because of earth's magnetic field. Every once in a great while it switches polarity and as it does it crosses over zero which leaves the earth vulnerable to solar radiation i.e. thats why everything on land died and animals tend to be nocturnal becaues their ancestors were on the other side of the planet when a solar flare struck. Its just another theory but it seems more likely than not.
Slashdot Mirror
because of earth's magnetic field. Every once in a great while it switches polarity and as it does it crosses over zero which leaves the earth vulnerable to solar radiation i.e. thats why everything on land died and animals tend to be nocturnal becaues their ancestors were on the other side of the planet when a solar flare struck. Its just another theory but it seems more likely than not.