An Atomic Clock in Your Pocket

Knowing what time it is down to the very last sliver of a second is easy — but only if you happen to have an atomic clock in your pocket.

Unfortunately, most such devices wouldn't fit. .......

In fact, there probably wouldn't even be room in the average studio apartment. But , all that may be about to change.

Researchers at the Massachusetts Institute of Technology (MIT) are developing what they say is a highly accurate atomic clock the size of a Rubik's cube, measuring about 2 inches (5 cm) in each dimension. The clock could one day be used to keep time in places where conventional clocks, like the ones on a cell phone, don't work — like underwater or in war zones, where signal jamming limits connectivity to satellite networks.

Like other atomic clocks, the MIT prototype keeps time by measuring the natural vibration, or oscillation, of cesium atoms in a vacuum. All atoms oscillate at a particular frequency when they move between two energy levels, but since the 1960s, cesium's frequency has been used to define the length of one second. Essentially, one second equals 9,192,631,770 oscillations of a cesium atom.

If the researchers can shrink their clock down to a portable size, it can be used in places where cell phones, which also run on atomic time, won't work. Submarine crews or deep-sea divers may even be able to use these highly accurate clocks underwater. Furthermore, soldiers on the battlefield could use the devices even if satellite signals are jammed.

There are other miniaturized versions of these clocks, known as chip-size atomic clocks (CSACs), already on the market.