why does the rotational axis of earth precess
The Earth rotates once in a few minutes under a day (23 hours 56 minutes 04. 09053 seconds). This is called the sidereal period (which means the period relative
to stars). The sidereal period is not exactly equal to a day because by the time the Earth has rotated once, it has also moved a little in its orbit around the Sun, so it has to keep rotating for about another 4 minutes before the Sun seems to be back in the same place in the sky that it was in exactly a day before. An object on the Earth's equator will travel once around the Earth's circumference (40,075. 036 kilometers) each sidereal day. So if you divide that distance by the time taken, you will get the speed. An object at one of the poles has hardly any speed due to the Earth's rotation. (A spot on a rod one centimeter in circumference for example, stuck vertically in the ice exactly at a pole would have a speed of one centimeter per day! ). The speed due to rotation at any other point on the Earth can be calculated by multiplying the speed at the equator by the cosine of the latitude of the point. (If you are not familiar with cosines, I wouldn't worry about that now, but if you can find a pocket calculator which has a cosine button you might like to try taking the cosine of your own latitude and multiplying that by the rotation speed at the equator to get your own current speed due to rotation! ).
On average it's 1,041. 666667 mph. And there you have it, according to NASA. We are also told Thuban was the pole star prior to 2700 BC and about the time the Egyptians were building pyramids. It seems Archeologists have determined several structures in Egypt were set up to align with Thuban at that time. It's interesting, if this is the case, since if structures were aligned to the North Pole to point at Thuban, then today they would simply point to Polaris, unless they were deliberately misaligned, or the interpretation is wrong.
Thuban is a star in the constellation "Draco". It just so happens that if it were the pole star in ancient times, it would retain the present 23 1/2 degree tilt to the ecliptic. However, most of Draco is in an area of the Celestial Sphere, where. There is a great deal of compelling evidence that the actual. There were 12 stars put into Draco reflecting the symbolism of the twelve. It seems reasonable to me that the center of Draco, was the direction of the axial tilt in the previous age. We know for a fact the Earth's axis is tilted at 23 degrees relative to the ecliptic and today points at Polaris, the North Star. At some time in the past, it has been suggested the axis pointed at Thuban. Therefore, some have invented a theory of precession to explain a change in the axis orientation according to some ancient observations. The axis may have changed orientation from Thuban to Polaris; there seems little reason to doubt it, since there is no question Polaris appears to be moving in a path of rotation, over time.
The question is, does the axis gradually move over the course of 26 thousand years and imitate the motion of a slowing wobbly top or is there some other mechanism that appears to have moved the axis. Gyroscopic precession, due to impact could have changed the Earth's axis orientation from the center of Draco and nudged it to a point near Thuban in a matter of days to remain in its present orientation ever since, and still, another mechanism may operate to make the axis appear to be traveling in rotation, currently to point at Polaris as observations of stellar motion suggest. Let's take a brief look at the evidence for gradual change, and then see how gyroscopic precession really works. Then in the section we can analyse other possible mechanisms.
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