What protects Earth from asteroids and comets?

Earth has been pummeled by asteroids and comets continuously over the eons, sometimes with catastrophic results. A strike by a 6-mile-wide (10 kilometers) body, for example, wiped out the dinosaurs 65 million years ago. The danger of death from above will never disappear. read more

NEOs include asteroids and comets whose orbit brings them in close proximity to the Earth. In order to protect the Earth from these potential hazards, the PDCO has two main roles. First, it is responsible for finding and characterizing these NEOs. read more

To be honest nothing protects earth from asteroids and comets . The physics behind hitting the earth is just the conservation of the mechanical energy. When a comet just enters the earth gravitational field then it has just kinetic energy and no potential energy and that kinetic energy gets converted t to potential energy and the point where the potential energy is maximum is called as the distance of closest approach. read more