Spacetime Crystal Could Tell Time Longer than the Universe

Would keep time even after the universe's heat death

A 'spacetime crystal' sounds like something Doctor Who might keep in his kit-bag—but it's actually much more dramatic than that: a clock that could keep perfect time forever, even after the heat-death of the universe.

It's a four-dimensional crystal that has periodic structure in time as well as space, and scientists at Berkeley Lab say they've come up with an experimental design for one.A 'spacetime crystal' sounds like something Doctor Who might keep in his kit-bag—but it's actually much more dramatic than that: a clock that could keep perfect time forever, even after the heat-death of the universe.