As the world’s most precise space clock prepares to launch, scientists are racing against time to harness its unprecedented accuracy and test the boundaries of Einstein’s theory of general relativity. But with a lifespan of just over a decade, will it be enough before it burns up in the atmosphere?
A network of Earth’s best clocks will be synchronised with the ESA‘s most accurate one ever sent into space. But the device has a short shelf life: it will burn up in the atmosphere at the end of the decade as the ISS deorbits.
The Atomic Clock Ensemble in Space (ACES)
The ACES is an ESA mission that will generate a time signal with unprecedented accuracy and then transmit it via laser to nine ground stations as it passes overhead at 27,000 kilometres per hour. This network of clocks will be in extremely close synchronisation and provide highly accurate timekeeping around the world.
The Science Behind ACES
The result is that ACES will be able to test Einstein‘s theory of general relativity, which says that the passing of time is affected by the strength of gravity, with great accuracy. It will also assist with research on everything from dark matter to string theory.
Albert Einstein was a renowned German-born physicist who revolutionized our understanding of space, time, and gravity.
Born on March 14, 1879, in Munich, Germany, he is best known for his theory of relativity.
In 1905, he introduced the famous equation E=mc², which shows that energy and mass are interchangeable.
Einstein's work also led to the development of nuclear power and atomic energy.
He was awarded the Nobel Prize in Physics in 1921 and continued to make groundbreaking contributions until his death on April 18, 1955.
How PHARAO Works
PHARAO is fundamentally modelled on an atomic clock in Paris that occupies an entire room. Miniaturising that technology into something that takes up less than a cubic metre, and can also survive the rigours of a rocket launch and life in space, was no mean feat. To generate an accurate clock signal, PHARAO spews a fountain of caesium atoms cooled to near absolute zero and observes their interaction with microwave fields.
Challenges of Building ACES
Simon Weinberg at ESA says that the device is so sensitive that simply putting a teaspoon near it could create an electromagnetic field strong enough to destroy the clock. “Just to put it in context, it’s better than a thousand million millionth of a second that we’re trying to measure here,” says Weinberg. “So it’s one hell of a challenging job.”
The Future of ACES
The concept for ACES dates back to the 1990s and was originally planned for launch on the Space Shuttle, which retired in 2011. Once it gets to space, the first signal won’t arrive at an Earthbound clock for a year and a half – it will take around six months to commission the device, and then a year’s worth of measurement will be needed to isolate noise and remove it from the clock signal.
After that, ACES will operate until 2030, after which the ISS will be deliberately crashed into Earth’s atmosphere and burned up. By that point, new super-accurate timepieces known as optical clocks are likely to have made atomic clocks all but obsolete on Earth, although they may not be small or robust enough for use in space by that time.
Weinberg says that at some point ESA will look to launch a new generation of ACES to replace what is lost on the ISS, whatever the most appropriate technology is at the time. “We would be a long way off from doing that, and we would have to gather together the support and the financing and so on to make sure that happened.”
- newscientist.com | Most accurate space clock to launch – and count down to destruction
