As EJ said, there is the Universal Acceleration hypothesis in which the universe accelerates upwards at a certain rate, which is a common FE belief. However, not all FEers believe it.
I think FEers assume that a universe wide thing called Dark Matter (which we REers have, but there's is different, I think) that pushes everything in the universe up. It is thought that if the earth is a finite disc (some think it's infinite) that the Dark Matter goes around the earth to, forming a dome like shape (possibly holding in our atmosphere) and pushing the Moon and Sun up in it's wake. I do not know why they orbit like they supposedly do in FE, though.