As the Muppets sang on their way to fame and fortune in Hollywood, “We’re movin’ right along!” This is to say, the Earth is movin’ right along. In one line in the Muippet Movie song, Fozzie Bear says, “Hey, I’ve never seen the sun come up in the West?” Have you? No. And, you have never seen the sun come up in the East. Sunrise is an illusion caused by the rotation of the earth.
Due to the astronomical scale of the universe, right down to our solar system, there are many changes daily in the precise moment of sunrise and sunset. You probably want to hear how the earth revolves in 24 hours, but that is not the case. Not at all.
A fascinating website, TimeAndDate.com, provides real-time changes in the earth’s rotation.
For example, today, August 1, 2022, the earth rotated once on its axis in 23 hours, 59 minutes, 59.9994316 seconds (-0.5684 milliseconds). Yesterday, July 30, 2022, the earth’s rotation was completed in 23 hours, 59 minutes, 59.9992364 seconds (-0.7636 milliseconds).
Perhaps you have on some occasion been tasked with hauling water with an open bucket. If so, you will remember the annoying sloshing of the water and how that motion of the water in the bucket affected your gait. Here is a video of a tank sloshing simulation.
If the truck in the video were to remain at a constant speed, the sloshing would stop. But, braking and accelerating are realities of trucking, so sloshing is inevitable.
Likewise, the human gait. It’s impossible for a human to maintain a constant speed while walking. Your body accelerates each step of the way and decelerates at the end of each stride.
Let’s imagine the liquid outer core of the earth. This is liquid iron (Fe) and nickel (Ni) that, like the sloshing tanker in the video, tend to advance and retard the rotational speed of the earth.
Next, let’s compare swinging a ball on a tether around yourself. Changes in the length of the tether between you and the ball affect your speed of rotation. Do you know the distance between the earth and the moon constantly changes, 1.5 inches per year, to be exact.
Let’s consider other things affected by the sloshing of the outer molten core of the earth: magnetic north. Unlike the idyllic graphic above, the molten outer core has two bulbous sections, one under Canada, the other under Russian Siberia. Well, that has been true for a very long time, but something is changing as the sloshing of the molten outer core rapidly moves magnetic north from within the Canadian Arctic Circle toward Russian Siberia.
General aviation uses magnetic north to orient runways. For example, the runway here in my city of Rockwall, F46, used to be 16/35 (160 degrees south/350 degrees north). It is now 17/34. Actual compass: 167 magnetic, 172 true.
Up to this point, this is fun information. Now for the not-so-fun information.
Article in Forbes, titled Earth’s Magnetic North Pole Is Shifting Dramatically From A Powerful Tug Of War: “At the turn of the 20th century, the magnetic north pole was firmly in the Canadian Arctic. It spent the next century meandering about ten degrees to the north, moving ever closer to the true North Pole. Around 2001 its movement began to accelerate, and by 2019 magnetic north had actually moved all the way north, crossed the International Date Line and began traveling south on the other side of the globe toward Siberia.” Read more from Forbes here.
What happens when the magnetic poles shift even greater distances? I’ll save the answer for another blog post. What happens as the spin speed of the earth increases?
John White
Rockwall, Texas
John N. White 