Most clocks, from wristwatches to the systems that run GPS and the internet, work by tracking regular, repeating motions.

To build a clock, you need something that ticks in a perfectly repeatable way. In a pendulum clock, that tick is the regular swinging of the pendulum: back and forth, back and forth, at nearly the same rate each time.

Our team of physicists studies whether an even better kind of clock could one day be built from the atomic nucleus. Today’s best clocks already use atoms to keep extraordinarily accurate time. But in principle, a clock based on a nucleus—the tiny, dense core at the center of an atom—rather than an atom’s electrons, could keep a steadier rhythm because it would be less sensitive to environmental disturbances such as temperature changes. In our research, published in the journal Nature, we measured and interpreted a unique nuclear property of thorium-229 in a crystal that could help make such nuclear clocks possible.