Bad Astronomy

Facts
My first fact was that we can predict the trajectory of meteors. I was right in that we can predict it, but it would take much longer than it did in the movie

My second fact was the you could be instantly blinded by the sun. He would not have been burned as quickly as he was and NASA would have given him some protection.

Fake
I thought the nukes would not blow up the comet. The amount of explosive they used would not have worked, however, given enough time and explosive it could be deflected.

The comet moving so slow was obviously fake. As fast as the comet was said to be moving the shockwave would knock everyone down even before the comet hit.