[mmooss]

> Earth was moving

They believed that the stars and Earth moved relative to each other, as far as I can tell. Why does it matter if they thought the Earth was moving or if they thought the stars were moving?

Maybe the math is simpler if it's the Earth.

[rcxdude]

The night sky obviously rotates, but that the earth translates relative to the stars is not so obvious. This was especially a problem because it was generally thought the stars were much closer than they actually are, because stars do have an apparent diameter to the naked eye (and through a telescope) which we now know to be an optical illusion (Airy Disk), and if you extrapolate this like with the planets they are either not that much further away or ludicrously big, like many solar systems, and parallax measurements were precise enough to at least put a high bound on their distance if the earth moved with respect to the stars, and gigantic stars wasn't a popular option.