I felt this was one of the best movies of the summer. Go ahead, hate me, but it really was. I saw it five times.
I happen to blow off most movies, as I did Star Trek and Transformers - Revenge of the Fallen. I have particular taste.
If our magnetosphere goes down (like it will when our magnetic poles reverse - anytime now up to 2,000 years from now, according to many scientists), and we are hit with a coronal mass ejection (CME) from our Sun (or a long past, far away supernova), we are goners.
Some UFOlogists speculate that before every mass extinction, ET (who planted us here to begin with) will come back and try to save as many of us as they can (if we are still able to reproduce). SPOILER - In the movie, they took only the small children. END OF SPOILER. ETs? We are their children. We resemble them. They are responsible for us.
The movie was very realistic with its portrayal of the CME devastating Earth and killing everything off. I guess I like realism. No matter how much it hurts.