At the foot of Wuzhou Mountain, the Yungang Grottoes Scenic Area in Datong City, Shanxi Province, attracts a constant stream of tourists. After more than 1500 years of wind and rain since its establishment, the Yungang Grottoes still have unparalleled charm. With the passage of time, how can this magnificent world cultural heritage remain forever youthful? On May 29th, a reporter from Science and Technology Daily came to Datong, Shanxi to explore the aging "secrets" of the grottoes. Equipping the Grottoes with "Doctors" The reporter walked into the sixth cave of Yungang Grottoes and happened to encounter the staff performing daily maintenance. "Every item needs to be memorized and written clearly. The climate, temperature, humidity, types and specifications of diseases on that day..." Sun Bo, a staff member of the Cultural Heritage Protection and Monitoring Center of Yungang Research Institute, told reporters that he is carefully guiding students on how to record relevant data for cave inspections. "Data is like a person's physical examination report, it's easy to tell where the problem lies at a glance." Sun Bo said that as an elderly person over 1500 years old, the Yungang Grottoes have suffered from wind and rain erosion and human damage, while also facing varying degrees of weathering. The overall stability of some caves also urgently needs to be strengthened. Since the 1960s, Yungang Grottoes have successively implemented emergency reinforcement, dangerous rock reinforcement, and waterproofing and drainage projects, effectively solving the stability problems of the grottoes. In recent years, while ensuring the safety of grottoes, Yungang Research Institute has carried out a series of preventive protection and refined maintenance projects. Zhang Shaoyou, a staff member of the Cultural Heritage Protection and Monitoring Center of Yungang Research Institute, opened the ultrasonic testing instrument, picked up the probe with both hands and aimed it at the surface of the cave rock mass. As the position moved, slowly fluctuating lines appeared on the screen of the testing instrument next to him... Zhang Shaoyou introduced to the reporter that this is a new means of cultural relic safety testing used in Yungang Grottoes in recent years. This ultrasonic testing instrument is a "B-ultrasound machine" tailored for cave statues. Ultrasound has a fast wave velocity and high numerical value in densely structured areas, while the opposite is true in areas with looseness. For those 'diseases' that appear inside the rock mass that are difficult to observe with the naked eye, a' B-ultrasound 'can clearly distinguish them Zhang Shaoyou introduced that the stone carvings in Yungang Grottoes mainly face 13 "diseases" such as hollowing, warping, and cracking. Among them, there are more than 800 "diseases" in Cave 6 alone. Many of these "diseases" are superimposed, and scientific diagnosis can only be made with the help of professional testing instruments. Recently, the real-time monitoring and early warning service platform for Yungang Grottoes cultural relics has been launched and put into operation. According to Hang Kan, the director of Yungang Research Institute, the platform is mainly responsible for special monitoring of the grotto cultural relics and preservation environment. It can monitor the meteorological environment inside the grotto, air quality in the grotto area, and soil environment. It can also respond promptly to issues such as weathering, condensation, and infiltration of cultural relics, just like a 24-hour online "private doctor". At present, this "private doctor" has covered 20 monitoring areas, covering 8 types of monitoring, and has set up 105 monitoring points to comprehensively safeguard the "health" of the grottoes. During the visit to continue the "life" of the grotto, the reporter saw a damaged standing Buddha statue on the west wall of the 20th cave of the Yungang Grottoes. This statue has long been damaged above the feet, which is regrettable. Hang Kan told reporters that thanks to 3D printing technology and virtual restoration technology, this Buddha has been "reborn". From rescue protection to preventive protection, and then to systematic research protection, the protection work of Yungang Grottoes is accelerating and upgrading. "While protecting the natural cultural relics of grottoes, digitization is a necessary path to achieve permanent preservation and sustainable utilization of cultural relics' information." Hang Kan said. In 2003, Yungang Research Institute began to venture into the field of digitalization of cultural relics. In 2005, the exterior facade of Yungang Grottoes was successfully collected, and the first centimeter level accurate orthophoto image of the exterior facade of Yungang Grottoes was completed, and the first exterior facade line map was drawn. Nowadays, using technologies such as 3D laser scanning and close range photogrammetry, high-precision digital protection projects have been carried out for the Yungang Grottoes. Two thirds of the total number of grottoes have been completed, and data accuracy can reach 8K and 0.03 millimeters. Among them, the digital reconstruction and 3D information system construction project of the 13th cave has overcome the technical difficulties of high-precision 3D modeling of the overall cave of large single high relief grotto temples in China. In addition, the Yungang Grottoes have also completed four local industry standards for digitalization of cultural relics, one of which has become a local industry standard for cultural relics in the six central provinces. Hang Kan introduced that nowadays, more and more tourists come to Yungang and fall in love with it. From the past few hours of hasty sightseeing, some people can even stay for a whole day now. While he felt relieved, he also felt that the responsibility to protect his work was significant. Over 1500 years ago, craftsmen gave life to these walls. Now, our mission is not only to continue the 'life' of Yungang Grottoes, but also to preserve the precious history behind them Hang Kan said. (Lai Xin She)