Mikhail Kotov — about what time astronauts live on the ISS and what is the peculiarity of the Moon to indicate its time The European Space Agency (ESA) proposes to establish a time zone system for the Moon.
To do this, a platform called LunaNet will be developed, which will contain "mutually agreed standards, protocols and interface requirements that allow future lunar missions to work together."
Sleepwalkers, what time is it?
The history of the formation of the system of time and calendars on Earth is very long in itself — gradually, but humanity was able to come to the model familiar to us, when the day is divided into 24 hours, seven days in a week and all this is tied to the length of the earth year so clearly that it requires very little adjustment. It began, as it is now believed, in Ancient Egypt, then the ancient Romans introduced the Julian calendar, which spread throughout the Roman Empire, and later it was gradually replaced by the Gregorian. But it was not until October 1884 that an International Meridian Conference was convened in Washington, D.C., to discuss the choice of a meridian suitable for use as a common longitude zero and a time standard around the world. The result is known — the Greenwich Meridian was taken as zero (Greenwich Mean Time is also called "geographical" — the solar time of the meridian passing through the Greenwich Royal Observatory near London), and the globe is divided into just 24 time zones. However, a number of countries did not agree to this immediately — only by 1922 most of the countries of the world had changed the old order (before that they lived according to local, solar time).
Thus, the time zone system on Earth is only a little more than a hundred years old. As for the Moon, even now there is no single system of time zones. Until recently, scientists simply did not see the point in this. Space missions were launched according to the time of the country that conducts them. Based on this, the cyclogram (spacecraft program, etc., divided into time periods) of each mission was calculated. Management, as a rule, was carried out from one place on Earth, so there were no problems with the need to introduce a time zone.
Why do they start from Greenwich Mean time on the ISS?
In recent years, they have begun to create more and more large-scale international missions, which will become increasingly difficult to manage, focusing on Earth time tied to a specific time zone. Such a problem has already arisen when the joint management of the International Space Station (ISS) by several countries was launched.
The ISS uses the so-called coordinated universal time. It is according to him that all existing space services (and others that require the most accurate time) of all states on Earth compare their watches. According to the belt principle, this is practically an analogue of Greenwich Mean Time. But still not quite. The coordinated universal time diverges slightly from it due to the inaccuracy of the geographical, created by the uneven rotation of the Earth and the Greenwich meridian along with it. The reference time (i.e. coordinated worldwide) is more precisely, it is based on the work of atomic clocks installed in metrological institutions around the world.
Why does the ISS use Greenwich Mean Time? The zero meridian is approximately in the middle between Houston, from where the American ISS module is managed, and the city of Korolev near Moscow, where our Mission Control Center (MCC) is located.
Problems of the Moon
With the moon, the situation is even more complicated. First, it is required to determine its zero meridian. Secondly, to agree on how many hours the period between two identical phases of the Moon — the change of illuminated and unlit time - will be divided into. This period is called the synodic lunar month and averages approximately 29.5 Earth days. Why approximately? The fact is that the value of the synodic month may differ from the average value by more than six hours. At the same time, the Moon orbits the Earth a little faster — in 27 days, 7 hours, 43 minutes and 12 seconds — this is called the sidereal month, and it is always shorter than the synodic month (since the Earth also does not stand still). Well, what time should a manned mission that landed on the moon be tied to, how to synchronize work with the lunar base in the future? And if the score goes by seconds and the accuracy of actions needs maximum?
Attempts to introduce a time zone on the moon have already been made. In 1970, Helbros Watches, an American watch company with Swiss roots, asked the chief astronomer of the New York Planetarium Hayden Kenneth L. Franklin to create a watch for astronauts who set foot on the surface of the moon. These clocks measured time in the so—called "lunatio" (lunatio - "lunar month" in Latin). The lunation was equal to one synodic month (the one that is approximately 29.5 days).
According to the Franklin system, the month of the Earth's natural satellite was divided into 24 lunar hours. The astronomer presented the local lunar time zones according to the standard time zones on Earth, and the lunar hour was a little more than one Earth day. To obtain a smaller unit (like Earth seconds), a dial was made that divided the lunation into one hundred parts, so one hundredth of the lunation was more than seven hours. Now this watch is only a collector's value and an interesting artifact.
A systematic approach
In fact, the European Space Agency has raised a very important issue. Without hourly time and a single reference system, joint missions on the moon will be much more difficult. However, it will not be enough to agree on a single frame of reference. In addition to all of the above difficulties, there is also a problem that time on the Moon does not flow the way it does on Earth, according to Einstein's theory of relativity. On the ISS, too, but there is a difference of millionths of a second. On the moon, time goes faster by a noticeable 56 microseconds per day. Therefore, in order to get the exact time on the Moon, you will need to launch a small satellite grouping that will be responsible for the exact time on the surface of the Earth's natural satellite.
Naturally, such issues must be resolved with the participation of all space powers, otherwise a useful project to determine the lunar time will not be a new standard, but only an attempt in a number of curious space initiatives.
