The Many Worlds of Today’s Physics: Not Even Wrong?
There is much hand-wringing today regarding the current directions and pronouncements of physicists. Has physical science lost its way as some suggest?
This if the fifth in the series Top-Down vs. Bottom-Up.
In the previous post we introduced the increasingly common idea that the universe is actually a multiverse — an infinity of separate and untouchable universes. It’s one of a number of current “discoveries” of recent science that are causing angst among many. Questions are being raised: what is science? Do ideas that have no possibility of being verified, tested or measured qualify as legitimate subjects for scientists? And why are so many scientists appearing to do more philosophizing than traditional science, even while they claim “philosophy is dead?”
Here we will explore some of these questions and why they are being raised, starting with the multiverse. One of many forms of the multiverse is what is known as the “many worlds theory.” To even begin to understand this theory, we have to start with that problem of the wave/particle duality. Particles, therefore everything material since all matter is made of particles, are described as wave-like. Dispersed, not localized. The wave function is a mathematical description of the particle which describes the operation of the wave/particle over time. It predicts the probability of the particle being located in a specific location in space-time. When the particle is not located it is in superposition, or it’s wave-like state. When you stand on a beach, where is a wave? Here. There. Way over there. That’s what the superposition of a particle means. It is here, there, everywhere. A “smear” as some call it. The wave function tells in numbers how the wave evolves over time and the probabilities of the location of a particle if and when the wave should suddenly take on its particle-like existence. How does it go from superposition to, oh, here it is? Here comes the strange part. When a conscious mind observes it. Does the particle actually leave its “home” of superposition? Does it stop being here, there, everywhere? Not for quantum mechanics to work properly. Dr. Kelvin McQueen, a philosophy professor at Chapman University and student of David Chalmers of the “hard problem” of consciousness fame, concisely explains what happens. Referring to the famous “double slit” experiment which vividly shows the wave-particle duality and where a single electron is sent through slits onto a screen:
“…after just one electron is sent through [the slits], the screen enters into a superposition of detecting a single electron in multiple places. The human observer then looks at the screen and enters into a superposition of experiencing a spot at one point on the screen, a spot at another point, and so on. Advocates of this view interpret this as the human observer splitting into multiple observers, each of whom sees a different spot. Since each interacts with the environment, the environment bifurcates too. This is the so-called many-worlds interpretation of quantum mechanics, which has become rather popular among physicists.
Let’s look at this a bit closer. Not only is the electron in a superposition (here, there, everywhere), but so is the test equipment and even the human observer. After all, we are all particles. So, when the observer sees the electron on the screen it means that one version of the observer is connected through the observation to the one blip on the screen marking the electron’s location in space and time. But, there are still a lot of other potential locations for that electron, the probabilities of which are described by the Schrödinger equation of the wave function. And if the electron is in superposition it also means the observer remains in superposition. And since the electron and observer are entangled with the environment, when the observer gains knowledge of the location of the particle every part of this branches into another world. So there are multiple copies of the electron, the observer and the entangled environment with each copy of the observer pointing out the precise location of the electron on the screen. But as those points, equipment, observers are different from the first, they all now live in a branched off universe. It’s a totally different one, sealed off forever without possible contact with the one they just left.
This, in far too simple form, is the “many worlds” theory. This is why popular science books have titles like Cox and Forshaw’s Quantum World: (Why Everything That Can Happen Does Happen). Because if there are unlimited universes branched off from the everyday moment to moment experiences of this universe, then indeed, a lot of very strange things can happen. Sci fi writers are having a field day.
While it was understood in the early days of quantum studies that a conscious mind caused what was called the collapse of the wave function: the change from here, there and everywhere of the particle to, oh, here it is. Today, some physicists believe that because of entanglement the interaction of particles with the environment also causes the collapse of the wave function. Introduced in 1970 by H. Dieter Zeh, this is called “environmental decoherence.” Those supporting the many worlds theory believe decoherence caused by particles entangled in the environment causes the world to split into another universe every time this happens just as it happens with the conscious observation of the particle. Some claim this explanation of environmental decoherence would help with the measurement “problem” in that it could be seen that decoherence or the collapse of the cloud of probabilities into a particle with some definition could be caused by more than a conscious mind. For rather obvious reasons physicalists have never cottoned much to the well established fact of a conscious mind somehow affecting the actual state of the physical world.
Either by contact with the environment or by observation, the collapse is not the end of the wave function. It continues. What changes is the location (or experience of reality or gaining of knowledge) from one particular universe to another particular universe. Since the wave function continues on seemingly undisturbed by the observation or decoherence it is not so much a collapse as a branching. That is the here, there and everywhere continues because that particle is now split into multiple different universes where the only difference is the specifics of that particle. We will let Sean Carroll in Something Deeply Hidden explain: (page 119)
“That simple process — macroscopic objects become entangled with the environment, which we cannot keep track of — is decoherence, and it comes with universe altering consequences. Decoherence causes the wave function to split, or branch, into multiple worlds. Any observer branches into multiple copies along with the rest of the universe. After branching, each copy of the original observer finds themselves in a world with some particular measurement outcome.”
How often does this happen? Professor Carroll confesses we don’t really know, but he gives a hint:
“We know there is a lot of branching going on; it happens every time a quantum system in a superposition becomes entangled with the environment. In a typical human body, about 5000 atoms undergo radioactive decay every second. If every decay branches the wave function in two, that’s 2 [to the 5000 power] new branches every second. It’s a lot.”
As we let that soak in a bit, we will turn back to philosopher McQueen:
Although consistent with physicalism, this is a radical hypothesis. However, any solution to the measurement problem is bound to have radical implications.
Other physicists, including those who have deeply studied the phenomenon of environmental decoherence are not ready to come to the conclusion that Carroll espouses. Henry Stapp suggests that while it is understandable that some would jump on this idea, those physicists who developed and studied the idea of environmental decoherence do not draw those conclusions:
It is indeed sometimes claimed that the interaction of a system with its environment effectively solves the `measurement’ problem (which is essentially the problem of how to connect the physically/mathematically described aspects of quantum theory to human experience). However, the principal investigators of the effects of this interaction (e.g., E. Joos, 1996; D. Zeh, 1996; W. Zurek, 2002) make no such strong claim.
Stapp concludes his discussion on the issue of environmental decoherence:
These comments make clear the fact that interaction with the environment (and the resulting technical effect known as environmental decoherence) does not by itself solve the measurement problem, namely the problem of accounting for the fact that an observer perceives just one classically describable world, not the continuous collection of them generated by process 2 [Schrödinger’s equation of the wave function] acting alone which includes all effects of the environment.
Carroll seems to suggest the same when he talks about the environmental collapse and then references what happens to “any observer.” It appears the observer is still part of the picture (quotation above).
As McQueen suggests, the many worlds theory, multiverse or “landscape” as Susskind prefers it, is radical indeed. But as more and more physicists insist that the multiverse is a necessary component of our understanding of the universe, others are increasingly uncomfortable. The primary reason is the fact that by the very definition of branching in the many world’s theory, the infinite universes cannot have any contact, any touch, any communication. We apparently have no way of showing they exist. No measurement. No microscope. No worm hole. It looks like a thought experiment that has taken on the semblance of reality. It’s as if Schrödinger’s cat was found sitting under a tree and yes, it actually is both dead and alive. That means that scientists are concluding from empirical science a description of reality that lies far beyond empirical science. A great many physicists and philosophers are very concerned about this direction, not just when it comes to the many worlds but in other areas of physics as well such as string theory.
In a Scientific American blogpost in 2018, John Horgan points to physicist Sabine Hossenfelder’s book Lost in Math. It is only one of a nearly endless series of books, articles, youtube videos and TED talks that feature serious hand wringing over where the science of physics is at and where it is going. This angst started some time ago. In 1994 David Lindley authored a book called The End of Physics: The Myth of Unified Theory. The Amazon introduction to this book states:
“Lindley argues that a theory of everything derived from particle physics will be full of untested — and untestable — assumptions. And if physicists yield to such speculation, the field will retreat from the high ground of science, becoming instead a modern mythology. This would mean the end of physics as we know it.”
Lee Smolin, a highly accomplished physicist, wrote The Trouble with Physics. Smolin also said,
“I am convinced that quantum mechanics is not a final theory. I believe this because I have never encountered an interpretation of the present formulation of quantum mechanics that makes sense to me. I have studied most of them in depth and thought hard about them, and in the end I still can’t make real sense of quantum theory as it stands.
Another leading physicist, Peter Woit, wrote: Not Even Wrong. The Amazon introduction to his book says:
“When does physics depart the realm of testable hypotheses and come to resemble theology? Peter Woit argues that string theory isn’t just going in the wrong direction, it’s not even science.”
Roger Penrose’s name is often listed with other scientific geniuses like Einstein, Schrödinger and Hawking. In a 2009 Discover magazine interview, Penrose was asked about the many world’s theory. He referred to the famous cat of Schrödinger, pointing out that Schrödinger presented the dilemma of the cat being dead and alive at the same time as suggesting there was something wrong with the whole quantum idea. But, accepting that idea as reality leads to the many worlds, as Penrose explained:
“It [many world’s theory] says OK, the cat is somehow alive and dead at the same time. To look at that cat, you must become a superposition [two states existing at the same time] of you seeing the live cat and you seeing the dead cat. Of course, we don’t seem to experience that, so the physicists have to say, well, somehow your consciousness takes one route or the other route without your knowing it. You’re led to a completely crazy point of view. You’re led into this ‘many worlds’ stuff, which has no relationship to what we actually perceive.”
He goes on further to note the divergence of today’s science from what science has traditionally been:
“The idea of parallel universes — many worlds — is a very human-centered idea, as if everything has to be understood from the perspective of what we can detect with our five senses. The trouble is, what can you do with it? Nothing. You want a physical theory that describes the world that we see around us. That’s what physics has always been: Explain what the world that we see does, and why or how it does it. Many worlds quantum mechanics doesn’t do that. Either you accept it and try to make sense of it, which is what a lot of people do, or, like me, you say no — that’s beyond the limits of what quantum mechanics can tell us.”
We started this post with a comment by Nima Arkani-Hamed. He’s one of the bright stars in physics today following in the footsteps of of Albert Einstein, J. Robert Oppenheimer, Hermann Weyl, John von Neumann and Kurt Gödel and many other science luminaries at the Institute for Advanced Studies. No spacetime? It’s not just the loss of spacetime, but the world of infinite universes, of six or more unseen dimensions, of most things in the universe proving undetectable that leads many to ask what physics is about anymore.
Sean Carroll says that all reality can be understood as a wave function in Hilbert space. He claims that means that there has to be innumerable universes as new ones are being created by the billions upon billions every second. Developers of the cosmic inflation model state that the near-instantaneous expansion of our universe in the first nanoseconds of time after the big bang requires an unlimited number of universes. The multiverse idea started by the requirement to avoid the conclusion of a designer when facing the miraculous coincidences of fine-tuning. Some string theorists appear to be turning to other more promising ideas to reconcile the classical and quantum laws of physics, this theory is still mentioned as requiring a multiverse as well as somewhere between 26 and 10 dimensions of space and time. Max Tegmark says that the universe isn’t described by math, but actually IS math. Taxpayers are spending likely hundreds of millions of dollars to try to better understand dark matter and energy. Dark energy makes up 68% of the known universe and dark matter 27% with the common ordinary stuff of the universe we know and love just 5%. But, what is this stuff? The evidence for it is the accelerated expansion of the universe driving galaxies further and further apart. But, it emits no light and has thus far escaped scientific explanations and detailed description.
The quotation by Arkani-Hamed came from a book by Donald Hoffman, titled The Case Against Reality: Why Evolution Hid the Truth from Our Eyes. Hoffman is Professor of Cognitive Science at the University of California, Irvine and was educated at MIT. Hoffman takes the question of physicalism to an entirely new level when he suggests that evolution and quantum mechanics combine to eliminate reality as we understand it. While he does not deny that there may be an objective reality that is so far inscrutable to us, what we think of as the reality of matter, forces, particles and smears is actually just an evolutionary-driven representation. The blind watchmaker of evolution has directed us to access through our senses a kind of vague representation of whatever reality there is behind it. These representations are no more an accurate depiction of reality than a desktop file icon accurately reflects all the details of the contents of the file and their construction. That blue icon may represent the file on your desktop but it most certainly is neither the words or images contained in that file, nor the bits of code that make the file possible, nor the ones and zeros that make up the content of the file, nor the electrons zooming around your computer and the server cloud that carries those ones and zeros, nor the individual particles smeared across the universe that are the fundamental elements of the computer, the cloud, the screen you look at, and the chair you are sitting on. His “interface theory of perception” says evolution has tuned us only for fitness, not for knowing reality at any level. Indeed, he suggests that evolution’s direction is for survival, not for arriving at rational truth.
We are getting far afield from physicalism here, and that is the point. While students at every level and interested readers of science are continually fed a story about the rock bottom truth of physicalism, that presupposition is increasingly under attack from just about every area of study. But even those who hold tenaciously to physicalism, fearing what the loss of it might mean for science, the results of their inquiries are leading them farther and farther from what non-scientists understand them to be saying about reality. Are dark matter and dark energy part of our physical universe? The evidence of it is in the expansion of the universe and movement of galaxies. But no one knows what it is. It is beyond our senses and our sensitive detection technologies. Is the idea of an infinitesimally small point that doesn’t and can’t exist in space and time but from which all matter, all forces, all dark matter and energy issued from — is that physical? It is science, for sure. But, it escapes what has been considered physical, and it escapes all known laws of physics. Yet, the idea of the Big Bang requires it or at least some starting point beyond the known laws of physics. What about 1o to 26 dimensions of space and time? Do they exist only on the whiteboards of super-brainy mathematical physicists? Or, are they in some sense “real?” No other proof or evidence of them exists or can likely ever exist. Is that physical? Or is Tegmark’s conclusion that what shows up on these whiteboards is more real than stubbing your toe on the corner of your bed? Then, there is the multiverse. By its very definition, particularly in the many world’s theory, there can be no crossover or contact from one branched off world to another. We are forever and inevitably separated. Therefore, it also can only exist in the computer models and whiteboards of those physicists and mathematicians. Is that physical?
The concept that everything that is can be submitted to physicalist descriptions and causes has advanced science beyond the wildest imaginations of our predecessors, and provided us with the marvelous tools and technologies that make our world in the second decade of the twenty first century so amazing. But, science now is proceeding where physicalism dare not tread. This is what has caused the angst among many in the science community. With talk of “the Landscape” as physicist Leonard Susskind wants to rename the many world’s theory, and talk of panpsychism or proto-consciousness, and the search for dark energy, and exploring the universe as only a mathematical construct scientists it seems quite clear that scientists have already fallen off the edge of pure physicalism. They may fear where it leads, but can they really deny they are here? As Peter Woit commented, this is now “theology,” at least of a sort. It is most certainly metaphysical, and philosophical.
Still, physicalism will not go away easily. A book by Brian Greene issued in early 2020, Until the End of Time, brilliantly and beautifully explores the outer reaches and fundamentals of today’s science. Greene notes that Steven Pinker commented the more the universe becomes comprehensible, the more pointless it all seems. That is the bottom line of physicalism and this conclusion is fully supported in Greene’s elegant writing. He “evangelizes” with this key theme: as there is no possible meaning in a totally random and purposeless universe that is heading toward nothing but destruction, we must find meaning in ourselves and in the joy of realizing that we live in a fortuitous universe that, reflecting the inevitability and pointlessness of our own death, is destined to a cold and empty ending through the second law of thermodynamics. This is not science. It is philosophy. But it is found in the science section of Barnes and Noble. The problem with this philosophizing by a very talented scientist and articulate writer is that it is understood to be science. That exacerbates the growing gap between where science is really at and what is declared as science in education, entertainment, the media and politics.
It is ironic physicists such as Greene are engaging in more or less pure philosophy while at the same time saying they have no use for philosophy. Carlo Rovelli, an Italian physicist and one of my favorite writers on physics, commented on this trend in a 2018 Scientific American article title Physics Needs Philosophy/Philosophy Needs Physics:
“Against Philosophy is the title of a chapter of a book by one of the great physicists of the last generation: Steven Weinberg. Weinberg argues eloquently that philosophy is more damaging than helpful for physics — it is often a straightjacket that physicists have to free themselves from. Stephen Hawking famously wrote that ‘philosophy is dead’ because the big questions that used to be discussed by philosophers are now in the hands of physicists.2 Neil de Grasse Tyson publicly stated: ‘…we learn about the expanding universe, … we learn about quantum physics, each of which falls so far out of what you can deduce from your armchair that the whole community of philosophers … was rendered essentially obsolete.’”
Since we are on the topic of philosophy, it seems appropriate to let Aristotle have the last word. In his work titled Ethics, he wrote:
“It is the mark of an educated person to look for precision in each kind of inquiry just to the extent that the nature of the subject allows it. It looks like the same kind of mistake to accept a merely persuasive account from a mathemetician and to demand demonstrations from an expert in oratory.”
So far in this Top-Down series, we have been exploring questions of physicalism as it relates to physical reality itself. If physicalism runs aground in the darkness of quantum weirdness leading to all kinds of theological, metaphysical and philosophical speculation and pronouncements, it crashes hard into the rocks of consciousness. The age old mind-brain or consciousness-physicalism question looms like a darkening cloud over the physicalist enterprise. It adds great depth and complexity to the essential question of top-down versus bottom-up thinking.
