Close this Window


1608 Telescope invented.

1629 Kepler predicts that a transit of Mercury and a transit of Venus will occur in 1631.

1631 November 7 At least four people see the transit of Mercury; they are the first witnesses to a planet's transit across the Sun.

1631 December 7 First predicted transit of Venus; no reports of any observations.

1639 December 4 Horrocks and Crabtree are the first to see a transit of Venus.

1672 Astronomers attempt to calculate the Earth-Sun distance by triangulating the Earth-Mars distance, with mixed results.

1679 Halley believes a transit of Venus can provide an accurate Earth-Sun distance.

1716 Halley develops a method to use transits of Venus to measure the Earth-Sun distance.

1725 Delisle improves on Halley's measurement technique.

1761 June 6 Transit of Venus.

1763-67 Mason-Dixon Line measured.

1769 June 3 Transit of Venus.

1776 American colonies declare independence from Britain.

1840 First astronomical photograph taken - a daguerreotype of the Moon.

1844 U.S. Naval Observatory established.

1846 Smithsonian Institution established.

1871 Congress establishes U.S. Commission on the Transit of Venus.

1874 December 9 Transit of Venus.

1882 December 6 Transit of Venus.

1895 Official value of Earth-Sun distance standardized at 92,867,000 miles; transit-of-Venus observations given little weight.

1976 Earth-Sun distance determined to be 92,955,859 miles by timing echoes of radar signals sent to Venus from Earth.

2004 June 8 Transit of Venus.

2012 June 6 Transit of Venus.