The steady tick of a clock usually feels simple and dependable. Something swings or vibrates in a controlled rhythm and marks ...

We have trillions of body clocks — a central one in the brain and others in each cell of our body. Here's how they work with light to control our health. When you purchase through links on our site, ...

(CNN) — Picture a clock ticking so steadily that it doesn’t lose a second, even after running for 1 billion years. Scientists are now closer than ever to realizing that level of timekeeping precision, ...