An impact event is a collision between objects in space. They happen regularly in planetary systems, such as our Solar System. They most often involve small objects, such as asteroids, comets or meteors. These have relatively little impact. When a large object collides with a planet like the Earth, it can have serious effects on the planet. We try to find out when one is going to hit Earth using impact prediction. Depending on the size of the object, much of the impact is reduced by the planet's atmosphere. Smaller objects explode or break apart as they enter the atmosphere. These are seen as bolides.