Question: how do you know how the worlds going to end and whats the evidence to prove that?

David Corne answered on 11 Jun 2011:

If by “the world” you mean this planet, we’re pretty sure that the Sun will expand into a red giant at some point way, way in the future (I don’t know how many billion years away that is – find out yourself by googling some appropriate phrases, and checking a few of the results to get a consensus). The evidence in support of that is that most of the accepted theories about the physics of stars (and what they’re made of) lead to predicting it, and these theories also match quite well lots of the things we can see in the cosmos. Basically, stars of a certain mass and composition and age will eventually expand into red giants. If you want to know why, the best thing to do is try to find out in the library or on the internet; the second best thing is to ask another question. Anyway, when the Sun expands, then, I think the prevailing theory is that the Earth will find itself skimming through a very thin outer layer of Sun, which will slow us down a little in our orbit, eventually causing us to spiral into its depths. Things may go pear-shaped much sooner of course. There may emerge superviruses that we can’t beat, or the climate may go crazy, perhaps through out-of-control global warming, or some other effect or cycle that we can’t predict. Or we may be hit by a giant bit of rock. Sorry, I don”t want to depress you, but you did ask. The most probable thing is that all will be fine for zillions of years.
Nobody really knows how the world will end, and nobody knows for sure if it will end at all. I may be wrong about the latter bit, because I think physicists would tell us that, if nothing else ends it all for us, the universe will eventually just die out, in the same way that a cup of hot tea eventually loses all its heat (but much much more slowly) – but personally I’m not convinced we can rule out something else kicking in before that, there really is so much we don’t know.