Did a comet strike the Earth 12,800 years ago, causing global wildfires and starting an age of cooling? Scientists are still arguing about it. Dr. Joanne Ballard, co-author of two new papers with evidence that it did happen. Comet expert Dr. Mark Boslough says the science is flawed. I close with my own impressions of the science, the believers, and why all this matters a lot for our future. After all, the next comet strike can come at any time.