[katana]

Sediment cores taken from the ocean bottom show that the Earth's magnetic polarity has reversed regularly over geologic history. That this happens has been common knowledge for decades.

But I think the effect on Earth's magnetic field shielding effect and the degree and duration of any exposure to solar winds and radiation is debatable. The evidence seems to show the "flips" happen quickly. One effect might be Auroras suddenly occurring for a time at temperate and tropical latitudes. Wouldn't that send folks scurrying to temples, churches, and the nearest shrink.

[blam]

"But I think the effect on Earth's magnetic field shielding effect and the degree and duration of any exposure to solar winds and radiation is debatable. The evidence seems to show the "flips" happen quickly."

I agree. I don't recall reading anything about a slow or lengthly shift.