00:00Time can be distanced or contracted depending on where you are.
00:05If you climb to the top of a very high mountain,
00:08time will flow a little bit faster than if you were in a valley.
00:12This phenomenon is due to gravity and the way it affects time.
00:16We hardly notice it in our daily life.
00:18But for scientists and space agencies preparing missions on the Moon,
00:23these tiny differences in time have a real importance.
00:26We will answer the question why a little later.
00:31At the moment, a new space race is underway.
00:36Many countries want to establish long-term bases on our satellite.
00:40With human beings on the Moon,
00:42it becomes crucial to have a reliable time measurement system.
00:46However, the Moon does not rotate at Earth time.
00:48A day on the Moon is slightly faster than a day on Earth.
00:52The difference is about 56 microseconds, and it seems insignificant.
00:56But over time, this slight difference can lead to an accumulation and considerable problems.
01:02That is why, in order to ensure the good progress of lunar missions
01:06and to avoid any desynchronization,
01:08NASA and scientists around the world are now facing a major challenge.
01:12Create a brand new lunar time scale.
01:18NASA should start using it by 2026.
01:21It is this same year that it hopes to send astronauts back to the Moon for the first time in 50 years.
01:26But this new time scale is not just a time-lunar fuselage.
01:30In fact, it is a complete system that will adapt to the faster time of the Moon
01:35and will ensure synchronization with the Earth's time systems.
01:39It is only on this condition that missions will be able to take place without trouble.
01:43On Earth, the time measurement is already surprisingly complicated.
01:47One might think that time is a simple concept.
01:50But measuring time with precision is in fact an exact science.
01:54Especially if we consider how much it affects our everyday life.
01:58Thus, to ensure the coordination of time on a global scale,
02:02scientists rely on what is called the Coordinated Universal Time, or UTC.
02:07This global time standard is based on ultra-precise atomic clocks
02:12that scientists have installed in various places around the world.
02:16Atomic clocks are interesting because they measure time
02:20based on the constant vibrations of atoms, which makes them extremely stable and precise.
02:25They allow scientists to ensure that their UTC is the same for everyone, everywhere.
02:31These atomic clocks also take into account the fact that time moves slightly slower
02:36as we get closer to the center of our planet.
02:39Thus, atomic clocks placed closer to the surface of the Earth
02:43rotate a little slower due to the stronger gravitational attraction.
02:47This effect, explained by Einstein's theory of relativity,
02:51is due to the fact that gravity affects time.
02:54By distributing atomic clocks at different altitudes,
02:57scientists establish an average of all the tiny temporal shifts caused by gravity.
03:03In addition, for a precise measurement of time,
03:05scientists occasionally add intercalar seconds
03:10to take into account small natural variations in the Earth's rotation speed.
03:14This seems very complex,
03:16but this synchronization process allows the modern world to function.
03:20After all, a well-defined time is essential for world trade,
03:23GPS navigation and Internet communications.
03:27But on the Moon, time works differently.
03:30The gravitational field of our natural satellite is weaker than that of the Earth.
03:34As a result, clocks rotate a little faster on the Moon.
03:37This difference means that, without correction,
03:40these clocks are likely to shift slowly from terrestrial clocks.
03:44This can cause big problems
03:46when astronauts have to stay in close contact with the Earth
03:50or navigate on the lunar surface.
03:52The solution proposed by NASA?
03:54A lunar time scale.
03:56Scientists will not adjust the lunar clocks
03:59so that they correspond exactly to those of the Earth.
04:02They want, rather, to establish a unique system
04:05that measures lunar time with precision,
04:07but which is also easy to convert to terrestrial time.
04:10It is, in a way, to create a brand new frame of reference for the Moon.
04:15To make this lunar time system work,
04:17NASA collaborates with its international counterparts,
04:20such as the European Space Agency.
04:22Together, they have put in place the Lunanet.
04:25This lunar network will be a bit like the Internet of the Moon.
04:28It will ensure that all lunar clocks work in concert
04:31and align on terrestrial time.
04:33Just as atomic clocks coordinate to determine their UTC on Earth,
04:37lunar clocks will coordinate with the Lunanet network.
04:42Scientists have a good experience of time management in space.
04:46Satellites of the Global Positioning System,
04:49orbiting the Earth at an altitude of about 20,000 km,
04:53are equipped with atomic clocks.
04:55These clocks rotate faster than clocks on the surface of the Earth,
04:59because they are very far from the Earth's gravitational attraction.
05:02But then, how can GPS navigation remain precise?
05:06Well, scientists have found a way to slow down these clocks
05:10so that they correspond to Earth's time.
05:12This experience with GPS clocks is an excellent basis
05:15for what scientists are looking to do on the Moon.
05:18In some respects, it could even be easier than managing the GPS.
05:22Scientists can work directly with lunar clocks
05:26instead of having to constantly adjust them so that they correspond to Earth's time.
05:30By setting up a precise lunar time,
05:33scientists hope to avoid some complications related to the management of GPS satellites.
05:39And now, here is the most exciting aspect.
05:41For the measurement of lunar time to become a reality,
05:44NASA and its partners want to install clocks
05:47both on the lunar surface and on satellites orbiting the Moon.
05:52Some will be atomic clocks with a long lifespan,
05:56while others will be crystal clock clocks,
05:59which offer stability over a short period of time.
06:02Together, these clocks will create a network on which scientists can rely.
06:07But atomic clocks intended for space are not cheap.
06:11They can cost several million dollars each.
06:14Crystal clock clocks, on the other hand, are more affordable.
06:17But they do not remain accurate over very long periods.
06:20Once these clocks are installed, they will work together thanks to the Lunanet network,
06:25which will be the framework of NASA for everything related to the time and data networks based on the Moon.
06:30Lunanet will act as an Internet for lunar operations.
06:34Various space agencies will contribute to it,
06:37as do Internet access providers on Earth.
06:40But there is another series of challenges,
06:42this time related to the rotation of the Moon.
06:44First of all, a day on the Moon lasts much longer than a day on our planet.
06:49Because it takes about 28 Earth days to complete a complete rotation on the Moon.
06:54In addition, the equator of the Moon has about 14 days of sunlight followed by 14 days of darkness,
07:00unlike the regular day-night cycle of the Earth.
07:03And at the south pole of the Moon, where NASA will establish its future lunar missions,
07:07some areas remain illuminated, or in the shade, permanently.
07:11This could complicate the task of astronauts, who want to keep the notion of time.
07:16NASA and its partners hope to involve more countries in this project
07:20through international organizations such as the International Astronomical Union.
07:25The idea is to make the Moon's time scale adopted by as many nations as possible,
07:30so that all those who explore the Moon are on the same wavelength.
07:34Another fascinating aspect of this project is that the determination of lunar time
07:38could be useful for other further space missions, such as trips to Mars.
07:44The experience and knowledge we will gain by establishing a lunar time scale
07:48will probably serve as a model for time management on even more distant planets.
07:53This is one of the reasons why scientists take this project very seriously.
07:57For astronauts living on the Moon, a coherent and reliable time system will be essential,
08:03not only for navigation, but also for all scientific experiments and everyday activities.
08:10The NASA project on lunar time is truly revolutionary.
08:14This is a first step when humanity begins to venture into space.
08:19If the project succeeds, future astronauts will not only have terrestrial time to guide them,
08:24they will also have this lunar time, and even, one day, a Martian time.
08:29Measuring time with precision is essential,
08:32both to understand scientifically how time flows on the Moon,
08:35and to set up the infrastructure necessary for the realization of missions.
08:39If scientists are so eager to create a new time scale,
08:43it is also because they are now able to apply everything they have learned on Earth
08:47over the last decades in terms of synchronization and timing.
08:51And now, my time is up. Bye!
Comments