Every several years in the US there is some fundamentalist christian preacher or whatever who claims that the world is going to end because of his expert understanding of the Bible. This has been going on since at least the 19th century. There was some guy in Florida I think a few years ago. Guess what, the world's still here...

I don't think aliens are going to save us. If life does exist elsewhere, it is thousands of light-years away. According to our currently understood concept of the universe, nothing can travel faster than the speed of light. Therefore, even if they were to develop space-craft capable of crossing deep space, it would take them thousands of years to reach us. So even if they were somehow able to pull this off, if these aliens are like us, with a life-span of 60-100 years maybe on average, then those aliens that would be alive, by the time their ship reached Earth, would be how many generations apart from those that originally left their home planet? It was Albert Einstein who demonstrated that the speed of light cannot be exceeded, in his theory of general relativity, most likely, which also stated that time is relative to speed. The faster and object moves, the slower time is for this object. I have read that this has been proven by clocks on the space shuttle. The shuttle moves at a different speed in relation to the Earth, therefore when the shuttle landed the clocks were at a slightly different time.

I don't think human could end by disasters. Before that people could have ended by ourselves.