Scientists at the National Institute of Standards and Technology (NIST) and the University of Colorado, Boulder have developed an atomic clock that is accurate to within one second over 15 billion years. The clock is not just accurate, it can also tell when it’s been moved more than two centimeters close or further from the earth’s core.
“Time can be intricately connected to gravity,” said Jun Ye, a physicist at JILA, a joint institute of the NIST and UC, Boulder and principal investigator on the paper documenting the new clock. “It sounds like science fiction, but these measurements are a reality.”
In his General Theory of Relativity (1907), Einstein predicted that time passes faster as you move away from the center of a gravity mass. This phenomenon, called gravitational time dilation, has been demonstrated by scientists on numerous occasions with less sensitive clocks at a greater altitude differential. More recently (five years ago), an atomic clock was developed that could measure the time difference over one foot in elevation change (90 billionths of a second.)
This clock is much more accurate. Ye explains that the clock measures the speed of an electron as it travels around the nucleus of a strontium atom.
A so-called “clock laser” is used to bombard a few thousand strontium atoms. The laser is then adjusted to synchronize it’s oscillations with those of the strontium atoms. The clock is more accurate to several orders of magnitude greater than the cesium atomic clock currently used by NIST for official time.
“The clock we use now is like a watch with a hand that moves 9 billion times per second,” Ye said. “The ‘watch’ we are working on moves at the speed of a million billion times per second; we are basically keeping track of ripples of light.”
A clock of this accuracy is probably not necessary to be sure you get your kids to school on time. It does, however, give scientists the tools to make accurate measurements regarding our universe.
“If we can make a clock 1,000 times more accurate, we could hear the symphony of the universe,” Ye said. “For instance, you would sense how space time shifts when a distant galaxy explodes.”