What if the visible universe is embedded in a larger universe that we can’t see? What if other universes exist just a microscopic distance away from us, but we can’t experience them, because the distance is measured in a fourth dimension of which we are not aware? It’s a big concept to wrap your head around, but cosmologists have been studying what’s called ‘Braneworld’ theory as a way to explain how everything came to be.

The idea is that our three-dimensional universe is located on a “brane” (short for “membrane”) inside a hyper-dimensional space called the “bulk.” Think of humans like two-dimensional stick men trying to understand a three-dimensional cube: essentially, since we’re imprisoned in our three dimensions, we can’t detect other universes - even if they did exist.

(I'm off for a lie down while I piece my brain back together.)