Recently, the team of Pan Jianwei of the University of Science and Technology of China cooperated with Shanghai Institute of Technology and Physics, Xinjiang Observatory and other units to realize the first international high-precision time and frequency transmission experiment of free space of 100 kilometers level internationally. The experimental results are expected to have an important impact on basic physics research such as dark matter detection, basic constant test of physics, and relativity test. The results were published in the international academic journal Nature on the evening of October 5, Beijing time.
In the field of science, the measurement accuracy of time has reached the minus 19th power of 10, that is, tens of billions of years, with an error of less than 1 second. As one of the seven basic physical quantities of , , time is currently the most accurate physical quantities measured. It is equally important to have the most accurate timing and time transfer technology that matches its accuracy.
The environment of the free space near the ground is complex. Various disturbances and turbulence in the atmosphere, link loss, environmental changes and other factors have brought great difficulties to long-distance time-frequency transmission in free space. Previously, optical frequency transmission technology in free space could only achieve transmission distances of the order of 10 kilometers.
The team of the University of Science and Technology of China challenged this problem. In terms of light sources, a high-power and high-stability optical comb has been developed, and a high-stability and high-efficiency optical transceiver telescope system has been developed in terms of optical signal transceiver channels. In addition, a high-precision time measurement is adopted using interferometry measurement method with linear optical sampling. After a series of technical research, the time-frequency transmission of the minus 19th power of stability was finally achieved between the Xinjiang Nanshan Observatory and Gaoyazi Observatory, which are 113 kilometers apart.
Professor Zhang Qiang, University of Science and Technology of China: Use our very precise time signal to hit another telescope 100 kilometers away through this telescope. Then, my signal is received by the same telescope on the other side. After receiving it, they perform some more precise time detection. At the same time, the same precise light source signal will also be called, and the same precise detection will be done here, and the signals on both sides will be aligned and corrected. The accurate measurement and transmission of
time will enable people to conduct experimental tests on the principles of relativity, various theories of gravity, dark matter models, and other basic physics.
At the same time, this is also closely related to our lives. For example, the navigation accuracy of satellite is closely related to the timing accuracy. If you want to position more accurately, such as being less than millimeters, you need better timing accuracy. In areas involving social and people's livelihood, precise time will also play an important role.
Now the definition of "second" was determined in 1967. After decades of development, the International Organization for Metrics plans to discuss changes in the definition of "second" in 2026.
Professor Zhang Qiang, University of Science and Technology of China: Then it also proves that in the future, this kind of intercontinental (time) comparison can be done based on satellites. So if intercontinental comparison can be achieved, then we can realize the new generation of "seconds" definition.
908 New Media Popular Science Link: Why do you need such accurate timing?
In the Olympic stadium, the 100-meter battle is the most exciting, and the winner is often between a slightest margin. We intuitively feel the importance of accurate timing. The Tokyo Olympics uses a high-precision timer that can capture 10,000 digital images per second. In the field of science, the accuracy of time measurement is much higher, and the accuracy has entered the order of 10-19. Time, as one of the seven basic physical quantities, is currently the most accurate physical quantities measured. Why are people constantly exploring theoretically and technically to improve the accuracy of time measurement?
Accurate measurement is expected to bring us a new understanding of the world. More than a hundred years ago, the famous physicist Lord Kelvin believed that "the future of physics will only be searched after the sixth decimal place", which shows the significance of precision metrology. 2005 Nobel Prize in Physics winner John Hall even said that "metology is the mother of science."The precise measurement and transmission of time will enable people to conduct experimental tests on the principles of relativity, various theories of gravity, dark matter models, and other basic physics. The slight difference in measurement results may bring us a change in the concept of time and space. The precise measurement of
time can also make our lives more convenient. For example, the navigation accuracy of satellites is closely related to timing accuracy. Our lives are already inseparable from navigation and positioning. If we want to position more accurately, for example, it is necessary to have better timing accuracy. In areas involving social and people's livelihood, precise time will also play an important role. The development of
optical clock and optical frequency transmission technology is expected to allow people to redefine "seconds". The definition of seconds was now determined in 1967 and was defined by cesium atomic clock . After decades of development, the accuracy of time measurement and comparison has been more than two orders of magnitude better than the original definition, so the International Organization for Metrics plans to discuss changes in the definition of "seconds" in 2026. Seconds are one of the seven basic physical quantities, and currently other basic physical quantities (except the amount of substance ) are directly or indirectly related to the time and frequency standard. Therefore, the new definition of "second" will bring changes to all aspects of the entire scientific field and even society.
Comprehensive: CCTV News Mozi Salon Wang Jia
Source: Anhui Traffic Broadcast
