First Observation of Transit of Venus

Date: December 4, 1639 • Location: Rome, Italy

Jeremiah Horrocks and William Crabtree made the first successful observation of a transit of Venus (example pictured) from Earth.

Jeremiah Horrocks, sometimes given as Jeremiah Horrox, was an English astronomer. He was the first person to demonstrate that the Moon moved around the Earth in an elliptical orbit; and he was the only person to predict the transit of Venus of 1639, an event which he and his friend William Crabtree were the only two people to observe and record. Most remarkably, Horrocks correctly asserted that Jupiter was accelerating in its orbit while Saturn was slowing and interpreted this as due to mutual gravitational interaction, thereby demonstrating that gravity's actions were not limited to the Earth, Sun, and Moon.