Dismiss Notice
Join Physics Forums Today!
The friendliest, high quality science and math community on the planet! Everyone who loves science is here!

Magnetic field of the Earth

  1. May 24, 2015 #1
    As we all know The Earth has a magnetic field. Why the objects on the surface of the Earth do not get magnetized? It is possible to measure the magnetic field frequency of the Earth?
     
  2. jcsd
  3. May 24, 2015 #2

    mfb

    User Avatar
    2016 Award

    Staff: Mentor

    They do. The magnetic field of earth is not strong enough to make powerful magnets, but it is sufficient to leave a measurable trace in some types of rock.
    It is a static field. It changes over long timescales, but not in a periodic way so "frequency" is not a very meaningful concept.
     
  4. May 28, 2015 #3

    Baluncore

    User Avatar
    Science Advisor

    They do.

    Steel ships built in the Northern Hemisphere are magnetised in the opposite direction to those built in the Southern Hemisphere. The “magnetic detector” mines used in WW2 detected Northern built ships but not the Southern ones. Degaussing ships became very important. By cancelling or reversing the field “the ship could be made invisible”, but only to German magnetic mines.
    http://en.wikipedia.org/wiki/Degaussing
    http://en.wikipedia.org/wiki/Deperming

    This appears to be the origin of the “Mare's Nest” now called the Philadelphia Experiment.
    http://en.wikipedia.org/wiki/USS_Eldridge_(DE-173)#Philadelphia_Experiment
    http://en.wikipedia.org/wiki/Philadelphia_Experiment#Alternative_explanations
     
  5. May 28, 2015 #4

    davenn

    User Avatar
    Science Advisor
    Gold Member

    did you really mean frequency or field strength ?
    The Earth's magnetic field strength is measures by a number of sites around the world on a continuous basis
    These warn of the start of geomagnetic storms that produce aurora ... the upsets in the magnetic field is caused by changes in the interplanetary magnetic field produced by the Sun

    Magnetometers are used to detect fluctuations in the geomagnetic field. during the onset of a geomagnetic storm I have seen variations in the field of up to 40 - 50 nT ( nano Teslas). But even variations in the 15 - 30 nT range are quite significant

    To just quickly expand on mfb's comment and link on magnetised rocks.
    The discovery of magnetic striping of rocks on the seafloor was the final significant proof of seafloor spreading and the plate tectonics ( continental drift) theory

    Dave
     
  6. May 28, 2015 #5

    Vanadium 50

    User Avatar
    Staff Emeritus
    Science Advisor
    Education Advisor

    I guess you could use the frequency of reversals, which is irregular, but of order 100 fHz.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook




Similar Discussions: Magnetic field of the Earth
  1. Earth's Magnetic Field (Replies: 12)

Loading...