Atomic clocks -- vital in such diverse fields as radio telescopy and geodesic measurements -- have come a long way from their beginnings, says the National Institute of Standards and Technology's Andrew Ludlow. Cesium models now incorporate lasers to cool atoms. "They're coming from incredibly hot temperatures, and you're cooking to millions of degree Kelvin," Ludlow says. "The best cesium clocks today all use some form of laser cooling on atoms that are hot and moving around to measure to their ticking."
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