July 10, 2013
Redefining Time With Innovative Optical Lattice Clock
Michael Harper for redOrbit.com - Your Universe Online
Atomic clocks are the standard in time, hailed as the most accurate and often used to keep other clocks on time. Now, a new kind of clock aims not only to replace atomic clocks as the most accurate, but to redefine the second as a measurement of time as well.The new device, called an optical lattice clock (OLC) is, theoretically, three times more accurate than current atomic clocks. In computer models, these clocks lost only one second in 300 million years. Though OLCs have been introduced before, Dr. Jerome Lodewyck and colleagues at the Paris Observatory have just completed a critical test to determine their ultimate accuracy.
Though many are content to define the second as the time it takes the small hand to pass from one click to another, scientists and physicists require a clearer definition in their work.
Ever since 1967, a second has been more precisely defined as the duration of 9,192,631,770 oscillations of the microwave radiation absorbed or emitted when a caesium atom jumps between two particular energy states, wrote Philip Ball in the International Weekly Journal of Science. Atomic fountains are used to accurately measure these oscillations and determine an actual second. Laser beams are used to hurl atoms upwards towards caesium in its gaseous state. The emissions from these atoms are then probed as they first pass upwards towards a microwave beam and then again as they fall prey to gravity.
These atomic clocks are used worldwide to set the national time. The Paris Observatory, for instance, uses these clocks to determine the precise time. This is important, as other nations look to the Paris Observatory for the correct time. GPS satellites, as well, rely on atomic clocks to ensure their signals are being synchronized between themselves and Earth. Without this synchronicity, the satellites would not be able to determine the receiver's location.
Atomic clocks are quite accurate and can generally (and theoretically) lose only one second every 100 million years, though some atomic clocks work with even greater accuracy.
Dr. Lodewyck claims that the new OLCs measure seconds in a more precise way, thereby making them even more accurate than today's atomic clocks.
"In our clocks we use laser beams. Laser beams oscillate much faster than microwave radiation, and in a sense we divide time in much shorter intervals so we can measure time more precisely," said Dr. Lodewyck in a statement to the BBC.
The team at the Paris Observatory also tested two OLCs against one another to determine their stability. After watching them for a time, the team claimed they worked in unison, measuring time in the same way and remaining very stable.
"For instance, if you have your wristwatch, and one day you are one second late, and one day one second early, then your clock is not stable. But it could still have good accuracy if over a million days the time is correct," said Dr. Lodewyck.
Though this new work proves lasers are more accurate rulers to measure time, another clock is being developed which takes this measurement one step farther.
The ion clock uses a single ion to measure seconds and is said to lose one second every few billion years. The ion clock hasn't yet been deemed stable, however, and therefore isn't ready to be used to measure time.