A bold new perspective suggests space-time isn’t a fundamental entity but emerges from quantum entanglement, says physicist Sean Carroll
LET’S say you want to meet a friend for coffee. You have to tell them where you are going to be – your location in space – but you also need to let them know when. Both bits of information are necessary because we live in a four-dimensional continuum: three-dimensional space and everything within it, from steaming coffee machines to stars exploding in faraway galaxies, all happening at different moments of one-dimensional time.
“Space-time” is simply the physical universe inside which we and everything else exists. And yet, even after millennia living in it, we still don’t know what space-time actually is. Physicists have strived to work it out for more than a century. In recent years, many of us have been trying to figure out what might be the threads from which the fabric of reality is woven. We have ideas, each with its own selling points and shortcomings. But for my money, the most exciting one is the most surprising.
It is the idea that space-time emerges from a weird property of the quantum world that means particles and fields, those fundamental constituents of nature, can be connected even if they are at opposite ends of the universe. If that is correct, we might finally have found a bridge between the two irreconcilable totems of physics, placing us on the threshold of a theory of quantum gravity. We would also have the most startling demonstration yet that the world we see isn’t the world as it is – that there is always “something deeply hidden”, as Albert Einstein put it – and that the only way to understand …