Throughout recorded history and certainly long before, people have noted the courses of stars and planets. However, unanticipated events such as meteors, novae and comets often evoked fear and consternation. Since these interlopers appeared to upset the “natural order,” they were generally regarded as malevolent influences, or omens of important events. Many Romans thought the Great Comet of 44 BC signified the deification of Julius Caesar. The 1066 appearance of Halley’s Comet was said to herald the coming of William the Conqueror to England.
Until the 18th century, comets were thought to be atmospheric disturbances. However, British scientist Edmund Halley (1656-1742) theorized they were celestial bodies orbiting the sun, and that the comets of 1531, 1607 and 1682 were the same object. Halley, a supporter of Isaac Newton, paid for publication of Principia, one of history’s most important scientific works. Using Newton’s Laws of motion and universal gravitation from the Principia, Halley calculated that the comet would return in 1758. When the comet returned on schedule (16 years after Halley’s death), it was named in his honor.
Comets are now known to be clumps of ice, dust and rock particles in the outer regions of our solar system. The paths of some become perturbed or modified so that they are carried into the inner solar system (the area of the orbits of Mercury, Venus, Earth and Mars). As comets enter this area atomic particles and light streaming from the sun exert a gentle push that shapes their volatile components into a tail.
Comets fall into two broad categories. Short-period comets return on known schedules ranging from a few years to several decades. Halley’s Comet is the only short-period comet visible to the unaided eye. Long-period comets, such as the Great January Comet of 1910, are unanticipated, surprising astronomers and the public. Their orbits extend to far greater distances from the sun and can have periods of thousands of years.
Tuscaloosans, like most Americans, were familiar with comets. In 1845, University of Alabama Professor Frederick Barnard presented a public lecture at the First Presbyterian Church. He spoke on the motions of celestial bodies and how the return of comets can be predicted. He also emphasized that comets presented no threat to earth because of their “light substance.” During the 19th century, several spectacular comets were visible, including Halley’s Comet of 1835, the Great Comet of 1843, Donati’s Comet of 1858 and the Great September Comet of 1882.
The return of Halley’s Comet in 1910, and anticipation that the earth would pass through its tail, triggered a worldwide comet craze. Comet themed items produced by entrepreneurs included jewelry, whisky, satirical or risqué postcards, cartoons, tobacco products and a multitude of other things. For those fearing the comet’s appearance, there were gas masks, comet pills and umbrellas to fend off falling debris.
An April 1910 issue of the West Alabama Breeze presented the “Itinerary of Halley’s Comet.” It detailed times and locations for the comet, concluding that it would return between 1985 and 1989. As predicted, the comet appeared in late 1985 and early 1986. A number of spacecraft (jokingly referred to as “Halley’s Armada”) were launched to study it. However, conditions for earthbound viewing were far less favorable than in 1910, since the comet was on the opposite side of the sun.
Halley’s next appearance is scheduled for the summer of 2061, offering some Tuscaloosans the opportunity to see it twice in their lifetimes.