How Can the Earth Be Flat?
Many observations and scientific laws can prove that the earth isn’t flat, and if I list them all, the list will be as long as the Encyclopaedia Britannia. I will not list them all, but with only simple gravity and physics laws I can prove that the earth isn’t flat.
According to General Relativity, gravity is caused by warped space, and anything that has mass warps space. Therefore, anything that has mass has gravity. A round earth, of course, has gravity, since it has mass. We also know that without gravity we will all float out to space. This is the Round Earth view of gravity, which I think is not only plausible but obvious.
General Relativity cannot co-exist with a flat earth. Massive things tend to transform into spheres, so a flat earth will crumple into a round earth. This is the reason behind the fact that all massive celestial bodies are roughly round in shape. Gravity loves a round earth, but no Flat Earther could accept that. They don’t even believe in gravity!
Flat Earth Society members believe that General Relativity is “part of the Round Earth conspiracy”, and the earth doesn’t exert gravity. Instead, they believe that the earth is accelerating upwards at a rate of 1G (9.8m/s²). This explains why objects accelerate at a rate of 1G when falling, but the theory has 2 huge glaring holes:
What force could make the earth accelerate? Without a constant force, nothing could accelerate. Are FE’ers crazy enough to think that an engine is underneath the earth? Even so, the fuel of the engine will get used up!

Even if the earth could accelerate by itself, it will reach the speed of light after a long time. Einstein’s Special Relativity does not allow an object to move above the speed of light. As an object nears the speed of light, it gets more and more massive, so accelerating will become harder and harder, and at last the object will stop accelerating.
This is completely enough to prove that the earth is, ultimately, not flat. I think that all Flat Earth Society members are wise enough to abandon the FE theories.
logicallyRE, 2008-7-1