How old is the sun? Is it true that at the end of 2012 the world will end? If it did how would it end?

Question: How old is the sun? Is it true that at the end of 2012 the world will end? If it did how would it end?
- Keywords:
  end of the world,
  fact or fiction,
  sun
Asked by sophiecampbell to Mike, Pip, Tianfu, Tim, Tom on 26 Jun 2012. This question was also asked by camel12, harricat, pineapple2000, lottieelizabethmk.
- Tom Lister answered on 26 Jun 2012:
  
  I have no idea how old the sun is, although the ‘birth’ of a sun is quite well defined. Try Google.
  
  If the world ends at the end of 2012, it will be because I turned the laser up too high!
- Tim Stephens answered on 26 Jun 2012:
  
  The sun is several billion years old. Some people believe that a prophet in the past predicted that the world would end this year, but then the same prophet is also supposed to have predicted that the world would end in 2008 and 2010, so I’m not too worried.
  
  The thing I think that is going to end the world for you and me is either going to be some sort of horrific war, global warming, or a meteor strike. Hopefully we’ll be able to prevent the first two by diplomacy and the last one with rockets or something.

Question: How old is the sun? Is it true that at the end of 2012 the world will end? If it did how would it end?