Hello all, first time poster here wishing to discuss  fairly, on a flat planet, how is the atmosphere actually contained? Does the underside the flat plane also have an atmosphere? Is this rounded or some sort of sphere??? Is the atmosphere's thickness even throughout the upper plane of the surface? If so, how do you explain the south pole (aka Antarctica) and the north pole both having similar temperatures but the amount of atmosphere the sun rays having to traverse not equal if a flat atmosphere thickness?

One would assume a flat plane would have a flat atmosphere which would make the north pole one of the hottest areas of the plane since it would be directly at the center?