Aces, the most precise watch ever in orbit, will tester theories of fundamental physics from the outside of the module
Columbus
of the ISS. Until 2030.
An ultra -pre -trial atomic watches network is ready to measure the passage of time from the terrestrial orbitand to compare these data with those captured by the most precise watches on Earth. The ACES (Atomic Clock Ensemble in Space) experiment of the European Space Agency has arrived on the International Space Station, where, for the next 5 years, the fundamental physical theories will be tested on the interaction between gravity and time.
Aces will measure time from space with a precision never reached before, testing Einstein’s theories and contributing to research on the fundamental constants of physics and dark matter.
The measurement campaigns. Aces was launched towards the ISS aboard an Spacex Falcon 9 on April 21; For April 25, its installation outside the Columbus module of the ASA by the robotic arm of the International Space Station, Canadarm2 is scheduled. Six months will follow to put the experiment in operation and a year of measurements to make sure to isolate its signal from the background noise. At that point Aces will be operational: over the course of 30 months of data collectionthe structure will carry out time measurements in orbit for at least ten sessions of 25 days each.
Winning coupled. The Aces package includes two watches: Pharao (Project d’Horogue atomique à refrioidissement of atomes en orbite) e Shm (Space Hydrogen Maser). The first is an atomic cesium watch modeled on an atomic clock in Paris that occupies an entire room, but miniaturized to occupy less than a cube meter thanks to the possibilities offered by the Conditions of free fall in which the International Space Station operates.
Shm is a device that uses hydrogen atoms to indicate the time: on the short periods it is incredibly stable, and this also helps to calibrate Pharao. Together, the pair of watches manages to be so precise from lose less than one second every 300 million years10 times more precise of the watches on board the GPS satellites.
The measure of time. The signal captured by Aces will be transmitted with two different methods (via laser and with a connection in the frequency of microwaves) nine terrestrial stations with the best optical watches of all continentswhile the ISS orbit around the Earth at 27,000 km per hour. The comparison between the measurements of time in space and on the earth will allow scientists to test the theory of gravitational temporal dilation provided for by the theory of the general relativity of Einstein, according to which gravity influences the passage of time.
On earth, Time flows faster to higher altitudesas on the top of the mountains, which at sea level. Aces will allow you to appreciate the difference between the passage of time at even higher altitudes, 400 km above the earth, so as to deepen our understanding of physics.
Time and speed. ACES will also be tested a consequence of the theory of restricted relativity by Einstein, according to which a body faster, the more slowly his internal clock flows. Since the ISS moves 8 km per second, the time on it expands (slowing down) of a small fraction of a second compared to the passage of time on earth. However, the effect is partly compensated by the greater distance of the ISS from the center of the earth, which – as first mentioned – on time has an imperceptible accelerating effect. An atomic clock should be able to appreciate both phenomena.
Short life. Aces will be operational until the expiry date of the International Space Station – 2030, when the ISS will be deorbited. At that point, in a few years, the technology of atomic watches will now be probably completely replaced by that of optical watches, much more precise. Although the new generation of devices may not yet be quite miniaturized and robust to go to space.
