You know why anti-gravity aircraft exist? Because gravity was just a theory.

of course a theory is a hypothesis or an educated guess. gravity is density and buoyancy. wait there's no such thing as gravity so it's density and buoyancy.

Have patience; I'm a retired English teacher. Do you mean density and buoyancy as in "fat floats and muscle sinks?

here's a song that explains it but kind of funny like

https://youtu.be/fAZyGasXI0E