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 centimeters) 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 — the researchers said.
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.
Original Source: http://www.livescience.com/48799-miniature-atomic-clock.html