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The transit of Venus

1631 & 1639: First observation

Johannes Kepler (1571-1630) was the first to predict a Venus transit for 1631, but it wasn't observed as his prediction wasn't accurate enough to determine that the transit would not be visible from most of Europe so none of his colleagues were in the right place.

Horrocks1Horrocks2
J. W. Lavender © Astley Hall Museum and Art Gallery Chorley ; Eyre Crowe © Walker Art Gallery, Liverpool

 

In 1639, when he was just 21 years old, Jeremiah Horrocks (1618-1641) examined Kepler's calculations (he had died in the meantime) and realised that there would be a Venus transit a few months later. This transit would be the first observed, by 5 people in the world: Horrocks, his friend and correspondant William Crabtree (1610-1644) and his family. Horrocks and Crabtree used a helioscope to observe the transit of Venus safely.

 

Crabtree
Eyre Crowe © Walker Art Gallery, Liverpool

 

Their simultaneous measurements, taken in different places with a well known distance between them, allowed J. Horrocks to estimate the size of Venus and the distance between the Earth and the Sun. He obtained the most precise measurement for the time, even though it was a third smaller than the real distance (0.639 AU).

 

Back to the Venus transits throughout history

 

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