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Question about the obliquity of the ecliptic

  1. Nov 5, 2007 #1
    Question about the "obliquity of the ecliptic"

    Hello guys, I hope I am in the correct forum for this question. If not, then I am sorry.
    How was it determined that the earth was tilted roughly 23 degrees from its orbital plane? Or, how did the current locations/definitions of the north pole, the south pole and the equator come about.
    Thanks:
    confused:
     
  2. jcsd
  3. Nov 5, 2007 #2

    russ_watters

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    Staff: Mentor

    The poles are the axis of rotation of the earth, the equator halfway in between, and the tilt was determined from that (it is easily measured by measuring the altitude change of the sun with the seasons).
     
  4. Nov 5, 2007 #3
    Thanks for your quick reply RW. I understand that of which you have explained. I guess my question is how was the earth's axis of rotation determined.
     
  5. Nov 5, 2007 #4

    russ_watters

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    Staff: Mentor

    You can see it when you look at the North Star at night. The location of the equator can also be determined by watching the stars and Sun.

    Early explorers of the arctic did, in fact, use celestial navigation to figure out where they were. It is actually slightly more complicated than just measuring the altitude of Polaris - Polaris isn't exactly on our polar axis.

    My telescope has a handy-dandy polar alignment scope which helps me align it with the earth's rotational axis to within a tenth of a degree or so. Then using several other methods, I can get even closer than that.
     
    Last edited: Nov 5, 2007
  6. Nov 6, 2007 #5
    I see and thanks for clearing that up for me. I haven't had any Astronomy classes yet but I plan to take several.
    Thanks again
     
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