![]() Diamond would work, but it's costly in large, ultrapure samples. This characteristic makes sapphire an ideal surface on which to propagate electromagnetic radiation. When cooled to –267 ☌ (6 kelvins) and made to oscillate, the symmetry of this type of crystal causes it to lose less energy than almost any other known material. That turned out to be sapphire, a crystal of aluminum oxide that can be synthesized in the laboratory. The sapphire crystal fits into a metal chamber (top), which is then enveloped in a cryogenic cooler and lowered into a vacuum can by engineers Ka Wu (middle, left) and Fred Baynes. Another way of putting this is that he needed a crystal with a greater spectral purity, one that would respond only to an exceedingly narrow range of frequencies, almost like a low-loss guitar string that can vibrate for an extremely long time and thus at a very pure frequency. To achieve very high precision, Luiten needed to find a material that could sustain electromagnetic oscillations for longer than a beam of cesium atoms can. ![]() In other words, each tick is really, really, really just like another. Luiten's device doesn't aim for the bull's-eye: instead, it is able to land all its darts at exactly the same point on the dartboard. Atomic clocks are able to land all their darts, or oscillations, broadly around the bull's-eye so that the average position is right on target, even though any given dart might be a centimeter or two away from dead center. Precision has to do not with delineating the perfect second but rather with creating extremely regular ticks, or oscillations. National Institutes of Standards and Technology in Boulder, Colo., is so accurate that it would have to run for 300 million years to gain or lose a second.īut for some applications, accuracy is less important than precision. The NIST-F2 cesium clock operated by the U.S. And make no mistake, even cesium atomic clocks are stunningly accurate. If you're reading this article on a smartphone or a laptop, the time displayed on the edge of your screen is derived from one of those atomic clocks.įor many applications, such as satellite-based global positioning systems, accuracy is paramount. ![]() Since 2013, even more accurate types of atomic clocks have been built, but over 400 atomic clocks based on cesium-133 atoms are still used to create civil time across the globe. That's because accuracy and precision are different things: Accuracy is how well a clock can measure a true second, now defined as the time it takes cesium atoms under controlled conditions to oscillate between two energy states exactly 9,192,631,770 times. The new clock-also known as the Sapphire Clock-isn't better than an atomic clock it's different. He and his colleagues are working on these applications at the University of Adelaide, also in Australia, where he now serves as director of the Institute for Photonics and Advanced Sensings. Luiten calls it the Cryogenic Sapphire Oscillator, and it could bolster technologies as varied as military radar and quantum computing. Developed by Andre Luiten when he was completing his studies at the University of Western Australia, it's built around a small, extremely cold crystal of sapphire. But how exactly alike are those ticks? For some vital applications, even vanishingly small deviations can be a problem.įor those applications, help is on the way, in the form of the most precise clock yet created.
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