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Why is there no West Pole and East Pole?

  1. Jul 29, 2015 #1
    Why is there no West Pole and East Pole? There's a North Pole and a South Pole, but no West Pole and no East Pole.
     
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  3. Jul 29, 2015 #2

    berkeman

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    What would be your guess...? :smile:
     
  4. Jul 30, 2015 #3
    I think that I remembered a discussion about this subject:

    Hmm....

    “There's the South Pole, said Christopher Robin, and I expect there's an East Pole and a West Pole, though people don't like talking about them.”
    ― A.A. Milne, Winnie-the-Pooh
     
  5. Jul 30, 2015 #4

    BWV

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    There is on Uranus (groan)
     
  6. Aug 23, 2015 #5
    Yes Uranus, if I'm not mistaken is tilted 98 degree. That they rotates from west to east.
     
  7. Aug 23, 2015 #6
    The poles mark the overall axis of spin for a planet, and there can only be one such axis, (with a pole at both ends).
    The naming of the poles is arbitrary, but by convention we use North and South.
    East is the direction the planet is spinning in, There is no 'Eastmost' point where you can't go further East
    West is the opposite direction.
     
    Last edited: Aug 23, 2015
  8. Aug 23, 2015 #7
    The simple answer is because the Earth rotates on an axis that is almost vertical (can't remember what angle it is tilted at). Because of this you can reach a maximum North and maximum South, meaning if you are at the South pole, no matter where you turn you can only go North, not more South, thus making it one of the poles. On the other hand, if you head East you can keep going East (or West) for as long as you want and you'll just circle the Earth without ever reaching a point where you can't go East. Thus, East and West have no poles.
     
  9. Aug 23, 2015 #8

    FactChecker

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    Long before anyone thought that the Earth rotated, early man noticed that the North Star remained fixed, while all others rotated around it. That direction would naturally be special. When the compass was discovered, it also pointed toward the north. Defining an East/West pole would contradict all of that.
     
  10. Aug 23, 2015 #9

    phinds

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    It (the word "North") is not arbitrary, and I do not believe that it is derived from the "North Star" but rather the North Star is derived from the same older word/concept. I think I recall it came out of something having to do with the direction that the sun rises.

    EDIT: I Googled it to double check and yeah, it came from some old phrase meaning more or less "to the left of the rising sun". I have no recollection of where the word "South came from". You can look that one up yourself :smile:
     
  11. Aug 23, 2015 #10
    But the compass does not "point" to the North Star, right. It points to magnetic compass which happens to be in the north. There is no south star. We use constellation "cross"
     
  12. Aug 23, 2015 #11
    South, "sud", Sol, means Sun.
    In French it's "Sud", I don't know what "South" in Latin.
     
  13. Aug 23, 2015 #12
  14. Aug 24, 2015 #13

    FactChecker

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    I think the point is not so much what word is used for the North Pole, but why did people think there was something worth naming in the North/South but not in the East/West. The derivation of the term "North Pole" is probably a question for an English language forum. Before people thought the Earth rotated, they could see that the North Star was stationary and all other stars revolved around it. They had a lot of beliefs related to stars and their motion. It would be surprising if they did not have a word for the North Pole.
     
  15. Aug 24, 2015 #14

    phinds

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    And the sun as well. My point was that the word North evolved out of interest in the sun.
     
  16. Aug 27, 2015 #15
    On a body that is tidally locked to what it orbits, there would be a total of 6 Poles!

    Consider the Earth's Moon. It has a North and South Pole. It also has an East and a West Pole, where you could stand and watch precisely 50% of the Earth, continually rolling towards you or away from you. In addition, there's a Pole with the Earth directly overhead, and another directly opposite. I've no idea what those poles would be called, however.
     
  17. Aug 27, 2015 #16

    mfb

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    There is a subsolar point, I guess "subterrestrial point" could work for one of them.
    Libration changes the position of Earth a bit over time. For the same reason, we can observe nearly 60% of the surface of Moon from Earth.
     
  18. Aug 16, 2016 #17
    They do exist! Mathematically, any point on the surface of a sphere can be defined as the pole. Loosely speaking, people associate "North" with one such point. Then, the point most distant from it on the surface of the sphere may be referred to as the opposite pole. Call it "South" or "Anti-North", it matters little (and the definitions are symmetric). Now, connect the two poles with a great circle around the sphere, and you have divided it into two hemispheres. There is a catch, however. There is an infinite number of great circles passing through the two poles. Verify that you are yourself on one of them even as you read this. Thus, you must designate a third point in order to uniquely determine a single great circle. People often use "Greenwich" for this point, and use "eastern" and "western" to refer to the resulting hemispheres. Logically, it follows that the "east pole" and "west pole" are the two points on the sphere most distant from this great circle. The choice of "eastern" versus "western" is also arbitrary, people seem to like having the sun rise in the "east" and set in the "west", do not ask me why.
     
  19. Aug 17, 2016 #18

    phinds

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    In standard usage, "pole" means a point on the surface corresponding to the axis of rotation. There are only two such points on a rotating sphere, so I disagree w/ what you have said.
     
  20. Aug 17, 2016 #19
    I don't think this is right. On the moon there would be a continuous ring of places such as you describe, and none of the points on that ring would be particularly special. That would make it more like an equator then a pole. The Earth Pole and Far Pole would be as you describe though.
     
  21. Aug 17, 2016 #20
    No. There are special points on the Moon, and there are 4 of them on Equator.
    Earth is axially symmetric, so while the North and South poles are special, the Equator is a line which is special - no specific point of Equator is.
    Moon is locked to Earth, so there are 4 special points along Moon equator - the subterranean point, the East and West poles, and the antiterran point.
     
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