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This Day in History

World History

Saturday, December 8, 1590. :   Sunspots are noted by sailor James Welsh in one of the few pre-Galileo observances.

     Sunspots are areas on the Sun's photosphere, or surface, where the temperature is considerably lower than that of surrounding areas. The temperature difference causes these areas to appear as black spots which are sometimes visible without the aid of a telescope. The cooling effect is due to a strong magnetic field in a particular localised area which inhibits the transport of heat via convective motion in the sun.

Chinese astronomers have observed sunspots since 28 BC, but more modern viewings were few and far between. On 8 December 1590, sailor James Welsh of the ship "Richard of Arundel" observed a large black spot on the sun's surface, whilst sailing off the coast of Guinea. He noted that the spot was still visible the following morning.

The phenomenon remained largely unnoticed in ensuing years, until Galileo brought it to the population's attention in 1612, complete with likely explanation of how it occurred. It was not until the 1820s that the cyclic variation of the number of sunspots was first observed by Heinrich Schwabe. Later astronomers and scientists plotted the variations, leading to speculation on the effect of sunspots on weather patterns.

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