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10 April 2014 11:44 am ,
Vol. 344 ,
The Pyrenean ibex, an impressive mountain goat that lived in the central Pyrenees in Spain, went extinct in 2000. But a...
Tight budgets are forcing NASA to consider turning off one or more planetary science projects that have completed their...
Ebola is not a stranger to West Africa—an outbreak in the 1990s killed chimpanzees and sickened one researcher. But the...
In an as-yet-unpublished report, an international panel of geoscientists has concluded that a pair of deadly...
Tropical disease experts tried and failed before to eradicate yaws, a rare disfiguring disease of poor countries. Now,...
Since 2002, researchers have reported that agricultural communities in the hot and humid Pacific Coast of Central...
Balkan endemic kidney disease surfaced in the 1950s and for decades defied attempts to finger the cause. It occurred...
- 10 April 2014 11:44 am , Vol. 344 , #6180
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Proving Copernicus Right
3 March 1999 8:30 pm
The name of 16th century Polish astronomer Nicolaus Copernicus became a household world because he proposed that the Earth revolves around the sun. But the man who finally gathered scientific proof of that theory was English astronomer James Bradley, born during this month in 1693.
Called the best astronomer in Europe by Isaac Newton, Bradley methodically observed the star Gamma Draconis and noticed slight seasonal shifts in its position, which he then observed in other stars as well. He called this effect "the aberration of light" and estimated its angle at 20 to 20.5 seconds; the modern value is 20.47 seconds. Eventually, Bradley realized that the displacement stemmed from viewing a stationary object from a moving one, the Earth--thus confirming Copernicus's concept.
Bradley later discovered a second process that causes stars to wobble in their places in the firmament. In an effect he called "nutation"--known to be true today--subtle changes in the angle of Earth's rotation, caused by the moon's pull on the equator, alter apparent stellar positions.