A small dot moving across the sun today is a rare celestial event, even though it will make the sun fade by a mere 0.1 per cent. The event is the transit of Venus across the sun’s surface and it last occurred in 1882. In layman’s terms, it means that for a brief period of six hours, the planet Venus will come between the Earth and the sun. Venus moves faster than the Earth because it is closer to the sun, and its orbit around the sun is tipped compared to that of Earth. This is what makes the three bodies coming into one line such a rare coincidence. The first predicted transit of Venus happened in 1631 and it was predicted by Johannes Kepler, the imperial mathematician to the Holy Roman Empire. Kepler, contrary to the belief of his times, upheld the heliocentric theory of the solar system and was the discoverer of the laws of planetary motion. But nobody saw the transit since Kepler had died in 1630 and it was not visible in Europe. While Kepler had rightly predicted the 1631 transit of Venus, he was wrong when he said that the next one would occur 130 years later. Jeremiah Horrocks calculated that another transit would happen in 1639. The transit of Venus which was most exciting for the inhabitants of Earth was the one of 1761. By this time, astronomy had advanced enough for astronomers to be ready to track the transit and make all sorts of calculations. James Cook went out on his first voyage and timed the transit in Tahiti. Cook’s voyage also resulted in the European discovery of the Great Barrier Reef off the coast of Australia.

A good quizmaster could well ask what the link is between the transit of Venus and the film industry. To better track the transit, Pierre Janssen, an astronomer from France, invented a multi-exposure camera, the revolver photographique — forerunner of the movie camera. Venus has thus fed more than love on Earth. Between Janssen’s contraption, which was used to see the transit of 1882, and today’s transit, the sun, Earth and Venus have not lined up even once. But the descendant of the revolver photographique has created a sensation comparable to any celestial event. Studying the transit of Venus has helped astronomers measure the scale of the solar system, a dream of Edmond Halley, he of the comet, and England’s second Astronomer Royal. It has also led to the tracking of transits of planets in other solar systems. A tiny dot that will be observed today, with due protection for the eyes, is imbued with scientific significance. Venus on the sun is not in pursuit of Adonis.