The mounds and earthworks of Chillicothe, Ohio mark the stars of Ursa Minor and calculate the position of the North Celestial Pole in ca. 300 B.C. as shown in the graphic below (that date coincides with e.g. the Grave Creek Mound):
To understand the above graphic image, one must appreciate that there is an astronomically crucial difference between the North Celestial Pole and the North Ecliptic Pole. A good explanation and graphic image are found at the University of Michigan Astronomy Department in an article on "Precession". A very useful presentation with multiple images is found at the Wikipedia at Axial precession.
The North Ecliptic Pole is a fixed, unmoving point which serves as "the north pole" for the plane of the ecliptic, the plane of the path of the Earth around the Sun. The North Ecliptic Pole is the same today as in yesteryear.
The North Celestial Pole, on the other hand, which is currently at the star Polaris at the bottom of Ursa Minor, is a moving point which serves as "the north pole" for the plane of the "celestial equator". Wikipedia: "The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the terrestrial equator out into space. As a result of the Earth's axial tilt, the celestial equator is inclined by 23.4° with respect to the ecliptic plane."
In ca. 300 B.C., the North Celestial Pole was at the faint stars that are "mounded" viz. marked by earthworks at Chillicothe.
Precession causes the North Celestial Pole to rotate in a circle around the North Ecliptic Pole -- maintaining a distance radius (angular separation) of ca. 24°, the angle of the axial tilt of the Earth viz. obliquity (currently ca. 23.4°)-- over a period of ca. 25,800 years. The ancients here appear to have known this.
25,800 years is a number that is easier to understand if we think of a great circle, so that 30 degrees of a 360 degree circle are "precessed" every 2150 years, or about 1 degree every 72 years. Ancient cultures thus could obtain knowledge of precession only if preceding generations had already observed stars over the course of many years and eras.
Precession causes the celestial equator to change its position in the course of that ca. 25,800-year cycle, which moves the position of the Solstices and Equinoxes with respect to the stars, and also changes the position of the North Celestial Pole in terms of the stars to which it is pointing. At Chillicothe, the makers of the mounds and earthworks were pinpointing this pole in their era.
These changes were of course a vexation for ancient skygazers, who did not know the causes, leading to the tale that ancient seafaring Norse (Vikings) -- who had to know their stars -- feared nothing except "the sky falling", which in a way it was and is, as the Celestial Equator shifts its positions.
In the following illustration, we show the change in the position of the North Celestial Pole over a full cycle of 25,800 years, and also mark 3000 and 300 B.C., since especially 300 B.C. is important for this posting. There was no other reason for the creators of the Chillicothe Earthworks and Mounds to feature otherwise faint and meaningless stars next to Ursa Minor, except that they marked the North Celestial Pole in their era:
We illustrate here also the change in the height of the celestial equator in the graphic image below on the example of Orion, from which one can understand the ancient fear of the Norse viz. Viking seafarers of the sky falling:
The lowest point of the celestial equator in the stars with respect to the ecliptic is always found at the Summer Solstice point. Currently, for example, that point is at the three "Belt Stars" of Orion (Orion's Belt). We have made an illustration to show how the celestial equator has changed over the eras, using Orion as the example:
The people who made the mounds and earthworks at Chillicothe were not just primitive "stargazers" but worthy of the title "real" astronomers, because they understood many of these technical if elementary things of astronomy at a time when much such knowledge was arguably unknown and definitely not widespread yet in Western Civilization.
THIS POSTING IS Posting Number 6 of
The Great Mound, Petroglyph and Painted Rock Art Journey of Native America
At the Center of the Ancient Land Navigation System in Native America: The North Celestial Pole and Ursa Minor as Marked by the Mounds and Earthworks in Chillicothe, Ohio
To understand the above graphic image, one must appreciate that there is an astronomically crucial difference between the North Celestial Pole and the North Ecliptic Pole. A good explanation and graphic image are found at the University of Michigan Astronomy Department in an article on "Precession". A very useful presentation with multiple images is found at the Wikipedia at Axial precession.
The North Ecliptic Pole is a fixed, unmoving point which serves as "the north pole" for the plane of the ecliptic, the plane of the path of the Earth around the Sun. The North Ecliptic Pole is the same today as in yesteryear.
The North Celestial Pole, on the other hand, which is currently at the star Polaris at the bottom of Ursa Minor, is a moving point which serves as "the north pole" for the plane of the "celestial equator". Wikipedia: "The celestial equator is a great circle on the imaginary celestial sphere, in the same plane as the Earth's equator. In other words, it is a projection of the terrestrial equator out into space. As a result of the Earth's axial tilt, the celestial equator is inclined by 23.4° with respect to the ecliptic plane."
In ca. 300 B.C., the North Celestial Pole was at the faint stars that are "mounded" viz. marked by earthworks at Chillicothe.
Precession causes the North Celestial Pole to rotate in a circle around the North Ecliptic Pole -- maintaining a distance radius (angular separation) of ca. 24°, the angle of the axial tilt of the Earth viz. obliquity (currently ca. 23.4°)-- over a period of ca. 25,800 years. The ancients here appear to have known this.
25,800 years is a number that is easier to understand if we think of a great circle, so that 30 degrees of a 360 degree circle are "precessed" every 2150 years, or about 1 degree every 72 years. Ancient cultures thus could obtain knowledge of precession only if preceding generations had already observed stars over the course of many years and eras.
Precession causes the celestial equator to change its position in the course of that ca. 25,800-year cycle, which moves the position of the Solstices and Equinoxes with respect to the stars, and also changes the position of the North Celestial Pole in terms of the stars to which it is pointing. At Chillicothe, the makers of the mounds and earthworks were pinpointing this pole in their era.
These changes were of course a vexation for ancient skygazers, who did not know the causes, leading to the tale that ancient seafaring Norse (Vikings) -- who had to know their stars -- feared nothing except "the sky falling", which in a way it was and is, as the Celestial Equator shifts its positions.
In the following illustration, we show the change in the position of the North Celestial Pole over a full cycle of 25,800 years, and also mark 3000 and 300 B.C., since especially 300 B.C. is important for this posting. There was no other reason for the creators of the Chillicothe Earthworks and Mounds to feature otherwise faint and meaningless stars next to Ursa Minor, except that they marked the North Celestial Pole in their era:
We illustrate here also the change in the height of the celestial equator in the graphic image below on the example of Orion, from which one can understand the ancient fear of the Norse viz. Viking seafarers of the sky falling:
The lowest point of the celestial equator in the stars with respect to the ecliptic is always found at the Summer Solstice point. Currently, for example, that point is at the three "Belt Stars" of Orion (Orion's Belt). We have made an illustration to show how the celestial equator has changed over the eras, using Orion as the example:
The people who made the mounds and earthworks at Chillicothe were not just primitive "stargazers" but worthy of the title "real" astronomers, because they understood many of these technical if elementary things of astronomy at a time when much such knowledge was arguably unknown and definitely not widespread yet in Western Civilization.
THIS POSTING IS Posting Number 6 of
The Great Mound, Petroglyph and Painted Rock Art Journey of Native America
At the Center of the Ancient Land Navigation System in Native America: The North Celestial Pole and Ursa Minor as Marked by the Mounds and Earthworks in Chillicothe, Ohio
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