Adam Tuff – answered on 24 Mar 2011:
The “cheat” answer is 1 astronomical unit (1AU) which we use as a measure of how far away other planets are (e.g. Jupiter is about 5 AU away from the sun). It’s about 92 million miles. The Earth’s orbit isn’t exactly cicular though – it’s ever so slightly eliptical (like an oval). We are sometimes a little closer, and sometimes a little further away – but this only changes by about 1%.