THE WORLD'S MOST PRECISE CLOCK HAS THE POTENTIAL TO CHANGE FUNDAMENTAL PHYSICS

 

WASHINGTON: According to Einstein's theory of general relativity, a huge object such as the Earth bends space-time, causing time to slow as you approach it — therefore a person on top of a mountain ages a fraction faster than someone at sea level.

US scientists have now demonstrated that clocks tick at different rates when separated by fractions of a millimetre, proving the idea on the smallest scale ever.

Jun Ye of the National Institute of Standards and Technology (NIST) and the University of Colorado Boulder told AFP that their new clock was "by far" the most accurate ever created, and that it could pave the way for new quantum physics findings.

Ye and colleagues described the engineering breakthroughs that enabled them to develop a device 50 times more precise than today's best atomic clocks in the prestigious magazine Nature on Wednesday.

Scientists couldn't validate Albert Einstein's 1915 theory until the invention of atomic clocks, which keep time by detecting the transition between two energy levels inside an atom exposed to a specific frequency.

The Gravity Probe A experiment, conducted in 1976 with a spacecraft 10,000 kilometres above Earth's surface, demonstrated that an onboard clock was one second quicker than an equivalent on Earth every 73 years.

Since then, clocks have improved in precision, making them more capable of detecting the effects of relativity.

When NIST scientists lifted their clock 33 cm (just over a foot) higher in 2010, they saw time moving at various rates.

- Everything's a theory -

Working with optical lattices, or webs of light, to trap atoms in organised configurations, was a major achievement for Ye. This is to prevent the atoms from falling due to gravity or migrating in any other way, which would result in a loss of precision.

100,000 strontium atoms are placed on top of each other like pancakes inside Ye's new clock, with a total height of around a millimetre.

The clock is so accurate that the scientists were able to discern changes in time between the top and bottom sides of the stack when they divided it in half.

Clocks, at this level of precision, are essentially sensors.

"Space and time are intertwined," Ye explained. "And, because to the precision of time measurement, you can literally observe how space changes in real time — Earth is a vibrant, living body."

Spread across a volcanically active region, such clocks could help geologists distinguish between solid rock and lava, allowing them to better anticipate eruptions.

Investigate how global warming is causing glaciers to melt and oceans to rise, for example.

What fascinates you the most, however, is the possibility that future clocks will usher in an entirely new physical realm.

The present clock can detect time discrepancies across 200 microns, but if it were reduced to 20 microns, it may begin to investigate the quantum world, potentially bridging theoretical gaps.

While general relativity beautifully explains the behaviour of huge objects such as planets and galaxies, it is famously incompatible with quantum mechanics, which deals with the extremely small.

Every particle, according to quantum theory, is also a wave that may exist in numerous places at the same time, a phenomenon known as superposition. However, according to Einstein's theory, an object in two places at the same time would disrupt space-time.

As a result of the junction of the two areas, physics is one step closer to developing an unified "theory of everything" that can explain all physical occurrences in the universe.