Physicists construct the most accurate clock the world has ever seen  

By Melissa Grey posted May 29th, 2013 at 9:33 PM31 

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Calling a clock the most accurate ever may sound like hyperbole, but physicists at the National Institute of Standards and Technology in Boulder, Colorado have built a pair of devices that can claim that title. The team used an optical lattice to address an issue that plagues atomic clockmakers: constantly shifting frequencies that negatively impact the accuracy of their measurements. For example, a single second can be defined by the frequency of light emitted by an atom when electrons jump from one state to the next, but those frequencies change as the atom moves. The optical lattice essentially suspends atoms to minimize the Doppler effect produced by that movement. By combining the lattice with the element ytterbium, the group was able to create a device that measures time with a precision of one part in 10¹⁸. To put that into perspective, Andrew Ludlow, one of the paper's authors, said, "A measurement at the 10¹⁸ fractional level is equivalent to specifying the age of the known universe to a precision of less than one second." To read more about the team's work, you can find the full PDF at the source.