Galileo Galilei was right: Earth moves around the Sun, just as Nicolaus Copernicus said it did in 1543. But had Galileo followed the results of his observations to their logical conclusion, he should have backed another system — the Tychonic view that Earth didn’t move, and that everything else circled around it and the Sun, as developed by Danish astronomer Tycho Brahe in the sixteenth century.

This is the conclusion that Christopher Graney, a physicist at Jefferson Community and Technical College in Louisville, Kentucky, came to after reading manuscripts from another astronomer who was active in the late sixteenth and early seventeenth century, at the same time as Galileo.

Graney suggested in 2008 that Galileo’s observations of stars were actually diffraction patterns called Airy disks — patterns of concentric circles that arise when light from a point source, such as a star, passes through a hole. Diffraction hadn’t been discovered in Galileo’s time, so he was unaware of the phenomenon and believed what his eyes, or his telescope, were telling him and used the observations to estimate the size and distance of stars. As a result, he got the distances of the stars too short by a factor of thousands (see ‘Galileo duped by diffraction‘).

Continues: http://www.nature.com/news/2010/100305/full/news.2010.105.html