[JocelynSachs]

Hi I'd be interested to hear an explanation. I've seen variations on this claim a few times:

"Visually circular star trails visible at different latitudes prove the earth is flat, because on a globe earth star trails would only be circular when viewed from the pole."

This is a very odd claim to make since it's exactly backwards, akin to saying something isn't on fire because flames and smoke only come out of something that isn't on fire.

Looking forward to your replies.

[Mark_1984]

Never heard that one before. It shows a remarkable lack of understanding of physics.  The circles, in themselves don’t prove a flat or globular earth.  They just prove the Earth is rotating.  The fact that the centre gets lower in the sky as you move away from the poles proves that the Earth is round.  Particularly as they go one way in the northern hemisphere and the other in the southern.  That and the fact that you see different stars in each hemisphere.

[JocelynSachs]

The fact that the centre gets lower in the sky as you move away from the poles proves that the Earth is round.

Sorry, yes: I should have included that; thought I had. It's the combination of the trails always being visually circular and the centre changing position at different latitudes that constitutes the proof.