Time and Two Doors

In the last week or so I read an interesting pair of books: Through Two Doors at Once, by author and journalist Anil Ananthaswamy, and The Order of Time, by theoretical physicist Carlo Rovelli. While I did find them interesting, and I’m not sorry I bought them (as Apple ebooks), I can’t say they added anything to my knowledge or understanding.

I was already familiar with the material Ananthaswamy covers and knew of the experiments he discusses — I’ve been following the topic (the two-slit experiment) since at least the 1970s. It was nice seeing it all in one place. I enjoyed the read and recommend it to anyone with an interest.

I had a little trouble with the Rovelli book, perhaps in part because my intuitions of time are different than his, but also because I found it a bit poetic and hand-wavy.

It seems presumptuous of me to think I know better than a highly trained award-winning theoretical physicist who has studied time throughout his career. Any opinions of mine should be taken with an entire salt shaker.

That said, I wonder sometimes if theoretical physicists (and deep thinking philosophers) don’t sometimes get lost in their own imagination. Sabine Hossenfelder has a book, Lost in Math, that argues theoretical physics has badly lost its way.

There is something of a stagnation in certain areas of physics, and it’s not hard to imagine sometimes that we’ve gone down a blind alley.

The vexing thing is that the alley (or rabbit hole) we’ve gone down is amazingly effective and matches all available data to very high precision. It’s hard to see where it could be wrong.

§ §

In Through Two Doors at Once, Ananthaswamy closes by using the book’s main topic — wavefunction collapse — as a metaphor for our (lack of) understanding regarding what’s going on.

There are many theories and ideas, but our waveform hasn’t “collapsed” into definite knowledge on the matter. (In this case, the wavefunction almost certainly reflects our ignorance.)

I like the metaphor. It seems to apply to several topics in physics.

For example, the exact nature of human consciousness: many ideas, but none have collapsed into definite knowledge.

Ananthaswamy’s metaphor directly connects with Rovelli’s book in that time is another aspect of reality that presents us with an as yet uncollapsed question:

Is time fundamental? Or does it emerge from some other process?

§

It is on this point that my intuitions about time conflict with Rovelli’s.

I maintain an old-school belief that time (and space) are fundamental — they are not comprised of smaller components and they do not emerge from some other system.

It’s obviously not “turtles all the way down,” so at some point you have to accept that some things just are. For me it’s spacetime and the quantum fields. I think that’s the basic fabric of reality.

[See: Thinking About Time and Got Time? for earlier posts on this. The latter post is my reactions to a blog post reviewing Rovelli’s book.]

There is an alternate view, going back to Leibniz, that time and space are just relationships, and there are modern theoretical views that time emerges from something else (for instance, entropy).

To be blunt (with full understanding I may also be wrong), I find these alternate views incoherent. I can’t find any sense in the idea that some other process “creates” time or that it “emerges.”

For one thing, the very idea of a “process” — or that something can “emerge” — requires time in the first place (according to Kant, we can’t even think about these things without assuming fundamental time).

For another, a relationship is an operator between two things. Distance, for example, is an operator that puts a number to the space between two points. It makes no sense to speak of distance without those two points in the first place.

§

An example Rovelli has used in interviews suggests that emergence doesn’t require time: He points out how flat the Earth looks to us, but from space its curvature emerges.

But note the implicit movement from a close to distant perspective. Or just note that first we speak of the close view and then we speak of the far view.

What I’ve found is that most discussions about timelessness always allow time to sneak in the back door. There is always a first this, then that scenario.

For example, from the footnotes, where Rovelli gets more specific about exactly how the “unnecessary” variable t (for time) is removed:

The general form of a quantum theory that describes the evolution of a system in time is given by a Hilbert space and the Hamiltonian operator H. The evolution is described by Schrödinger’s equation iħ∂tΨ = HΨ. The probability of measuring a pure state Ψ a time t after having measured a state Ψ′ is given by the transition amplitude 〈Ψ | exp[–iHt/ħ] | Ψ′〉. The general form of a quantum theory that describes the evolution of the variables with respect to one another is given by a Hilbert space and Wheeler-DeWitt equation CΨ = 0. The probability of measuring the state Ψ after having measured the state Ψ′ is determined by the amplitude 〈Ψ | ∫ dt exp[iCt/ħ]|Ψ′〉.

Note the phrasing: “after having measured”

Time always sneaks in the back door. (I’d also like to know more about exactly what C is in his equation.)

Kant found time to be a irreducible a priori intuition, and an internal one at that. We can’t think without a background notion of time. I think Kant got this one right.

§ §

Another plank in Rovelli’s argument involves how General (and Special) Relativity have scrambled our common notions of time.

Under SR, the idea of “now” becomes personal and local. Your “now” is not the same as anyone else’s “now.” The further away someone is, the more meaningless is the idea of a simultaneous “now.”

Under GR, the scrambling gets worse. Your feet aren’t experiencing the same “now” as your head because they are (usually) deeper in the gravity well.

We now have clocks capable of detecting the difference of a few feet or of walking speeds. Rovelli suggests at one point that what we feel as gravity is actually a seeking for the slower time of being deeper in the gravity well.

That every particle exists in its own timeline doesn’t, to me, require that time isn’t fundamental. It just means the fabric of spacetime is complex and twisted.

I’m more compelled by how every particle, despite having its own proper time, has essentially the same proper time as every other particle. By that I mean every particle’s “clock” ticks at the same rate — the fundamental passage of time.

This is a basic tenant of physics: that everything behaves the same regardless of your position or motion. All proper clocks tick at the same rate even if they appear to run faster or slower to relatively moving observers.

§ §

Besides the question whether time is fundamental is a question of whether time is quantized.

We believe there is a minimum distance, the Planck Length, below which the concept of distance is considered meaningless. We also believe there is a minimum time, the Planck Time.

Whether these represent a quantizing of space and time is an open question. It’s possible they represent accessible limits. And it is true that assuming spacetime is smooth leads to some impossible math.

So current modern thinking (although there are exceptions besides yours truly) is that spacetime is quantized just like energy-matter. The search for quantum gravity mostly involves quantizing GR.

BTW: Rovelli is one of the founders of loop quantum gravity, one approach to quantizing spacetime.

A question I have involves how the quantum aspects of energy-matter reared their head a long time ago. There were things (like ovens) we just couldn’t account for, that had impossible results (like ovens melting into white-hot slag, which they clearly don’t).

We all but stumbled over quantum mechanics. For that matter, both SR and GR answered existing questions — apparent gaps in our understanding.

Where is that for quantum time or space? So far nothing we’ve seen gives us any pause. (Other than the assumption space can be infinitely small which leads to some weird math results.)

§ §

In the discussion of time, entropy is a key player. Some think time arises from entropy; I think that’s putting the cart in front of the horse.

I laughed out loud at one point that, to my eyes, said it all. He writes:

The conventional logic for interpreting this relationship is therefore:

time → energy → macroscopic state

Which I think is not just conventional but correct. Then he reverses it:

macroscopic state → energy → time

Which clearly is putting the cart in front of the horse. I had to laugh, because it’s exactly what I’ve always thought about emerging time being backwards, and here Rovelli waves his hands and proclaims it explicitly.

§ §

Entropy figures in Rovelli’s thinking, and he seems to give it center stage in a tragic play:

From the most minute events to the more complex ones, it is this dance of ever-increasing entropy, nourished by the initial low entropy of the universe, that is the real dance of Shiva, the destroyer.

I added a note to the text at this point: “This focuses on the Yin and ignores the Yang. Everything we are lies in the temporary increases of structure and order. Life uses the energy and emits waste entropy.”

To me, entropy is the result of the behavior of particles in time. It’s what happens in any physical system. It’s not the source of time.

It does, however, seem connected with the “arrow of time” — that despite the basic physics having no preferred direction — time marches forward due to entropy, it is presumed.

If one views the basic laws of physics as a wheel that can turn forwards or backwards (in time), then entropy is seen by some as a ratchet that forces it to only turn forwards.

But if entropy is an effect, then we’re left with the understanding of a fundamental aspect of reality: Time.

And it marches forward just fine on its own.

§ §

To be honest, I mostly just skimmed the last two chapters. By then Rovelli was wrapping up and had gotten (to my eye) particularly poetic and hand-wavy.

He seems to place a lot of weight on our perception of time, not so much as a filter preventing us from fully understanding it (which is certainly true), but as somehow involved in creating time.

He talks a lot about our “blurred” view of reality and how entropy is relative through that blurred view. I found myself repeatedly disagreeing with his assessment, although as I said up top, who am I to doubt the word?

Well, I’m just me, and I think what I think.

Stay timely, my friends!

About Wyrd Smythe

The canonical fool on the hill watching the sunset and the rotation of the planet and thinking what he imagines are large thoughts. View all posts by Wyrd Smythe

25 responses to “Time and Two Doors

  • Wyrd Smythe

    Here’s Carlo Rovelli speaking about time at the Royal Institute:

    And here’s the Q&A from after the talk:

  • SelfAwarePatterns

    Not being particularly well read in this area, I don’t have strong feelings about whether time is emergent or fundamental. I do think we always have to be cognizant of the possibility that anything we think is fundamental, may only appear that way at the present, because we haven’t manage to reduce it yet.

    But to me, if we’re going to posit a model where it’s emergent, and it’s not being forced on us by empirical results, then there needs to be a clear epistemic benefit. It needs to answer some problem or solve some paradox. In other words, it needs to add as least as much as it takes. Sometimes I get the impression that some of these people are simply throwing hail-Marys, marking positions in hopes they eventually turn out to be meaningful.

    • Wyrd Smythe

      “I don’t have strong feelings about whether time is emergent or fundamental.”

      I’m a bit like Rovelli in that it’s something I’ve pondered much of my adult life. Not on his theoretical physics level, of course, but it’s been a topic of interest a long time.

      “In other words, it needs to add as least as much as it takes.”

      Very much so. Accepting time as fundamental is fairly parsimonious. Most emergent theories have more pieces.

      As I mentioned in the post, what is missing or unexplained regarding time?

      I read an old article (by Chaitin!) in SciAm that tied theories to Kolmogorov complexity. It gives a measure of effectiveness: The explanans should be much smaller than the explanandum. The best (most effective) theory is the smallest one that accomplishes the task.

      The corollary is that if the explanans is about the same size as the explanandum, do you really have a theory at all? The Kolmogorov parallel is how the shortest possible program to produce Hamlet must contain Hamlet.

      Kind of a neat idea. Almost kind of a formalized Ockham’s razor.

      “Sometimes I get the impression that some of these people are simply throwing hail-Marys, marking positions in hopes they eventually turn out to be meaningful.”

      Very possibly. I’ve always thought that about Dr. Lisa Randall’s “dark matter killed the dinosaurs” thing.

      • SelfAwarePatterns

        “The explanans should be much smaller than the explanandum.”

        Somebody a while back made the point that the laws of nature can be seen as compression algorithms. When someone presents a model that doesn’t compress, it seems to be pointless. Which is right along the lines of what you’re saying here.

        “I’ve always thought that about Dr. Lisa Randall’s “dark matter killed the dinosaurs” thing.”

        Hmmm, I hadn’t heard that one. Randall seemed pretty level headed in most of the interviews I’ve seen of her. I find it surprising she’d come up with something that speculative. I’ll have to dig it up and see what it’s about. Maybe I was wrong about her.

      • Wyrd Smythe

        “Somebody a while back made the point that the laws of nature can be seen as compression algorithms.”

        An interesting way to look at it!

        “Randall seemed pretty level headed in most of the interviews I’ve seen of her.”

        Oh, make no mistake, I’m a fan of Dr. Randall (on several levels). But as speculative theoretical physicists go,… she’s pretty speculative.

        I thought her Warped Passages, which I have, was pretty good, but it’s still a WAG. It’s kind of like betting on a specific number in roulette — unlikely to pay off, but if it does, wow! (But instead of being rich, you’re another Einstein.)

        Her “dark matter killed the dinosaurs” idea involves dark matter interacting with itself enough to form a disk of more concentrated DM exactly the way that star systems and galaxies form disks.

        The Earth’s passage around the galaxy actually brings it up and down relative to the galactic plane (where the DM disk would be), so Earth periodically, on a long time scale, passes through areas of more concentrated DM.

        This, Randall hypothesizes, might have changed orbits of objects in the Oort cloud such that there was increased comet activity. And hence a greater chance of a dinosaur-killing impact.

        It’s entirely level-headed… but also science-fiction level speculative.

      • SelfAwarePatterns

        Ah, ok, thanks. That makes a bit more sense, although as you said, it’s extremely speculative. The Oort cloud could also have just been perturbed by a close passing star. Or variations in gravity due to the angular change in our relation to galactic arms. Or…just about anything with gravitational effects.

      • Wyrd Smythe

        Exactly so. Randall’s idea is that one could look for a correlation between the regular passing through that concentrated DM zone and increased comet activity. A strong correlation would imply there really is a DM disk (and that it can perturb a star system).

        I read an SF short story long ago where the black hole at the galaxy center caused huge beams of radiation that extended “horizontally” in the galaxy (think lighthouse beams). It was the Earth’s regular passage through those beams that caused mass extinctions. Randall seems to be reaching for something similar.

      • SelfAwarePatterns

        I’ve read speculation the mass extinction level events might be correlated with where we are in relation to the overall galactic disk. The solar system is thought to oscillate above and beyond the disk. Maybe there’s something about either the disk itself, or intergalactic space that leads to those events. The dark matter scenario seems like a variant of that overall genre.

        It is sobering to realize how many things have to be going right for life on Earth to continue unabated. The sun has to have the right luminosity, the Earth’s magnetic field has to be functioning, the sun’s overall magnetic field might be a thing, and even the galaxy’s magnetic field could potentially be a thing.

        Sometimes you have to wonder if we’re any better than the ancients worrying about the gods getting angry at them, although at least in the modern scenarios, the events are rare and separated by tens or hundreds of millions of years, and none of them require burnt offerings to stay away.

      • Wyrd Smythe

        “The dark matter scenario seems like a variant of that overall genre.”

        Yep, exactly.

        “It is sobering to realize how many things have to be going right for life on Earth to continue unabated.”

        Oh, so many things! I’ve heard that gas giants in the outer system shield the inner planets from overly distructive bombardment. I’ve heard that the Moon is instrumental (tidal pools). That we have heavy elements requires a nearby neutron star collision. So many things!

        Just consider our neighbors, Venus and Mars. Grew up in the same neighborhood, but turned out quite different.

        “…worrying about the gods getting angry at them…”

        Now our model is of an uncaring and generally hostile universe. Yeah, maybe we haven’t come so far as all that. 😀

      • SelfAwarePatterns

        I read a few years ago that even volcanoes (in moderation) might be essential. Apparently volcanic ash is an important fertilizer.

        “Now our model is of an uncaring and generally hostile universe.”

        From one perspective, you could say we have new gods, who don’t care anything about the traditional libations. Although these new gods can be studied and their energies harnessed, that energy can be misused, with consequences. And the new gods are utterly indifferent to whether we live or die.

      • Wyrd Smythe

        “Apparently volcanic ash is an important fertilizer.”

        Absolutely. Even lava, once it breaks down, makes decent soil.

        “From one perspective, you could say we have new gods,…”

        That’s exactly the core premise of Neil Gaiman’s American Gods. (And the old gods are pissed!)

        More seriously, that’s what Tim Maudlin said to Lawrence Krauss regarding his hypothesis about how “something came from nothing.” Maudlin (and others, including myself) kinda see modern physics as replacing a humanistic god with a Spinoza-type “god” of laws — the something that just is.

        “And the new gods are utterly indifferent to whether we live or die.”

        Heh. Often, so were the old ones.

      • SelfAwarePatterns

        “Maudlin (and others, including myself) kinda see modern physics as replacing a humanistic god with a Spinoza-type “god” of laws — the something that just is.”

        I was being metaphorical above, but I do know a lot of people have that view, a sort of naturalistic theology. My biggest issue with it has always been that I don’t see the emotional appeal. But I’m also cognizant that what doesn’t appeal to me may have enormous appeal to others.

      • Wyrd Smythe

        “I was being metaphorical above, but I do know a lot of people have that view, a sort of naturalistic theology.”

        Oh, indeed. When I included myself, it was on Maudlin’s side, not Krauss’s. I agree many have replaced god in their thinking with physics. That doesn’t reflect my personal view. (I think you know my spiritual sensibility includes an actual god. If you’re gonna believe in something irrational, might as well go all the way.)

        “My biggest issue with it has always been that I don’t see the emotional appeal.”

        That seems true to the neural net named Mike I’ve gotten to know. 🙂

        A question I have for you: What kind of music to you listen to? When was the last time you went an listened to live music (concert or band)?

        “But I’m also cognizant that what doesn’t appeal to me may have enormous appeal to others.”

        True on so many levels. I can’t fathom why anyone would actually eat fried eggs (or, far worse, actually crave them). They revolt me on every level. 😀

        FWIW, as an aside, my spiritual faith comes, in part, from finding a non-teleological reality a huge waste of a universe (let alone multi- more many). Since I have a choice, I prefer to believe there is some teleology. The virtual reality hypothesis has a “turtles all the way down” problem, so (to my eye) a single universe created by some entity with purpose is one parsimonious way it all starts (plus then I get teleology). The only other sensible belief (to me) is a single universe springing into existence for, I guess, meta-physics (not metaphysical) reasons (i.e. some set of meta-laws that allowed the big bang), but then nothing actually means anything.

        Something just is. Since I find all of them a bit preposterous, I feel I’m free to adopt the one that least offends me. A whole universe created by nothing and for no purpose… well, that’s pretty offensive! 😀

      • SelfAwarePatterns

        “What kind of music to you listen to? When was the last time you went an listened to live music (concert or band)?”

        I’m actually pretty much a music moron. I used to listen to rock and country when I was younger, but it was mostly peer pressure driven. My tastes today are eclectic and fragmentary.

        Looking at my phone, I have Gun & Roses, Evanescence, and a lot of John Williams soundtrack stuff. But I never listen to any of it. If I’m listening to anything, it’s a podcast of some type.

        The last time I went to live music? It was probably at a bar somewhere. But the last major concert I went to was decades ago, in the early 90s, to see Paul McCartney.

      • Wyrd Smythe

        I said before that I think, when it comes to experience, that you are missing something. Of course, we’re all missing something in terms of experience. There’s always more outside the scope of our understanding than in. For instance, it’s true of me, and I believe of you, that we have no direct experience of fatherhood. (I had step-kids, but it’s still not the same as having your own child.)

        What I’ve suggested you’re missing involves the more “visceral” side of life — the sort of thing people mean when they say someone has “the soul of an artist” (or poet). I’m not suggesting it’s a lack in need of fixing, not at all. It’s just that some people are more focused on intellect and others on a more emotional view. A classic example is the mother defending her criminal son, because logic loses to family. I’d turn the bastard in (not “for his own good” mind you, but for the good of society).

        Your preference for podcasts over music, indeed your relationship with music, shows that aspect. I’m very much like you intellectually, but my music teacher mother (who taught me to play so young I have no memory of not being able to play) instilled another aspect. I can’t imagine not listening to music all the time.

        It would be interesting to me to try to sort opinions and intuitions about consciousness by this sort of background. Are those who are more, let’s call it, “artsy” more inclined towards seeing consciousness as something special or “magical” or somehow dual? Is there any inverse correlation between Type A materialism and a love of the arts?

        Unrelated: Another question I like asking people (this having to do with how people think): If I were to give you instructions on how to get someplace you’d never been, would you prefer a set of instructions (where to turn) or a map? Basically, are you word-based, or image-based?

      • SelfAwarePatterns

        A number of people have commented that they find me overly analytical. To some degree, that’s a factor of what I let show in my online persona. When someone gets under my skin, I have the luxury of getting up and going for a walk or doing something else before answering, allowing my response to be more analytical than it would likely be in real life.

        In person, I’m usually pretty laid back and casual until there is something that needs to be done, then I’m pretty task driven, and become impatient with people who aren’t.

        “Is there any inverse correlation between Type A materialism and a love of the arts?”

        There may be, although it’s probably complex and filled with exceptions. A science fiction author, for instance, is probably a lot more likely to be a physicalist. But I suspect a lot of fantasy authors wouldn’t be.

        “would you prefer a set of instructions (where to turn) or a map? Basically, are you word-based, or image-based?”

        I’d be annoyed if you wouldn’t just give me the address so I could put it in Google Maps or something similar. 🙂

        If I had to choose between the map or instructions, I’d probably go for the instructions. They’d be easier to reference while driving.

      • Wyrd Smythe

        “A number of people have commented that they find me overly analytical.”

        You and me both. For me, especially before I got into theatre in high school. I was a total geek (and a nerd) before that. Theatre (and then filmmaking) changed me a lot.

        I realized recently that my external self-image hasn’t been good for me. We all have an internal self-image, but we also have an external one comprised of all the feedback about ourselves we’ve gotten from others. For me, and perhaps for you, a large share of this involves my intellect — how “superior” it is. The bad part is that it’s been not a little alienating. (I smoked weed in college explicitly to try to dumb down and be more socially acceptable. Didn’t work; I get prolix when I’m stoned. I mean, even more so.)

        So we have this self-image imposed on us of being Spock-like. (If only that attracted women the way Spock seemed to. If only they flocked to us hoping to break through. 😀 )

        “I’m pretty task driven, and become impatient with people who aren’t.”

        Another trait we share in spades. “Get it done!” is a good slogan.

        “A science fiction author, for instance, is probably a lot more likely to be a physicalist. But I suspect a lot of fantasy authors wouldn’t be.”

        That feels right-ish. It’s a spectrum and some authors are hard to classify, but a correlation wouldn’t surprise me.

        “I’d be annoyed if you wouldn’t just give me the address so I could put it in Google Maps or something similar.”

        ROFL! Modern technology really has screwed up the value of that question.

        Your choice reflects both my guess you’re word-based and your pragmatism, another trait I’ve marked. Instrumentalism is a pragmatic point of view!

        I share it to an extent, but I do have pronounced romantic notions that dilute it.

  • James Cross

    If our future were behind us and our past in front of us would time be moving in the opposite direction?

    “Linguistic and gestural analysis by Núñez and Sweetser also asserts that the Aymara have an apparently-unique (or at least very rare) understanding of time. Aymara is, with Quechua, one of very few languages in which speakers seem to represent the past as in front of them and the future as behind them”.

    https://en.wikipedia.org/wiki/Aymara_language

    Or maybe space is flat and we have to learn how to unflatten it?

    “The most famous case study in science, prior to Freud, was published in 1728 in the Philosophical Transactions of the Royal Society by the English surgeon William Cheselden, who attended Newton in his final illness. It bore a snappy title: “An Account of Some Observations Made by a Young Gentleman, Who Was Born Blind, or Lost His Sight so Early, That He Had no Remembrance of Ever Having Seen, and Was Couch’d between 13 and 14 Years of Age.”

    The poor boy “was couch’d”—his cataracts removed—without anesthesia. Cheselden reported what he then saw:

    When he first saw, he was so far from making any Judgment about Distances, that he thought all Objects whatever touch’d his Eyes, (as he express’d it) as what he felt, did his Skin . . . We thought he soon knew what Pictures represented, which were shew’d to him, but we found afterwards we were mistaken; for about two Months after he was couch’d, he discovered at once, they represented solid Bodies.

    The boy saw, at first, patterns and colors pressed flat upon his eyes. Only weeks later did he learn to perform the magic that we daily take for granted: to inflate a flat pattern at the eye into a three-dimensional world.
    The image at the eye has but two dimensions. Our visual world, vividly extending in three dimensions, is our holographic construction. We can catch ourselves in the act of holography each time we view a drawing of a Necker cube—a few lines on paper which we see as a cube, enclosing a volume, in three dimensions. That cubic volume in visual space is, of course, virtual. No one tries to use it for storage. But most of us—both lay and vision-science expert—believe that volumes in visual space usually depict, with high fidelity, the real volumes of physical space, volumes which can properly be used for storage.”

    https://www.edge.org/response-detail/27026

    • Wyrd Smythe

      “‘…one of very few languages in which speakers seem to represent the past as in front of them and the future as behind them.'”

      Seems quite sensible. You can see what’s in front of you, just as you can “see” the past. But you can’t see the future, just like you can’t see what’s behind you.

      The idea of facing forward to an unknown future suggests a society prone to exploring and expanding boundaries. That’s not a feature of all societies.

      As an aside: That group famous for always using cardinal directions and not having concepts for “left” or “right” also tend to order time from east to west. Which is also quite sensible for a society highly aware of cardinal directions given the apparent motion of the sun. (Also: any group so aware of cardinal directions is likely to be one that’s outside a lot and so would naturally be aware of the sun.)

      “‘The most famous case study in science, prior to Freud,…'”

      I don’t follow what meaning you attribute to this or how it connects with time. Can you elaborate?

      (I know blind people are perfectly aware of volume, spatial extent, and time, so I’m confused.)

      • James Cross

        “For me it’s spacetime and the quantum fields. I think that’s the basic fabric of reality.”

        The case study connects to the notion of space. We have to “learn” the 3rd dimension. From the standpoint of physics it seems to tie to the holographic universe idea.

        Of course, no unification so far of relativistic space-time and QM so if that is what you mean by “basic fabric” there is still some work to do.

      • Wyrd Smythe

        “The case study connects to the notion of space. We have to ‘learn’ the 3rd dimension.”

        I don’t see it as having much to do with notions of space but of the need for our neural nets to learn to navigate given its inputs. As I mentioned, blind people have a fine notion (often better than sighted people) of space. Eyes are not required.

        My dad had a blind friend he used to drive places, and as they drove (let’s call him) Fred would often ask my dad about things along their path. My dad though he’d fool him one time by taking a different route. But at a stop light Fred asked my dad about the new construction on the corner and, sure enough, there was a new building going up there.

        Fred, even as a passenger in a car, knew exactly where they were.

        Obviously someone who has never processed visual information would need to learn to do it if they suddenly gain the ability to receive visual input. But they’ve been processing 3D spatial information (through movement and touch) all their lives.

        I’ve heard of experiments that raised kittens in an environment without vertical lines, and the kittens never learned to process that type of visual information. Visual systems are complex, and ours need to be trained.

        “From the standpoint of physics it seems to tie to the holographic universe idea.”

        I’m sorry, but I don’t see that it has anything to do with that. To me it only speaks of how our neural net needs to learn to process input.

        “Of course, no unification so far of relativistic space-time and QM so if that is what you mean by ‘basic fabric’ there is still some work to do.”

        Absolutely! But our lack of understanding doesn’t at all imply spacetime isn’t real.

  • Wyrd Smythe

    I was reading the Wiki page for Planck units, and it’s kind of funny how good old t appears in three-out-of-five.

    The Planck units — universal constants — are:

    1. the speed of light (in a vacuum), c
    2. the gravitational constant, G
    3. the reduced Planck constant,
    4. the Coulomb constant, ke
    5. the Bloltzmann constant, kb

    The first, c, has the value:

    299,792,458 metres per second (The metre is defined as how far light travels (in a vacuum) in 1/299,792,458th of a second.)

    The second, G, has the value:

    6.674×10-11 m3·kg-1·s-2 (meters cubed per kilogram per second squared)

    The third, , has the value:

    6.62607015×10-34 J⋅s (joule-seconds)

    So time appears in all three!

    Planck time is derived from these:

    t_P\equiv\sqrt{\frac{\hbar G}{c^5}}

    Its value is 5.391245×10-44 seconds. (Very, very short!)

    The Planck coin has the tiniest quantities on one side and some very large quantities on the other.

    For instance, Planck power is 3.628×1052 watts!

    Or Planck voltage, which is 1.04295×1027 volts!

    This speaks to the energy necessary to probe the very, very small. It’s exactly why CERN needs a big honking collider to probe inside protons. (Note that CERN isn’t anywhere near, by many orders of magnitude, the energy needed to get down to Planck length.)

    • James Cross

      By the way on Less Wrong, there is a good explanation of Barbour:

      https://www.lesswrong.com/posts/rrW7yf42vQYDf8AcH/timeless-physics

      There are followups to it also. Still reading and not sure of the total view on it but this is an interesting quote:

      “Ready for the next big simplification in physics?

      Here it is:

      We don’t need the t.

      It’s redundant.”

      • Wyrd Smythe

        From what I can tell it’s just hand waving and science fiction. (I just finished a book by a theoretical physicist who has studied time all his life, so I’m not compelled by the blog of an AI guy with ideas. Hell, this blog is by a CS guy with ideas. I wouldn’t trust either one of us! 😀 )

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