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The general idea that has been taught to people is that there is an imaginary axis that crosses the earth from the north pole to the south pole (or vice versa).And that is the axis of rotation.

But I have always thought that idea is not so accurate and that there are other poles that are the true and the geographics don't coincide with the true poles.

If I am correct with that idea, I can affirm that there is also a true equatorial line that doesn't coincide with the geographical equatorial line.

Am I right?

[Update]

I asked that question because I live in Ecuador and here there is a commemorative monument of the French geodesic mission (between 1736 and 1744) and besides being a tourist center in which visitors are shown experiments as a container full of water with a siphon in which no swirl occurs because they are in exactly the equatorial line, in addition to other tricks.

Here you can see a video of different experiments:

https://www.facebook.com/nasdaily/videos/923542644464555/

I have reasoned and I think that the effects caused by being on the equatorial line would happen if the axis of the earth did not have wobbles and according to what it says here:

https://en.wikipedia.org/wiki/Equator

"Precise location The precise location of the Equator is not truly fixed; the true equatorial plane is perpendicular to the Earth's spin axis, which drifts about 9 metres (30 ft) during a year. This effect must be accounted for in detailed geophysical measurements"

Then the true equatorial line would change in a range of +/- 9 meters each year and the effects shown to tourists on the equatorial line may have been for the following reasons:

  1. They are false tricks since the effects of the equatorial line move throughout the year in an area of ​​approximately 9 meters and for such "experiments" to happen they should move the devices to find the effects of the equatorial line constantly throughout the year.

  2. The tricks are true, but they do not happen exactly on the geographical equatorial line, but within a range of 9 meters.

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  • $\begingroup$ What draws you to think it's inaccurate? $\endgroup$
    – JeopardyTempest
    Apr 26, 2018 at 20:12
  • $\begingroup$ nationalgeographic.org/encyclopedia/axis $\endgroup$
    – user3249244
    Apr 26, 2018 at 21:29
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    $\begingroup$ They are false tricks because the Earth's rotation is too slow to affect a sink. en.wikipedia.org/wiki/… ems.psu.edu/~fraser/Bad/BadCoriolis.html physics.stackexchange.com/questions/7738/… $\endgroup$
    – Keith McClary
    Apr 29, 2018 at 3:04
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    $\begingroup$ Indeed, all the stuff shown (other than shadows) in that video is misleading, or often intentional deception, and can be accomplished at any latitude on any day with equal likelihood. (An SE question about the egg) $\endgroup$
    – JeopardyTempest
    Apr 29, 2018 at 4:41
  • $\begingroup$ I think you change the nature of the question by adding your additional information. I'm thinking we should remove the part about the 9 meters, since that's what prokilgrammer already took the time to answer from your original question. And then you can ask about those tricks in additional questions if needed (though as shown, answers have already been given). Indeed, more proof of the scam nature of such "experiments" is that they don't take into account the 9 meters in their positioning :) $\endgroup$
    – JeopardyTempest
    Apr 29, 2018 at 4:48

2 Answers 2

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Perhaps you are thinking about the discrepancy between true north and magnetic north. The former is where the earth's axis of rotation intersects the earth's surface in the northern hemisphere. The latter is the location where the magnetic field lines of the earth are vertical, meaning a magnetic compass will point to this location. If you follow your compass to the magnetic north pole, you will be roughly 500km from the true north pole which lies on the earth's rotational axis.

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  • $\begingroup$ I asked that question because I live in Ecuador and here there is a commemorative monument of the French geodesic mission (between 1736 and 1744) and besides being a tourist center in which visitors are shown experiments as a container full of water with a siphon in which no swirl occurs because they are in exactly the equatorial line, in addition to other tricks. Here you can see a video of different experiments: facebook.com/nasdaily/videos/923542644464555 $\endgroup$
    – user3249244
    Apr 28, 2018 at 19:26
  • $\begingroup$ I have reasoned and I think that the effects caused by being on the equatorial line would happen if the axis of the earth did not have wobbles and according to what it says here: en.wikipedia.org/wiki/Equator "The precise location of the Equator is not truly fixed; the true equatorial plane is perpendicular to the Earth's spin axis, which drifts about 9 metres (30 ft) during a year. This effect must be accounted for in detailed geophysical measurements" $\endgroup$
    – user3249244
    Apr 28, 2018 at 19:28
  • $\begingroup$ Then the true equatorial line would change in a range of +/- 9 meters each year and the effects shown to tourists on the equatorial line may have been for the following reasons: 1. They are false tricks since the effects of the equatorial line move throughout the year in an area of ​​approximately 9 meters and for such "experiments" to happen they should move the devices to find the effects of the equatorial line constantly throughout the year. 2. The tricks are true, but they do not happen exactly on the geographical equatorial line, but within a range of 9 meters. $\endgroup$
    – user3249244
    Apr 28, 2018 at 19:28
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Geographic axis is NOT fixed.

North and south poles are NOT fixed.

Ideology is reverse of what you are thinking.

First suppose that Earth is rotating about some arbitrary axis => Then this axis intersects on Earth's surface at two points => Now, if you see earth from above and observe earth rotating in counter-clockwise direction then this point is defined as North pole and hence other will be south pole.

In short, first we see earth rotating about an axis and then north and south poles are defined according to it.

Also, the axis of rotation wobbles and as a result north and south pole wanders a bit. This is known as Chandler wobble.

Note: It is very important to realize that according to chandler wobble axis of rotation wobbles with respect to Earth. Earth itself is NOT wobbling due to chandler wobble, it is only changing the axis of rotation.

So, there is no concept of true axis here, but only one axis -> geographic axis which wobbles.

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  • $\begingroup$ Then I could also say that there is no constant or true equatorial line, but there is an equatorial line that also moves to the wobble of the axis and possibly has a sinosoidal shape on the geographic equatorial line. Is that possible? $\endgroup$
    – user3249244
    Apr 27, 2018 at 12:23
  • $\begingroup$ (To be clear to some folks who may read this answer and may not realize: there are magnetic poles [which do move] and there are rotational poles [which are rather fixed]... see this Wikipedia article) $\endgroup$
    – JeopardyTempest
    Apr 27, 2018 at 12:32
  • $\begingroup$ I understand that they are fixed, but things in the universe are not eternal. By stating that they are "rather fixed", it implies that they may move away from the geographical axis. The questions would be: How far does the true axis move away from the geographical one? Is the axis currently moving away and returning to its geographical position? Or is it moving away in the distant future to be in a different position? $\endgroup$
    – user3249244
    Apr 27, 2018 at 13:22
  • $\begingroup$ Precise location The precise location of the Equator is not truly fixed; the true equatorial plane is perpendicular to the Earth's spin axis, which drifts about 9 metres (30 ft) during a year. This effect must be accounted for in detailed geophysical measurements. en.wikipedia.org/wiki/Equator $\endgroup$
    – user3249244
    Apr 27, 2018 at 13:43
  • $\begingroup$ @JeopardyTempest Rotational poles (North & South poles) are NOT fixed. Earth rotates about geographic axis which wobbles with respect to Earth. So, instantaneous points of intersection of geographic axis - N & S Poles, wander and are not fixed. $\endgroup$
    – shul
    Apr 27, 2018 at 19:24

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