A clock based on just a single atom - the simplest clock yet - has now been devised, researchers say.

This new device to measure time could help lead to a radically new way to define mass as well, scientists added.

In addition, this achievement suggests that researchers might one day build even more exotic clocks - ones based on antimatter, or ones based on no particles at all.

Fundamentally, all clocks measure time by relying on parts that repeat behavior in regular patterns. For instance, a year is defined by how long it takes for Earth to complete an orbit around the sun.

The most accurate clocks that currently exist are atomic clocks. These depend on how atoms switch between two distinct energy levels. Essentially, these clocks rely on at least two particles - the nucleus of an atom, and an electron leaping back and forth between different levels of energy.

Defining time

However, could clocks get simpler still?

‘We were interested in what the simplest clocks are to explore the question of what time is,’ said researcher Holger Müller, a physicist at the University of California at Berkeley. ‘If you say that, say, you can’t measure time with less than two particles, does that […]