The world's nine oldest surviving "antique" astronomical observatories

Since the birth of man on earth, man's reverence for the heavens and his search for the mysteries of heaven and earth has rarely ceased. Astronomers and artisans have also built various observatories. Even today, one cannot help but admire the subtlety of the ancients in their grasp of the planets, constellations, and seasons. The significance of astronomical observation at that time has always been a combination of politics, religion, and science, and is far from the scientific significance of today. Let's go back to that distant time and explore nine of the world's oldest astronomical observatory sites.

Chengguan Xingtai is the oldest surviving astronomical observatory in China. It was founded in 1276 by Guo Shoujing, a famous astronomer of the Yuan Dynasty. This astronomical observatory is 12.6 meters high. There is a platform on top. There are two houses used to store astronomical instruments. There are brick troughs on the floor to help astronomers observe the length of the sun's shadow. 180 years later, Guo Shoujing compiled the "Time Calendar". The difference between the calculated length of a year and the actual time was only 26 seconds, more than 300 years before the European Gregorian calendar.

This observatory is located at the site of Chichen Itza, a Mayan city built in the 7th century. It is a cylindrical building known as the "Kelocor" because of its spiral stone steps. Some believe it was a Mayan observatory because of the stone cups in the building. The Maya could fill the cups with water and observe the stars through the reflection of the water. However, johncarson, an astroarchaeologist at the University of Maryland, says this view is unfounded. The building is believed to be an observatory because it resembles a modern observatory, which was a temple dedicated to the god of wind.

On the site of Chichen Itza, there is also the famous Pyramid of Chichen Itza. The Chichen Itza pyramid tower is 30 meters high and has 9 floors. At the top is a temple. There are 91 stone steps on each side of the tower leading to the top. The total number of steps plus the top level is 365, representing the number of days in a year. Each year, on the spring and autumn equinoxes, the plumed snake head carved in one corner of the pyramid casts the shadow of the snake on the stone steps to the north. The spring and autumn equinoxes are very important dates. To this day, descendants of the Mayans still perform rituals on these two days.

Machu Picchu, built in 1460, is an important symbol of the Inca civilization. Just a century later, the city was abandoned due to the invasion of Spanish colonists. One of the landmarks of this ancient city is the Toerien or Stone Tower, a stone with grooves and curved stone walls around it. At sunrise in summer, the sun shines through the window on the stone wall, illuminating the grooves in the stone. Also, the shape of the Pleiades star cluster can be observed through this window.

Gyeongju Observatory was built in the 7th century and is considered one of the oldest astronomical observatories in Asia. Gyeongju Zhanxingdae is a bottle-shaped structure made of 365 blocks of granite with windows and is about 9.4 meters high. Although its exact purpose is unclear, archaeologists believe that the building's 365 rocks may mean 365 days a year.

A site in Chacillo, Peru, maybe the world's oldest solar observatory, dating back to 3,000 B.C., according to a study. Along this 300-meter-long ridge are 13 rectangular stone towers with the same north-south distance, shaped like bone plates on the back of a stegosaurus. At the winter solstice, the sun rises directly from the southernmost tower. It takes about 10 days to move from one notch of the sun tower to another. This suggests that people at the time probably used this interval to divide the year into fixed periods, just as people today divide 365 days into 12 months.

This tomb was built around 3200 B.C. The heart-shaped mound covers an area of 4,000 square meters and is surrounded by 97 stones, many of which are carved with intricate designs. A 19-meter-long passage leads to the tomb. Every year at sunrise on the winter solstice, a ray of sunlight shines through the entrance into the chamber. This strange phenomenon lasted for about 17 minutes. Archaeologists have found several mummies in the tomb. Perhaps the ancients believed that the dead could be reborn when the sun shone at the winter solstice.

This wheel-shaped stone cairn is located on top of a hill in Wyoming, USA. Many shoebox-sized stones are arranged in the shape of a wheel with a diameter of about 25m. The direction from the cairn at the center of the circle to one of the outer rock piles is exactly the direction of the sunrise at the summer solstice. The other three directions pointed out by Shibi are Sirius, Arudibar, and Sensual Four. These three bright stars have strange legends in Cheyenne Indian mythology. There are about 70 of these rock piles in North America, some of which are 1,000-2,000 years old.

Stonehenge was built around 3100 BCE. The purpose of Stonehenge remains controversial. Some believe it was a typical ancient funerary and ritual site, while others believe it was a place for astronomical observation. A circle of tall stones forms a "horseshoe-shaped" formation, with its openings pointing directly to a giant "heel stone" outside the formation. At the dawn of the summer solstice, the sun rises slowly from the top of the heel stone, starting from the center of Stonehenge.