Will Neptune and Pluto collide one day? Would that affect the Earth? What if things outside the solar system collide?

No. Pluto's orbit is tilted with respect to Neptune, so at the point
where Pluto and Neptune's orbits cross (in other words, are the same
distance from the sun), Pluto's orbit is several million miles _above_
Neptune's orbit. So, in reality, the orbits never cross. Also, Pluto and
Neptune are locked in what is called a "resonance" orbit - Pluto goes
around the sun three times in the time it takes Neptune to orbit the sun
twice. Because of these resonances, the planets never even come close to
each other.

Probably not. Neptune and Pluto are so far away, over 2 billion miles,
that very little would happen to the Earth. Think about a gigantic
earthquake in California - the people in New York know nothing about it,
even though California could be destroyed.
In addition, Neptune is much bigger than Pluto, and would
probably just swallow pluto up, although there would be a lot of fireworks!

It depends what is colliding! If two stars collide, they could explode,
which would have a major effect on the Earth if the stars are within a
few light-years. But two planets in another solar system colliding would
have no effect on the Earth at all.

Thanks for writing! Sincerely,

Kurtis Williams

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