Portside

How, and whether, to keep atomic time in sync with Earth's rotation is still up for debate.

According to our best theories of physics, the universe is a fixed block where time only appears to pass. Yet a number of physicists hope to replace this “block universe” with a physical theory of time.

The laws of physics work both forward and backward in time. So why does time seem to move in only one direction? One potential answer may also reveal the secrets of the universe’s missing mass.

Cellular clocks are almost everywhere. Clues to how they work are coming from the places that they’re not.