The size of the Moon and the Earth
The notion that the Moon is smaller than the Earth is an illusion. To those of us resident on the Earth the Moon appears to be smaller than the Earth and much further away than the Earth. However, if the Earth and the Moon were interchanged, the Earth would appear further away and smaller than the Moon. This establishes an equivalence class, which shows that the Moon and the Earth are equivalent. From this we must concluded that the Earth and the Moon are the same size and the same distance away, and that the apparent differences in size and distance are an optical illusion.
This page was last updated March 1, 2005.