Archived Articles

How Anomalous is the
Current Polar Motion?
Jonathan Eagle

The Earth rotates about its axis once per day but does not do so uniformly. The Earth wobbles as it rotates, and that wobble was detected in 1891 by American astronomer Seth Caro Chandler, Jr. In fact, Chandler observed that the Earth has two distinct wobbles. One wobble has an annual (12-month) period; the other has a period of 14 months. The annual wobble is a forced motion of the Earth caused by seasonal variations in the atmosphere, oceans, and hydrosphere. The 14-month wobble, now known as the Chandler wobble, is a resonant, free oscillation of the rotating Earth that exists because the Earth is not rotating about its figure axis. Dissipation processes associated mainly with the wobble-induced deformation of the solid Earth cause the Chandler wobble to decay on a time scale of about 30-100 years. Over the last century, the amplitude of the Chandler wobble has been observed to increase occasionally. Thus, one or more mechanisms must be acting to excite it.

"Since its discovery the excitation of the Chandler wobble has been an intriguing problem that has stimulated research in various geophysical and geodetic fields. Nevertheless, the actual mechanism in the Earth system that is most responsible for sustaining the Chandler wobble is still under investigation."1

Any of THC's subscribers who have examined the most recent animated Polar Motion Plot will have undoubtedly noticed the abrupt change in the path of the North Pole during the last month or so (non-subscribers will have to wait until this article is released in June 2006 to see what is being referred to in this article). Close examination of the track taken by the pole shows that during the months of November and December 2005 the pole seems to have come to an abrupt halt as if it "ran into something," and then turned left like it was "going around" that "something". The first figure shows the last frame of the January 2006 subscriber's version of the animated graphic. The end of the line that terminates in cyan represents the last six months of polar motion, with the extreme end representing the movement of the North Pole for December 1, 2005 thru January 1, 2006.

PSResearch/UandM_PS2001/1-03to1-06.gif Figure 1. Plot of three year's motion of the north rotational-axis pole relative to the geodetic North Pole, which is designated by the center point of the axes of intersection. The four axial directions represent the first 100 feet of the four respective longitude lines.

For those that are new to THC, and may not be completely familiar with our animated polar plots, or perhaps have not read "Understanding And Monitoring Polar Motion" what follows is a brief orientation. The graphics in this article's figures represents a "bird's-eye" view of the Earth's north pole, or the point on the surface of the earth where all the northern longitude lines converge at the north pole. However, in the interest of not cluttering up the diagram we have removed all but the four principle meridian lines, those going in the four cardinal directions. The traces, which start as grey lines, and end in bright cyan, are a path created by the daily plotting of where the Earth's spin axis intersects the Earth's surface relative to the north pole. It is the apparent irregularity of this plot that is being discussed in this article.

As unusual as the current trace may appear, the pole's motion, also known as Chandler's wobble, has demonstrated some even more unusual motions in the last 32 years, since daily records of Earth's North-Pole position started being kept in 1973 by the International Earth Rotation Service. Before 1973, records of the pole's position were determined about every 18 days primarily using celestial fixes to determine variations. Actually, records of celestially-determined polar values have been kept since 1846, but the precision was relatively coarse, and before 1890 positions were only determined 10 times per year, or about every 36 days. After 1973, and with the advent of high-precision satellite positioning systems, the Earth's pole position has been determined daily with a great deal of accuracy.

And so, looking at just the last 33 years worth of positional data, we see several examples of "erratic-looking" motions of the Earth's rotational axis.

PSResearch/UandM_PS2001/1-75to8-75.gif Figure 2. Plot of 32 months of Earth's North Pole motion showing the "erratic" changes in direction of the rotational axis during that time that Chandler's wobble was winding down to a minimum.

The first example we find occurred during the first 32 months of daily position data starting on January 1, 1973. As can be seen in Figure 2, the smoothly inward-arcing motion of Earth's wobble abruptly takes a 90° turn to the left in March 1973. Then, between June of 1974 and June 1975, the pole's motion exhibited several erratic back and forth motions before settling down to a more normal motion by August 1975.

/PSResearch/UandM_PS2001/1-75to1-78.gif Figure 3. Five years of polar motion from January 1973 to January 1978. Note the asymmetrical "bulges" in the path of the wobble during the last two years of movement.

However, as the Chandler wobble started expanding its spiral path, outward from its normal minimum, it displayed some additional abnormal behavior, as is shown in Figure 3. This figure, which is a continuation of Figure 2, shows that instead of returning to a more typical circular spiral track, the path instead "bulged" and "pushed" asymmetrically outward in a couple of places. By January of 1978, the track describing Earth's Chandler wobble for the five preceding years looked anything but "normal".

/PSResearch/UandM_PS2001/1-78to1-82.gif Figure 4. Four years of polar motion showing irregularities in the path during the minimum period throughout most of early 1980.

During the next five years, from January 1978 to January 1983, the pole's motion settled down and behaved more normally, as it continued to transition from an outward spiraling track through an inward spiraling track to one ending with an outwardly track. However, during most of 1980 when the track was again going through its minima, the track displayed some irregular motions. This can be seen in Figure 4, which shows four years of north-polar motion from January 1978 to January 1982.

During the next fourteen years (not shown graphically), between January 1983 and January 1998 the path of the pole went from a maximum through a minimum and back to a maximum. During the latter part of 1987, when the path was going through its first minimum, the motion again became somewhat irregular, but significantly less than shown earlier.

/UandM_PS2001/1-98to1-02.gif Figure 5. Four years of polar motion showing some irregularity during the minimum bend of the pole path..

By the beginning of 1998, as the path of the pole was starting to wind inwardly toward it's minimum, it again became somewhat more "ragged". As shown in Figure 5, during the four years between January 1998 and January 2002, the Chandler wobble went through a minimum and exhibited some irregularities. Given the limited data, the irregularities, which frequently show up during a Chandler wobble minima, seem to be more of a rule than an exception, and may be a characteristic of the Earth's loss of circular momentum during the times of minima.

As was stated earlier, The International Earth Rotation Service has records of the pole's position going back to 1846. Attempts to plot these data using only the 18 or 36 positional points per year created graphs that were extremely hard to interpret. The dearth of available points meant that the lines defining the pole's interpolated motion could look very jagged and hard to follow as it zigged and zagged in straight-line segments on the graph. To add to the problem, the older observations carried with them large error values due to the lack of precision in measurements available to the geometers at the time. To add the (sometimes considerable) error values to a conventional plot would mean rendering that plot even more incomprehensible.

To remedy that problem we devised a new type of animated plot, similar to the pre-1973 data, except that it shows each pole location's fix as an ellipse that is proportional to the error value associated with each data point. Like the pre-1973 data versions, we made the older data points fade to grey as they aged on the display. In this way one is able to track the motion of the pole over time, including each point's error value, without being confused by earlier positional information.

Figure 6. A single frame from the pre-1973 polar motion animations showing the anomalous position of the Earth's rotational axis on June 14, 1902.

What we find as we look back to the record of Earth's polar motion before 1973 is that the relatively smooth spiraling motion, so typical of the last 30 years, seems to be the exception rather than the rule. The record of Earth's polar motion during the century from 1846 to 1946 shows polar motions that are much less circular, but which are much more angular and erratic. As is illustrated in figure 6, the record even shows that during early June 1902 the pole apparently took a brief excursion outside of its "average envelope" (defined by the points that came before and after it) by almost a full radius' distance. Assuming that the plotted data point represents accurate positional observation, it is clear that none of the anomalous motions that have occurred during the last 50 years even approach the 1902 level of erratic behavior.

It is interesting to note that examination of the period of time from 1933 to 1942 (and beyond) shows no obvious indication that the "catastrophes from outside forces" forecast in the following quote from reading 3976-10, created any discernable change in Earth's rotational behavior.

These {political changes in Italy} will not come, as we find, as broken, before the catastrophes of outside forces to the earth in '36, which will come from the shifting of the equilibrium of the earth itself in space, with those of the consequential effects upon the various portions of the country - or world - affected by same.

The point of this analysis of the motion of Earth's North Pole of rotation is simply to provide a sort of baseline against which one can compare any future pole motion paths that might appear to be irregular. With comparable data for only 33 of the thousands of years since Earth's last pole shift, it is imperative that we do not overreact to what may be small anomalies in the greater scheme of ongoing motions of the Earth's rotational axis. While the Hutton Commentaries does not have any hard and fast rules for what constitutes the beginning of a genuine pole shift, we do have some rules of thumb that we use to gauge the irregularities in Chandler's wobble.

One of those rules of thumb is that the extremity of poles circular "orbit" not exceed the boundaries of the previous cycles maxima by more than 50% of the diameter defined by previous motions. Likewise, if the bounds of the wobble stay within "normal" ranges, but the "average" position of the wobble shows an historically unprecedented acceleration in any direction (but most especially along the 58°W meridian) we will consider that anomalous.

Chandler's Wobble: Erratic Sample of THC's "yellow alert" in the case of erratic motions in Earth's pole of rotation.

Another rule of thumb is that the average position of the trace of the wobble should not become overly linear, that is, if the normally arcing trace shows a pronounced "flattening" for more than 0.3 or 0.4 arcseconds (about 30 or 40 feet on the graph) in a particular direction, we will consider that sufficiently anomalous to issue our "yellow alert", shown here. Meanwhile, subscribers can view our monthly updates of the track of the North Pole from the link found at the top of each bulletin.

How fast will the poles shift?

One primary indication we expect will quickly make evident that a pole shift is underway is a drastic change in the average annual position of the Chandler wobble. Since the turn of the last century, the Earth's rotational axis has moved about 41 feet as is shown in Figure 7.

Figure 7. Plotted yearly average position of Earth's axis for the years 1900-2005 relative to the Earth's geodetic axis. Each 0.100" represents a distance of about 10 feet.

It seems obvious that the kind of pole shift that THC envisions will cause a significant change in the fairly staid and stately drift that the pole has undergone for the last 105 years. The pole shift that we envision will move the pole to a new position on the Earth approximately coinciding with latitude 89°N and longitude 58°W. That is, for reasons outlined in our articles entitled, "A Small Pole Shift Can Produce Most, If Not All, of The Earth Changes In Cayce's Readings", and "Calibrating The Hutton Commentaries' Model For a 1° Pole Shift to 89.0°N", the Earth's rotational north pole is slated to move about one degree of latitude south from its current position.

The big question is "how fast is the pole going to move?" Will the pole make the predicted one degree pole shift in a day? A week? A month? A year? How about a century? The Creative Forces may know, but we don't have a clue. However, we can tell how long the pole would take to traverse the 60 to 70 miles it will have to move during a pole shift if it continued at its current rate. Using a figure of exactly one degree for the distance the pole will move during the pole shift, and using its current drift rate of 41 feet per century, we find the trip would take almost 890,000 years!2

Clearly, the poles are going to have to move substantially faster than that for anyone to call it a "pole shift". Perhaps reading 364-8 gives us an upper bound to the length of time it will take for the poles to shift:

(Q) Please explain what is meant by "He will walk and talk with men of every clime". Does this mean he will appear to many at once or appear to various peoples during a long period? (A) As given, for a thousand years He will walk and talk with men of every clime. Then in groups, in masses, and then they shall reign of the first resurrection for a thousand years; for this will be when the [Earth] changes materially come.

Again, nobody knows whether the pole shift is going to take a day or an entire millennium, but even if the pole shift took a thousand years to complete, it would have to move almost 1000 times faster than it is right now.3 Therefore, however fast the pole ends up moving, when the poles really do start to shift, it will be so obvious that a pole shift is underway that there is no chance of anyone confusing the shifting with the present bumps and wiggles that are apparently so typical of Chandler's wobble.

  1. Eos, v. 86, n. 3, 18 Jan. 2005.
  2. The figure for the length of time it will take the pole to travel one degree of latitude was computed using the distance formula (D = R * T) solved for time as follows:

    Distance = 1° = 60 minutes = 60 nautical miles = 60nm * 6076.1 ft/nm = 364,566 feet
    Rate = 41 feet per 100 years
    T =   D   =   364566 ft   = 889,185 years
    R   41 ft  
          100 yr  
  3. Again, using the distance formula solved for rate:
    Rate = Distance = 364,566 ft = 364.6 ft/yr
    Time 1000 yrs