What is the strange stone geometry built for?

There is a very strange geometric figure made of stone on Bighorn Mountain in Wyoming, USA. It is like a big stone ring, with a diameter of 25 meters and a large cone-shaped stone pile in the center. Draw 28 radial lines from the center of the ring around, and the distance between lines is different, of which 6 lines are marked with small stones at the end.

As early as when white people immigrated to the United States, some people noticed this mysterious stone ring. Being in the hunting area of Indians at that time, people mistakenly thought it was the product of religious superstition. The stone ring has also attracted the attention of astronomers because its ray number "28" is very close to the number of days in the lunar month. Scholars further infer that the symmetrical arrangement of light and stone piles on both sides may be related to the determination of sunrise and sunset. Just like Stonehenge found in the north of Salisbury, England, the arrangement of stones constitutes the direction line of the summer solstice sunrise. So they came to the conclusion that this mysterious stone ring is the most primitive instrument for observing astronomical phenomena.

Later, after long-term investigation, measurement and calculation, scientists and scholars found that the light from the center of the stone ring to the farthest stone pile was just aimed at the sunrise position of the summer solstice, and the other three lights pointed to the right ascension point of the three brightest stars, namely the Pleiades, Betelgeuse and Sirius. According to historical research, the summer solstice can be determined according to the positions of five stars in the Pleiades when the stone ring was formed. But this opportunity is only one day, when the Pleiades will coincide with the sun. After that, it overlapped with Betelgeuse for 28 days and Sirius for 28 days. Is it a coincidence that this number of days coincides with the number of rays in the stone ring, or is it that the ancient Indians knew the starry sky far beyond the imagination of modern people?

The stone ring of Dajiao Mountain is not unique. A large number of stone rings have also been found on the eastern slopes of Loki Mountains and nearby hills. In addition, a similar stone ring was found in the central plateau of Alberta, Canada, but its size was larger than that of Dajiaoshan stone ring, and the stone pile in the center was also higher.

According to the identification of archaeologists, these stone rings may be relics of ancient Egypt when it built the pyramids four or five thousand years ago. Experts found that these stone rings have one thing in common, that is, they are located at the highest terrain and have a wide horizontal view. Some smaller, simpler stone rings with less rays may belong to another system. Their rays point to stone rings and piles as far away as 15 ~ 80 kilometers.

The mystery of the stone ring has not been completely solved. Are these stone rings just a few priests celebrating the arrival of the summer solstice? Where did the indigenous Indians get such a high level of astronomical knowledge under the backward scientific and cultural conditions at that time?