Sean Carroll and the many worlds interpretation of quantum theory

[Magical Realist]

Interview by Tom Casciato with Sean Carroll. Video available.

https://www.pbs.org/newshour/show/sean-c...l-there-is

"The "many worlds" theory in quantum mechanics suggests that with every decision you make, a new universe springs into existence containing what amounts to a new version of you. Bestselling author and theoretical physicist Sean Carroll discusses the concept and his new book, "Something Deeply Hidden," with NewsHour Weekend's Tom Casciato."

[C C]

Interview by Tom Casciato with Sean Carroll. Video available.

https://www.pbs.org/newshour/show/sean-c...l-there-is

"The "many worlds" theory in quantum mechanics suggests that with every decision you make, a new universe springs into existence containing what amounts to a new version of you. Bestselling author and theoretical physicist Sean Carroll discusses the concept and his new book, "Something Deeply Hidden," with NewsHour Weekend's Tom Casciato."

Max Tegmark, of course, favors the multiverse conception, too. Including more categories of parallel universes than just the Everett kind: https://space.mit.edu/home/tegmark/multiverse.pdf

And that's what Tegmark's mathematical universe hypothesis seems to have stemmed from. The simple block-universe depiction of time can't accommodate a multiverse, so he had to expand to considering broader and more sophisticated mathematical structures than it: https://arxiv.org/pdf/0704.0646.pdf

Even the conventional, specious "flow of time" itself is like a procession through the equivalent of a developmental sequence of parallel universes. That in the short term only incrementally differ from each other slightly at the subatomic level, but in the long run accumulate into differing significantly at the macroscopic level. It is their apparent arrangement that follows a developmental logic of a single cosmos progressing from a compact Big Bang state to the diverse complexity of today which drives the commonsense inference that it's always the same universe rather than "travel" through a chain of many different versions of it.

Such an analogy being a set-up for jumping to Julian Barbour's Platonia...

Addressed in the excerpt at bottom, Platonia (The End of Time) is arguably an unconventional multiverse scenario (others like Lee Smolin have apprehended it as that). In Platonia, every possible configuration of the universe -- from primitive to complex -- resides in that mathematical structure. If time flowed in that structure (which it does not), then it would NOT follow a predictable, straight line through that sea of parallel universes, but instead wander along a crooked path of quantum probability.

In Platonia, the past that we each individually remember is actually just one path among a multitude of alternative, meandering routes that we might otherwise be personally concatenated with in terms of recall. The memory my brain features in a particular static universe configuration (or Now) is only going to include memories of prior brain states that it is consistent or compatible with. That's why the chain of events we remember seem organized or rational rather than random, disconnected, nonlinear, or crazy.

Each brain state of a human body in a specific Now is only cognitively concerned with itself (perception of only itself and the immediate environment). That is, in solipsistic style it only represents itself and the world of that particular Now as real, and regards those stored in its memory (the past) as not existing and those it anticipates in the future as likewise being non-existent. But in turn, another brain state in a different Now contains it as a disparaged part of its memory ("not real"), and thereby the two are -- in a sense, connected by that relationship.

The immortality that Barbour refers to, however, really isn't much different from that inherent in ordinary Eternalism. One difference is that in block-time everything is fixed (there's only one objective sequence of "parallel worlds" developing into each other), whereas in Platonia there may be multiple, quirky, alternative routes that speciously deliver one to what is apprehended as the current Now (which is "immortal" like all the rest).

From Here to Eternity
https://www.discovermagazine.com/the-sci...ternity-02

EXCERPTS: Barbour is not alone in recognizing that the pictures of time in general relativity and quantum mechanics are fundamentally incompatible. Theoretical physicists around the world, spurred by Nobel dreams, sweat over the problem. But Barbour has taken perhaps the most unorthodox approach by proposing that the way to solve the conundrum is to leave time out of the equations that describe the universe entirely...

[...] Every possible configuration of the universe, past, present, and future, exists separately and eternally. We don't live in a single universe that passes through time. Instead, we— or many slightly different versions of ourselves— simultaneously inhabit a multitude of static, everlasting tableaux that include everything in the universe at any given moment. Barbour calls each of these possible still-life configurations a "Now."

Every Now is a complete, self-contained, timeless, unchanging universe. We mistakenly perceive the Nows as fleeting, when in fact each one persists forever. Because the word universe seems too small to encompass all possible Nows, Barbour coined a new word for it: Platonia. The name honors the ancient Greek philosopher who argued that reality is composed of eternal and changeless forms, even though the physical world we perceive through our senses appears to be in constant flux.

Before allowing himself to be interrupted by the stream of questions he knows will come, Barbour continues to press his point. He likens his view of reality to a strip of movie film. Each frame captures one possible Now, which may include blades of grass, clouds in a blue sky, Julian Barbour, a baffled Discover writer, and distant galaxies. But nothing moves or changes in any one frame. And the frames— the past and future— don't disappear after they pass in front of the lens.

[...] Don't we then somehow shift from one "frame" to another?

No. There is no movement from one static arrangement of the universe to the next. Some configurations of the universe simply contain little patches of consciousness— people— with memories of what they call a past that are built into the Now.

The illusion of motion occurs because many slightly different versions of us— none of which move at all— simultaneously inhabit universes with slightly different arrangements of matter. Each version of us sees a different frame— a unique, motionless, eternal Now.

"My position is that we are never the same in any two instants," Barbour says. "Obviously, as macroscopic human beings, we don't change much from second to second. And there's no question that we're the same people. I mean only an extreme madman would deny that," he says reassuringly. "To that extent, it's true that we do move from one Now to another. But in what sense can you say we're moving? The way I see it, not exactly the same information content, but nearly the same information content, is present in many different Nows." Nothing really moves, he says.

"The information content or the consciousness that makes us aware of being ourselves, of having a certain identity, is just present in many different Nows. There are two things that distinguish my position from what people might just intuitively think. First of all, the Nows are not on one timeline. They're just there. And second, there is nothing corresponding to motion. I'm taking a very radical position on that. I'm saying the Nows are really like snapshots. The impression of motion only arises because the snapshots have got an extraordinarily special structure." We are part of that special structure.

[...] Julian Barbour is convinced we are all immortal. Unfortunately, in a timeless universe immortality does not come with the same kind of perks that it does on Mount Olympus. In Barbour's vision, we are not like Greek gods who remain forever young. We still have to buy life insurance, and we will certainly seem to age and die. And instead of life after death, there is life alongside death.

"We're always locked within one Now," Barbour says. We do not pass through time. Instead, each new instant is an entirely different universe. In all of these universes, nothing ever moves or ages, since time is not present in any of them.

One universe might contain you as a baby staring at your mother's face. In that universe you will never move from that one, still scene. In yet another universe, you'll be forever just one breath away from death. All of those universes, and infinitely many more, exist permanently, side by side, in a cosmos of unimaginable size and variety.

So there is not one immortal you, but many: the toddler, the cool dude, the codger. The tragedy— or perhaps it's a blessing— is that no one version recognizes its own immortality. Would you really want to be 14 for eternity, waiting for your civics class to end?

[Zinjanthropos]

Barbour calls each of these possible still-life configurations a "Now."

Not sure if I’m interpreting all this correctly…

Nows would be every probability then? Is this multiverse of all things possible accessed by AI and to some degree by our brain. If so then why do we appear to be limited or are we just slow? For humans, the ability to access the multiverse would be the difference between moron and genius I’m guessing. IOW satisfying some Nows that are available?

Is this Russian Dolls all over again? If one possibility is to access all Nows then at some point perhaps someone has. Omniscient God believers might want to jump on that.

[C C]

Barbour calls each of these possible still-life configurations a "Now."

Not sure if I’m interpreting all this correctly…

Nows would be every probability then? Is this multiverse of all things possible accessed by AI and to some degree by our brain. If so then why do we appear to be limited or are we just slow? For humans, the ability to access the multiverse would be the difference between moron and genius I’m guessing. IOW satisfying some Nows that are available?

Is this Russian Dolls all over again? If one possibility is to access all Nows then at some point perhaps someone has. Omniscient God believers might want to jump on that.

Below, he uses simple arrangements of three particles (triangles) to illustrate the multitude of different configurations of the universe, each of which constitutes a Now. (Or topic-wise, consider each Now akin to a parallel universe like in the multiverse, only a static island rather than a single event in and belonging to a discrete framework sequence of changes).

I think there's a problem correlating the elephant-sized "present moment" of human consciousness (measured in milliseconds) with what might arguably be the Planck-time unit measure of Barbour's Now for one state or configuration of the universe. (I.e, the larger unit of human cognition/experience would have to extend over many of those objective Nows). But the same problem occurs with the conventional, everyday view of time called presentism, which also features a universal now that would have to accommodate the changes of subatomic events rather than anthropocentrically conform to the "slow" human rate of change awareness. Barbour "seems" to maybe address that with his idea of "time capsules" discussed elsewhere in the interview.

As he mentions in the second half below, Newton's outdated conception of absolute space and time (already rendered obsolete then by Einstein's work) was utilized by Schrodinger for practical reasons (allowing statistical predictions). Thereby, QM was (accidentally?) designed to be in conflict with Einstein's conception. Which is something I've heard before, that it was QM's own architects who created the incompatibility issues that today's quantum gravity pursuits struggle to remedy. (The formalism of QM was invented, not discovered under a rock. If fell out of personal and group choices.)

THE END OF TIME: A Talk With Julian Barbour
https://www.edge.org/conversation/julian...nd-of-time

BARBOUR: Let's take a simple model; suppose there were just three particles in the universe and nothing else. In some instant they would be in certain positions relative to each other and would form some triangle. Newton claimed that this triangle has in addition some position in absolute space and that it's changing in time. What I'm saying is that there isn't any of that external framework of space and time, there's just the possible triangles that the particles form.

The triangles do not occur somewhere in absolute space at some instant of time, some Now. The triangles are the Nows. You are forced to some view like this if the invisible framework is denied.

If we had a universe with a million particles in it there would be some relative configuration of those million particles and nothing else. That would form one Now, and all the different ways you could arrange all the million particles would make all the different possible Nows.

I think the actual Nows of this universe are more sophisticated constructs involving fields, but Nows formed by arrangements of particles can get the idea across.

JB: Didn't Einstein abolish Nows?

BARBOUR: In fact no. He only showed that they do not follow one another in a unique sequence. There is no absolute simultaneity in the universe, or at least not in the classical universe. But relative simultaneity remains, and Nows as I define them form an integral part of Einstein's theory.

Actually the discovery of Dirac that started all my interest in time was that Nows appeared to be far more significant in the quantum world than one might have expected coming from the normal interpretation of Einstein's relativity.

What really intrigues me is that the totality of all possible Nows of any definite kind has a very special structure. You can think of it as a landscape, or country. Each point in the country is a Now. I call it Platonia, because it is timeless and created by perfect mathematical rules.

Most strikingly, it is lopsided with a most definite end and frontiers that are there by sheer logical necessity. For example, if you consider triangles as Nows, the land of these Nows comes to an absolute end in the degenerate triangle in which all three particles coincide. This point is so special I call it Alpha.

Other frontiers, like ribs, are formed by the special triangles in which two particles coincide and the third is at some distance from them. Finally, another kind of frontier is formed by collinear configurations — all the three particles are on one line.

The Platonia for triangles is like a pyramid with three faces. Its apex is Alpha. All the points on its faces correspond to collinear configurations, and the faces meet in the ribs formed by the triangles with two coincident vertices.

[...] JB: So what do you do in Platonia?

BARBOUR: There are two tasks: first of all, can you describe classical physics using that picture? That's really where my main work has been done, showing that everything Newton could do with absolute space and time can be done more economically in Platonia. That's the first thing Bertotti and I showed.

Then we found that Einstein's general relativity, which was created as a theory of space — time, can be recast as a timeless theory in the appropriate Platonia. This is closely related to the discovery that Dirac made and leads on to the second task: what are the implications of the 'Platonic structure' of general relativity in the quantum universe? This is relevant because quantum theories are generally arrived at by starting from a classical picture and performing something which is called quantization.

For non — physicists it's a rather difficult thing to grasp. But you can see where the idea of a timeless universe will come from if you consider the way quantum wave mechanics was discovered by Schrodinger in 1926.

In classical Newtonian physics, if you have three particles they will always be at definite positions at definite times. They will form some triangle, and the center of mass of the triangle will be somewhere and it will have some orientation. Now what quantum mechanics says is that, until observations are made, for all these quantities, there are no definite values, but only probabilities, all of which change in time.

The reason that Schrodinger could create a picture of quantum mechanics like that is because he was using the Newtonian concepts of absolute space and time. The framework that they create makes it possible to give probabilities for the triangles formed by three particles to be in different positions and for the probabilities to change in time. There's an independent time which is nothing to do with the contents of the universe.

But if you are trying to construct a universe where you say there's no external framework of space and time in which the contents exist, then you can't give probabilities for the particles to be in certain overall positions in the universe and have some overall orientation, because there's no meaning to that. And nor can the probabilities change in time, because there isn't any time in which they can change.

The most simple — minded attempt to reconcile quantum physics with the idea that there's no invisible framework holding up the universe — and that idea is made very plausible by the 'Platonic structure' of general relativity — leads you to a picture in which there are just probabilities given once and for all for the relative configurations of the universe. So if we had a three — particle universe the probabilities would just be for where the three particles are relative to each other, say, two close together and one further apart. That's the complete story — static probabilities for static configurations, which are what I identify with Nows.