How many miles is it thru earth?

Answer 1

The answer is interesting, because it depends on where you are!

If the Earth were a perfect sphere, of course the answer would be the same everywhere. But the Earth is what we call and oblate spheroid, meaning it's flattened a bit, and is wider around the equator than around the poles. In other words, if you were to drill from the south pole to the north pole, the hole would be smaller in distance than a hole drilled between two points on the equator.

Anyway, the average radius of the Earth is 6371 km (3958 miles), with the polar radius being 6356km, and the equatorial radius being 6378km.

http://en.wikipedia.org/wiki/Earth

If you were going all the way through, you would have to double those lengths to get the answer.