There is a lot of strange stuff in quantum mechanics, we’ve all known this for a while and at the heart of the theory is Schodinger’s equation which has its roots in a scientific discovery that happened early in the 20thcentury. It turns out that when you pass a stream of electrons - which are discrete subatomic particles - through two slits, they make an interference pattern on the detector as if they were a wave. So when people saw this, they went, “Hey wait a minute! How can a discrete particle like an electron act like a wave?” In one of the greatest scientific surprises of all times, it seems that particles, indeed all of matter, can also act like waves. Cutting a really really long story short, Schrodinger’s equation describes the wave-like properties that all matter has. It answered the question, “What does the wave-like properties of a particle look like mathematically?” Schrödinger’s equation is to quantum mechanics what Newton’s second law of motion is to classical mechanics: it describes how a physical system, say a bunch of particles subject to certain forces, will change over time. Now I know this is a bunch of poindexter stuff and I don’t expect you to fully get this, I’m not going to sit here and claim that I understand it either (I got a C in my quantum class so that should tell you something), but if you don’t get anything else from this, just remember this one thing. Unlike a classical description of a physical system like what Newton gives us, the wave function does not give us definite information about the location of a particle at a given time — it only gives us the probability of finding the particle in a given location at any given time. Schrodingers equation is a probablility distribution and when applied to more complicated things like cats in boxes and stuff like that, we get probable outcomes from Schodinger’s equation. Now look, I get that I’m really oversimplifiying a complicated subject, so all you quantum nerds out there just keep your pedantic comments to yourself, I’m setting the stage up here for a larger point, not to teach quantum mechanics. But people need to know these items before I get to my point. So if this equation is a probablility distribution, in other words, a picture of the possibilities of where a particle might be, then questions like ‘where is the particle when we aren’t looking?’ don’t have any meaning. Is the cat alive or dead? Again quantum mechanics has only one answer to this: The particle is in all of those places and the cat is both alive and dead. And scientists don’t just mean this rhetorically - this is important - they mean it LITERALLY. When we’re not looking at it, a hypothetical particle is everywhere as defined by that equation and the cat is ACTUALLY BOTH alive and dead. According to quantum mechanics, until you look at something or try to measure it, any particle you try to pin down to one spot is not possible. That particle is actually in all locations defined by Schrodinger’s equation. All of them. I can’t overstate this enough, the particle is actually in all those places. At once. Setting aside for the moment the complete brain melt down this gives me, we have to ask one more thing. “What happens to the particle or the cat when we are looking?” And the next question that always pops into my mind is, “Why does it matter if I look or not?” I don’t know the answer to the second question, I don’t think anyone does, but the answer to the first one is, the wave function collapses. By looking upon a particle or opening a box with a cat in it, we’ve gone from “all of it is happening” to “just one of the things” happening. Why does it collapse? No one knows. Which of the possible things do we see? That’s determined by the probability. I’ll give you an example, if you’re out fishing on a river and you’re looking for a fish, according to quantum mechanics, you’re more likely to see a fish, but seeing a rhinocerous is not precluded by quantum mechanics, you might actually see one, it’s just not very likely. But the crazy thing is, you actually could see a rhino in a river full of fish according to this theory. What I’ve just outlined to you is a somewhat retarded and most definitely incomplete discription of what is known as the Copenhagen Interpretation of Quantum mechancs and was developed by lots and lots of really smart people in the early 20th century. OK let’s fast forward to the 1950’s to a smart guy named Hugh Everett III who asked the really important question that apparently everyone else was avoiding, “What if when you observe something, the wave function doesn’t collapse?” Everett wrote his doctoral thesis and got his PhD and then promptly left academia, I guess he said, ‘My work here is done’. Now I’m currently reading Sean Carroll’s book on this and I invite you to do the same (link in the description box), I’m not done with it yet but my overlying point doesn’t require that I finish it, only get through these ideas so I can make my point. So, what if the wave function doesn’t collapse? What would that look like? If the wave function doesn’t collapse when you make an observation, then all of the possibilities are real. All of them. Real. At one time Everett said that it’s our concept of reality that’s the problem. We only think that there’s a single outcome of a measurement. But in fact all of them occur. We only see one of those realities, but the others have a separate physical existence too. This implies that the entire universe is described by a gigantic wave function that contains within it all possible realities. This “universal wave function,” as Everett called it in his thesis, begins as a combination, or superposition, of all possible states of its constituent particles. As it evolves, some of these superpositions break down, making certain realities distinct and isolated from one another. In this sense, worlds are not exactly “created” by measurements; they are just separated. This may be total crap, but the image that came to my mind when thinking about this was that of a comb. The comb is the wave function and the teeth of the comb are all realities. When you choose one tooth, the others are all still there just right along side of you. And of course the comb is infinitely long. I dunno, it helped me. If all the possible outcomes of a quantum measurement have a real existence, where are they, and why do we see (or think we see) only one? This is where the many worlds come in. All the other outcomes of a measurement must exist in a parallel reality: another world. To use a very simple example, if you measure the path of an electron, and in this world it seems to go this way, but in another world it went that way. And for that other world, you’d need a parallel, identical apparatus to detect that electron. And, naturally, it requires a parallel you to observe it — because only through the act of measurement does the wave function seem to “collapse.” If this is the way things are, then duplication seems to have no end: you have to build an entire parallel universe around that one electron, identical to the one you’re in in all respects except where the electron went. You avoid the complication of wave function collapse, but at the expense of making another universe. OK so now I’ve botched up talking about the Many Worlds Interpretation of Quantum Mechanics and I think I’ve done enough damage to make my point. If this theory is right and these other worlds - an infinite number by now - exist, then how can we test this theory to see if it’s right? What data back up this claim? For this to be a scientific theory and be considered science, I think we need to be able to test this theory, right? Well you can’t. There is no way ever to interact with those other parallel realities. This theory has no hope of coming into contact with actual, empirical data that we can see. It may trouble you to know, it was for me, that many prominent physicists, Martin Rees, Britain’s Astronomer Royal, David Deutsch and others - among them my personal cosmological hero Sean Carroll from Caltech - have all claimed strong support for the idea. Going so far as to say that it is real and we should just get over it. This is the way things are. No data. No problem. The theory is true because it’s the “best explanation” with no indication of who it is best for or who is making the judgement that it ‘still might reasonably be true”. But from where I sit, and admittedly I’m sitting in a pretty small chair, this isn’t science. The many-worlds interpretation of quantum mechanics has no hope of making any contact with verifiable data. On what grounds can the claim be made that this is science? But let’s be clear for a moment, answering the question of what science is is surprisingly hard, many smart people have tried and failed to give us a definition of science that is coherent and consistent. So to cut another very long story short, no one really knows what science is, and so we are basically left with the notion that while we don’t exactly know what science is, whatever it is, we’ll know it when we see it. I’m serious, that’s the punchline to the entire history of philosophy of science in a few sentences. And many-worlds isn’t the only area in science where this has happened. Our best theory for what matter is leaves out 95% of what’s actually out there. Where’s the other 95%? “Well, it’s around and between galaxies making them spin a certain way.” What is it? “Dunno.” Same with the energy content of the universe: why is the universe accelerating? Dunno. What is it? Dunno. Our best theories about really important things are disturbingly incomplete and while people are making honest attempts to understand what’s going on, the language we’re hearing is remarkably non-scientific. “We may never measure dark matter” “We may never see what dark energy really is” We can never ever interact with dark matter in any way. Jeebus that’s sad. Similar stuff is said when talking about multiverses and string theory. None of it’s testable, observable nor verifiable. But oh it’s there trust me. Folks, we are living in an era of post-empircal science. All of this is suspiciously snake oil salesman-ey. And maybe we will one day uncover what dark matter and dark energy is, but according to the many-worlds interpretation of quantum mechanics, we will never, ever, ever be able to interact with our parallel selves or see anything having to do with these other universes. Same with string theories and cosmic landscapes. Is the many-worlds interpretation of quantum mechanics science? While we may not be able to say what exactly science is, I can say that I prefer to have my science with a little bit of data. For me to recognize science when I see it, it has to come with some observations or something verifiable. But hey that’s just me, and apparently I’m in the minority on this issue. You may very well ask, oh c’mon what’s the big deal? Who cares if a bunch of cosmological poindexters write some papers that only get read among themselves, that have a bunch of math in it and have no practical value to us at all. My answer is, first you can bet they aren’t the only ones reading these papers, the science news outlets get this stuff all the time and mangle it up, but the big deal here is that we now live in a world of enormous distrust in science and everyday knowledge in general. From climate change deniers, antivaxxers to flat earthers, there is a massive distrust coming from these groups and they flourish by sowing misinformation, pseudo-science and just plain nonsense. And I can tell you this, if I were someone who believed in intelligent design and in an omniscient creator, I’d be very interested in this discussion surrounding the many-worlds theory because I’d be listening to a lot of respected scientists accepting unverifiable, untestable ideas and saying it’s science and wondering if there’s not more than a little bit of a double-standard being applied here. If many-worlds is just as untestable as an intelligent designer, then why isn’t the latter considered science? So while all of this stuff is really interesting to think about and play with, I don’t think it’s science by any real meaning of the word. If science is defined by “I’ll know it when I see it.” Then I have to conclude, this ain’t it. I’m reminded of Thomas Kuhn’s book, The Structure of Scientific Revolutions. Maybe this era of post-empircal science is a stressor. Maybe all these untestable ideas we’re hearing about almost every day is a strain on the current scientific paradigm that is really struggling to explain a lot about our universe. The amount and nature of almost all the matter in the universe, the reason for universal expansion and even the rate at which it is doing it, seems too elusive for our current scientific paradigm. Now, it should be said that maybe that strain will be relieved when a new discovery is made. Maybe Kuhn’s right and science progresses in jumps and fits and starts that ultimately lead to progress. I dunno about that for sure, but things are getting really weird in science right now and I sincerely hope Kuhn is right, and the next discovery brings back some data-enhanced science again.