@ssssanna Welcome to Fluther, and thanks for the great question. I base my beliefs not on blind faith but on observed evidence. There is lots of evidence to lead us to believe that the world as we know it will end. There is the Law of Entropy. The Universe itself appears to be headed for heat death in the distant future, many billions of years from now.
Before that fate, we face the evolution of our Sun from a yellow dwarf to a red giant as it runs out of hydrogen and gravitational collapse transitions it into nuclear fusion of heavier elements. As that occurs, the sun will likely expand until its photosphere encompases the earth, and we will be melted down to become part of the Sun’s mass. Thankfully, there is a chance that we won’t get consumed completely by its Red Giant phase. In that case, all water on Earth will be vaporized and all life extant at that point destroyed.
When our Sun runs out of all nuclear fuel, it will collapse back to a brown dwarf. If Earth still exists outside the Sun at that point, all the water of Earth that the dying Sun previously vaporized will come out of the atmosphere as snow and ice, and the Earth will become one giant ice-ball.
Only if intelligent life on Earth shows itself intelligent enough to not self destruct before the Sun does so 5.4 billion years in the future, do we stand any chance of avoiding that the melt-down or ice-ball fate. It could be done by moving the Earth’s orbit further out in the Solar System during the Sun’s red giant phase, then back in close, say about where Mercury is today, when the brown dwarf phase hits. But that still doesn’t get us around the universal law of entropy. So yeah, I believe the Earth as we know it will end.
Oh, and happy Fourth of July. Look at the bright side of the above. The bills that we agonize over, the insults our loved ones heap on us, and the political blunders that enrage us are really trivial matters. No matter which way they go, entropy will end it all anyway. In the end, the ice-ball theory rules!