Collision in our solar system
This is interesting. The moon is 3,476 kilometers in diameter. The Earth's core is a liquid layer about 2,300 km thick composed of iron and nickel that lies above Earth's solid inner core and below its mantle.
Then factor in the scientific theory that the moon crashed into the earth a long time ago. The two metal cores collide - there is a bounce and a magnetic repulsion explaining why the moon with has a side permanently facing the earth/sun, why we have more water than an average planet as (we probably took most of the moons softer outer core), that bulge the earth has, some of these comets whizzing by, meteorites that wiped the dinosaurs, the ice ages, The Chelyabinsk meteor, the last meteorites and comets which are coming this way in a few years time.