A transit of Venus occurs when the planet crosses the face of the sun, as seen from Earth. In this gallery, we look at the Venus transit as recorded throughout history. The ancient Babylonian Venus Tables of Ammizaduga (shown here) contains information about the movements of Venus, but mentions no transit, though the Babylonians had opportunity to see ones in 1512, 1520, and 1641. [See our Transit of Venus 2012: Complete Coverage Special Report.]
Could Montezuma, the great Aztec leader, have seen the Venus transit in 1518 AD? It would have been visible to him at sunset. In the British Museum, a jade figure of the god Quetzalcoatl, related to Venus, wears a sun as a neck ornament, possibly marking the rare event.
Around 1610, Galileo discovered that Venus has phases similar to the moon's. (His drawing is shown here.) These phases are only possible if Venus orbits the sun, thus the planet helped confirm the heliocentric model of the solar system developed by Copernicus.
Johannes Kepler analyzed the astronomical data of Tycho Brahe, and formulated three important laws of planetary motion. He predicted the Venus transit of 1631, though was not able to witness it, having passed away in 1630.
English astronomer Jeremiah Horrocks is considered the first human to have witnessed a Venus transit. He concluded that existing information about planetary positions was incorrect, so he gathered his own data, allowing him to correctly predict a transit of Venus in 1639 (which Kepler had not foreseen).
On June 5, 1761 the transit of Venus was observed by 176 scientists positioned all over the world. Russian astronomer Mikhail Lomonosov noticed a halo of light that surrounded the disk of Venus as it crossed the edge of the sun, and deduced that Venus must possess an atmosphere. Shown here are drawings of Venus and the "black drop effect" by Torben Bergman, later discovered to be caused by image blurring and solar limb darkening.
The atmosphere of Venus seen during the 1761 transit was sketched by Russian astronomer Lomonosov. Here the atmosphere is sketched as a ring in figs. 6 and 7.
James Ferguson's sketch of the path of Venus across the sun disk on June 6, 1761 emphasized the dryly technical aspects of the event.
The transit of Venus on June 3, 1769, led to the publication of 400 sightings. Benjamin Franklin observed it in the United States, as did explorers Mason and Dixon at the Cape of Good Hope. Many international expeditions were launched to observe the event.
Benjamin Franklin of the U.S. Continental Congress sponsored the publication of the 1769 Venus transit measurements taken by Biddle and Bayley. This image shows the first page of the article in the British publication, Philosophical Transactions of the Royal Society.
Captain Cook undertook perhaps the most famous expedition to observe the transit of Venus on June 3, 1769. Aboard the H.M.S. Endeavor, he and his crew reached Tahiti, where an observatory was set up on a high point still known as "Point Venus" today. The expedition astronomers made many measurements successfully, and the Black Drop Effect was studied carefully.
By the Venus transit of December 8, 1874, photography had been invented, and hundreds of photographs were taken of the event, though few were useful enough for scientists. Over $1 million was spent worldwide on observations. The sketch shown here is of the transit as observed in London.
The United States Naval Observatory expedition practices for the event on the USNO grounds. Professor Simon Newcomb, director of the USNO, sits in the foreground. Newcomb's calculation of the Earth-sun distance using the transit data edged out Joseph Harkness' calculation for international adoption, though perhaps Newcomb's popularity had an effect on the decision.
Composer John Philip Sousa took a great interest in the Venus transit of 1882. During 1882-3, he created the "Venus Transit March." The Smithsonian Institution commissioned Sousa to compose the piece in honor of American physicist Prof. Joseph Henry, so the march was not specifically produced in commemoration of the transit.
The December 6, 1882 transit of Venus generated enormous public interest. Smoked glass and amateur telescopes were put into use abundantly. One of the first photographs of the transit of Venus 1882 is shown here.
Astronomer William Harkness labored mightily using data from the 1882 Venus transit to determine the distance to the sun. His value was 92,797,000 miles, with a probable error of 59,700 miles. However, his calculations were not adopted by the international astronomical community, who instead took up Simon Newcomb's figure. Harkness, though, taking the long view, is quoted as having said, "There will be no other transit of Venus till the twenty-first century of our era has dawned upon the Earth, and the June flowers are blooming in 2004. When the last transit occurred the intellectual world was awakening from the slumber of ages, and that wondrous scientific activity which has led to our present knowledge was just beginning. What will be the state of science when the next transit season arrives, God only knows." [See our Transit of Venus 2012: Complete Coverage Special Report.]
