The Time Lords: Scientists battle to build the universe's most accurate clock

When people think of time, they imagine the ticking of a second hand on a clock - but scientists are vying to create ever more accurate ways of measuring time, including one clock that would only have lost 1/20th of a second since the Big Bang.

The “official” time on Earth - International Atomic Time - is measured by a network of atomic clocks, and averaged for even more accuracy. It’s used as the basis for Coordinated Universal Time (UTC), which is used to set computer clocks around the world.

But new technologies could change the official way we measure a second - and could be key to new communications technologies. Ultra-accurate clocks are needed in a world where fibre-optic communications are measured in nanoseconds.

Below are some of the most accurate clocks in the universe - including a “stopwatch” that will use the entire Large Hadron Collider to count “yoctoseconds”, one septillionth of a second, or 0,000000000000000000000001 of a second.

The clock that could “redefine” the second

A new atomic clock undergoing testing at the Paris Observatory could be used to measure seconds more accurately than any on Earth today. Since 1967, the official definition of a second has been “the duration of 9,192,631,770 periods of the radiation corresponding to the transition between the two hyperfine levels of the ground state of the caesium 133 atom,” referring to the atomic clocks used today.

The optical lattice clock - using lasers and strontium atoms - is accurate to within one second every 300 million years, and is more stable than current atomic clocks. It could provide the basis for a new official definition of the second.

"These sorts of colourful descriptions accurate to within one second in 300 million years are useful for illustrating to a layman the degree of precision we can achieve," says Jerome Lodewyck of the Paris Observatory. "But it isn't the super-long timescales that interests us, but rather the very short ones. Even an accuracy of a second in 300 million years still means a lag of about 0.01 of a nanosecond over the course of a day - and that is not really so little when you think about fiberoptic communications and realize that a single telecommunications slot is 0.1 of a nanosecond.”

The clock that loses 1/20th of a second every 14 billion years

Sadly, the “single-ion clock” proposed by Professor Victor Flambaum of the University of Nevada wasn’t around at the moment of the Big Bang - otherwise it would have kept time so accurately it would only have lost 1/20th of a second in the 13.77 billion years since.

The device hasn’t been built yet, but would use lasers to use the orbiting neutron of an atomic nucleus as a “pendulum” - offering unbelievable accuracy. "This is nearly 100 times more accurate than the best atomic clocks we have now," says Professor Flambaum.

The Large Hadron Collider: the world’s fastest stopwatch

Measuring very, very short periods of time is hard - so far, we can only measure time in attoseconds (billionths of a billionths of a second) -  but a new “clock” could use the Large Hadron Collider to measure time 1,000 times more accurately. Researchers noticed that when they fired heavy ions at one another, they created light pulses so short they can’t be measured by today’s technology.

A new detector to be installed at CERN may be able to use these pulses to measure events that happen at very, very short time scales - which are currently measured using short laser pulses.

"Atomic nuclei in particle colliders like the LHC at CERN or at RHIC can create light pulses which are still a million times shorter than that", says Andreas Ipp from Vienna’s Technical University.

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The atomic watch

Even the finest Swiss clockwork loses or gains a couple of seconds per day -  British horologists Hoptroff wouldn’t settle for this, though, and have unveiled a movement with an atomic clock built in. It is the first watch that is accurate to within a second every 1,000 years - many times the lifespan of its potential owners.

The Quantum SA.45s “chip scale atomic clock” is used in Cruise missiles in case their GPS signal is jammed - here, the laser-heated caesium gas provides a watch accurate to a second every 1,000 years. So far, the prototype movement is too big for a wristwatch - but will fit in an old-style pocket watch pefectly.

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The clock that’s a rock

The head-scrambling quantum physics behind Holger Muller’s “clock” has inspired debate and controversy - Muller claims that all you need to measure time is a bit of radioactive caesium.  "A rock is a clock, so to speak," Müller said. Matter can be both a particle and a wave, Muller says - so all you need is one large atom, and you can tell time by counting the oscillations of these waves.

'What is the simplest thing that can measure time?' Mulller says. “One single massive particle is enough." So far, the clock is less accurate than current atomic clocks, but Muller believes that its precision can be boosted. Others are less sure. "This is a beautiful experiment and cleverly designed, but it is going to be controversial and hotly debated," said John Close of The Australian National University in Canberra.