Does the Universe Create Itself? (script) (Patreon)

Imagine you’re leading a game of 20 questions and you forget the thing you chose half way through. You have to keep answering yesses and nos and hope that you think of something that’s consistent with all your previous questions before the game is done. Well it could be that’s what the entire universe is doing. I hope it thinks of something good before we run out of questions.

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Scientists are fairly attached to the idea that the universe is real. We’re fond of the realist viewpoint: that there’s an objective reality out there that’s entirely independent of our subjective experience of it. That seems innocent enough, and it served physics awfully well. But take this viewpoint to the extreme and we imagine the scientist as this perfectly detached observer of the world, capable of monitoring and modeling physical reality without ever disturbing it.

But then came the 20th century, and quantum mechanics. In quantum mechanics, not only does the act of measurement profoundly influence the thing being measured, but it seems we can’t even assign physicality to the world between measurements. As Niels Bohr put it “no phenomenon is a phenomenon, until it is an observed phenomenon”. Bohr led the charge with this observer-dependent view, encapsulated in his Copenhagen interpretation of quantum mechanics, which insisted that the world only became meaningfully defined through the act of measurement. Others were desperate to maintain a physical and realist universe, including Albert Einstein himself. We’ve talked about this debate between the founders of quantum theory before, and of some of the supposed resolutions, which I’ll come back to. Today I want to begin a discussion of a family of quantum interpretations which say that the universe exists not so much in physical particles and quantum fields, nor solely in the mind of the observer, but rather in the interaction of the two.

To give a better sense of why we need to go to these crazy lengths to explain the universe, let’s review some quantum weirdness. We’ll start with the good ol’ Schrodinger’s cat thought experiment, devised by ardent realist Erwin Schrodinger to highlight the absurdity of the Copenhagen viewpoint. We have a cat in a closed box that is either killed or not killed by a random quantum process. For a scientist running the experiment, the cat is in a twin state of both alive and dead until the box is open - a superposition of states. Or so quantum mechanics seems to suggest. This seems even more absurd when you add the so-called Wigner’s friend extension, where a second scientist waits on the report from the first, rendering both cat and first scientist into a superposition of states. And doesn’t the cat get to observe its own state? Perhaps to the cat, the scientists are in a similar superposition,

The heart of the problem was a simple question: in a world where observation plays a role in defining reality, how is it possible for separate observers to share a single, consistent reality?

Solutions to this seeming paradox spanned the spectrum. For example, the Hungarian physicists John von Neumann and Eugene Wigner doubled down on the observer-centric view, in which the act of observation in some way creates reality. Others found schemes by which a real, physical universe could be interpreted in the behavior of the wavefunction, such as de Broglie-Bohm pilot wave theory or objective collapse interpretations. Still others sought to explain the observer’s influence as a sort of selection bias - for example, Hugh Everett’s many worlds interpretation and the ideas of quantum decoherence. And then we have Richard Feynmann’s “no interpretation” interpretation of quantum mechanics, in which he suggested that his colleagues quit philosophizing and to “shut up and calculate”.

In the end, most physicists took that advice. They were eager to put the whole mess behind them and get on with the job of actually using quantum mechanics to invent the modern world. But a very select few physicists refused to let it go. One of those was John Archibald Wheeler, the prolific physicist whose students included Feymnann, Everett, Jacob Bekenstein, and Kip Thorn among others. Wheeler was never completely satisfied with any of the proposed quantum interpretations. Although he started out as a pure realist, he came to believe that the observer must in some way be fundamental.

And yet he couldn’t accept what he saw as the solipsistic view of von Neumann and Wigner, in which the observer was in a sense the primary causal agent and center of its own reality. After decades of thought, Wheeler came to a view that  is summarized in his expression “it from bit.” In his words, “Every it — every particle, every field of force, even the spacetime continuum itself — derives its function, its meaning, its very existence entirely… from the apparatus-elicited answers to yes or no questions, binary choices, bits.” In other words, he came to believe that the universe is fundamentally informational.

He felt that reality must have its primary existence not in the observer nor in the subject of observation, but rather in the connection between the two. One of the thought experiments that led Wheeler to his view is his delayed-choice experiment, which is an analogy to the double-slit experiment. Here’s one example of this. Imagine a single photon hitting a beam splitter - a semi-reflective mirror that has a 50-50 chance of transmitting or reflecting the photon. If we add a pair of detectors we see that each photon randomly arrives in detector 1 or detector 2, revealing whether it was transmitted or reflected. But remember I said that the quantum world appears to live in a state of uncertainty until it’s observed? In this case, quantum mechanics states that the photon is in a state of having been both transmitted and reflected until we make an observation to check which happened.

We can see this  if we add a second beamsplitter to scramble the beams so that we don’t know which path brings the photon to detectors 1 versus 2. Now detector 1 always registers a photon and detector 2 never does. Why? Because the combination of phase shifts in the beamsplitters causes the photons wavefunction to perfectly line up in detector 1 - constructive interference, and to perfectly cancel out in detector 2 - destructive interference. For that to work this pair of “possible photons” had to travel both paths.

This was called the delayed choice experiment because, in principle, the second beamsplitter could be put in place only after the photons passed through the first. After they’d made their decision of a path to take. This experiment, and many clever variations of it, have now been performed. They seem to verify that the universe really does exist in a superposition of all possible states until the measurement is made, and the choice of that measurement can be made after the superposition is formed. That means that the reality that emerges depends in a profound way on the choice of measurement.

Here’s another experiment. If we measure the spin of one member of a pair of entangled particles - the choice of the direction of the spin measurement seems to have an instantaneous influence on its partner, even if that partner is on the other side of the lab - or the galaxy. We’ve talked about this entanglement stuff in a previous episode. So it seems that when you interrogate the universe, the answers that you get depend on the questions you ask. Wheeler became convinced that that process of interrogation in some way created reality.

To help explain what he meant, Wheeler invented a pathological version of the game 20 questions. In the usual game, someone, let’s say Alice, thinks of an object, and another person, Bob, asks yes/no questions to narrow down the possibilities until he arrives at only one possible answer: the object that Alice had in her mind from the beginning.

But Wheeler’s version is a little different. He called it “negative 20 questions,” and it works like this. Unbeknownst to Bob, Alice never thought of an object to begin with. Instead, she answers the quest ions as they come, maybe completely randomly, maybe according to some secret pattern. Every answer narrows the space of possible correct answer, even if Alice still doesn’t know what the object is.

Let’s say the rule is that Alice will answer yes and no alternately no matter what the question. So Bob asks, “is it smaller than a bread box?” “yes.” Then “is it living?” “no.” This line of questioning has narrowed Bob to the realm of papercl ips and pebbles. But had Bob reversed the order of the questions he’d have interrogated his way towards tigers, trees and T-rexes. And depending on Alice’s rules, you can imagine scenarios where it looks like Bob’s choice of question influence the past. But it doesn’t, his questions are helping reality define itself on the fly.

Wheeler came to the view that the universe was one giant game of negative 20 questions, in which the reality we observe is the only reality that is consistent with the questions asked of it by all observers. The universe, according to Wheeler, was a giant, closed, “self-excited circuit.” The relationship between the observer (us) and the observed (the universe) brought *both* into existence. Take this yet further and you have a version of the Strong Anthropic Principle: The only reality that can exist is one that can have observers whose questions can make that reality real.

Wheeler called this the “participatory universe.” He symbolized his idea with a sketch of a giant “U”. On one side of the U is the big bang. As the universe expands, the line of the U gets thicker, until we reach the present day, the other side of the U. An eyeball here symbolizes the observer. All the astronomers with their telescopes and observatories are aimed back at the Big Bang.

Their observations *now* cause the Big Bang *then*. Well, sort of. As Wheeler once wrote, “the past has no existence except as it is recorded in the present.” Only the self-consistent now can have a real existence.

As I said, this all sounds very mystical. Let me be clear: Wheeler wasn’t saying that conscious minds have direct power over reality, as claimed by some of the worst practitioners of quantum woo. But the role of consciousness was something Wheeler really struggled with. He said “About no feature of “It from Bit’ do I feel less comfortable than whose bit.” After all, information implies a thing to KNOW that information. But non-conscious entities can, in a sense, know something if information of that something is recorded in their being. He once wrote that it was “Not consciousness but the distinction between the probe and the probed” that was central to the act of observation. So “Observation” could well be code for “interaction”, in which every time two particles bump together and become entangled we have an act of measurement.  If this all seems a little vague and wishy washy, it’s because it is. Wheeler was still obsessively thinking and writing about and trying to solidify these ideas until his death in 2008.

In John Archibald Wheeler’s version of an informational universe, he felt that the information - the bits - resided in the answers elicited by acts of observation. It appears to pull the comforting ground of realism from under our feet. But others have taken Wheeler’s ideas and put them back on firm ground. It’s possible to think of the universe as being “informational” without altogether giving up on realism. In the broad category of “participatory realism” we have things like quantum bayesianism and relational quantum mechanics, in which the universe emerges from the information that some set of real entities have about each other. Importantly, these acknowledge the importance of the observer in defining the observed, while still allowing that there’s some kind of substrate to reality. We’ll talk about these ideas soon, in our long quest to find that substrate. The trick is to just keep asking the right questions of a participatory space time.