TODAY comets are regarded with casual disdain or some curiosity, but centuries ago, comets were regarded as harbingers of disaster, violence, wars, pestilence, disease and what not! The arrival of a comet in the sky would usually spell disaster for the rulers who were scared by its presence, both for its unpredictability and the fiendish tail it developed, which evidently grew longer with each passing day, and grew shorter on its way out, circling right around the Sun. For its ever developing and then gradually contracting tail, many people thought that it was a living thing sent into the sky by ‘gods’ to punish them for their sins.

Stories and fables and all sorts of predictions were made without any knowledge of what comets really are. The same was for their fear of eclipses, solar or lunar, which portends fear and panic to this day. But it is the arrival of comets which was nothing short of a horror story.

It is from the Greeks of the old that we get its name. ‘Aster kometus,’ the hairy star! The Greeks took a keen interest in comets just like they did in astronomy, the earth sciences, philosophy, etc. But the genius displayed by the Chinese leaves all others way behind. They had been observing comets, as well as the eclipses with far more acumen and better results than anyone else except the Babylonians before them.

But come 17th century — everything changed. That is when a highly respectable, resourceful and renowned scientist, Edmond Halley, a scholarly friend of the great Isaac Newton, followed the lead provided by earlier scientists like Tycho Brahe, Johannes Kepler, Newton himself, besides many others, with the difference that Newton was his contemporary. Halley threw his energies in the comet that made its chance appearance in 1680, then another one in 1682 as the godsend opportunities. He noted their perihelion (the point of a body’s closest approach in its orbit around the sun; the farthest is aphelion) and discovered to his amazement that the perihelion of the comets of 1607 and 1531 was very nearly the same point in the sky.

Calculating it backwards Halley found that comets seen in 1455, 1378, and 1301 had similar orbits as that of the 1682 apparition. Except for a minor margin of a year or so, the same comet returned with the regularity of a clockwork, once every 76 years or so. (The shortest period of the same comet is about 74 years and the longest is about 80 years as meticulously worked out over the comet Halley’s 30 appearances since 240BC).

If the period differed just a little bit in time on each visit, it was on account of the en route planets whose gravity worked a drag (or a pull) on this comet, slowing it down, or hastening it a bit. It was wondrous of Edmund Halley to work up the comet magic. Halley predicted that the comet would next appear in our skies in 1758. This would be full 16 years after the great man’s death in the year 1742. He had made the prediction and it was left to others to prove that he was right.

On Christmas night 1758, Johann Palitzcsh, a German farmer-astronomer, discovered the comet which the entire astronomer community of Europe promptly ratified much to the delight and relief of a whole continent. The fuzzy dot they spotted in the sky was indeed a comet, and in the place and time exactly when it would return. The same comet made its appearance after his death, just as he had predicted. In order to know the comet well we must first know the man who unravelled the secret of comets for everyone to understand this phenomenon well. He was one of the true educators of humanity.

Edmond Halley (1656-1742) was an Englishman born near London, where he also died at the ripe old age of 86 years. The whole world owes him a debt on not one but two counts. The first is of course the comet. The second and equally important is his friendship with Isaac Newton. When Newton (1643-1727) wrote his first book that changed the world in many ways (Principia Mathematica, originally written in Latin in 1686-87, but first published in English in1728), and above all, the way that people thought and surmised their scientific problems. It changed their perceptions on various world views. But by the time he had completed his labour of several years he was too tired, too indifferent and somewhat scared to let out new ideas. Besides, he had many enemies in the scientific community too, above all, Robert Hooke (1635-1703).

When Edmund Halley heard about it, he immediately persuaded Newton to publish his earth-shaking ideas. Despite Newton’s reluctance Halley persisted and offered Newton all the money for the undertaking and the courage required to publish it. That is how his remarkable ideas and philosophy were let loose on a people who were stunned to discover the great man’s mind and his grand ideas on statistics, astronomy, mechanics, optics, which two centuries later made another great man, Albert Einstein (1879-1953) suggest vast and serious improvements and changes that amounted to virtually knocking down portions of Newton’s ideas. In a way Einstein’s work replaced that of Newton’s. But this does not, in any way, reduce the significance of Newton’s work that is of monumental nature, and changed the scientific world. About Einstein’s work, we shall set it aside for another occasion.