Notice I use the plural for something that represents a collection of universes. That’s because there are multiple versions of them; according to Max Tegmark there are 3 levels of multiverses.
I’m about to do something that I criticise others for doing: I’m going to challenge the collective wisdom of those who are much smarter and more knowledgeable than me. I’m not a physicist, let alone a cosmologist, and I’m not an academic in any field – I’m just a blogger. My only credentials are that I read a lot, especially about physics by authors who are eminently qualified in their fields. But even that does not give me any genuine qualification for what I’m about to say. Nevertheless, I feel compelled to point out something that few others are willing to cognise.
This occurred to me after I wrote my last post. In the 2 books I reference by Paul Davies (The Mind of God and The Goldilocks Enigma) he discusses and effectively dismisses the multiverse paradigm, yet I don’t mention it. Partly, that was because the post was getting too lengthy as it was, and, partly, because I didn’t need to discuss it to make the point I wished to make.
But the truth is that the multiverse is by far the most popular paradigm in both quantum physics and cosmology, and this is a relatively recent trend. What I find interesting is that it has become the default position, epistemologically, to explain what we don’t know at both of the extreme ends of physics: quantum mechanics and the cosmos.
Davies makes the point, in Mind of God (and he’s not the only one to do so), that for many scientists there seems to be a choice between accepting the multiverse or accepting some higher metaphysical explanation that many people call God. In other words, it’s a default position in cosmology because it avoids trying to explain why our universe is so special for life to emerge. Basically, it’s not special if there are an infinite number of them.
In quantum mechanics, the multiverse (or many words interpretation, as it’s called) has become the most favoured interpretation following the so-called Copenhagen interpretation championed by Niels Bohr. It’s based on the assumption that the wave function, which describes a quantum particle in Hilbert space doesn’t disappear when someone observes something or takes a measurement, but continues on in a parallel universe. So a bifurcation occurs for every electron and every photon every time it hits something. What’s more, Max Tegmark argues that if you have a car crash and die, in another universe you will continue to live. And likewise, if you have a near miss (as he did, apparently) in this universe, then in another parallel universe you died.
In both cases, cosmology and quantum mechanics, the multiverse has become the ‘easy’ explanation for events or phenomena that we don’t really understand. Basically, they are signposts for the boundaries or limits of scientific knowledge as it currently stands. String Theory or M Theory, is the most favoured cosmological model, but not only does it predict 10 spatial dimensions (as a minimum, I believe) it also predicts 10500 universes.
Now, I’m sure many will say that since the multiverse crops up in so many different places: caused by cosmological inflation, caused by string theory, caused by quantum mechanics; at least one of these multiverses must exist, right? Well no, they don’t have to exist – they’re just speculative, albeit consistent with everything we currently know about this universe, the one we actually live in.
Science, as best I understand it, historically, has always homed in on things. In particle physics it homed in on electrons, protons and neutrons, then neutrinos and quarks in all their varieties. In biology, we had evolution by natural selection then we discovered genes and then DNA, which underpinned it all. In mechanics, we had Galileo, Kepler and Newton, who finally gave us an equation for gravity, then Einstein gave us relativity theory that equated energy with mass in the most famous equation in the world, plus the curvature of space-time giving a completely geometric account of gravity that also provided a theoretical foundation for cosmology. Faraday, followed by Maxwell showed us that electricity and magnetism are inherently related and again Einstein took it further and gave an explanation of the photo-electric effect by proposing that light came in photons.
What I’m trying to say is that we made advances in science by either finding more specific events and therefore particles or by finding common elements that tied together apparently different phenomena. Kepler found the mathematical formulation that told us that planets travel in ellipses, Newton told us that gravity’s inverse square law made this possible and Einstein told us that it’s the curvature of space-time that explains gravity. Darwin and Wallace gave us a theory of evolution by natural selection, but Mendel gave us genes that explained how the inheritance happened and Francis and Crick and Franklin gave us the DNA helix that is the key ingredient for all of life.
My point is that the multiverse explanation for virtually everything we don’t know is going in the opposite direction. Now the explanation for something happening, whether it be a quantum event or the entire universe, is that every possible variation or physical manifestation is happening but we can only see the one we are witnessing. I don’t see this as an explanation for anything; I only see it as a manifestation of our ignorance.
Addendum: This is Max Tegmark providing a very cogent counterargument to mine. I think his argument from inflation is the most valid and his argument from QM multiple worlds, the most unlikely. Quantum computers won't prove parallel universes, because they are dependent on entanglement (as I understand it) which is not the same thing as multiple copies. Philip Ball makes this exact point in Beyond Weird, where he explains that so-called multiple particles only exist as probabilities; only one of which becomes 'real'.
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