Defining time is one of the biggest mysteries of science. If we pause to ask what physics has to say about why time flows at all, we find it struggles. Albert Einstein’s ideas warped time, quantum theory barely considers it, and no other facet of modern physics can satisfactorily explain it.
Now, though, one of the most audacious proposals for how time really works is getting a second look. Back in the 1980s, physicists sketched out the hypothesis that time is an illusion, conjured from an essentially timeless universe by the strange workings of quantum mechanics. Back then, this idea, known as the Page-Wootters mechanism, impressed many – but it was beyond any experimental test. Forty years later, however, new research into the working of clocks is showing how we might finally probe this elegant proposal and revealing the mysterious role that black holes may play in the ticking of time.
