Things fall down because of gravity. The mass of the Earth causes everything to fall down at 9.8 m/s² near the surface of the Earth. This constant is called ‘gravitational acceleration’ and usually denoted by ‘g’.
Most flat-Earthers deny the existence of gravity. According to them, things fall down because of density or buoyancy, not gravity. They are wrong.
To test their version of ‘physics’, we can ask them a simple free-fall problem:
A rigid object is released at the height h above the ground. What is the velocity of the object right before it hits the ground?
This is a basic problem in elementary kinematics/physics class.
These flat-Earthers will not be able to solve the problem without using the gravitational acceleration constant g = 9.8 m/s². They will avoid solving the problem if they can. And if ‘forced’ to answer it, they have no choice but to use g = 9.8 m/s² reluctantly.
To save face, some of them will call the constant with another name. They invented the name only to avoid calling it ‘gravity’. Calling it ‘gravity’ is forbidden, but in reality, the problem only lies with the name. It is simply a branding problem and the underlying concept they use to solve the problem is practically the same, at least for things near the Earth’s surface.
Ironically, after they stubbornly insist things fall down because of density, most of the time, they don’t even use density at all to solve the problem.
Things fall down because of gravity, whether they like it or not. It is the law of nature. Calling it by another name does not make it any more different.
But is it possible to solve the problem without g=9.8 m/s²?
It is possible, but we can’t escape from the concept of gravity.
- By using the complete gravitational equation.
- By assuming it happens not on Earth’s surface, then g≠9.8m/s².
- By using general relativity.
- Free fall – Wikipedia
- Free fall on a planet using General Relativity – Physics Stack Exchange