Shows > Venus Transit 2012 - Last Time In Your Lifetime

Past Venus Transits Revealed Solar System’s Size | Video Part 1

By the end of the 19th Century, the relative spacing of the planets was known but the absolute distance between them was not. This scientific mystery spanning centuries was finally solved by accurate measurement of Venus Transits of 1874 and 1882.
credit : NASA/GSFC/Sun-Earth Day