If a ghost can walk through solid objects
 

How come they don't fall through the floor?

Forward inertia...

Wingardium Leviosa

And how do they throw stuff?

they are floating just over the floor, but to the casual observer, it looks like they are walking .

Ghosts don't.

Poltergeists do.

expense of energy?

hahahahahah. i dont even know what this means, but damn...

can i guess? harry potter?

They have no mass therefore no weight. That's why they are transparent. ;)

But sometimes they emit light, which is a form of energy. If energy cannot be created or destroyed, where does the energy come from?

It also takes energy to create motion in a wave (such as light) so where does that energy come from?

biofuels (scaring people sh_tless).

Duracell.

Just more ignorance...

the energy comes from ambient heat, which is why it is cold where a ghost is, and why you will never see a ghost in Antarctica.

The Japanese think ghosts sink - and are not on mountains. That is why shrines are near the ocean, at sea level..

Come to think of it, I've never seen a ghost in Antartica.

NOoooooooooooo.........you guys have it ALL wrong........it's the EVP's and ecto-plasm. Any fool would know that if they watched "ghosthunters"

Somebody's not looking very hard.....

Are you questioning our knowledge of ghosts? I want you to know that I knew Casper the friendly ghost on a first name basis. Well, I knew his first name anyway. Was his last name The Friendly Ghost?

If an African guy becomes a ghost, what color is he? If he stays his natural color, how do you see him at night?

Why are there no Asian ghosts? I've never seen one.

For that matter, what color would Michael Jackson's ghost be?