JISHOU, HUNAN — The planet Venus passed in front of the Sun today, but clouds here kept us from seeing it. This event happens only twice every century; the last was in 2004, and the next will be in another 105 years. Guess I’ll need to live to be 161 years old.
This photo was taken in Hong Kong, using a camera with a special filter. (Source: Wikipedia)
Astronomers of the 18th century used the 1769 transit to measure the distance of the Earth to the Sun, which enabled them to calculate the distances to the other planets known at the time. In the 1600s, a young British astronomer, Jeremiah Horrocks, calculated when future transits would happen and was the first astronomer (at the age of 21) to predict the 1639 transit.
Interestingly, Horrocks was born just two years after Johannes Kepler published his revolutionary model of the solar system. Kepler himself, relying on inaccurate observation tables of Venus, had predicted a near-miss transit of Venus. Horrocks also determined that the Moon orbits in an ellipse around the Earth, as Kepler’s laws would predict.