A scientific research team from the National Institute of Standards and Technology (NIST) recently systematically calculated the difference in time passage between Mars and Earth for the first time, providing a key reference for the future extraterrestrial time measurement system. New research published in The Astronomical Journal shows that on average, clocks on Mars run about 477 microseconds, or one millionth of a second, faster per day than Earth's. Although this difference is extremely small, it has important engineering significance in navigation and communication systems that rely on high-precision time synchronization.
Research points out that this time difference is not constant, but fluctuates periodically with changes in Mars' orbit around the sun. Due to the high eccentricity of Mars' orbit, the non-standard circular orbit, and the combined effects of the gravitational pull of the sun, earth, moon and other planets, the average daily time difference within a Martian year can vary within a maximum range of approximately 226 microseconds. The scientists also identified smaller repeating patterns of variation associated with the synodic period, tiny fluctuations of about 40 microseconds per day, which reflect the slow accumulation and waxing and waning of time biases caused by the different geometric arrangements of the solar system's multiple bodies.
In order to give an accurate estimate, the NIST research team systematically compared Mars with the Earth and the Moon, focusing on the analysis of the so-called "relativistic intrinsic time." The so-called intrinsic time refers to the time actually measured by a clock at a certain location under the framework of Einstein's theory of relativity. It depends on the strength of the gravitational field and the speed of celestial bodies at that location. The research results once again verified the basic predictions of general relativity: the stronger the gravity, the slower the clock runs; the weaker the gravity, the faster the clock runs. "Moon and Mars research has never been more relevant now, and we've never been closer to the science-fiction vision of expansion to all parts of the solar system," said NIST physicist Bijunath Patla.
Different from the well-known "a day on Mars is about 40 minutes longer than the Earth and a year is equivalent to 687 Earth days", the core focus of this study is "the speed of the passage of time itself." According to the research team's assumption, if a high-precision atomic clock is deployed on the surface of Mars, it will operate normally locally. However, compared with an atomic clock placed on the Earth, the two will experience slow but continuous time drift due to differences in gravity and motion. This means that future interplanetary navigation and communication systems must accurately calculate and correct the "time rate deviation" between planets in the same way as dealing with intercontinental and cross-time zones.
In terms of specific methods, the researchers set a reference surface for Mars and incorporated the gravitational disturbances of the sun, earth, moon and other planets into a unified model. This is equivalent to introducing a fourth massive celestial body on the basis of solving the classic "three-body problem", making the system dynamics calculation more complicated. They first described the motion of Mars with the ideal Keplerian elliptical orbit, then superimposed the effects of multi-body gravity, solar tides, etc., and finally gave the fine correction of Mars' intrinsic time relative to the Earth. These relativistic intrinsic time differences, the so-called "intrinsic time offsets", form the theoretical basis for cross-planetary clock comparison and calibration. Patla laments, “The really hard work was a lot more complicated than I initially thought.”
Although the difference of a few hundred microseconds per day is almost unnoticeable in daily life, it is enough to cause errors to accumulate in precision technology systems. Mobile communication networks and satellite navigation systems on modern earth all rely on time synchronization at the nanosecond level or even smaller to complete positioning and data transmission. For deep space communications between Earth and Mars, current one-way signal propagation times range from about 4 to 24 minutes, depending on the relative positions of the two stars in their respective orbits. Researchers believe that if a unified and highly accurate "cross-planetary time system" can be established in the future, it is expected to reduce confusion and misjudgment in navigation and data exchange to a certain extent. Patla said, “Once strict synchronization is achieved, the communication experience will be as smooth as near real-time, and there will no longer be information loss waiting for results to be returned.”
The scientific research team also emphasized that a complete and mature interstellar communication network is still far from reality, but now conducting research on differences in time behavior can lay a solid foundation for future systems. Neil Ashby, who participated in the research, pointed out that it may take a few decades before the surface of Mars will be "covered" with the tracks of more rovers, but it is necessary to study the key issues of establishing navigation systems on other planets and satellites in advance. Similar to the current Global Positioning System (GPS), this type of future interplanetary navigation network will also have high-precision clocks as its core. The impact of the gravitational field of each celestial body on the clock rate must be quantitatively analyzed using Einstein's general theory of relativity. neowin
Patla further stated that this research not only provides the first systematic answer to Mars time, but also enriches human understanding of time and relativity itself to a certain extent. "For the first time we really know how time passes on Mars in a relativistic sense - no one has had a complete answer before," he said. In his view, this work has improved our overall understanding of "how clocks tick" and the general theory of relativity, and laid a theoretical and engineering foundation for the future deployment of high-precision time and navigation systems on the moon, Mars and even further in deep space.