If there were a meteorite heading our way that would spell our impending doom I don't believe that we would be told about it.

We can see things that happened thousands of light years away and the universe seems to be so infinite that it is hard to imagine that there is something flying directly towards us that hasn't been picked up yet, they may have worked out it won't hit us for another 10 years, maybe a hundred, maybe a thousand, they wouldn't tell us because whilst the good people of todays world couldn't give two shits if the world is going to end in 200 years time the closer that date got the more bat shit crazy people would be getting.

Also if there are extra terrestrial beings out there I believe we already know about them, again just going off how far into space we have investigated and how many planets there must be which are capable of carrying life.

oh and Paul McCartney is dead