Bubble universe theory says that there are many universes, perhaps connected by black holes, which are altogether a sort of “multi-verse”. Some think that it was two of these universes, two higher dimensions, which collided to cause the Big Bang.
And many think that there’s a sort of “natural selection with universes” going on – that many of those universes never developed the right physical laws to be stable, and collapsed; it’s only ones like ours which have the right balance of the 4 principal forces to “survive” and eventually form life. There’s also a theory that these universes are constantly being created and destroyed, and only the stable ones survive.
Many modern theories of fundamental physics predict that our universe is contained inside a bubble. In addition to our bubble, this `multiverse’ will contain others, each of which can be thought of as containing a universe. In the other ‘pocket universes’ the fundamental constants, and even the basic laws of nature, might be different.
Until now, nobody had been able to find a way to efficiently search for signs of bubble universe collisions – and therefore proof of the multiverse – in the CMB radiation, as the disc-like patterns in the radiation could be located anywhere in the sky. Additionally, physicists needed to be able to test whether any patterns they detected were the result of collisions or just random patterns in the noisy data.
A team of cosmologists based at University College London (UCL), Imperial College London and the Perimeter Institute for Theoretical Physics has now tackled this problem.