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Mgnetic field

  1. Jun 6, 2005 #1
    is it true that the earths magnetic field is changing so that magnetic north will be directional south and vice versa.
    and if so how is it doing it
  2. jcsd
  3. Jun 6, 2005 #2
    http://science.nasa.gov/headlines/y2003/29dec_magneticfield.htm [Broken]
    Last edited by a moderator: May 2, 2017
  4. Jul 16, 2005 #3
    Yes, the poles do reverse every so often. I'm not sure how they do it though. I just know that we can see it in rocks. Rock keeps a long history of where the poles were at such and such time. They do this like a compase with a needle. The poles attract certain elements in the rock, which make them piont at where the pole is attracting them from. Theres probably more to this but just to give you the basic idea I posted.
  5. Jul 21, 2005 #4
    The "more to it" is that to be susceptible to picking up the same orientation as the then current magnetic poles, the rocks have to be hot enough for their magnetic domains to realign with the earth's field. Because of this, it should be clear why most of this rock with ancient compass orientations frozen into it is found around volcanos.

    However, they have also discovered a hot fire can do the same thing to underlying soil. Ancient firepits have been roughly dated by finding the magnetic orientation of the iron in the soil beneath the charcoal, and comparing it to the dates they ascribed to the earth's poles being similarly oriented.

    The poles are never fixed. They are constantly wandering around. They don't know why for sure because no one knows the cause of the Earth's magnetic field for sure. Many, many teams of people are working on trying to solve this mystery.
  6. Jul 25, 2005 #5
    So would there also be compass orientations on the bottom of the ocean from sea floor spreading?
  7. Jul 25, 2005 #6


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  8. Jul 31, 2005 #7


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    Some believe the magnetic force field is expected to reverse in the near future. The reasoning being that the force field fades before reversal, and measurements indicate a 10% decrease in strength over the last 100 years or so. Currently the poles are moving about 10 miles each year. The decrease results in loss of atmosphere and increased exposure to solar flares. Aside from havoc it causes to instruments and even animals that also rely on directional magnetism, theoretically the entire atmosphere could be lost if the field is too weak for too long.
  9. Jul 31, 2005 #8
    But do they really? We know now that the Earth Magnetic field had collapsed about every 100,000 year in the current Brunhes Chron, the last ~800,000 years ago. If the migrating birds and other animals really relied on a biologic compass, how did they cope with that? It doesn't appear to have led to multiple extinctions.

    Don't worry about the effects on human orientation. We'll all have GPS in our camera/MPEG payer/cell phone in less than a decade
  10. Jul 31, 2005 #9
    I hadn't heard this. You wouldn't happen to have a link to a discussion/explanation of this would you?
  11. Aug 4, 2005 #10


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    A quick Internet search with "Magnetic Field and Atmosphere" yielded several sites on the topic. There are different variables, the sun's magnetic field or "Interplanetary Magnetic Field" or "IMF," the solar winds, the density of a planet's atmosphere, etc.

  12. Aug 4, 2005 #11
    That site links to this site:

    The Solar Wind at Mars
    Address:http://science.nasa.gov/headlines/y2001/ast31jan%5F1.htm [Broken]

    which explains how Mars was stripped of its atmosphere by solar winds when its magnetic field stopped working. That stripping is, apparently, ongoing.

    I think we are probably safe from a seriously damaging amount of atmospheric stripping so long as the magnetic field doesn't take too long to flip.
    Last edited by a moderator: May 2, 2017
  13. Aug 4, 2005 #12
    okay, that explains the origin of that remarkable statement, loosing atmosphere due to a lack of magnetosphere. But something doesn't add up.

    Mars does have a magnetosphere, on the other hand "http://www.worldalmanacforkids.com/explore/space/venus.html [Broken] lacks a magnetic field of its own, but the solar wind seems to generate an induced magnetosphere, probably by a dynamo action involving its own magnetic field". However, despite lacking a magnetic field of its own, Venus has the densest atmosphere by far.

    So if we go with the explanation (magnetosphere sustains atmosphere) then Mars and Venus both seem to falsify it and worse, if we scrutinize a http://www.earthsci.unimelb.edu.au/mars/icar6398.pdf [Broken].
    Last edited by a moderator: May 2, 2017
  14. Aug 4, 2005 #13
    Yes, mars has a magnetospere, but the site you linked to says it is only 1/800 as strong as earths. The site I linked to (via SOS) says that the martian magnetic field is very degraded and spotty, there are only certain places you can get a reading as strong as earth's.

    So, magnetosphere does protect atmosphere, but it has to be of a certain strength to do so. Apparently, Venus' unconventionally generated magnetosphere is of the correct strength.
  15. Aug 17, 2005 #14


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    Ultimately it appears unlikely that Earth will become like Mars due to loss of magnetic force field. Perhaps Earth is more likely to become like Venus because of the greenhouse affect?
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