In the opening sequence, there is an opening sequence (by Charleton Heston) showing an asteroid heading for earth....we are told this is the asteroid that killed the dinosaurs 65 million years ago. Mr. Heston says that the force of the asteroid exploded with the force of 10,000 nuclear weapons.....

This is not what you may think...they actually UNDERESTIMATED the size of the explosion!! If we assume the asteroid was 10 kilometers across (a typical size) and moved at 11 kilometers per second (a MINIMUM speed), the force should be somewhere near 80,000,000 megatons of energy! No nuclear weapon ever donated has ever been larger than 100 megatons. Considering, the force of the impact should have been closer to 800,000 nuclear weapons, MUCH more than 10,000......

This goes to show that they DEFINITELY didn't do any research whatsoever, as they were going for a dramatic number, but ended up severely underestimating the size of the explosion.

note: taken from BadAstronomy.com