Next, I'll talk about the functions of Cheomseongdae. Because almost no firm record exists, there are many arguments and theories. The strongest of them is that Cheomseongdae was built as an astronomical observatory. And then, because its shape resembles Sumisan Mountain in Buddhist scriptures, some people argue that it's a representation of Sumisan. Another theory is that it was a gnomon that functioned as a sundial. And then, some people claim that it was used to indicate seasons. There's also the Zhoubi Suanjing theory claiming that it is related to astronomical mathematics. Then, there are arguments that it was a personal shrine or a Sumerian goddess. And other various functions are reported. And yet, the astronomical observatory aspect of theory has the most supporters. An authoritative article by the Korea Astronomy and Space Science Institute, agrees that observations at the three kingdom period, as you can notice here, increased a lot after Silla constructed Cheomseongdae. On this table as well, it shows that there actually was a significant change in the number of observations. Another thing is diurnal motion. They could observe diurnal motion from Cheomseongdae. From here, at that time, meteors or shooting stars were observed five times around Cheomseongdae. These would not have been possible if not observed at Cheomseongdae. These observations of shooting stars constitute a good example that support its function as an astronomical observatory. So, as you can see here, these five locations, these were all observed from near Cheomseongdae. This is strong evidence that Cheomseongdae was indeed an astronomical observatory. Another argument is the Sumisan Mountain theory. As you see on the slide, doesn't the shape of the mountain resemble Cheomseongdae? There is Doricheon at the very top, and the sun and the moon are all below Doricheon. This is a cosmological concept of Buddhism, their philosophical view of the universe. For this reason, some people support the Sumisan theory. Next, led by some mathematicians there is an argument that Cheomseongdae was based on Zhoubi Suanjing. Zhoubi Suanjing is an astronomical/mathematical text written around 11th century BC during the period of the Zhou Dynasty. For example, please look at the picture on my right. For example, the ratio of the height and the diagonal length of the base layer is 5 to 4. And, the ratio of diameters of the first layer and the 27th layer is 5 to 3. The numbers 3, 4, and 5 are commonly called the Pythagorean numbers. Zhoubi Suanjing greatly precedes Pythagoras. Pythagoras was in the 6th century BC, but in the 11th century BC, the concept of the Pythagorean Theorem was already in Zhoubi Suanjing according to the Zhoubi Suanjing argument. Another argument is the gnomon theory. The gnomon theory claims that Cheomseongdae functioned as a sundial. And, some people claim that Cheomseongdae was a personal shrine. And then, some people argue that it's a Sumerian goddess. None of these arguments fits perfectly. For example, with the astronomical observatory theory, there is some evidence that strongly supports this theory. But it would have been so inconvenient and troublesome to climb up and down ladders located in and out of Cheomseongdae every time. And for this reason, some argue against the astronomical observatory theory. The Sumisan claim is considered too theoretical, and therefore, some people are pretty skeptical. With the gnomon claim, a sharp structure would have worked better as a sundial. But because Cheomseongdae is round, it's hard to tell which part was used to indicate the time. So all of these theories and arguments are still highly debated and disputed.
