Physicists have created atomic clocks that are so precise, they can measure spacetime distortions from pulls of gravity and, eventually perhaps, dark matter.
In a new study, physicists from the National Institute of Standards and Technology discussed the exquisite precision of the pair of independent atomic clocks and how they were able to achieve it.
A Record-Breaking Clock
Both clocks were created using thousands of ytterbium atoms in optical lattices made of laser beams that hold them immobile. If struck by a laser at exactly the right frequency, the electrons of the atoms get excited then oscillate before they pass through another component called optical frequency comb. The process creates a signal that produces the tick of the clock.
Physicists measured the accuracy of the clocks by comparing them on three important measures: systematic uncertainty, stability, and reproducibility.
"Systematic uncertainty, stability, and reproducibility can be considered the 'royal flush' of performance for these clocks," explained Andrew Ludlow, project leader and co-author of the study. "The agreement of the two clocks at this unprecedented level, which we call reproducibility, is perhaps the single most important result because it essentially requires and substantiates the other two results."
The results were astounding. The clocks were in sync with the natural frequency of the ytterbium with an error of 1.4 parts in 1018 or a billionth of a billionth, the change was just 3.2 by 1019 , and with a difference below the level of 10-18 or, again, less than one billionth of a billionth.
With these measurements, the clocks would take longer than the age of the universe before they lose a second. That is about 14 billion years.
Other Possible Uses
Atomic clocks can also be used to measure gravity. If placed on a higher altitude here on Earth, for example, the time would pass a little faster because, as Albert Einstein famously theorized, time is affected by the pulls of gravity. Therefore, the clocks could be used for experiments that involve measuring the distortion of spacetime.
Moreover, the physicists revealed that the clocks could be used to detect dark matter, the stuff in the universe that cannot be seen by the human eyes or through even the most sophisticated telescopes. However, scientists are aware of dark matter's existence because of its gravity.
The physicists behind the study think that the clock might be able to detect the presence of dark matter by looking at how its gravity alters spacetime. Theoretically, when it interacts with dark matter, the clocks would either speed up or slow down.
The study can be found in the journal Nature.