Imagine for a moment that some physicists are right, and that the universe we inhabit is one of trillions or even an infinity of others. (If you’re hearing this for the first time you might think this very strange, but a surprisingly large number of physicists have arrived at this viewpoint.)
This multiverse idea holds not just that there are many, many universes, but that inevitably there are many, many copies of you or close-enough-to-you. Slightly different versions of your current self.
In fact, the many worlds interpretation has it that every single decision or action you ever take, and that everyone else does, leads to the formation of a new universe – each one splitting off from this one at each inflection point: instant, spawning universes. It’s not just a commonplace occurrence: a new universe beckons every nanosecond, splitting from every event that happens every day.
Even stranger, if that is possible, these are not alternative possible universes that may occur – they are in existence right now, parallel to this one, subsisting simultaneously. To explain this, time is likened to a tree with many branches. Every possible outcome is realised, with each outcome manifesting in its own self-contained world. Each is no less real than the universe you and me (or at least, this version of you and me that are experiencing things right now) are currently occupying. Actually splitting, existing worlds, no less. Bewildered? You have every right to be.
What’s the mechanism for this? It’s to do with the way our world works at the quantum level – way below the level of the atom. Down there, where the smallest things imaginable are going on, subatomic particles are popping in and out of existence, and can take on different values at the same time. Adherents to the multiverse idea think that every possible outcome of a quantum measurement – that is, when an observation is made – stimulates the branching of a new universe. In human terms, a measurement is effectively being when a decision is made with alternative possibilities. That’s what leads to the many worlds.
On this account, every possible alternative outcome in the world is not just theoretically possible – it actually eventuates. There are many Jeffreys in those universes grappling with this view of the way things work – and I hope they are less puzzled about it than this one.
There it goes – as I have that idea, another universe just branched from this one, right this moment – one where I am beginning to explain the multiverse better than I am in the rest of this piece.
Let’s put this in a frame for you, the reader. All the other choices you could make every time you make one from now, off into the future, also happens in another similar universe as well. You decide to stop reading. Another universe. You determine to continue (thank you). This one.
If you are persuaded by this theory, I think it’s safe to assume you can stop counting how many universes there might be. We will just have to make do with the word infinity to describe that number, although, in a story for another day, the idea of infinity is not a trivial one to grasp.
But can you know for sure? Once the branching occurs the new universe that is created can’t be accessed by us – you, or anyone in this one. It’s closed off to those of us on this path because it’s mathematical space not a physical place you can visit. However, if you believe this theory you might start to think about all those other near-yous and feel vaguely something like a kinship attraction. After all, they are as near to you as you can get – much closer than an identical twin. A doppelgänger, to use that wonderfully evocative German compound noun.
Just so we don’t all think physicists are crazy, by the way, when in 1952 the Austrian-Irish Nobel-prizewinning physicist Erwin Schrödinger made the first reference to this idea at a lecture in Dublin, Ireland, he playfully forewarned that what they were about to hear might “seem lunatic”. There’s no record of how many in the audience thought his talk lunacy, yet I’m guessing at least some did – but many subsequently have come round to this re-imagining of the way the world works.
All of this no doubt leads to many questions for us mere non-physicists, striving to understand – but here are two of mine, personalised for you. Does this make you feel stressed, or even distressed by this idea? Or do you feel more in tune with the cosmos knowing not only that you are not alone on this planet or even in this universe?
Whilst physicists as a group tend to be mathematical and objective, when I first started coming to grips with it, I couldn’t help thinking that the inventors of this idea might even be taking emotional comfort from it. Rowan Hooper, writing for New Scientist, tells us that David Deutsch, the devilishly smart University of Oxford physicist and proponent of the theory, asks us to be mindful of our important life activities and decisions not just because they are important here and now, but because when you make your choices, you are choosing in many of those other universes. Such a responsibility, which not many of us realised we had. And Max Tegmark, another famous physicist, this time at Massachusetts Institute of Technology (MIT), indicated to Hooper that he feels connected in a kind of kinship to all the other corresponding Maxes everywhere else – despite having no actual confirmation they exist, and knowing that he’ll never be able to meet up with them.
Perhaps non-physicists can take comfort as well. Say you lose one of your parents to cancer. In another universe close to this one they didn’t get cancer in the first place. In another they went through radiotherapy, surgery or chemotherapy and got better. In yet another universe you were orphaned at an age where you were too young to have ever known your parents in the first place.
So less pain for all those others versions of you, at least those in those scenarios. This might cheer you up considerably.
For me, and maybe for you, this is all an intellectual mind-game. I find it hard to hold the idea that there’s other things going on in other universes which have separated from every instant of my existence because of my decisions across my life-cycle. It’s all for me a what-if thought experiment, so I feel neither cheery or non-cheery, nor do I feel, like Max Tegmark, close to all those other mes. To be frank, I don’t spend that much time even thinking about them.
But I can’t rule out, eerily, that if all this is true, and there really are multiple universes, then there are other (for want of a better phrase) Jeffrey-clones who think similar to me, and yet other near-dopplegängers who think differently to me – even just by a tiny degree.
And as I have that thought, there goes another universe popping into existence somewhere. And I’m having another thought, so there’s another one, again.
Hmmhh … Oh no, just deciding to write “hmmhh” created another universe, if this theory is correct. And there’s another. Now I’m in a never-ending loop. Better stop right here … .
Further reading:
Deutsch, David (2002). The structure of the multiverse. Proceedings of the Royal Society of London. Series A: Mathematical, Physical and Engineering Sciences 458 (2028), 2911-2923.
Hooper, R (2014). Multiverse me: Should I care about my other selves? New Scientist. Issue 2988. September 24. https://www.newscientist.com/article/mg22329880-400-multiverse-me-should-i-care-about-my-other-selves/
Vaidman, Lev (2021). “Many-Worlds Interpretation of Quantum Mechanics”, The Stanford Encyclopedia of Philosophy (Fall 2018 Edition), Edward N. Zalta (ed.) January 7. https://plato.stanford.edu/archives/fall2018/entries/qm-manyworlds/
Podcast
BBC 4 (2007). In Our Time. The Multiverse. https://www.bbc.co.uk/programmes/b008z744