Debris from asteroids and comets continually bombards the Earth.
Impacts by big bodies launches ejecta on trajectories that transports
it thousands of kilometers from the impact site.
These events are recorded in discrete layers of sub-millimeter size
spherules in sea floor sediments. Larger, rarer, and interestingly
shaped objects are found on land. I will describe the physical processes
that occur in energetic impacts. Emphasis will be given to the mechanisms
that determine the sizes and shapes of the ejecta and the cooling
of the fireball. An analogy with structure formation in the expanding
universe will be exploited, and a possible relation to the origin of
chondrules will be explored.