Scientists Watch a Clock Tick for 14 Years to Prove Einstein's Theory of Relativity

Monday, June 11, 2018 - 15:05

Patla’s team, based at the National Institute of Standards and Technology in Boulder, Colorado took 12 of the world's most accurate clocks and watched them for about 450 million seconds for 14 years.

In total, the team documented over 450 million seconds. And the work seemed worth it. Team leader Bijunath Patla and the other researchers have successfully performed the world's most accurate test of a key principle of Einstein's famous theory, Wired reports. In a paper published in Nature Physics, Patla’s team reveal a profound result from an exceedingly monotonous experiment.

The ticking of the clocks, Patla says, actually illustrates one of the most fundamental principles in the laws of physics: that no time or place in the universe is special. It is one of the basic ideas in Einstein’s theory of general relativity, a set of rules that correctly describes how the planets orbit the sun and how neutron stars collide to produce gravitational waves.

Einstein saw the Earth as a freefalling elevator, the NIST team explained in a press statement. The famous physicist theorized that objects found in such a slow moving elevator would accelerate at the same rate almost like they were in a uniform gravitational field. Einstein also predicted that these objects properties relative to each other would stay the same during the fall.

And it was those thoughts the researchers put to the test. The NIST study makes it possible to have continual improvements in atomic clocks by using the best atomic clocks around. NIST compared the data of ticks from two different styles of atomic clocks found throughout the world in order to show that they remained in sync for 14 years, despite the gravitational pull from the 'elevator' changed with Earth's rotation and orbit.

"In their experiment, the NIST team regarded Earth as an elevator falling through the Sun's gravitational field. They compared recorded data on the "ticks" of two types of atomic clocks located around the world to show they remained in sync over 14 years, even as the gravitational pull on the elevator varied during the Earth's slightly off-kilter orbit around the sun. Researchers compared data from 1999 to 2014 for a total of 12 clocks -- four hydrogen masers (microwave lasers) in the NIST time scale with eight of the most accurate cesium fountain atomic clocks operated by metrology laboratories in the United States, the United Kingdom, France, Germany and Italy."

Those figures were also more accurate than their previous best measurement. The improvement largely comes from more accurate cesium fountain atomic clocks and better time transfer processes.

"But the main reason we did this work was to highlight how atomic clocks are used to test fundamental physics; in particular, the foundations of general relativity," Patla said. "This is the claim made most often when clockmakers strive for better stability and accuracy. We tie together tests of general relativity with atomic clocks, note the limitations of the current generation of clocks, and present a future outlook for how next-generation clocks will become very relevant."


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