The world’s first nuclear clock is on the horizon
1 min read
14 Nov 2024, 05:16 PM IST
It would be 1,000 times more accurate than today’s atomic timekeepers
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PremiumFOR THE discerning timekeeper, only an atomic clock will do. Whereas the best quartz timepieces will lose a millisecond every six weeks, an atomic clock might not lose a thousandth of one in a decade. Such devices underpin everything from GPS and the internet to stock-market trading. That may seem good enough for most. But in a paper recently published in Nature, researchers report being ready to build its successor: the nuclear clock. Ekkehard Peik, one of the field’s pioneers, says such a clock could be a factor of 1,000 times better than today’s standard atomic clocks.
In atomic clocks, the electrons around an atom’s nucleus are jolted into a higher energy state by incoming radiation of a specific frequency. Each wave cycle of the radiation therefore corresponds to a “tick" measuring a small fraction of a second. Nuclear clocks would follow the same principles, but use the transitions of neutrons and protons inside the nucleus.
The most promising candidate nucleus is thorium-229, which, uniquely, has a nuclear transition that lasers should be able to trigger. The exact frequency at which this occurs, however, has long been unknown. The authors of the latest paper, led by Chuankun Zhang and Jun Ye from the University of Colorado in Boulder, circumvented the problem by using a custom-built laser capable of exposing thorium-229 to a range of similar frequencies. When they fired it at the target, one particular beam matched the nuclear transition frequency. The system needs further optimising, but “It’s the first demonstration that all the components of a nuclear clock are here," says Mr Zhang.
Because atomic clocks are more than accurate enough for most practical uses, scientists are not seeking to replace them. They are more excited about having two independent ways of measuring time: atomic clocks, which depend solely on the electromagnetic force governing the electrons’ movement; and nuclear clocks, which also obey the strong nuclear force. One use to which this could be put is testing Einstein’s theories of relativity. These posit, among other things, that clocks will tick more slowly in stronger gravitational fields. Those relativistic effects should be the same regardless of the clock. If the nuclear clock responds differently, then the theories may need revising.
Another question concerns the physical constants on which the different forces rely, such as the fine-structure constant, which determines the strength of the electromagnetic force. These seem to have fixed values, an oddity in a constantly evolving universe. Measuring time in ways that depend on different forces would offer a sensitive way to test any drift. If an atomic clock fell out of sync with a nuclear clock, for example, some change in the underlying physics might be responsible. Only time will tell.
© 2024, The Economist Newspaper Ltd. All rights reserved. From The Economist, published under licence. The original content can be found on www.economist.com
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Published: 14 Nov 2024, 05:16 PM IST
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