Teaching bleeding-edge science to a general audience (me) without making it feel watered down is done nowhere else as well as here. Thanks to all involved.

"Be careful! The devs WILL notice." - This has got to be the funniest yet most existentially disturbing reply ever made on this channel.

Years ago, I was a physics major. Life didn't turn out the way I initially expected and now I'm in CS classes, including Theory of Computation. This video is very much the intersection of stuff I've studied/studying and hits hard.

7:45 We've had an "algebra of possibility" for over 70 years. It's called modal logic, and the standardly used semantics for it is possible worlds semantics (also known as Kripke semantics). It has it's own operators, theorems, etc, and is used extensively in philosophy

So if I understand Constructor Theory correctly... "In this world there are only two laws that matter. What a man can do, and what a man can't." - Captain Jack Sparrow, a physicist ahead of his time.

Rough shade on Newton with that whole "you can't transmute apples into gold" line

Wouldn't constructor theory fundamentally be assuming we know all the base sets of rules in order to be correct? Otherwise it could rule out things that are possible, but they just don't have a truth statement for in the base set of rules.

oh my god, mobs tapping on walls and measuring frame rates had me rolling

The Devs already noticed, and they're literally making things up for us to measure.

I watched a lecture right here on KZfaq about this topic, and while the idea of counterfactuals were discussed at length I walked away from the conversation feeling that the whole thing sounded kind of dumb. But I don't think it was idea of Constructor Theory itself, but instead how the participants danced around the topic, delving into philosophy debates instead of explaining existing ideas behind it. Like they were discussing the meta of Chess without ever explaining what the game even was. But here in just 8 minutes I was able to go, "Oh that's what they meant!"

I sleep with your astrophysics theories & videos. Well, this has been my Naptime channel. Whenever I feel stressed or a need for nap, I watch this. Love from India 🇮🇳

This is the best explanation of counterfactuals and Constructor Theory I've seen. I am sure a lot of good work went in to making it so simple to understand. Thank you.

Constructor theory seems to parallel David Hilbert's efforts to formalize all of mathematics before Kurt Gödel showed that such a task was impossible.

This sounds reminiscent of Gödel's incompleteness theorem. He was able to abstract away the mathematical operations and describe any possible equation as a binary choice between it being true or false, much like how the counterfactuals are either possible or impossible and allow you to ignore the specific equations themselves.

Constructor Theory reminds me of fractal math, and especially the way the Mandelbrot set is built. You test a number through an equation and if it blows up toward infinity, it's out. If it stays within certain bounds, it's in.

It would definitely revolutionize how science is taught in schools anyway. Whether it is the all in one thing that ties them together, or not. It could be incredibly useful as a learning tool.

This feels a lot like what Gödel did but in the context of physics. Mathematics is extremely rigorously formalised and consistent across all areas of study and as much pain as that brings me in my maths lectures, I think a similar level of purity and formality in our language and axioms could really benefit physicists.

Do equivalent forms of Gödel’s Incompleteness Theorem and Turing’s Halting Problem exist within Constructor Theory? Could something (say for example Quantum Gravity) be unprovable in Constructor Theory yet still be possible?

Dev coming home from school: " Mom, I told you NEVER SHUT MY COMPUTER O....."

Soon on "intelligent design" websites: "PHYSICISTS CONFIRMED THE UNIVERSE HAS ITS CONSTRUCTOR!"

This sounds an awful lot like an approach to leaning geometry through construction. In fact, Constructor Theory seems to have a lot in common with how we do mathematical proofs in the first place. I'm surprised it took this long for it to be applied to physics.

Sounds like it should be called the Sherlock theory - “when you have eliminated the impossible, whatever remains, however improbable, must be the truth”.

It is always interesting that with every new methodology, we continuously think that now we've got, and thereby can explain everything. But the only thing we can explain is what we know, by what we think we know and actually know, we are just talking about new ways to connect that knowledge to understand what we don't understand, we know and the more we know the more questions arise and by answering those we find new questions and thereby understanding how much more we still don't know. I love this journey, may it never end.

OK, so only part way through but seems to me, there's a possible 'bump' in the constructor road. Who or what decides what tasks are 'possible' and what constructor is needed to make them happen? If we don't already know of a specific constructor, wouldn't this lead to a task being called impossible even though it is just our lack of knowledge?

Isn't this more of an epistemological framework than a theory? Not that there's anything wrong with that. I think everything would be better if physicists and philosophers of science collaborated more or if more physicists were more philosophically inclined (like Sean Carroll, for instance)

To me, constructor theory always sounded like a more complicated way to say things we already know. The kind of topic that gets some philosophers excited and most physicists shrugging, yawning, or raising eyebrows. I may well be missing something, but I don't even think that the thought experiment that Matt gave, of gravity mediating entanglement, is pointing us in any direction we haven't already been looking for a long time already. We already know a fair bit about Quantum Field Theory on curved spacetimes, e.g. Hawking radiation and the Unruh effect, that is stuff from what, 40 or 50 years ago? It all sounds like an answer in search of a question.

I like a lot that part at around 13 minute mark. Showing us how the world works very differently from what we intuitively expect, what we expect by using what some would call common sense. I feel lucky to live in the age where I can hear the answers to these questions, as opposed to the age of ancient Greece, where philosophers had to make guesses and essentially make stuff up. These philosophers never stood a chance of predicting how reality actually works, because it is so different from what we experience on our scales. This is a great channel which answers the questions which we all head as kids, and which all people asked themselves during thousands of years (if not way more than that). Even without the theory of quantum mechanics and gravity, and without knowing why mass pressure etc. cause gravity, or whether time and space are emerging properties or not, just presenting things that we know is so fascinating to hear. I am actually excited about the fact that on the smallest scale universe doesn't work the way we would imagine. It only makes it more interesting.

Hey Matt, have you read David Deutsch's book? The Beginning of Infinity? It's absolutely amazing. The most influential book I've ever read, by far.

Now I want a T-shirt that only says: "Be quiet everyone. The Devs will notice." 😁

Q: How is Construtor Theory different from creating formulae to describe a system? Coming up with principles to determine valid vs invalid paths sounds very much like creating equations.

I feel like I'm missing the part where Constructor Theory is a theory, and not just a process..?

Matt this is great, I can envision using principles of constructor theory and counterfactual assertions you break down to apply in innovations when "greenhousing" new ideation; the essence in this is a developer can practice thinking creatively outside any particular mechanistic rigid means before resolving logic that a task is potentially possible or not.

I'm not sure I understand how this theory can predict how a system will behave, wouldn't it need some external definition of what is possible or not?

One of the first videos where I don't feel like things were explained properly. I don't understand how can new knowledge be extracted if we only rely on known facts. The idea with equations is they make predictions you can then try to observe or contradict. But suppose I start with the "fact" nothing travels faster than light, how could I apply this constructor theory to be like "actually neutrinos might be moving faster, go and take a look."

Basically the physical application of Sherlock Holmes truism saying, “eliminate the impossible and whatever remains, however improbable, must be the truth.”

Wow, prob top 3 vid on this channel so far! Im amazed, thanks for explaining and sharing

This sounds too similar to Formal Proofs in CS, and I sense a halting problem in the making. Something along the lines of "A true system of everything will be able to solve the halting problem, and thus cannot exist". That's not to say it's a bad thing, it's some conclusion to say the least.

Constructor Theory reminds me of the Sieve of Eratosthenes, except this is a Sieve for the models of reality. en.wikipedia.org/wiki/Sieve_of_Eratosthenes

Its crazy when you hear theories like this thinking, how has this not be thought of before? Its like a back to basic approach.

Seeing the quantum entanglement example reminded me of metronome synchronization. Is this how that works? He said that two entangled particles either need to directly interact or indirectly interact through a chain of interacting particles. This is how metronomes synchronize as well but the interaction occurs via a ground that can move with their beat.

I’d like to see all of the non-possible mathematics, that are carved off…that’s the “No formula left behind!” list!!

kind of comes across as a pretty 'new' wrapper, aka formalism, for logical techniques that have long been well established. aside from some physicists using this theoretical framework to reframe their lack of progress in certain quantum or cosmology fields I don't know what you gain from placing poorly understood dynamical systems in a black box and then discuss output so generalized it's not relevant without understanding the black box in the first place, but as a software engineer that has to put up with new frameworks promising before impossible progress seemingly every few months I am skeptical this fits in that category as well

I wish I could remember the details of a tale I heard, but I found it interesting and kinda relevant here. I will paraphrase wildly: A sculptor was asked how he made a statue. His reply was that he took away everything that wasn't the statue. (I seem to recall this was said of Michelangelo.. but... ???)

Haven’t even watched the vid yet but thank u pbs space time and Matt for ur work! Incredible! A young me couldn’t have dreamed of a better source to fuel my interest in the universe!

Isn't finding what is possible and impossible just physics? I've gotten into a conversation with someone trying to explain the constructor theory, but I just kept hearing "physics with extra steps"

Constructor "Theory" feels too meta of a take on the process of physics and mathematical modeling. I don't really see how moving the question back one step to understanding what's "impossible" versus what's "possible" is supposed to help us make progress. If we knew a priori what events were possible and which ones weren't, wouldn't we already be done with physics?

This reminds me of Aristotle's "possibility", where he splits being into it's necessity, that which exists in material sense, and possibility, that which is possible but it's not yet present (it is present precisely as a chance, i.e. as not-existent). In philosophical tradition there was and still is the never-ending debate if this "possibility" is a part of thing itself or is it just a property that we ascribe to things because of our knowledge etc. I think this applies very well with this theory. Thanks to bring it to our attention, even though it's not accepted as "physics".

So an off topic(for the vid) question: If heat(energy) is nothing else than the speed at which molecules vibrate and if moving faster mean slowing time down in your frame of reference does that mean that the hotter someone is the slower time passes for them?

It sounds like constructor theory is an interesting way of generating thought experiments which might lead to actual discoveries, but I don't see how it can serve as an underpinning of physics in general. Perhaps more information about quantum information theory would be helpful.

How can you decide which true or untrue statements are valid for describing an outcome without relying on classical physics and reasoning? Like, this is cool, but it can't be more fundamental than the facts (and counterfactuals) we rely on to derive new truths.

This is how I solve problems in my hyperphantasia. My mind's eye is like a holodeck, and I can access a lot of memories and visualise anything. Easier to do it this way than pay attention to someone else's ideas with my executive disfunction. I have lots of relatives with Aspergers and ADHD...

"you don't need to know what is inside to know everything about the thing, only the boundaries are enough" -The Fundamental theorem of calculus

Thank you! It's amazing how your previous videos led me to look for research and about 10 months ago discover Constructor Theory. I certainly see this Theory as helpful in describing what will be quantum gravity or relativity.

This reminds a bit of how property based definitions can be created in mathematics. For example the natural exponential function can be defined as e^x (with an appropriate definition for e) or as a Taylor series like (x^n)/n! sum from n=0 to infinity. For both of those definitions you can show that the function is its own derivative. However it's possible to flip that and define the natural exponential function as the function that is its own derivative. You can show any function that satisfies the property is equivalent to the ones above.

thanks for that, interesting. known about this for a while but not really sure "how" it could be formalised. on that topic, the way maths is going, one has to wonder whether a REALLY formal system like a Type Theory-based computer system might be best suited (like Lean in maths), as we would be kinda starting "over" almost.

Constructor theory (at least as it's presented here) doesn't seem 'more fundamental' _at all_ ; if it relies on binary facts about what is possible and what is not possible - how do we derive these if *not* from the mechanistic approach in the first place? If constructor theory had none of the previous physics to go on, it wouldn't get anywhere? If feels like a glorified Eratosthenes' sieve but for physics instead of prime numbers - it doesn't get us closer to the pattern that produces it... but it does help rule out what is & isn't possible. But maybe I just don't get it?

Are the "laws of physics" as we know them now then just the observation of what tasks are and are not possible? So in the math of constructor theory they'd be a sort of boundary conditions? If constructor theory is the more fundamental approach, how does it tell us the laws of physics, or the possible tasks, without knowing them beforehand?

I get off work installing windows and I spend my downtime watching stuff like this which I can barely grasp the concepts of. what a kick ass time to be alive

I very often find myself not wondering what David Deutsch is up to these days, and I would be entirely happy to hear about constructor theory after it has accomplished some accomplishments or gathered some buy-in within the discipline, instead of (as currently seems to be the case) before.

At this point, we should just name The Universal Constructor: Bob.

Interesting how physics is taking a page from computer science. When you start describing phenomenon as abstract concepts, you have to shift from measuring data directly to describing how that phenomenon alters data.

I think this is my favourite new YT series. I can't wait until I have a job again so I can chip in towards keeping this going.

One of favs. Along with Veritasium. Glad these guys take the time, really am. Thanks guys!

It strikes me that -- as a layman -- typically in physics there's only one or two right answers about how a system can evolve. Seeing as this is something of an epistemological framework (I like epistemology and they're important for getting new perspectives), and there's a functionally infinite expansion of the number of ways a complex system can evolve, I'm struggling to see how we're going to find this needle in a haystack of can's and can't's. That is, without lots and lots of ways to generate new ideas about how the system will evolve and new razors for eliminating impossible actions.

You know it’s a big video if the intro looks funny.

What a fascinating video! Thank you for translating this really complex idea for a simple social scientist.

Interesting theory, the concept was discussed in one of the Star Trek novels about 15 years ago. A Tellerite scientist proposed and promoted it.

didn't expect you to talk about this, looking forward to watching this one

The first thing I'm wondering is what about Gödel's incompleteness theorem? His theory formally proves that some 'can do' or possible true facts are impossible to prove true. And this applies to ALL systems.

Brilliant show, and the tunneling QA was awesome.

All the people that you mention at the beginning arrived at their theories not by seeing them, but by working on them for years. It took several steps for all of them. This is the usual romanticized version of the story that is told years later, but it is not how the story went. The truth is that it takes hard work and a bit of luck.

On Wikipedia, they give as motivation for constructor theory the example of a drop of dye dissolving in water and the observation that the reverse process is effectively impossible. I do not see why we would need a new theory for that. As far as I know, we can perfectly explain it with the theories we already have. And to claim that it was absolutely impossible would even be wrong as far as I know. So far, this theory seems very artificial and little useful to me. But I am not a great expert. I will wait a few years and see if the scientifc consensus finds a good point in this.

This seems more useful for creating computer simulations based on *known* mechanistic physics than a means of actually discovering any new physics. As a lot people here already said: how are you supposed figure out the "cans" and "can'ts" of the universe if you *don't* already have a working mechanistic approach?

December 24, 2022 Matt, you gave an example of differences pertaining to possible/impossible in quantum vs. classical theory - namely, the entanglement… Well, how about this: 1) It is the colder part of the year, so I’ll describe it the following way: I set my air conditioning to a certain temperature to be maintained, and device starts the heating process. When the temperature is reached, thermostat turns the heating off. After a while, temperature drops, so the device turns on again… To an observer, these two physical “variables” (high-low room temperature and air conditioning ON-OFF status) are correlated (with a slight delay), aren’t they? 2) Two people in love [oh, isn’t it delightfully charming] pretty much “behave” as a correlated system (of two otherwise independent humanoid units) when it comes to choosing social activities… (E.g. “Shall we go to the movies?” - “Yes, of course!” | “Should we split the cheesecake?” - “Oh, that’s exactly what I’ve been meaning to ask you!” [So pathetic! Just kidding…]) | So the probability that these “two particles” are entangled with each other [and, please keep it decent] at the same space & time violates Bell’s inequality - which means their whereabouts are statistically correlated… 3) When I play your video on KZfaq, the progress indicator is not independent but rather correlated with the frames of the video file in hand; that’s by design. When I or anyone else watching the video “observes” either one - the progress bar or the current video frame - we will immediately know the “state” (i.e. relative position) of the other. Even more: when the indicator is dragged to a certain position, the playing video will reflect that; likewise, when Google A.I. is told to seek certain position - the progress bar will follow. Entanglement. 4) At the start, (that is, when the file is blank) all cells in Excel spreadsheet are “independent”; one sets their value as one wishes… But, if we allow the concept of “simplex entanglement” [I just “invented” this virtual mechanism] to be interpreted as “entanglement, period”, then when I put formula in a cell referencing some other cell’s value, the former cell is no longer “independent”: it’s value (interpreted as state) is entangled… Now, as I’ve said, this has to be one-directional, otherwise Excel will object to “circular reference”- but the idea is there. However, I’m sure the “true duplex entanglement” can be simulated with software (and I mean in classical programming). There are many variations on all four examples. These cover technical systems with a feedback loop, visual controls in software, human societal interactions and, probably, biological processes, too… Maybe I overextended it, but the principle is there, isn’t it? One more thing (and this may or may not be trivial)… When we measure some quantum property of two entangled particles, these measurements’ outcomes will always be correlated; one “snaps out” the other, and it works both ways… What happens when we do the measurement simultaneously? (P.S. “E.R.” is NOT equal to “E.P.R.”)

Ao ver isso, me sinto impressionado e extremamente burro ao mesmo tempo, enquanto tem gente pensando em como funciona o universo, eu estou aqui pensando no que vou almoçar e quando vai chegar a hora de ir embora do expediente. De qualquer modo, muito obrigado por esse ótimo vídeo.

Isn't this just Expert System style knowledge engineering and constraint satisfaction applied to Physics? I didn't understand what was novel about this approach other than maybe physicists don't regularly use those tools? Is "Constructor Theory" just the name for the CSP domain or knowledge graph for physics?

I hope Wolfram makes some more progress on his new ToE physics project and this show can get into computational irreducibility and stuff.

Darkest reality: We are the devs. We were bored so we built our own prison. We just haven't figured out how to escape yet. But we're getting there.

7:15 what an insanely good way of putting things.

I don't think the perpetual motion machine example is useful. As Matt mentions, the physics behind it would explain mathematically why it can't worth through torque and other variables. But the Constructor Theory version basically says "We know it's impossible from two other theories, so all perpetual motion machines are impossible including this one." I can't imagine how this sort of logic gate thinking could possibly generate new insights or discoveries. It's like physics for toddlers. The final example of quantum gravity is silly too: If you can cause a quantum phenomena using just gravity, you've discovered a connection between the two! That's a trivial statement.

Hmm, this sounds like Formal Proofs in Computer Science (and given the Information Theory underpinning I'd be very surprised if they were not fundamentally connected). Trouble is formal proofs have been around for decades now and despite initial optimism they haven't really gone anywhere outside esoteric debate in CS departments with little application in anything approaching the real world. Colour me sceptical - this looks like the same rabbit hole.

This sounds like taking our very limited understanding of the universe and trying to complete a picture we don't have enough paint to finish yet.

That commenter's metaphor of unobserved particles not being fully rendered by the universe, and things glitching through walls as a consequence… was a thing of true beauty.

If the starting point involves stating what is/isn't possible, then isn't this whole system working backwards from the outcome already?

Still, the theory is based/"needs" existing physics theories to say what is possible and what is not. So we are actually back to square one.

Seems like constructor theory would be useful for taking in formulas/axioms as inputs, combining them to develop implications, which then can be used to point towards some potential mechanism worth investigating in the classical sense (formulas to pursue)

I can see this theory finding imaginary tasks eventually - the search for the illusive imaginary special task or "ability" that just "must" exist and will be found someday to make this and that theory true.

It's been a while, but during my studies for my degree in philosophy of science, I've often wondered about the applicability of such more general analysis of counterfactuals wrt state-space-trajectory-possibilities in physics. In researching such avenues of thought, I've also found the ideas of Jürgen Schmidhuber (whose work creating LSTMs contributed majorly to modern deep-learning AI) on generalized algorithmic information, Kolmogorov-complexity and the computability of physical universes deeply fascinating. It seems as though some fruitful cross-pollination might be possible. Of course from a logical and epistemological POV, the real difficulty is to not mis-characterize the counterfactuals, since the conceptualizations of the theories used to define/determine the counterfactuals are never free from ontological and epistemological assumptions which may - in one form or another - be mistaken, and in fact probably are. A good example wrt counterfactuals themselves is Bell, who, not having conceptualized counterfactual definiteness and its import, proposed that there cannot be consistent and empirically adeuqate, locally real, deterministic quantum-mechanics. The work of Everett, DeWitt and others led to an inclusion of a distinction wrt counterfactual definiteness - and showed that by abandoning this preconception, a locally real, deterministic quantum mechanics can be consistent and empirically adequate.

Constructor theory sounds like category theory, studying categories whose morphisms are tasks. Category theory is inherently constructivist. I would like to see constructor-theory proponents tackle the topological portions of particle physics using standard category-theoretic language rather than these vague handwaves.

Forgive me if this has already been mentioned, but after a few days of thought, I was struck with a conceptual idea that in a fashion breaks quantum entanglement as it is presented. Within the video, it is described that for the two particles to be entangled, they had to have interacted with each other at one point or, as the quantum field mesh idea fleshes out, they need to interact with other particles that have in turn already interacted with the first particle. When explaining this to a friend earlier, I equated it to essentially the same type of configuration as the very Internet we currently use. That being said, going from let us say Partle A, to Particle B, could very well be traveling through an innumerable number of other particles in its journey, and as such wouldn't that mean that entanglement cannot actually be "instantaneous"?

there's a good book by Gregory Chaitin called Meta Math! that talks about the similarities between the Turing Halting Problem and Godel's Incompleteness Theorem, i wonder if constructor theory also is susceptible to the same 'unsolvability' cases that come about at the crux of these theories

But how does Constructor theory address unknown faults in its premises. This is the beauty of the scientific method. It is able to identify when a basic assumption is wrong (ie as happened with General Relativity).

While I see a lot of people seeing CT as having some statement about what physics is possible/impossible, I think the better way to see it, is that if we assume the universe operates under certain assumptions (infinite/finite, discrete/continuous spacetime, invariance, quantum etc.) then CT gives us insights as it what math is possible, and what math we should be restricting our models to. One thing that I've always been curious about is given the assumption of quantized energy levels, what are the implications that come with assuming that spacetime is continuous? The implications of discrete spacetime would mean that only a subset of the mathematics could be constructed that otherwise could be constructed if spacetime is continuous. Would the set of real numbers even be able to exist in a universe governed by QM and discrete spacetime?

Mr. Space Time: Direct question about space/time: If we believe that space is not really empty, but made up of some sort of "vibration field" or fundamental "fabric" - and we believe that ALL space is expanding in all directions, including the space we currently occupy, then it stands to reason that field would have to continually generate new field "material" or create new vibrations to fill in the gaps in space caused by the expansion. If this were not true, then we would have gaps or "holes" in space - which we do not detect - although our primitive technology may not be able to detect such a thing. Is anyone looking for holes in space? If new vibrations are being created, where does the energy come from to create them? Alternatively, if new vibrations are NOT being created and the fundamental vibrations/fabric is simply expanding, per the theory, might that explain the red shift of astronomical objects? This would imply that distant galaxies are not "necessarily" moving at such great speeds, but that space itself is distorting our perceptions of what we see. Do you have insights to this concept? Anyone else?

What about a unified theory between Quantum field Theory and String Theory where the strings in String Theory are the constant flow of quantum field energy (Quantum Field energy flows hence the flow could either be Lamina [Open Strings] or Turbulent [Closed Strings]) that flow through all particles that are formed in the quantum field. Theory: Quantum Field Theory describes a Particle's Space component while String Theory describes the Time component on the Space-Time coordinate geometry

This episode warped my brain more than a black hole warps spacetime.

This is like Getting an Answer on an Exam Question, without showing your work.

I am an engenneer , so nothing super fancy but. Using counterfacuals seem to wif a bit of the famus quote "mashines heavier than air cant fly". If we were aplaying that kind of methodology it would be super easy to rulle out airplanes . I dont wat to argue it just reminded me of that haha

What a magical mind/Mind trip! I’ve been reading CRovelli and Paul Sen, next: Marletta Chiari! Thank you for the challenge and the reward!!

In just a few seconds Matt gives the best explanation of entanglement I think I've heard, 9:00-9:10. Overall this is a perfect video to show senior high school physics students and any others, especially the economics students (I have a BEc), to help broaden their approach to the questions or conundrums in any field of knowledge.