How do they perdict where a planet and any object in space may or may not collide?

Question

How do they perdict where a planet and any object in space may or may not collide?

Answer 1

calculate where they will be in the future, then look for times when two objects will be in the same place at the same time.

Answer 2

they do this by using velocity, gravitational forces between everything around the objects, and many other factors.  It's a more complex way of solving physics problems such as where a ball in air with forward velocity and gravitational pull of the earth acting on it will land.

Answer 3

Through their trajectory. It's a very complex mathematical process.

Answer 4

You figure out the trajectory of the planets or objects in question.  In the case of planets and most comets, it's an orbit.  If the trajectories cross, they have a remote chance of colliding.  Note - no planet trajectories cross each other.  Then they just need to figure out when each object reaches that point, and if they will ever reach the point at the same time.