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

Stargazing Movement of Stars in North Pole

  1. Mar 16, 2016 #1
    From the perspective of someone at or near the exact north pole (where, for all practical purposes, they are not rotating), ignoring the gradual change of the stars as the Earth orbits the sun, would the stars appear to move at all in the night sky? Or would they be stationary because the observer is not rotating? I can't seem to find any documentation of this, so I'm just wondering if I'm correct on this.
     
  2. jcsd
  3. Mar 16, 2016 #2

    Drakkith

    User Avatar

    Staff: Mentor

    Someone at the north pole is absolutely rotating.
     
  4. Mar 16, 2016 #3
    As in, at the point where the Earth's axis of rotation intersects with the surface, there is still rotation?
     
  5. Mar 16, 2016 #4

    Drakkith

    User Avatar

    Staff: Mentor

    Indeed! Here's a 24-hour time lapse of the Sun moving through the sky at the south pole.

     
  6. Mar 16, 2016 #5
    Is that caused by being not exactly at the south pole, but near it, thus still rotating (which is why the sun appears to move in a circle)? I don't theoretically see how a point along the axis of rotation could be moving at all. The speed of rotation on Earth varies by the cosine of latitude, so at a latitude of 90 degrees, your speed of rotation would be 0 since cos(90 degrees) = 0.
     
  7. Mar 16, 2016 #6

    Drakkith

    User Avatar

    Staff: Mentor

    Nope.

    That's tangential velocity, not angular velocity. A point at either pole still rotates at the same angular velocity as the rest of the Earth, which doesn't vary with latitude at all.
     
  8. Mar 16, 2016 #7
    Ah, I see what you mean there. In a purely theoretical sense, though, is it not true that the point exactly along the axis of rotation would not be rotating, even though every single other point would be rotating with the same angular speed? For example, with a merry go round, although no matter how close you get to the center you are still rotating, would there still be any rotation in technicality at the exact center?

    Also, although there is still rotation at the poles, shouldn't the stars still appear stationary very near the exact pole? When very near the exact pole, although your angular speed is the same as anywhere else, you aren't moving nearly as much as you do at a lower latitude, causing you to see much less movement of the sky, I would think.
     
  9. Mar 16, 2016 #8

    Drakkith

    User Avatar

    Staff: Mentor

    I don't know honestly.

    You aren't moving tangentially with respect to the Earth's axis, but you're still rotating. This rotation is what makes the stars move across the sky. This is no different than standing outside, looking up and rotating your body. The stars would certainly appear to move even though you aren't moving tangentially with respect to anything during your rotation.
     
  10. Mar 16, 2016 #9
    Thanks, I can see it now after a bit of visualization.
     
Know someone interested in this topic? Share this thread via Reddit, Google+, Twitter, or Facebook

Have something to add?
Draft saved Draft deleted



Similar Discussions: Movement of Stars in North Pole
  1. Pole Star - Help! (Replies: 18)

  2. Aurora in North pole (Replies: 2)

  3. Martian pole star (Replies: 6)

Loading...