How many miles in diameter was the head of the comet of 1811?

Question

It tail was 112,000,000 miles long.

Answer 1

Here's the Wikipedia entry for that comet. What you are looking for seems to be on the right of the page:

http://en.wikipedia.org/wiki/Great_Comet_of_1811

(Sorry about that first incorrect website. Good luck.)

Answer 2

It is not how big but the speed. The comets as they approach us are about 100,000 mph. The asteroids are larger but in our vicinity they may be going 13,000mph. the kinetic energy is the velocity squared times the mass.