With what resolution is it possible to locate the North Pole (or South Pole, for that matter)? How is it determined and what is the precision with which is can be measured? (I’m talking about the rotational pole, not magnetic.)
Is 0[sup]o[/sup]N intended to be that exact point, or is it an approximate point selected by convention?
Bonus round: I know the Earth wobbles but doesn’t the axis, and therefore the pole, remain the same w.r.t. to the Earth?
I recall seeing a map once where it showed the location of the North Pole as a function of time. In other words, the NP moves around.
The North Magnetic Pole moves around, yes, but isn’t the North Geographical Pole defined as the reference? In other words, if the geographical pole and the crust of the earth are shifting relative to each other, it’s the crust that is considered to have moved?
Geographic north is currently defined as a fixed location for purposes of accurate navigation and such, but the actual geographic north pole does move around some.
<insufferable pedant> I think you mean 90[sup]o[/sup]N. </insufferable pedant>
When it comes to defining any point by latitude and longitude, you have to ask: what datum?
That’s the important point - e.g. the Greenwich Meridian in Greenwich is either straight through the middle of Airy’s telescope, or 102.5 metres east of it, or 6 metres west of it, depending on whether you use the original definition, or the OSGB36 datum used by British maps, or the WGS84 datum which is used by GPS.
Similarly, the equator by the extended OSGB36 datum is hundreds of metres away from the WGS84 equator.
It is simply a matter of definition. By using a decent differential GPS unit you could probably pinpoint the WGS84 North Pole to within a few centimetres (subject to satellite visibility which I believe is not great at high latitudes). That is a North Pole… but you can’t say it is the North Pole.
Not that it really matters, but I got those in the wrong order. It’s the WGS84 meridian that’s 100-odd metres east, and the OSGB36 which is a few metres west. My point still stands, though.
More info on WGS84 from Wikipedia.
The earth wobbles wrt the stars, but the axis of rotation wrt the earth remains constant I would say, just by definition.
This leads to a follow up question. Are the GPS satellites fixed to the earth?
GPS satellites are not geosynchronous. They are at a much lower altitude of around 20,000km, IIRC. Geosynchronous orbit is around 42,000km high.
It does not remain constant. Per QED post 4 it looks like it moves around.
Okay, go north. More. More… keep going north. More. Keep going north. Right there. That’s the north pole.
No, I don’t have anything real to add. Sorry.
HANG on, I’ll go check…
The North Pole is, by definition, the northern point at which the Earth’s axis of rotation intersects the surface. And by convention, it’s 90 degrees north latitude.
It “moves” relative to the surface of the Earth (in geologic time) and relative to the surface of the Arctic ice pack (in normal days/weeks/months time) in much the same way as the Sun “rises and sets” – it’s stationary [in any Earth-as-a-whole frame of reference], but the reference point moves relative to it. In other words, if at the end of November 2006, it’s at this given point on the Arctic ice pack, which is directly above this point on the ocean floor, movement of the ice pack and of the ocean floor will shift it (in two dramatically different time frames) as being a marked point. But it’s actually the ice pack and the ocean floor doing the moving, not the pole.
Precession of the equinoxes changes the point at which the pole “points” in the sky, i.e., the point round which the stars appear to move over the course of a night. But I do not believe this has anything to do with movement of the pole, rather a shift in the axial tilt of the Earth relative to the visual stellar sphere over the course of 36,000 years or so.
This would be accurate if there was no wobble. But there is a wobble. The South Pole moves too, even though the ice cap is fixed solidly on Antarctica.
Hmmm. If you went down to the south pole and put a stake in the ground there I believe the stake would move over the course of time. Isn’t the Antarctic ice pack continually sliding off the land and into the ocean?
Motion of the earth’s axis relative to the stars or the sun has no effect on where the north pole is relative to the earth’s geoid. The north pole is 90[sup]o[/sup] north of the equator. As was said above, the survey description of where the north pole is located depends entirely upon your reference benchmark.
Yep. They stick a new pole in the ice every year, but leave the old ones in. This is a neat picture that shows the current marker and the line of “old poles”.
About this wobble business. I had always thought that the wobble meant that the axis itself wobbled but the earth was fixed w.r.t. the axis. After reading Q.E.D.'s post, I am now getting the idea that the earth also has a small amount of shifting on its axis. Am I reading that correctly?
Oh, good point. :o
Ever see a spinning top wobble ? I just can’t get my head around its axis wobbling wrt to the whole top.
Aaargh! It’s not just the ice that moves! The whole planet is wobbling! You can see a map of it at http://www.iers.org/MainDisp.csl?pid=95-89. The dotted line shows the pole’s location over the course of three years, at intervals of about five days. See the circle it makes? That’s not ice!!!