Movement of Stars seen from the North Pole

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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.
 

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  • #2
Drakkith
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Someone at the north pole is absolutely rotating.
 
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  • #3
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Someone at the north pole is absolutely rotating.
As in, at the point where the Earth's axis of rotation intersects with the surface, there is still rotation?
 
  • #4
Drakkith
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As in, at the point where the Earth's axis of rotation intersects with the surface, there is still rotation?

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

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

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.
 
  • #6
Drakkith
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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)?

Nope.

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.

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.
 
  • #7
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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.

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.
 
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Drakkith
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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?

I don't know honestly.

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.

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.
 
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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.

Thanks, I can see it now after a bit of visualization.
 
  • #10
sophiecentaur
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I don't theoretically see how a point along the axis of rotation could be moving at all.

would there still be any rotation in technicality at the exact center?
If there were no rotation of the axis, the Earth and the merry go round would have to be constantly distorting or there would have to be an infinitely small and frictionless bearing running through the axis. That would not make sense. If you were standing so that your feet were astride the North pole, a part of you, down through the middle would have to be rotating relative to the rest of you. (This is making me feel positively queasy!!)
Rotation and translation are two entirely different and independent motions.
 
  • #11
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I am not sure whether it was part of your question, but if we eliminate the apparent movement of stars due to daily/seasonal changes, like rotation of the earth and orbiting around the sun, there exists an observable movement of some of the nearest stars. However, don't expect that you could observe such movement during a night. Apparently, the "fastest" moving star is Barnard's Star, which angular change in position is around 10.3 arcseconds per year. By this rate, it would take around 350 years to observe its change in angular position by 1 degree! Consequently, stars might be considered reasonably "static" (from human point of view).

You might look for "proper motion" on google for more details.
 
  • #12
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Stars would not rise and set, but would still appear to rotate.
Looking at a star close to the horizon it would appear to move laterally with respect to features on the ground.
I think the person standing on the North pole looking at the horizon would see the stars as moving towards the righthand side of their field of vision..
 
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  • #13
I’ve been looking everywhere for somewhere to post about this and after about 30 minutes I’ve ended up here.
Sorry if it’s not quite on topic, but it seems like a good community to bring it up in.
For the past year or two I’ve taken to watching the night sky and multiple times now, with the most recent being about an hour ago, I’ve noticed that a few stars in the sky tend to move, almost dance. Up, down, left, right, circular patterns. I know it’s not my vision getting wonky as i can turn my attention to a different star and it stays absolutely motionless. Another way of confirming the movement to myself is keeping track of other still stars in the immediate area of the moving one and noticing the change of distance between them, I’ve also used tree branches that obstruct the view and the Star clearly is traveling in the sky.
Given the distance, they have to be moving very fast, and very fluid. Turns are smooth, almost as if someone was taking a laser pointer and calmly moving it around as if writing something. It’s not a rare occurrence either. Whenever the stars are visible I can always find at least one if not a handful of them that behave like this.
Anyways, just has me wondering if other people have noticed this, and what the current explanations have been. I urge people to look up and search these things out. It’s quite an amazing feeling seeing something that’s so unexplainable and who knows, could possibly be a life form in my opinion. Whatever it is, it’s not something I was taught that is supposed to be up there happening.
Anyways, thanks for reading, and if u respond, thanks in advance. :)
 
  • #14
sophiecentaur
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From a stable platform there should be no visible movement of those objects and you seem to imply that this is a selective effect against other stationary stars. I can only suggest that there is some local atmospheric disturbance due to hot air from a heater flue.
Another possibility is that you are seeing some things that are not stars - aircraft or land based with some mirage effect.
One thing you could do is to try to actually identify the 'stars' in question. A free application like Stellarium will show you what you can expect to see in any direction.
Have you seen the same effect in a telescope or binoculars on a stand? There is always the possibility that it's something to do with your vision; eye control can do strange things that you may not notice in a normal daylight scene. I suggest you ask a companion if they get the same experience at the same time.
Avoid considering 'life forms' unless it's fireflies or the like.
PS Edit: You could maybe have started a separate thread about this topic.
 
  • #15
Drakkith
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Anyways, just has me wondering if other people have noticed this, and what the current explanations have been. I urge people to look up and search these things out.

I used to be a pretty avid astrophotographer and I can say that in all my time out under the stars I've never seen anything like what you're describing.
 
  • #16
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I also used to do a lot of astrophotography and I have seen it a couple of times. It's called the Autokinetic effect (wp).
 
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  • #17
davenn
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I’ve noticed that a few stars in the sky tend to move, almost dance. Up, down, left, right, circular patterns. I know it’s not my vision getting wonky as i can turn my attention to a different star and it stays absolutely motionless

yes, it is your vision

I also used to do a lot of astrophotography and I have seen it a couple of times. It's called the Autokinetic effect (wp).

and that is close enough to proving that it is a vision related thing
 

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