Researchers at JILA (formerly also referred to as the Joint Institute for Laboratory Astrophysics) used a combination of strontium atoms and an array of laser beams to create a clock so precise it might be able to measure the interaction of gravity at smaller scales than ever before. In doing so, it might shed light on the nature of its relationship to other fundamental forces, a mystery that has baffled physicists for decades… More at LiveScience.

It is accurate to 1 second out every 90 billion years.

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