>>Denton Ebel: We have evidence of lots of
impacts on the Earth. In the United States, in Arizona, we have
the best-preserved impact crater on the surface of the Earth. It’s called, “Meteor Crater.” It should be, “Meteorite Crater,” shouldn’t
it? Because we have pieces of the actual iron
rock that made that crater that came off before the actual cratering event. That was about a kilometer in diameter. It’s a tiny crater. On the moon, you wouldn’t even notice it.
But it happened 50,000 years ago. So, that gives you an idea of how often big
things like that actually happen on the Earth. A thing moving faster than the speed of sound—much
faster than the speed of sound—will actually build up air pressure in front of it—it’s
called RAM pressure— and will essentially explode. This happens way up in the atmosphere
30 to 50 kilometers, depending on how fast an object is going and what angle it comes in at. And so, once these pieces of an object then
continue to come to Earth, they will spread out and slow down and eventually fall more
or less in free fall to the Earth.