This article about a previous change in the earth's magnetic field is interesting, and shows how some of the evidence for an event 42,000 years ago was gathered -
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Last edited by Dave2002; 01-03-21, 12:23. -
Love the DNA reference at the end.Originally posted by Dave2002 View Post
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This one - https://youtu.be/Qs1dLe3GsQY ??Originally posted by Bryn View PostLove the DNA reference at the end.Comment
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I'll check that link later. The audio on this laptop is tied up in WASAPI (exclusive mode) at the moment.Originally posted by Dave2002 View PostComment
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As I understand it, magnetic poles have flipped (i.e. done a complete reversal) several times in the Earth's history*
In out present time, magnetic north is on the move Eastwards. Nautical charts always have a compass rose which shows the variation of magnetic North from true North. In these days of GPS navigation, most sailors tend to work on true (geographical) North, but some like to watch the ship's compass and do navigation the old fashioned way. It's good to know about it anyway in case the boat's electronics go belly-up. Incidentally, any metalwork on a boat (and engines are basically a huge lump of iron) will affect a magnetic compass. This is called deviation, and also has to be allowed for as well as variation.
* I think the primary evidence comes not from old trees (as in the link above) but from core samples taken from the ocean floor where the molecules of ferrous or other magnetic compounds demonstrate complete changes in polarity; and this evidence goes back millions of years, not just a few thousand.
This may be of interest: http://www.geomag.bgs.ac.uk/education/reversals.htmlLast edited by ardcarp; 01-03-21, 23:42.Comment
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