re: Ancient comet recorded on stone.
You know, one problem with interpreting ancient carvings and paintings is the odd assumption that anything that was depicted in artwork somehow represents something happening in real life. A man picture riding a fabulous beast does not mean they actually did this, or even that the beast existed other than in their imaginations. If this continues into the future, it will be interesting to see what archeologists five thousand years from now make out of our comic books.