IN ANCIENT times the appearance of a comet was a sure sign of great disorder in the heavens, and a portent of impending chaos here on Earth. As Jonathan Swift put it: "Old men and comets have been revered for the same reasons: their long beards and their pretences to foretell events."
With all eyes these days closely focused on Comet HaleBopp, currently clearly visible, beard and all, in the northeastern early morning sky, we could be forgiven, perhaps, for wondering if all is well above.
The 16th century philosopher William Fulke, for example, was very clear on this point. Comets, he said, brought disease, "for so much as this kynd of Exhalations corrupteth the ayre, whiche infecteth the bodyes of men and beasts". He also deduced that they had "civile and politikal effects", which included "warres, seditions, changes of commen wealths and the deaths of noble men".
As a somewhat edgy Calpurnia remarked to her husband Julius Caesar when she noticed a comet in the sky on this very day, March 14th, in 44 BC:
When beggars die there are no comets seen;
The heavens themselves burst forth the death of princes.
We, of course, know better. We know that a comet circles the sun, just as the planets do, but that it moves in very eccentric and elongated orbit, spending most of its time so far away from Earth that we cannot see it. It consists largely of separate lumps of rock or gravel, held together with ice, sometimes aptly described as resembling a "dirty snowball".
As this wanderer approaches the sun, it vaporises under the influence of the intense heat; it leaves behind it streams of dust and gas, the ionised gas forming a straight tail pointing away from the sun, and the glowing dust tracing a curving path to make a second tail. Both tails grow longer as the comet nears the sun.
Comet Hale Bopp is named after two amateur astronomers, Alan Hale and Thomas Bopp, who discovered it independently, but almost simultaneously, on July 23rd, 1995. Although it can be seen at present very low in the northern sky just after sunset, it is best observed in the very early morning.
If you find the thought of getting up at 5.00 am discouraging, however, you can wait until after March 22nd, the day on which Hale Bopp will be closest to the Earth, and after which it will become a striking feature, high in the northwest sky, at evening time. It will be more prominent than the Dog Star, Sirius, usually the very brightest star, and both tails will be clearly evident to the naked eye.