Quantum Rocks Can Tell Time

By Sally Appert
Epoch Times Staff
Created: January 11, 2013 Last Updated: January 15, 2013
Related articles: Science » Inspiring Discoveries
Print E-mail to a friend Give feedback

Quantum mechanically, mass can be used to measure time and vice-versa. (Holger Müller lab)

Quantum mechanically, mass can be used to measure time and vice-versa. (Holger Müller lab)

A physics professor has invented a new way to make a clock using cesium atoms, based on quantum mechanics and the wave-particle duality of matter.

Holger Müller, an associate professor at the University of California-Berkeley, had the idea to count the oscillations of a matter wave and use them to tell time.

“A rock is a clock, so to speak,” Müller said in a press release. “When I was very young and reading science books, I always wondered why there was so little explanation of what time is.”

“Since then, I’ve often asked myself, ‘What is the simplest thing  that can measure time, the simplest system that feels the passage of time?’ Now we have an upper limit: one single massive particle is enough.”

Müller’s clock is called a Compton clock since it uses the Compton frequency of matter waves.  Matter, such as cesium atoms, oscillates a certain number of times per second.

Müller’s method also uses Einstein’s theory of relativity, in which time slows down for a moving object. For example, a twin goes traveling through the stars, and when he returns, he’s younger than his twin back on Earth because time slowed down for him.

In the same way, time slows down for a cesium atom that moves. Müller used a laser to make some cesium atoms move while others stayed still.

The cesium that stayed still oscillated 10 million billion billion times per second. The cesium that moved oscillated 100,000 fewer times per second than that, and Müller figured out how to measure this tiny difference.

He measured it with an atom interferometer, and he used that measurement to tell time.

“Our clock is accurate to within 7 parts per billion,” Müller said.

“That’s like measuring one second out of eight years, about as good as the very first cesium atomic clock about 60 years ago. Maybe we can develop it further and one day define the second as so many oscillations of the Compton frequency for a certain particle.”

The paper was published in the journal Science in the Jan. 11 issue.

The Epoch Times publishes in 35 countries and in 20 languages. Subscribe to our e-newsletter.

Follow EpochTimesSci & EpochTimesSpace on Twitter

Find us on Facebook: & Youtube:

Please send any feedback to

  • Me

    I don’t understand… Time is already measured using cesium. The international second has been defined in terms of vibrations of a cesium atom since 1967.

  • guest

    The frequency of a cesium clock is, roughly speaking, the difference of two different orbits of an electron bound to the cesium atom. This new clock measures a frequency which is proportional to the rest mass of the entire cesium atom (mostly the mass of the nucleus plus the electrons’ mass and binding energies).


Selected Topics from The Epoch Times

Between You and Me