Perhaps one of the most thought-provoking mysteries in the universe lies in the subtle differences in the passage of time. The time on the top of the mountain passes faster than the time in the deep valley. This phenomenon has minimal direct impact on daily life. However, with the increasing number of human lunar exploration activities, setting time standards for the moon has once again become a focus of attention. So, is the time on the moon the same as on Earth? The latest calculation by NASA shows that the surface time of the moon is 57.5 microseconds faster than the surface time of the earth per day. In human lunar exploration, this difference may be crucial. What is' Coordinated Lunar Time '? In April of this year, the White House issued a memorandum directing NASA to collaborate with other government departments to develop' Coordinated Lunar Time 'by the end of 2026. The memo shows that the system must possess four qualities: logical traceability with Coordinated Universal Time; Sufficient specificity and accuracy to time extremely short moments; Being able to be self-sufficient in the absence of contact with Earth; Scalability, so that other celestial bodies or space environments can also refer to this time standard. Setting a time for the moon helps with communication, landing, and navigation of spacecraft. The White House memo states that establishing a suitable standard, one that can operate in challenging lunar environments with both accuracy and resilience, will benefit all spacefaring nations. Xie Yi, a researcher at the Zijinshan Observatory of the Chinese Academy of Sciences, said in an interview with the Science and Technology Daily, "Imagine that there is such a space port, which needs to accurately inform passengers of the departure and arrival time of the spacecraft. At the same time, the time on the moon is also related to the time on the earth, because some day in the future, the people on the earth will probably have to interact with the people on the moon." How to calculate the time on the earth? Human's pursuit of time accuracy has never stopped. At the beginning of the 20th century, Einstein proposed the theories of special relativity and general relativity, making the precise measurement of the "second" in time more complex in the scientific community. General relativity holds that the stronger the gravitational force, the slower the passage of time. Due to the gravitational force on the moon being only one sixth of that on Earth, time on the moon is faster than on Earth, which is the result of time dilation. According to CNN, scientists have deployed hundreds of atomic clocks worldwide to solve the time measurement challenges posed by relativity. These ultra precision instruments that utilize the principle of atomic vibration can capture every subtle change in the passage of time. By synthesizing readings from atomic clocks around the world, scientists have developed "Coordinated Universal Time" and timely introduced "leap seconds" to correct changes in the Earth's rotational speed. However, the calculation of time goes far beyond that. More complexly, according to Einstein's theory of special relativity, the faster a person or spacecraft moves, the slower time passes. Therefore, some spacecraft are equipped with their own clocks, called crystal oscillators (referred to as "crystal oscillators"). However, despite the presence of crystal oscillators, time on spacecraft often requires ground calibration. Why is the moon's time faster than Earth's, and what impact do general relativity and special relativity have on calculating lunar time? Xie Yi told reporters that if two clocks were placed on the Earth and the Moon respectively, the gravitational strength and motion of the two would be completely different (clocks on Earth would experience stronger gravitational effects), and there would also be significant differences in their motion speeds. This difference will cause even if the two clock readings are consistent at the initial moment, they will gradually deviate over time. NASA calculated the relative motion between the Moon, Earth, and Sun and determined the daily difference of 57.5 microseconds. This means that in 50 years, astronauts on the moon will be about one second older than people on Earth. Xie Yi stated that the value of 57.5 microseconds was calculated based on the principles of general relativity, taking into account the "drift" between ground and lunar time caused by differences in gravity and motion in general and special relativity. During the interview, Xie Yi revealed to reporters that her team is also conducting relevant research. They found that in addition to daily variations, there are also periodic changes in the Earth Moon time. This change will have a very important impact on China's satellite navigation system built near the moon. Should we use an atomic clock or a crystal oscillator to time the moon? Cheryl Granlin from NASA's Goddard Space Flight Center said that atomic clocks are excellent in long-term stability, while crystal oscillators have advantages in short-term stability, and scientists will continue to discuss and study this. According to reports, the definition of lunar time will be determined by multiple institutions including the International Bureau of Weights and Measures and the International Astronomical Union, with some discussions scheduled for August (Xinhua)