01-29-2009, 08:45 AM
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Last I heard Apophis is going to miss us, not by much, it'll be close, but it's not going to be a hit. The uncertainty about the 2036 approach will be cleared up sometime around 2013 and even then all it means is if you take the extreme end of the margin of uncertainty and apply it in one direction Apophis might hit earth. Even then the odds of it hitting the earth are extremely low. What Apophis really should be is a warning that we need better tracking for objects like this lest we not spot the next one in time.
GRB's are dangerous, the big danger from one is that if we were hit by the beam it would fry the ozone layer and the surface of the earth would be bathed in x-rays. Enough x-rays that survival would be unlikely for anything. There's some speculation that at least one of the major extinctions might have been due to a GRB, with the Permian/Triassic extinction even being a good candidate due to the severity. They don't have enough power to vaporize a planet though, not unless our sun was the culprit. It won't though because its not massive enough to collapse into a neutron star when it dies, and there's no other neutron star anywhere near us that might collide with the even then. Of course all that could change when our galaxy collides with Andromedra and the stellar mix up happens, assuming our sun isn't one of the unlucky stars that gets cast off into deep space. Of course it's all moot since the swelling of the sun into a red giant just before it dies would pretty much mean that all life on earth would be ended anyways. Something to worry about in about 4,500 million years.
No, if anything happens to the human race it'll be at our own hand in my opinion. Nuclear weapons, chemical weapons, biological weapons, we've got some great ways to kill ourselves.