How heavy is the universe? It’s a tantalising question, and now it has an astonishing answer. In cosmic terms, weight just doesn’t add up in the normal way.
We can measure the density of the universe near to us – it is about 10-26 kilograms per cubic metre – but weighing the whole thing is difficult. “Our universe is supposed to be infinite and expanding,” says astrophysicist Andrew Jaffe at Imperial College London. Einstein’s general theory of relativity tells us that the expansion affects how we measure both distance and mass, so you can’t just multiply the volume by the density.…
