On the other side, Ling Tan and the members of the scientific expedition team have been looking for the location of the tower along the Yellow River, but the ancient road of the Yellow River recorded in the ancient books is not the same as the current Yellow River. Because it was recorded in the golden book that he could no longer enter the tower after July, Ling Tan anxiously searched for the cave recorded in the golden book while waiting for the information of the ancient map analyzed by Li Han and the others.

During this period, Ling Tan and Li Yan found many local residents to inquire, but unfortunately they gained little. On the way back to the camp, Li Yan asked Ling Tan, "Brother Tan, does the Taixi Palace really exist?" There has always been a legend in my ancestors, 'When the Taixi Palace enters, the soul is scattered, and if it is not a special weapon, do not enter', I have never known what this special weapon is. ”

Ling Tan, who was pondering, heard her words, thought for a moment and said, "The special weapon must be shocking to the world, with your ancestor saying so, it proves that he has seen the real Taixi Palace." We can only wait for the cash to wait until Xiaoyun sends back the specific information of the star map, so that the location of the Taixi Palace will be easily solved. ”

Li Yan was a little frustrated when she heard this, and she didn't know when she would be able to find the location of the tower, and Li Moyun didn't know what was going on.

In the few days after returning to the camp, Li Yan rarely saw Ling Tan again, and he did not see anyone several times, and it is said that he found experts in various fields to study the secrets of the Golden Book Astrolabe.

Ling Tan and the experts of the Chinese Astronomical Observatory also looked for the principle of the chronology of the number system from the Chinese historical records, from the "Emperor's Ancient Calculation" to Li Chunfeng's commentary on the "Nine Chapters of Arithmetic", that is, "if the underworld is the same, the product is not easy to 'follow' The mathematical determination of the shadow length of the twenty-four air days in order to calculate the daily shadow length, as well as the correct calculation of the volume of the sphere, successfully transformed from the problem of gravity difference measurement at different heights into the general daily height formula on the plane, and carried out mutual exchanges with ancient Egyptian astronomical experts, the ancient Sumerians created an advanced hexadecimal counting system, sixty as the base number, because they found that the earth's period of operation for the sun is about 360 days, and the frequency and duration of the moon full moon can be divisible by sixty for the convenience of calculation, so sixty will be used as the base number of the counting system。 Later, they put forward the concept of 24 hours a day, 60 minutes per hour and 60 seconds, and for the observation of celestial phenomena by the 'Si Tianjian' of the Ancient Tai History Bureau, the five planets of the sun, moon, metal, wood, water, fire, and earth, the stars such as the 28 constellations, comets, and meteors, as well as the 'Rising Star' and 'Demon Star' that we do not know what they refer to, in addition to the weather phenomena such as clouds, air, rainbows, winds, thunder, fog, frost, and snow, they found the 'glowing confusion and guarding the heart' event that occurred in the 36th year of Qin Shi Huang, that is, the occurrence of lunar eclipses.

Ling Tan compared the Zhushu chronology with the number chronology and found that the conclusions reached by the two were consistent. And from the relevant records in the historical books, they are basically on the facts, there is no fixed law, as long as the astronomical stars are present, and the basis can be found. For example, the appearance of comets is often considered a bad omen, and the 'gathering of five stars' (the presence of five planets in a small area of the sky at the same time) is often seen as a sign of a change of dynasty. Just when Ling Tan and other researchers were at a loss, they saw the illustrated exhibition of Yin Shang oracle bone inscriptions held by the National Museum, and Ling Tan heard the narrator tell about the strange scene of the rainbow absorbing water recorded in the oracle bone inscription, and the text said, "The Gengshu stratus clouds came from the east, casting a sun, which was dark, and when the sun was westward, a rainbow appeared in the north, drinking water in the Yellow River." At this time, the International Center for Astronomical Aerospace Exploration and Exchange sent pictures and texts to the forest farm scientific expedition team to explain the analysis results of the astrolabe on the Golden Book. The sun, moon and stars represent the units of year, season, and hour, respectively, and the meaning of them is roughly to say that there will be some special circumstances on a given day.

Although the meaning of the astrolabe is roughly understood, a cloud under the astrolabe still cannot explain what it is. Ling Tan couldn't crack it even after searching for all kinds of astronomical data, and after a while, he heard an expert discussing the scene of the mirage, and suddenly had an inspiration, and took the golden book to investigate again along the first bay.

And Ling Tan has been here for an unknown number of times, looking at the rushing water of the Yellow River, I can't see anything special. It happened that on this day, a burst of rain suddenly fell in the clear sky, Ling Tan hurriedly found a place to hide, and after a while, the rain stopped, and a rainbow bridge appeared in the sky, the color was very beautiful, at this time Ling Tan took out the golden book, and saw the sun and seven stars carved thin lines on the astrolabe, which were exactly the same as the scene in front of him, but the direction of the rainbow, not facing the Yellow River. At this time, Ling Tan remembered the record of 'rainbow water absorption' that the oracle bone explainer said. It's just a pity that there is no date, and Ling Tan vaguely feels that by solving the mystery of the golden number, he will be able to know exactly when he can enter the tower of the first bay and take out the treasure bottle.

The last round sun was surrounded by clouds, and the six crescents next to it, seven small suns, seven straight lines, and numerous orthorhombic star carvings were not cracked, and the rest were clear. Ling Tan came to the first bay again, and saw a sheepskin raft leaning against the shore by the Yellow River, and a fisherman was looking for something on it, so he hurriedly went over to help him find the lost glasses and talked to him. At first, the fisherman who ferried Ling Tan thought that Ling Tan was a tourist, so he said to him, "You are nothing special in this season, and every June, the rainbow water absorption landscape here is the most beautiful." Ling Tan perked up and asked the fisherman, "Is that a sight only seen in June every year?" ”

Ling Tan thanked the fisherman excitedly when he heard this, and immediately rushed back to the camp, reconvened all the members of the scientific expedition team, opened the golden book to recalculate the date, and finally determined the argument that a round sun was covered by clouds with seven straight lines, six crescents, and seven stars. In a year with 60 stars for 360 days, the meaning of the six moons and seven stars is exactly the summer solstice solar term on the calendar, and the strange scene of rainbow absorbing water appears in the sky above the first bay of the Yellow River, which is called the sun-Chinese phenomenon in astronomy. However, there are colorful auspicious clouds that appear in the horizon arc around the earth, and the ice crystals in the earth are refracted, showing the astronomical wonders of red, orange, yellow, green, blue, and purple.

The expedition team finally solved the astronomical problem that had plagued them for many days, congratulated each other with great joy, and waited until June 20 to enter the tower.