Which Universe Are We In Again?
When considering the many worlds of the multiverse the picture that probably springs to mind, born of a thousand popular physics documentaries, YouTube videos or books, is of the universes like a sheaf of A4 paper or the pages of a book, all stacked neatly on top of one another, running in parallel, minding their own business until the science communicator sticks a sharp pencil through the stack for some reason.
It's not that though.
Another common mental model is of a constant bifurcation and splitting so that whenever a decision is made a new universe is created (which seems a bit of a waste if the decision is just about which pair of socks you're going to wear that day).
It's not quite that either though.
The multiverse is much more like a dark smoke-filled room, a continuum of possibility, probability and particles that simultaneous contains all conceivable universes and sock choices. What you decide doesn't create a universe, it just moves you into that part of the continuum.
Human consciousness can be thought of as the beam of a laser pointer in that dark smoke filled room, illuminating one set of possibilities, one path. This explains the curious counterintuitive nature of quantum physics. The double slit experiment shows that when left to its own devices a photon will pass through two slits at once and interfere with itself at the detector. And yet when someone tries to observe it passing through both slits it suddenly stops doing this. How can an act of observation affect the universe?
Well it doesn't really.
By observing in this way the observer is merely confirming which part of the smoke filled room they are in by shining their laser on it - they're not affecting the universe they're affecting themselves. The illumination defines them; out of all the myriad possibilities in the smoke filled room, they have decided to be this one.
Schrödinger's cat remains both alive and dead after the box is opened; it's just that by observing it Schrödinger traps himself in a room with either a dead cat or a pissed off alive one.
So if each of us is a beam of light does that mean that each of our universes are probably all slightly different? Maybe. But perhaps as individuals our consciousnesses are just part of a larger beam and together we make up a colossal coherent whole, a consensus of consciousness as to which direction our laser is pointing and the world we expect to see even though there may be a better one at a very slight angle from the one at which we're currently looking.
The more people there are who buy into the same world view the more coherent the beam of light is and the harder it becomes to see an alternative. But there always is one and it's always already there.
We just need to challenge the consensus.