And before you say “gravity” just remember that the graviton has never been the input or output of any experiment in known history. So explaining this away with gravity is like saying unicorn magic is the solution. Fact is, the earth is not a spinning space ball, and gravity being such a weak force can not explain this. Open a pop can and the pressure escapes. Without a seal on the pop can, pressure can never build up. We maintain pressure because the earth is completely enclosed…as in a sealed up concave earth.