Scientists Reveal the World’s First Nuclear Clock

Meet the “nuclear” clock: a device that marks the passage of time via minute signals from the nucleus of an atom. A team of researchers led by scientists at JILA, a joint institute of the National Institute of Standards and Technology (NIST), announced the clock today, and published its findings in Nature.

“Imagine a wristwatch that wouldn’t lose a second even if you left it running for billions of years,” said Jun Ye, a physicist at NIST and JILA, in a NIST release. “While we’re not quite there yet, this research brings us closer to that level of precision.”

Atomic clocks are very stable over long periods of time, meaning they are reliable for some of the most careful measurements scientists have to make. Ordinary clocks like those in your wristwatch use a quartz crystal oscillator to keep time; the crystals vibrate at specific frequencies that measure time’s passage, similar to a pendulum in a grandfather clock. But the highest level of precision is necessary for high-risk measurements, like checking the positions of spacecraft.

Atomic clocks use laser light to make electrons orbiting atoms jump between energy levels, replacing the function of a swinging pendulum to keep time. According to the NIST release, nuclear clocks would behave similarly, capitalizing on energy jumps in an atom’s nucleus for timekeeping.

The nuclear clock would also be less noisy than an atomic clock, as its operation doesn’t rely on measuring electrons, which can be harried and hassled by errant electromagnetic fields. But to get a nucleus to make the necessary energy jumps for timekeeping, scientists generally have to blast the nucleus with a type of specifically crafted X-ray. That’s why the newly described clock runs on thorium, whose nucleus only requires ultraviolet light to make energy jumps.

“With this first prototype, we have proven: Thorium can be used as a timekeeper for ultra-high-precision measurements,” said team member Thorsten Schumm, a physicist at TU Wien, in a university release. “All that is left to do is technical development work, with no more major obstacles to be expected.”

The newly unveiled nuclear clock isn’t more precise than today’s best atomic clocks, but Schumm said his team should overtake those timekeeping devices in a few years. “The first cars weren’t any faster than carriages. It was all about introducing a new concept,” Schumm said. “And that’s exactly what we’ve now achieved with the nuclear clock.”

In July, a different team of researchers presented the most precise atomic clock yet. That clock traps thousands of atoms to keep time and will only lose a second every 30 billion years. For scale, our universe is not yet 14 billion years old, and the Earth is not yet 5 billion.

These are heady times indeed for, uh, time itself!