Earth’s Rotational Axis

The tilt of the Earth is not a fixed number, fluctuating over time and demonstrating a distinct wobble.

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The woman I was talking to seemed very sure of her facts, but they didn’t add up to me. She declared that the axis of the Earth had shifted six degrees and somehow it was the fault of “environmentalists” (I could not follow that part). “Six degrees?”, I questioned. I am not an earth scientist, but that seemed extreme to me. Surely, a six-degree change in the axial tilt of the Earth from the 23.5 degrees of the past millions of years would have had dire consequences for all of us. I determined that her “facts” were cow pucky, but wondered, what could be the source of such an exaggeration? Could there be a grain of truth there that was just exaggerated through conspiracy-type hype?

First, I had to gain a better understanding of the rotation of the Earth. The axis of the Earth is tilted about 23.5 degrees from the sun. This gets complex pretty fast, but it is sufficient to know that our planet does not face the sun directly, but rather, obliquely. This is incredibly important as it helps to create the seasons. We also rotate at about 1,000 miles per hour, giving us day and night.

When I spin the world globe on my desk, it turns smoothly around an axis centered on the south and north poles, as if a giant pencil were placed exactly between those two points. In reality though, if you were to sharpen that “pencil” and place it through the real Earth and give it a paper to draw on, the result would not be a clean single point, but rather, an elliptical shape. That is because the Earth wobbles slightly around its axis. Astronomers call the subsequent movement precession.

Precession is a result of s slight bulge at the equator, formed by the centrifugal force generated by the Earth’s rotation, making the Earth 26 miles wider than it is tall. The ellipsoid shape instead of a pure spherical one causes the Earth to wobble slightly. A single precession of Earth’s axis is a long process, taking nearly 26,000 years (25,772 years, to be exact) to complete. The wobble is unnoticeable in daily life, but must be factored in to get accurate results from GPS and for Earth-observing satellites as well as ground-based observatories. It is also the reason that star charts used by sailors must be periodically updated because the Earth’s precession changes its orientation to them. This is so dramatic that over time, the North Star, Polaris, will no longer be directly over the north pole and another star will have to be designated as the North Star.

So, there is a kernel of truth in the woman’s statement. The Earth’s degree of rotation does change slightly, slowly, and predictably through wobble, as one source stated, “throughout a cycle that averages about 40,000 years, the tilt from the axis varies between 22. 1 and 24.5 degrees,” 1.4 and 1.0 degrees respectively.

However, evidence from geological records (ice cores etc.), has revealed that the planet’s axial tilt may have ranged from as low as 10 degrees to as high as 60 degrees over the past 500 million years. This is real change and not wobble.

As it turns out, the tilt of the Earth has changed 31.5 inches in the past 20 years. While not significant enough to influence the 23.5-degree number (changing by approximately 46.8 sixtieths or less than half of a degree per century) it is interesting and so is its cause.

About the year 2000, Earth's spin axis took an abrupt turn toward the east and is now drifting almost twice as fast as before, at a rate of almost seven inches a year. When noticed, scientists scrambled to explain it. At first it was thought to be due to the rapidly melting glaciers in Greenland and Antarctica. As the ice melts and becomes water, it shifts the weight distribution and balance of this spinning top we call Earth. However, there just wasn’t enough change to account for the global axial shift. The change had to be coming from somewhere east of Greenland and the answer came from Eurasia. The area had lost a lot of water due to groundwater pumping combined with drought, and while the actual amount wasn’t near what was lost from the icesheets, researchers determined it was enough to cause the shift because the spin axis is very sensitive to changes occurring around 45 degrees latitude, north or south.

So, while a change of six degrees over a short time is blatantly wrong, the fact is, this planet we live on is dynamic, not static. And while some of that change is normal, some of it is human-caused. It is scary to think that we can literally change the way this globe spins and that influences life on the entire planet.

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Help Idaho Wildlife

When we traveled across the state in October 2017, we visited most of the Idaho Department of Fish and Game wildlife management areas. Most of the vehicles we saw using the wildlife management areas did not have wildlife plates. Buying wildlife plates is a great way for non-hunters and hunters alike to support wildlife-based recreation like birding.

C'mon folks, let's help Idaho's wildlife by proudly buying and displaying a wildlife license plate on each of our vehicles! 

See below for information on Idaho plates. Most states have wildlife plates so if you live outside Idaho, check with your state's wildlife department or vehicle licensing division for availability of state wildlife plates where you live. 

And tell them that you heard about it from Nature-track.com!

Wildlife License Plates

Great news! as of 2024, there are three NEW designs for license plates. They still are bluebird, cutthroat trout and elk, but they are beautiful.

Idaho Wildlife license plates provide essential funding that benefits the great diversity of native plants and wildlife that are not hunted, fished or trapped—over 10,000 species or 98% of Idaho’s species diversity. Game species that share the same habitats (such as elk, deer, antelope, sage-grouse, salmon, trout) also benefit from these specialty plates.

No state tax dollars are provided for wildlife diversity, conservation education and recreation programs. Neither are any revenues from the sale of hunting or fishing licenses spent on nongame species. Instead, these species depend on direct donations, federal grants, fundraising initiatives—and the Idaho Wildlife license plates.

Both my vehicles have Bluebird Plates. I prefer the bluebird because the nongame program gets 70 percent of the money from bluebird plates, but only 60 percent of the money from elk and trout plates - 10 percent of the money from elk plates supports wildlife disease monitoring and testing programs (to benefit the livestock industry) and 10 percent from cutthroat plates supports non-motorized boat access.

Incidentally, in 2014, the Idaho Legislature denied the Department of Fish and Game the ability to add new plates or even to change the name of the elk and cutthroat plates (very specific) to wildlife and fish plates, a move that would have allowed for changing images occasionally and generating more revenue. It would seem that they believe that we Idahoans don't want a well funded wildlife program.

I think it is time we let the Legislature know that Idahoan support wildlife funding and that we would like to see these generic plates come to fruition.