A neglected rare-earth element could change the way we tell time

Among the rare-earth elements, lutetium doesn’t get enough attention. But this may soon change as a new type of clock that uses lutetium could tell more accurate time to the second, an article in Live Science states.

Starting in 1967, a second was officially defined as the amount of time it took a cesium atom to absorb a very specific amount of microwave radiation. Upon getting pulsed with exactly 92,631,770 cycles of MW energy, the electrons of the atom would get excited and jump to another energy state.

Cesium atomic clocks keep track of global time. They also play a big role in GPS navigation. But they are not the most precise timekeepers available. That honor goes to optical clocks.

First appearing a decade ago, optical clocks use different atoms that can be excited by visible light. The higher frequencies of “optical” light enable a more detailed measurement of a second, so optical clocks enjoy 100 times the precision of their cesium predecessors.

The drawback to optical clocks is that they are very sensitive to room temperature, especially over long periods of time. A change in room temperature can affect the electromagnetic fields that excite their atoms. This alteration will reduce the accuracy of the clock. (Related: Scientists discover a trove of rare-earth metals in Japanese waters.)

Forgotten rare-earth element could enable stable and accurate optical clocks

Associate professor Murray Barrett of the National University of Singapore (NUS) led efforts to investigate alternative materials for optical clocks. His team reported that a lutetium ion handled temperature changes much better.

Furthermore, lutetium atoms are able to resolve another problem of optical clocks. The atoms used by these timekeeping pieces are electrically charged. When they are hit by an electromagnetic field, the atoms slightly wiggle back and forth at high speed in what is called “micromotion shift.”

The need to correct this micromotion shift forces atomic clocks to use just one ion. But using multiple ions would increase their practicality.

Barrett’s team reported that a certain type of lutetium ion naturally prevented micromotion shifts. Lutetium optical clocks could thus use more than one atom for timekeeping.

The drawback is that lutetium atoms also become more sensitive to room temperature. A lutetium optical clock ends up trading one source of inaccuracy for another.

Barrett admitted that lutetium optical clocks will not replace cesium atomic clocks any time soon. He did believe that improved optical clocks could provide new capabilities.

Optical clocks might be able to detect dark matter and dark energy

Einstein’s theory of general relativity established that time is distorted by gravity. Clocks are therefore sensitive to where they are positioned.

Earthbound atomic clocks are not sensitive enough to detect the tiny time-warp caused by the planet’s gravity. However, optical clocks can register the effects of gravity. A world-wide array of lutetium optical clocks could help researchers map out the Earth’s gravitation field.

Paris Observatory physicist Jérôme Lodewyck pointed out another possible use for lutetium optical clocks. The highly precise clocks might be able to sense energy and matter that cannot be detected by electromagnetic means.

One example is dark matter, a hypothetical form of matter that does not interact with light. It does exert a gravitational pull – and as mentioned above, optical clocks are quite sensitive to gravitational effects.

If Earth passes through dark matter, its gravitational effect might alter the accuracy of optical clocks. This alteration would be measurable and could be used to indirectly determine the properties of dark matter.

Likewise, there is dark energy, an unknown force that is supposedly making the universe expand outwards. This mysterious energy might also affect the sensitive processes of optical clocks.

Read up on more scientific and technological breakthroughs at Discoveries.news.

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