A transit of Venus was the reason Captain James Cook set sail for Tahiti in August 1768. He wanted to be on site for the passage of Venus across the Sun on June 3, 1769. His observations enabled French astronomer Joseph Lalande to calculate that the distance from
the Earth to the Sun was a little over 150 million km. Two further transits in 1874 and 1882 refined the distance to 149.59 million km. Today we know the distance to nine decimal points as 149.597870691 million km.
A great video (3 min 7 sec) has been released by NASA of this week’s Venus transit. Millstone readers can watch it on YouTube at