One would think NASA would have a good handle on astronomical movements. After all, they did get a man on the moon, satellites to orbit and robots to rove on Mars. So, if one wanted to know about precession of the equinoxes, and NASA had an article on it, one might assume they could rely on NASA. But that doesn't seem to be the case.
Precession according to NASA.
According to NASA: Around the year 130 BC, Hipparchus compared ancient observations to his own and concluded that in the preceding 169 years those intersections had moved by 2 degrees. How could Hipparchus know the position of the Sun among the stars so exactly, when stars are not visible in the daytime? By using not the Sun but the shadow cast by the Earth on the moon, during an eclipse of the Moon! During an eclipse, Sun, Earth and Moon form a straight line, and therefore the center of the Earth's shadow is at the point on the celestial sphere, which is exactly opposite that of the Sun.
Hipparchus concluded that the intersection marking the equinox slowly crept forward along the ecliptic, and called that motion "the precession of the equinoxes. " The rate is about one full circle in 26 000 years. In ancient times the intersection marking the spring equinox was in the constellation of Aries, the ram, and for that reason the intersection (wherever it might be) is still sometimes called "the first point in Aries.
Around the year 1 it moved into the constellation of Pisces (pronounced "pie-sees" in the US) and currently it is again in transition, to the constellation of Aquarius, the water carrier. If you ever heard the song "The dawning of the age of Aquarius" from the musical "Hair," that is what it is all about. To astronomers precession is mainly another factor to be taken into account when aiming a telescope or drawing a star chart; but to believers in astrology, the "dawning of the age of Aquarius" is a great portent and may mark the beginning of a completely new and different era.
What does this motion tell us about the Earth's motion in space? If you ever had a spinning top, you know that its axis tends to stay lined up in the same direction--usually, vertically, though in space any direction qualifies.
Give it a nudge, however, and the axis will start to gyrate wildly around the vertical, its motion tracing a cone (drawing). The spinning Earth moves like that, too, though the time scale is much slower--each spin lasts a year, and each gyration around the cone takes 26 000 years. The axis of the cone is perpendicular to the plane of the ecliptic.
|Spinning a Top
The cause of the precession is the equatorial bulge of the Earth, caused by the centrifugal force of the Earth's rotation (the centrifugal force is discussed in a later section). That rotation changes the Earth from a perfect sphere to a slightly flattened one, thicker across the equator. The attraction of the Moon and Sun on the bulge is then the "nudge" which makes the Earth precess.
Through each 26 000-year cycle, the direction in the sky to which the axis points goes around a big circle, the radius of which covers an angle of about 23.50. The pole star to which the axis points now (within about one degree) used to be distant from the pole, and will be so again in a few thousand years (for your information, the closest approach is in 2017). Indeed, the "pole star" used by ancient Greek sailors was a different one, not nearly as close to the pole.
Because of the precession of the equinoxes, the position among the stars of the celestial pole--the pivot around which the celestial sphere seems to rotate--traces a circle every 26,000 years of so. The celestial pole is now quite close to the pole star Polaris but it will not be so in the future, and wasn't in the past. The ancient Egyptians regarded as pole star the star Thuban or "Alpha Draconis," the brightest star (=alpha) in the constellation Draco, the serpent
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 if the axis pointed more generally to bulk of stars in Draco, then the axial tilt would be more perpendicular to the ecliptic. There is a great deal of compelling evidence that the actual climatic conditions in Pleistocene time, require a more perpendicular tilt. 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 ½ 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 Celestial Hemisphere section we can analyse other possible mechanisms.
First let's look at the Hipparchus story. We are told Hipparchus deciphered a 2 degree move of the equinox during a 169 year period. This is because Hipparchus observed, during an eclipse of the moon by the earths shadow. The eclipse established a near perpendicular line from the sun to a reference point that differed from an observation made by someone else 169 years earlier. Other sources say Hipparchus discovered his observations differed from Babalonian observations of 2000 BC. Therefore, NASA leaps to a conclusion that each of the 12 signs of the zodiac move through the reference point every 2166 years and the entire zodiac rotates in 26,000 years.
It just seems unlikely that measurements could be made that exactly over that time period, but since it has to do with astrology, the age of Aquarius, Greeks, and the musical "Hair" and since this is according to NASA, how could anyone question such empirical evidence?
But wait a minute! The Persians invented astrological time, and describe the series of millennium reigns of the signs of the Zodiac to be 1000 years each; not 2166 years. The time of the Great Year in the Persian scheme was for 12,000 years and not 26,000. This information is preserved in their sacred document of Creation, the Bundahishn. See Chapter 34. Must we now assume the Persians were wrong about their astrological tradition? I don't think so.
Then we are shown a spinning top as a graphical representation of empirical evidence of the NASA idea of the precession of Earth's axis. The top is spinning on a surface (a sidewalk?) and as anyone that has ever seen a spinning top knows, the friction of that surface restrains the bottom axis and the wobble only occurs as the top slows its spin to the point of instability. The southern axis of the Earth is not restrained, however, and the rotation speed seems empirically constant at this time, and has increased if ancient calendars correctly record a change in rate from 360 days to 364 days and now to 365 1/4 days in the year. An increase of over one percent.
The real motion of gyroscopic precession is explained at this site and there is a large video of a precessed gyroscope here.
Here we see a gyroscope spinning and rolling. The poles are not restrained like the spinning top graphic of NASA, but are placed in a gimbal. There is a weight attached to one end, which applies a constant torque that causes the gyroscope to roll at a right angle to its spin.
Imagine the gyro is the Earth spinning in space. (You will have to rotate the figure 90 degrees in your mind to see it properly, in relation to the video.) Imagine the weight is a torque applied to the South Pole of the Earth.
If a torque were applied perpindicular to the South Pole of Earth, it would produce a rolling motion, just like the gyroscope. We can now confidently hypothesize that if a sufficient torque were applied the South Pole of the Earth and perpendicular to the pole, the Earth would roll during the time the torque was applied. When the torque was lifted the Earth would stop rolling and resume a stable declination. This would change the orientation of the axis and it would appear to observers on the surface, that the Pole Star had changed. This is simple logic based on the observed motion of the gyroscope and has nothing to do with the zodiac, or ancient observations during moon eclipses that don't appear to be well understood.
If the Center of Draco was the Polar orientation in the past, then what could have caused the direction of the axis to roll away from it? Since we have already observed where a large mass impacted at high speed, near the South Pole, severing the connection between Antarctica and South America, let's consider it the candidate. This impact would have put a brief perpendicular torque against the southern pole of the axis and caused the Earth to roll. Likely, the extent of the roll could have been the angle now observed between the center of Draco and Polaris and the shift could have taken place in a matter of days.
NASA is right about one thing. The axis of a gyroscope tends to stay lined up in the same direction, until you give it a nudge. And that is exactly what a comet impact at the South Pole did. But not in the way they describe.
It must have been quite a nudge. The Center of Draco is located about 18 to 24 degrees from Polaris on the Celestial Sphere and if the nudge was applied as a torque perpindicular to the South Pole along the Latitude of Drakes Passage, the roll would have been clockwise observed from a viewing position over the Pacific Ocean. This is as observed in the gyroscope movie, but relative to the South Pole the Earth spins clockwise and the roll is perpindicular to the spin at a right angle.
How fast would the roll have taken place? If the spin increased four degrees over four days, due to the tangential impact along the equator, as is suggested by the observations by Native Americans, when the Pacific Ocean retreated over 4 days, then we could likely conclude the impact against the South Polar region caused the Earth to have had a precessional roll for 18 to 24 days, assuming a similar roll rate of one degree per day. We have already calculated that the impact would have more than enough energy to increase the spin by four degrees. To precipitate a roll of as much as 26 degrees would require 6.5 times the energy required to increase the spin (26/4). If the energy required to increase the Earth's spin was 2.8 times 10^23 Joules equivalent to Newton Meters squared, then it would take 1.82 times 10^24 Joules to roll the Earth 26 degrees, impacting near the southern axis and perpindicular to the axis. Remember, a silicon sphere of 20 km diameter at a velocity of 13.5 km/sec would contain 5 times 10^24 Joules. So again, there is more than enough energy contained in the impact, to do the work.
The roll would have had a dramatic effect on the oceans. In addition to the momentum of the oceans backing up to the west for four days as a result of the increase in spin caused by the impact, they also would have backed up to the north as a result of the precessional roll. These changes in motion, would have created an overflow of the oceans due to the difference in momentum between a liquid and its solid container. The oceans backed up and flooded over all the land areas of the globe with water flowing from the east and south. Then as the momentum of the Oceans caught up with the movement of the solid earth, the waters surged over the now dry areas where the water receded, flowing from the west and south in turn and the momentum of the water carried it even over the mountains.