comet what? first of all, comets are wandering boulders of ice, and as it enters in the earth's atmosphere, the air molecules collides with its trajectory and thus causes immense friction, so the comet would most likely dissolve as it whirls around our airfield.
second, the only calculated NEO(near earth object) that we, astronomers/astrophysicists, doscoevered is the Asteroid Apohphis, which will probably drop by to say hello to the earthlings by 2029-2036.
third, this end of days topic is really attracting businesses(monkey businesses at that). they say it will happen during galactic alignment. for those who don't know, we have been alignment zone since 1980 and will go on until 2016. the perfect alignment actually happened between 1995 to 1998. the alignment peak isn't on 2012 even. the planet Nibiru? it is a great fallacy. a planet has to be gravitationally bound by its star-planetary system. so there is no such thing as a wandering planet. it has to have a fixed orbit relative to its star. just like the earth to the sun.
