How Muslims believed earth was spherical long before anybody mentions it.

[JuliaL]

Right! If Muslims were serious about it, they'd do a bit more detailed calculation and then strap themselves to something at an angle, so they are praying at the floor, through the earth and then on to Mecca. Or are prayers affacted by gravity and so will bend round?

Or...

It has nothing to do with correspondence with reality.
It is an emergent meme of a human sub-society which serves to keep that community united and working towards a common goal (generally world domination.) It is a successful strategy inasmuch as it has been shown to persist and expand in the recent past.