I was having a conversation this afternoon about the Tunguska event: a huge explosion that occurred in Russia in 1908. I had always heard that it was caused by a meteor impact, though apparently some other explanations have also been considered. One that I just heard about is the possibility that it was caused by a collision between the earth and some antimatter.
Wikipedia suggests that this explanation isn’t credible, but it does leave me wondering: in the event of a collision between a particle of matter and a particle of antimatter, where the two particles are traveling at different velocities in opposite directions, how does the net momentum of the two translate in their annihilation? If antimatter did hit the earth, it would start to strike particles of matter in the upper atmosphere, the particle pairs would annihilate one another, and energy would be released. Would all that happen before the antimatter hit the ground? Presumably, it would strike its mass in antimatter before then. If so, what would the effect on the surface of the planet be?
Conservation of energy dictates that the kinetic energy in the faster particle would need to go somewhere. Presumably, it would manifest in the production of more energy during the annihilation event. As such, I suspect the antimatter clump would get blasted apart in the upper atmosphere and produce some kind of horrible shower of radiation, though nothing in the way of direct physical debris.