[jazzmosis]

Problem with this theory:

Yes, on Earth we would go around in a loop because although it doesn't seem like it, we're not walking on a direct path. The gravity holds us to the Earth and keeps us from walking in a direct straight line. If we were to go off in space and try this, there is no gravity so we wouldn't travel in a slight arc (assuming no gravitational interference from anything.). So it is easily conceiveable that we'd reach the "end of the Universe", but then no matter which way we went, eventually we'd end up back in the same place. It's impossible to end up in the same place from anywhere other than the outer edge of the Universe because that'd be the only way we could know the diameter. This is because we don't know where the exact centre of the Universe is, so if we're not walking around the centre, we could end up anywhere.