Greenwich moon time? The high-stakes race to set lunar clocks

{"text":[[{"start":8.25,"text":"World powers are pushing to agree how to measure the passage of time on the Moon, as a tiny difference with Earth threatens navigation and communications just as international efforts at lunar colonisation grow. "}],[{"start":19.75,"text":"Countries are due to vote in October on a plan to deal with how Moon-based clocks tick fractionally faster than their terrestrial counterparts, due to gravitational effects."}],[{"start":29.7,"text":"The proposal for the International Bureau for Weights and Measures (BIPM) to take a central role in setting Moon time could be a first step for the organisation to expand its coverage to other cosmic realms. The low-profile body based on the outskirts of Paris is the guardian of reference measurements such as the metre and the kilogramme that underpin modern life."}],[{"start":52.75,"text":"“So far all of the space agencies that we’ve spoken to agree that without a co-ordinated lunar time they won’t be able to implement their own aspirations for interoperable technology on the Moon,” Annette Koo, the BIPM’s director, said in an interview. "}],[{"start":69.35,"text":"“We want to do it in a way which actually foresees the future. So when space agencies come to us to talk about, for example, time on Mars, we should be able to just simply take what we’ve done now and then duplicate it.”"}],[{"start":null,"text":"

"}],[{"start":82.6,"text":"The lunar clock adjustment is needed because of a phenomenon known as time dilation, described by Albert Einstein’s theory of general relativity. In essence, the greater a celestial body’s mass, the more it curves space-time — and the slower time nearby will pass."}],[{"start":99.64999999999999,"text":"This means that a person spending 30 years on Jupiter, the solar system’s largest planet, would be about 18.4 seconds younger than if they had spent those three decades on Earth. Conversely, a person who spent 30 years on the Moon would be about 0.629 seconds older than if they had been terrestrially bound, according to a rough-and-ready reckoner drawn up by the US National Institute of Standards and Technology."}],[{"start":125.39999999999999,"text":"That equates to time passing about 57 microseconds a day faster on the Moon than on Earth. This margin is inconsequential in human perception but potentially existential for a lunar mission. Light waves used in communication systems travel about 17km even in that short time. "}],[{"start":146.04999999999998,"text":"A failure to allow for this could lead to a disastrous error in navigation. It might cause a craft to land on a lunar crag instead of in a crater, or the position of an astronaut orbiting the Moon to be incorrectly calculated."}],[{"start":158.49999999999997,"text":"Precision lunar timing is essential for the smooth operation of cellular communication networks too. It helps ensure signals stay within allocated bandwidths and do not interfere with each other."}],[{"start":null,"text":""}],[{"start":170.84999999999997,"text":"The need for a standard time for the Moon has grown increasingly urgent as governments have stepped up their interest and activity there. Both the US and China are aiming to put astronauts on the Moon in the next few years, with longer-term plans to build lunar bases."}],[{"start":187.19999999999996,"text":"Nasa has been considering how to set a lunar time, in part in response to a White House directive issued in April 2024. It is developing a “LunaNet” plan for Moon communication and navigation services with the European Space Agency, Japan Aerospace Exploration Agency and commercial providers."}],[{"start":206.19999999999996,"text":"The BIPM is an obvious candidate to bring global lunar timing efforts together. The organisation, based in a historic pavilion originally built as a retreat for King Louis XIV’s brother, was created in 1875 to standardise measurements on which societies and economies rely."}],[{"start":222.74999999999997,"text":"It has since expanded its remit to areas including radiation and chemistry. Its 68 member states include China, India, the US, Japan, Russia, Brazil and many European countries."}],[{"start":null,"text":""}],[{"start":234.89999999999998,"text":"A resolution submitted to a meeting of BIPM countries in October calls on the organisation to work with space agencies, national measurement institutes and international organisations to set a lunar reference time. The proposal mirrors the BIPM’s job in determining Coordinated Universal Time (UTC) on Earth, based on data gathered by member states."}],[{"start":256.54999999999995,"text":"“In principle, we would provide a service which means that any clocks placed on the Moon could report to us their time and we would report back to them their difference from co-ordinated time — which is effectively what we do here on Earth,” Koo said."}],[{"start":270.34999999999997,"text":"So far there are few signs of political tensions over a possible universal lunar time although technical questions remain to be answered, she added. "}],[{"start":279.34999999999997,"text":"“By and large we find people working together to try and come to a common understanding of how to do it,” she said."}],[{"start":null,"text":""}],[{"start":285.59999999999997,"text":"If the BIPM becomes the keeper of Moon time, it could potentially be a blueprint for the organisation to take an expansive extraterrestrial role in standardisation, wherever humanity places clocks — provided its funding countries are prepared to give it the resources to do so. "}],[{"start":303.15,"text":"“We can’t commit necessarily to providing the solution unless the member states come back and say: ‘Yes, it’s important enough — and we can support it to the level at which it needs to be in order to be successful,’” Koo said."}],[{"start":315.25,"text":"The lunar time work is part of the BIPM’s broader effort to improve the precision of fundamental measurements, including a long-running effort to redefine the kilogramme. The project began after the mass of the platinum-iridium cylinder used to standardise the kilogramme since 1889 was found to have diverged from that of copies made of it. "}],[{"start":335.05,"text":"That showed the dangers of relying on degradable physical objects for reference, triggering a rethink about the nature of modern metrology — the scientific study of measurement. The new kilogramme method uses a formula based on an unchanging number fundamental to quantum physics, known as Planck’s constant."}],[{"start":343.25,"text":"The move to a universally accessible mathematical definition was the next step in an expanding process of the “democratisation” of measurement, Koo said."}],[{"start":352.15,"text":"“It’s available at any time, to anyone,” she said of the newly defined kilogramme. “Certainly not locked in a safe in Paris.”"}],[{"start":366.9,"text":""}]],"url":"https://audio.ftcn.net.cn/album/a_1787358415_5434.mp3"}