The flat earth's sun is much smaller compared to the spherical earth's sun. Would it be logical for such a small sun to emit so much energy? My answer would be no.

The outer part of the plane (south) would be too large. You can see this by the squares of some flat earth maps, look it up. Each square represents the same amount of distance.

According to flath earthers everything falls down because of mass, they deny the existence of gravity. That's not logical to me.

Flat earthers say many weird things like the moon creates it's own light. But everytime when I see the moonlight it's the sun who's shining it's light on the moon. It's never from an other direction.