Nuclear clock: How the most precise timepiece ever could change our view of the cosmos

Ekkehard Peik is a clock-maker. But instead of spending his days looking at tiny cogs and springs through a magnifying glass, the tools of his trade are powerful lasers, wires and, occasionally, radioactive atoms. Peik, director of the German metrology institute (PTB), is one of a handful of physicists who have spent the best part of three decades trying to make the most accurate timepiece in the universe.

Since the 1950s, researchers have been constructing atomic clocks, the very best of which are now so accurate they only lose a second in around 31 billion years. But these are about to be replaced by a new model: the nuclear clock.

This promises to outperform its atomic counterparts both in terms of precision and accuracy. A nuclear clock would, in principle, only drop a second every 300 billion years. Why, you might ask, would we ever need something with such mind-blowing precision? Because it will be used for something much more exciting than simply telling the time. Nuclear clocks could help probe some of the deepest mysteries of the universe, including the nature of dark matter and some of the elusive fundamental forces that shape our cosmos.

The tick of today’s atomic clocks is the result of electrons that oscillate between a pair of shells around the nucleus of an atom. The transitions between these shells are driven by shining lasers at the atoms involved at just the right frequency to match that of the oscillations, a state that is known as resonance. This resonant frequency, the number of oscillations of light per second, sets the…