If ghosts can walk through walls, why do they not fall through floors as well? If a ghost fell through a floor and the ground, would they stop at the center of the earth, or keep passing through to the other side of the planet?

They are without gravity.

Excellent question, Noldea! I think they would have the ability to CHOOSE when they wanted to go through solid objects so they wouldn't have to fall through the floor.

I think it's just because they usually reside in places like Limbo or Purgatory, and are allowed passage to the realm of the living, and whatever laws by which they're governed requires that the ghost accomplish something within our world. They go through stuff because I guess both worlds are different and the masses, or lack thereof, which reside in both are also different...but they don't actually "fall". Other beliefs may be a dead person does not realize that they are dead, and keeps on reliving their last moments, their deaths, or even banal activities over and over until the realization is made. In this case, perhaps a ghost is more like a projected image, or like a light, which goes through anything, or at least, is not subject to physical obstacles and doesn't require any specific source of light or darkness to be "seen".

They can pretty much choose how and where to go. Like in dreams.

They aren't walkin through walls buddy. They are walkin through ghost doors...you know, doors that used to be there before the house was renovated. . duh +6

They can control their powers, obviously lol.

I've always wondered that! I theorize that they exist on a different plane, and have complete space-time position control, thus allowing them to move about as they please, above or below the floor! ;)

Why would a ghost fall? it has no mass (and so doesnt feel gravity) which is why it can pass through walls.

They are no such thing as Ghosts. What's wrong with you people?