Question: how large was the comet when landing into earth when dinosaurs were living? How did it go around the whole Earth destroying everything? is it i true that dinosaurs died from it?

Julian Onions answered on 20 Nov 2014:

I think the meteor that hit was about 10km across, so about the size of a small city. It would have been travelling at probably 17,000 mph, much much faster than a bullet, so it would have contained a lot of energy.

This started a fireball, that wiped out everything nearby, but also threw up lots of the earth on impact as rock dust and gas into the atmosphere, which would have blotted out the sun, leading to a sort of continual night. That would have made the temperature drop. It would also release a lot of gases which in turn would later raise the temperature like a greenhouse. So it was like a triple whammy!