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Sometimes, the poles completely flip -- and presumably when that happens, many bigger changes are afoot than modest tweaks to airport signs. The last time the planet experienced a polarity flip was 780,000 years ago.

How would anyone be able to state, as a fact, that the planet experienced a polarity flip 780,000 years ago?

Is this the same crew that is telling us about global warming, when I look out my window, and see 6-7 inches of snow, single digit temps, and it's been exceptionally cold since early November.

Certain sedimentary rocks with iron particles in them “record” the direction of the earth’s magnetic field at the time they are deposited. Peel back the rock, layer by layer, and you can generate a chart of the direction of the field as a function of time.

How would anyone be able to state, as a fact, that the planet experienced a polarity flip 780,000 years ago?

Test it yourself. Take molten rock. Cool it. Now see which direction that newly solidified rock's magnetic orientation is.

If you live next to, say, a volcano, or a mid ocean ridge, you can harvest core samples and see which way the magnetic fields are aligned.

Geology isn't rocket science, but it rocks!

How would anyone be able to state, as a fact, that the planet experienced a polarity flip 780,000 years ago?

The classic way is the examination of the sea floor basalts as they are created at mid-ocean ridges, where the sea-floor spreads and new rock is formed at the ridge. When it cools, it locks into place the magnetic orientation. The rock age is determined by principles similar to those used in carbon-dating, atomic clocks, and medical devices.

Sedimentary particles can be used in areas away from magnetic ridges, allowing for determination of tectonic plate movements.

Is this the same crew that is telling us about global warming, when I look out my window, and see 6-7 inches of snow, single digit temps, and it's been exceptionally cold since early November.

I guess that's sorta the next step from seeing Russia from there, huh? You claim you can see the entire globe?

I hear there was a warming trend in Australia over that same time period.

Or maybe you missed the word "global." You wouldn't be alone--many FReepers do.