The atmosphere also shields the Earth from GCR.

Going back a bit, I like this claim as reported by Effendi:
What is more, the doomsayers usually claim that the pole shift will cause the Earth to stop spinning and then start again but in opposite direction (and of course that happened 11,500 years ago resulting in a 90% or 99% extinction). I don't know what is their view on evolution and fossil records, because from my understanding only bacterias would servive such a thing and the continents would liquidate.

Imagine the energy required to suddenly stop and reverse the Earth's rotation. We'd still be cooling off 115 centuries later... Of course, this would have the side benefit of preventing the Astros' bullpen from coughing up yet another lead.

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