There are many ways that the world could end. War, volcanoes, plagues, solar flares, etc. One disaster scenario that has gotten a lot of publicity is the possibility of a big asteroid strike that would destroy civilization. There have been attempts to catalog asteroids that regularly cross the orbit of the Earth that might pose a risk. There are a lot of that type of asteroid but the probability of any particular such asteroid striking us is very small.
At the dawn of the Atomic Age, there was talk of using nuclear bombs for civilian purposes such as digging canals and harbors. In the Soviet Union, there was even a plan to use nuclear bombs for fracking natural gas. Fortunately this plan was never carried out. However, it turns out that these proposals were tame in comparison to ideas expressed by an astronomer named Fred Zwicky at CalTech.
The start of the Space Age is usually thought to be the launching of Sputnik by the Soviet Union in 1957. While Sputnik was the first Earth orbiting satellite ever launched and did start the Space Race, the actual roots of the Space Age reach back much earlier to World War II.