Page:Open Skies (Kellermann).pdf/24

CHAPTER 1

A New Window on the Universe

In April 1933, at a small gathering at a meeting of the US National Committee of the International Scientific Radio Union (URSI), Bell Labs scientist Karl Guthe Jansky announced that he had detected 20.5 MHz (14.6 m) radio emission from the Milky Way. Jansky used a novel directional antenna based on an invention by AT&T Bell Labs colleague, Edmond Bruce, that rotated every 20 minutes to determine the direction and source of the interfering noise that was plaguing the telephone company. Jansky’s remarkable discovery of what he called “star noise” was widely publicized in the media, but had little immediate impact in the astronomical community, as astronomers, who typically had little background in electronics or radio, saw no relation to their own work.

For more than a decade, the only significant progress was made by one individual, Grote Reber, who had just graduated from college with a degree in electrical engineering. His 32 foot parabolic dish, which he built in the yard next to his mother’s house using his own funds, was the forerunner of the much larger radio telescopes later built in the UK, in Australia, and later the United States, as well as the millions of smaller dishes which have proliferated throughout the world for the reception of satellite-based TV broadcasting. With his home-built radio telescope, Reber detected galactic radio noise first at 160 MHz (1.9 m) then 480 MHz (62 cm), which he called “cosmic static.” Reber recognized the nonthermal nature of the galactic radio emission, made the first radio maps of the Milky Way, discovered the intense radio emission from the Sun, and brought radio astronomy to the attention of the astronomical community.

1.1   Star Noise at the Telephone Company1

The first transatlantic telephone circuits were established by AT&T in 1927 between New York and London using very long wavelength 5 km (60 kHz) radio transmissions (Bown 1927). The following year, the AT&T Bell System