After watching the slideshow, I think that scientist believe the Earth has been around longer than 6,000 years because: some land is completely on different levels than others. The Earth has very weird shapes and at one time it was probably even. If you look at old graveyards, the very old gravestones will be tilted and sideways, but when they were first put there, the land was level. So, even though the gravestone might be a little sideways after a few hundred years, that must mean that the canyons that are really steep and not even have been around longer than the gravestones, so more than a few hundred years. More like the billions for that much movement/difference of level. - Leisa