsor: This episode of “365 Days of Astronomy” is sponsored by Joseph Brimacombe.

Transcript:

The day was May 5, 1933, Franklin Roosevelt was in his first year as president, it was the fourth year of the Great Depression, and there was an important headline on the front page of the New York Times. It read, “New Radio Waves Traced to Center of the Milky Way.”

This was the birth of radio astronomy; announcing Karl Jansky’s discovery of ‘cosmic static’ coming from outside our solar system. Being the father of radio astronomy, you might think that Jansky went on to study this static from the sky, but this wasn’t the case. You see, Jansky was an employee of Bell Labs, and he was paid to improve the trans-Atlantic telegraph, not study the stars. And in 1933, there was no profit to be made in the newly born field of radio astronomy. This is why it was an amateur that pioneered this branch of science. This amateur’s name was Grote Reber.

Grote Reber, was born in 1911 in Chicago, Illinois. He was an avid, amateur scientist, measuring anything measurable. He pushed the topics he studied to their limits and was particularly interested in the radio. At the time of Jansky’s discovery, Reber claims to have contacted over 60 countries and all continents from his home at 225 West Wesley Street in Wheaton, Illinois. In his own words, “There did not appear to be any more worlds to conquer.” It was only logical then that he start listening to the radio waves from other parts of our galaxy or Universe. You see, contacting South Africa from Illinois isn’t nearly as impressive when you compare that to recording emission from Cygnus A, a galaxy over 700 million light years away!

But in 1933 no one knew about Cygnus A. The only thing anyone knew about the radio sky was that at 20 MHz there was static coming from the general direction of the Milky Way. To study the cosmic static, Reber would have to start from scratch. Since he was working in Chicago during the day, he had to use his nights and weekends to design and construct the world’s first radio telescope. He decided to use a meridian-transit design which is a telescope that cannot turn about it’s axis, but always points toward the meridian. This allowed Reber’s telescope to use no motors, but it did incorporate a differential from a Ford Model A truck. This was used to change the altitude, or declination, of the telescope.

Reber built his telescope almost entirely on his own over four months in the summer of 1937. To reduce cost, the structure was built almost entirely out of two by four lumber which was quadruply coated in paint to protect it from the elements. In fact, 72 years after it’s construction, Reber’s telescope is still standing, but it has been moved to the Green Bank Observatory in West Virginia where it is currently on display.

The dish of the telescope was 31 feet across and constructed of galvanized iron sheet metal. When completed, the telescope was over 40 feet in height. The people of Wheaton had never seen anything like it. As Reber wrote, “When parked in a vertical position, great volumes of water poured through the central hole during a rain storm. This caused rumors among the local inhabitants that the machine was for collecting water and for controlling the weather.”

By September 1937, Reber had finished building his telescope and started taking measurements. But Reber didn’t hear any cosmic static. He had made a very logical mistake that would set him back two years in his research.

A major reason why the radio spectrum had not been investigated by professional astronomers was that until this time, all observed objects emitted light as thermal radiation, or in other words, they glowed because they were hot. Physicists had calculated how bright an object should be at any wavelength for a given temperature and in the radio, there should be more energy at shorter wavelengths. But an object would have to be incredibly hot to be observable from earth.

Jansky, who discovered cosmic static, had only collected measurements at one frequency, so it wasn’t known yet that this static actually gets stronger at longer wavelengths, not shorter. This is because these radio waves are not coming from a star or other hot object, but from electrons being accelerated in space. So Reber’s mistake was that he had built his receiving system to measure shorter wavelengths than Jansky and his equipment just wasn’t sensitive enough.

So Reber worked his day-job during the day and listened to the sky at night. Another reason he had to observe at night was that spark plugs from passing cars created enough radio interference that it ruined his data. Not because spark plugs emit super powerful radio waves, but because the signals he was searching for were so weak.

Finally, after two years of experiments, he succeeded in detecting the cosmic static that Jansky had discovered six years earlier. This was only the second time that radio waves from outside the solar system had been detected. But Reber did much more than just detect these radio waves. With his pointable dish and a new recorder, he mapped the entire sky visible from Illinois at several wavelengths. He published his results, as an amateur, in the Astrophysical Journal, an impressive feat. Reber’s paper demonstrated that the cosmic static was an interesting, observable phenomenon, and not just a strange curiosity.

After several more years, Reber, ever the intrepid amateur, moved on to study an eclectic mix of science including astronomy, botany, and even anthropology. He relocated to Tasmania to further his studies of very long wavelength radio astronomy with wavelengths longer than 100 meters. He was in Tasmania when he died in 2002 at the age of 90.

Radio astronomy has become a way to observe another facet of the Universe. There are now radio telescopes hundreds of feet across that regularly measure signals from all over the Universe. And it was Grote Reber who paved the way for this from his backyard in Wheaton, Illinois.

End of podcast:

365 Days of Astronomy
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The 365 Days of Astronomy Podcast is produced by the New Media Working Group of the International Year of Astronomy 2009. Audio post-production by Preston Gibson. Bandwidth donated by libsyn.com and wizzard media. Web design by Clockwork Active Media Systems. You may reproduce and distribute this audio for non-commercial purposes. Please consider supporting the podcast with a few dollars (or Euros!). Visit us on the web at 365DaysOfAstronomy.org or email us at info@365DaysOfAstronomy.org. Until tomorrow…goodbye.

About Destry Saul

Destry Saul is currently a graduate student at Columbia University. He attended UC Berkeley where he earned a B.A. in Astrophysics, Physics, and Theater Performance Studies. His research interests include radio observations of nearby galaxies, masers, and transient astronomy. Outside of astronomy, Destry enjoys cycling, playing the mandolin, and knitting. His website is: http://astro.columbia.edu/~destry

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One Response to August 31st: Grote Reber: The First Radio Astronomer

  1. web design chicago December 22, 2010 at 4:37 am #

    Hi There,

    The mirror was 31 feet in diameter with a focal length of 20 feet

    Thanks,
    Chirst