L'incroyable machine atomique à fabriquer l'heure d'hiver | Archive INA

Subscribe http://bit.ly/InaSciences May 6, 1972 A visit to the Paris Observatory, to the International Time Bureau, where Bernard Guinot, the director, explains that time is manufactured, and in a complex way, because scientific research requires extremely precise time. In scientific work, he says, several time scales are needed: astronomical time, or universal time, given by astronomy, and atomic time, given by atomic time standards. He explains in detail the difference between these two. Astronomical time is insufficient because it is not very regular, whereas atomic frequency and time standards provide a more uniform time that can be read with much greater precision. Bernard Guinot defines "sidereal time," a variant of astronomical time used in observatories and rarely outside their scope; it is used by astronomers. The time on our watches is a compromise, a kind of third time called Coordinated Universal Time (UTC), which is very close to astronomical time. To verify the time at the various timekeeping offices, several methods exist, including transporting working clocks. This was done for the Apollo 16 mission to check that the clocks were synchronized before the mission. Bernard Guinot then explains the purpose of the devices surrounding him and gives a very detailed description of the speaking clock and its specific features. The scientist concludes, "Time is a very complicated thing!" INA archive footage National Audiovisual Institute http://www.ina.fr Subscribe http://www.youtube.com/subscription_c... #INA #Science