-Yes a planets can collide, it really cant happen today in the solar system all the planets are in stable orbits it would take some thing big to knock them out of there orbits.But in the early solar system the plants were not in stable orbits and they often crossed one each other.In the early days there were hundreds of small rocky planets orbiting the sun. So every now and them they hit each other forming a larger planet.Over a course of a few hundred years those small hundred worlds formed into the 4 inner planets today.......
This is all of coarse just my opinion I've gathered over the years of reading/watching science/cosmic documentaries books and websites.
And on a lighter note, Earth has been so harmonious for such an extremely long time, in contrast to human lifetime, that the possibility of a collision with another planet is unlikey, at least in our lifetime :)
Yes it can, but it wouldn't be caused by any of the planets in out solar system- at least not for millions of years! If like meteorites can do it, then planets can lose their traditional orbital path and change to another, if these cross then yes there would be a collision.
The UN would sit and have a long meeting (because that's all they do), and the US government would deny everything. Because honestly, what else can they do?
Yes a planets can collide, it really can't happen today in the solar system all the planets are in stable orbits it would take some thing big to knock them out of there orbits.
But in the early solar system the plants were not in stable orbits and they often crossed one each other. In the early days there were hundreds of small rocky planets orbiting the sun. So every now and them they hit each other forming a larger planet. Over a course of a few hundred years those small hundred worlds formed into the 4 inner planets today. 4.5 billion years ago the Earth got hit by a Mars sized object called Theia. This collision formed the Moon (Luna).
Gas Giants don't tend to undergo the collision part of development, at first they might but they tend to form from icy rocky cores, once they get big enough they can start to collect massive amounts of gas. And the more gas they collect the more mass they get as well dragging in more gas. But I'm sure that they have had some collision of smaller gas planets that crossed there orbit as well.
But back to your question even though these days days a planet collision is very very very unlikely. Lets say that a star wanders too close to the solar system, and disrupts Neptune's orbit. And it starts to fall into the sun. It would take about 80 years of it to get into the inner solar system. If Earth was in Neptune's path we are all doomed there is no thing we can do from Neptune from hitting us. But if Neptune were to fall into the sun it would most likely miss us. This has a greater chance of happening it could disrupt the orbit of another rocky planets and it could send us our way, or Neptune could even disrupt your orbit and send us crashing into another planet. Or it could just send our moon from crashing into us. If some thing like this were to happen there is no thing we can do about it, the only thing we can do is just sit back and watch the show.
