📅 4 December 1639
Jeremiah Horrocks predicted and observed Venus crossing the Sun; William Crabtree made an independent observation nearby.
📅 4 December 1639
Horrocks revised existing astronomical tables and used mathematical reasoning to predict a transit others had not expected.
📅 4 December 1639
Later astronomers used Venus transits and geometry to estimate the scale of distances between Earth, Venus and the Sun.
📅 4 December 1639
Horrocks and Crabtree worked outside major academies, showing that knowledge circulated through correspondence and local observation as well as institutions.
📅 4 December 1639
Jeremiah Horrocks watched Venus pass in front of the Sun from England.
📅 4 December 1639
William Crabtree also saw the transit from England; the two observers are the earliest documented witnesses.
📅 4 December 1639
Horrocks's calculation enabled the observers to watch a transit missed by earlier forecasts.
📅 4 December 1639
Projected solar viewing made the planet's angular size measurable during the event.
