Atomic clocks are letting physicists tighten the lasso around elusive phenomena such as dark matter.
Quanta Magazine said:In the late 1990s, Jun Ye, a young physicist at the research institute JILA in Boulder, Colorado, decided to dedicate much of his career to making the world’s best atomic clock. He spent some time getting to know different atoms — magnesium, calcium and barium. Eventually he settled on strontium for its internal stability. He then set to work building a laser that would tickle strontium atoms at just the right frequency.
What Ye didn’t know is that he was also designing a dark matter detector. That realization came only in April 2015, when he got an email from Victor Flambaum, a physicist at the University of New South Wales in Sydney, Australia. Flambaum told Ye that according to certain theories, dark matter could subtly tweak the fundamental constants of nature, ever so slightly changing how fast clocks tick. Ye’s latest device — improved 20,000 times over his first version — was one of the few in the world sensitive enough to have a chance of picking up this faint signal.
Ye is now carrying out one of the world’s most unconventional searches for dark matter. The hypothesized substance is thought to outweigh “ordinary” matter 5 to 1, but so far it has made itself known only through its gravitational influence. By carefully measuring whether the frequency of his clock meanders up and down in time, Ye could reveal an interaction between a hypothetical ultralight dark matter particle and the internal constituents of atoms. Such a find would shake up physics.
Flambaum and Ye are among a growing number of physicists who aren’t looking solely to massive high-energy particle colliders for the answers to their field’s biggest questions. Instead, they’re taking advantage of the exquisitely precise control of atoms and lasers to listen to the universe’s softest songs. Though such experiments may fit on a humble tabletop, they’re proving powerful enough to take on dark matter, relativity and other areas of fundamental physics. Eventually they could probe gravitational waves and quantum gravity.
“People often ask me: What do you think is the usefulness of a clock like this? GPS? Often they have very practical views of clocks,” Ye said. “To me, the most exciting aspect of a clock has always been to probe fundamental physics.”
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