Question

When will pluto and neptune hit each other (or smash into one another)?

Answer 1

No. From 1979 to 1999, pluto was the eighth planet from the sun. In 1999, it slipped beyond Neptune to become the ninth.

First reason : Pluto's 248-year orbit around the sun takes it 17 degrees above and below the plane in which Neptune and the other planets travel. So their paths don't actually cross as they swap positions

The second reason that Neptune and Pluto can't collide is because Neptune's orbital period of 164.8 years means it makes three orbits for every two made by Pluto, with its 248.8-year orbital period. That puts them in a so-called gravitational resonance, where each planet speeds up or slows down as the other approaches, which alters their paths and prevents them coming closer than around 2600 million km to each other.