Until the middle of the 20th century the Earth's magnetism seemed to be a happy accident of nature. Too many factors had to fit just right--the fluid core of the Earth, its electrical condctivity and its motions, all had to satisfy the strict requirements of dynamo theory.
That was before other planets in the solar system were visited and examined. Now we know that among those planets, only Venus lacks any magnetism. The planets differ greatly in size and properties, and their fields differ too. Yet they all seem to have dynamo fields, or (in the case of Mars and the Moon) have had them in the past.
In early 1955, two young radio-astronomers started working with a cross-shaped antenna array of the Carnegie Institution's Department of Terrestrial Magnetism (DTM). The array stood on the north shore of the Potomac River (upstream from Washington, DC and slightly south of White's Ferry; more here) and could select signals from a narrow range of directions. Ken Franklin and Bernie Burke calibrated it using a known source, the Crab Nebula, then began surveying the surrounding sky.
Posted by Jay Roberts at 02:21 AM | Permalink