Beware of aliens

If it's really the "end of the world" then I do believe that the human species would be wiped off from the face of the universe. We're not very good at adapting to drastic changes -- let alone cosmological catastrophes.

I have seen a similar episode on Discovery Channel and they had a segment there about the possibility of alien invasion. That raised a question for me: if there is a possibility that something else is out there - why are we broadcasting our soundwaves to them?

Shouldn't we keep quiet and hope that they'd leave us alone? If they're good enough to detect our soundwaves from a billion light years away, then they're strong enough to crush us or to conquer us, right?