Is The Wave Function The Building Block of Reality? 

The internet has me locked in a superposition of wondering _“How could humans be so unbelievably stupid?”_ and _“How could humans figure out something so brilliant?”_ at the same time

I like how this theory explains why gravity can't be quantized like the other three forces because it isn't quantum. And, it makes sense since gravity isn't supposed to be a force when following General relativity.

I always get a deep appreciation for Matt as he breaks down these ideas for everyone. Truly one of the great resources for curious minds in the world.

I don't always fully understand everything in the videos, but I'm happy you make them in a way to bring it down to laymen terms. I find this stuff absolutely fascinating and have been binge watching your quantum videos.

Wow! Diósi-Penrose model makes a lot of sense! The fact that the more particles implies the greater the curvature of space-time in a specific point in space it "forces" the wavefunction to collapse and to define a position. It explains why gravity cannot be quantized because gravity is curvature of space-time.

I like how Roger Penrose uses a ceramic cat and a hammer attached to a detector. Instead of a living cat and a vile of poison attached to a detector. So as to avoid the absurd spectacle of the thought experiment.

Penrose's idea sounds so elegant that it feels like it must be close to the underlying truth...

I'd love it if there was an episode going deeper into the experiments that can be done to probe and constrain objective collapse models, e.g. getting deep into literature on things like dual slit experiments with ever larger molecules, the experimental set up and connecting it to theoretical work. Love PBS Spacetime!

10:32 "Unlike the interpretations that we've discussed, for example Bohmian mechanics or many worlds, OCMs can actually be tested." FINALLY. This is the most exciting part of this video, for me. I was thinking, from the very beginning of the video, "Yeah, new theories are great, but... do they agree with the data?" and it took 'til halfway through for that discussion to start. That was a super long ten minutes. :P

Thanks to PBS for continuing to produce a high-quality stream of content that will inspire the generations to come to seek out truth and understanding

The Internet would be a much worse lace without, Matt. This is the most consistent, intelligent science show in YT.

Wait, wait, wait. So if I have this right. The Higgs field gives particles mass, that mass causes particles to warp space time, that warping of space time gives the appearance of an attractive force, that attractive force cause the density in an area to increase, that increased density causes a higher chance of particles to collapse, and that gives us a solid non-superposition reality?

I really wish I had had a professor like Doctor O'Dowd back when I was in school and thinking about what I wanted to do with my life.

These are my personal favorite "interpretations" of quantum mechanics! I just recently brought this up in our university journal club and nobody had head of these before. So glad to see a spacetime episode on this!

I have no background in physics nor do I understand half of what you're saying. But it is fascinating trying to wrap my mind around physical theories and the nature of reality they are trying to describe.

Excellent! I almost didn't stick with you when you brought up Copenhagen, but hooray! Finally an episode that talks about modern, viable, testable theories that push QM to the next level. My only quibble would be that Many Worlds should be considered a theory as well. It's the null hypothesis. It's linear Schrodinger QM at its leanest and purest. Copenhagen, Pilot Wave Theory, and most others are mere interpretations because they basically look at the simplicity and elegance of the Schrodinger equation and go, "Nah, that can't be right," and bolt on ad-hoc explanations of what they feel needs to be different to make it not so. _These_ theories, as I've mentioned before, are genuine competing theories, with testable hypotheses. That doesn't make Many Worlds _not_ a theory; it just makes it the null hypothesis, the one that's assumed true if the others end up being disproven... until one of them builds up enough evidence to make a convincing case that it _can't_ be disproven, and becomes the new null hypothesis. Calling Everettian Mechanics just an interpretation is like claiming that pre-20th century, Newtonian mechanics was just an interpretation, along with the Luminiferous Aether and Aristotalian Mechanics (an object wants to be at rest, and will return to rest if disturbed, etc). That just wasn't the case... Newtonian Mechanics was the null hypothesis. It was the simplest version of physics that fit the observations that could be made at the time. Luminiferous Aether is very much like Pilot Wave and other hidden variables theories. "Surely that can't be right... action at a distance? Light traveling through nothing, self-propagating? No no, there must be a substrate for light to travel through, to translate gravity from one object to another." And it... wasn't a _stupid_ idea, by any means. It just wasn't the null hypothesis; a simpler theory, without the ad-hoc addition of a substrate, was available, and the burden of proof was on Luminiferous Aether to detect the Aether, just as the burden is on Hidden Variables to, well... _show the hidden variables._ Copehnagen, to me, is very much like Aristotle. Both of them were very early attempts to rationalize and explain the behavior they saw, but with absolutely no evidence. Both are prone to deeply regrettable misinterpretations... objects having _wants,_ for Aristotle, and collapses needing _observers_ for Copenhagen. Both run into paradox after paradox, with more and more bits and bobs having to be added on ad-hoc to explain new observations (why does an object on ice take so long to come to rest? Is the ice providing a force to keep it going? If so, why doesn't it accelerate? - vs the Observer problem, the whole bugaboo about Conservation of Quantum Information, the Delayed Choice Quantum Eraser, which appears utterly paradoxical in Copenhagen but is completely trivial in Many Worlds, etc). Many Worlds is like Newton. It's probably wrong-or, more precisely, it's probably a simplification with validity within the proper domain destined to be seen beyond-but it's the simplest theory, the one that doesn't _need_ to prove itself. It's the one that other theories must supplant. It is very much _not_ "just another interpretation". It's the ultimate distillation of everything we can currently _prove_ about the universe around us, with no ad-hoc additions or stubborn concessions to our own intuition that says "but I don't see many worlds around me". It's just a huge and very long-lived sort of crowd-think that so much of the scientific community mistakes Copenhagen for having that spot... but that's okay. Nobody realized how silly Aristotle's ideas sounded for quite a long time, either. Edit: Actually, quite amusingly, it just occurred to me that the Delayed Choice Quantum Eraser is _exactly_ the same sort of paradox as the "why do objects on ice take so long to come to rest" quandary in Aristotle's world-view. To make ice and other low-friction surfaces work in that interpretaion, you have to ad-hoc some kind of force, or maybe even motivation that ice wants objects to keep moving, or some nonsense, then maybe add on something to explain why it doesn't want things to move if they aren't already moving, or that the object's will to remain at rest is stronger than the ice's will to keep it moving, but only just barely... I see basically no difference at all between that and having to accept and come up with explanations for why entangled particles can communicate backwards through time, and then maybe adding on something to explain why they don't _normally_ and so on. Quite amusing. xD Actually, I might even go so far as to say that the Delayed Choice Quantum Eraser is the nail in the coffin that once and for all disproves Copenhagen and shows it for what it really is: an early attempt to deny what science was telling them and make sense out of it to our macroscopic intuition, but that has very little basis in reality, and no evidence at all.

I wonder if in the future, once we've finally figured it all out, people will remember all the different yet fascinating theories that were competing to explain the weirdness of quantum theory. It also makes you wonder how many amazing ideas that were later proven wrong have been lost to the sands of scientific time. All these quantum theories are in agreement with all the experiments we've ran, and yet only one of them can be true. I mean it must be so, they can't all exist at the same time, in a sort of theoretical superposition of explanation... right?

An absolute banger of an episode. Its good to see physicists are still working on interpretations of QM. It often feels as though all the issues are just pushed under the rug.

Wonderfully made video and I am very proud so many fellow Italians and Italian laboratories are involved in this line of work.

I've noticed you have expanded you mind to possibilities beyond your classical science training full of "no's, not's and never's". Possibilities are exciting!!

Great episode, I especially loved the breakdown of the experiment on the ball emitting radiation. That was nuts how they were able to isolate it so much, they managed to detect single photons at a time. As necessary and fun theoretical physics is, experiments are the true heart and soul of physics and are the ones that bring us a step closer to understanding the reality we reside in. Just wanted to show some appreciation for the breakdown of an actual experiment and its results.

I’ve always been frustrated by the “mystical consciousness” reason for collapse and was delighted to learn more about other testable theories! After all, why should a wave or a particle care about our cognitive processes? Kind of implies consciousness is made of the same “fabric” as the quantum field, and when we observe, it’s like giving that fabric a shake. Neat to think about, but this is way more exciting! Best video yet!

This is one of your best episodes, please go into more detail on this subject!

I understand everything from every episode of PBS Space Time, just barely. It's the perfect carrot to chase down the search engine rabbit hole. It forces me to learn and to understand more, and it's addicting. Thank You!

I am grateful to be an observer in a relative location that allows me to understand a fair amount of the information coming from this and other Space Time videos. Videos like this let me scratch the QM itch I've had since high school without me having to sweat the math...

If gravity can collapse a wavefunction, does this mean that acceleration can as well? I.e. can an atom tell the difference between a rocket sitting on the surface of the earth and a rocket accelerating in empty space at 1g?

This is the best channel on RU-vid. Full Stop. You approach the impossible, and not only make it real, but make it understood!

Thank you so much, everyone at Spacetime, for these videos. You structure and write them in such a way that both a layperson and physics students with varying levels of understanding can grasp and enjoy the videos. In my opinion, you include just the right amount of technical information, equations and concepts to keep the interest of someone who has already learned about many of these topics, but not so much that you lose them entirely, and not so much that a person with much less understanding grows bored and confused to the point they turn it off. Goldilocks zone videos. Love them.

We need to sign a petition to stop the torture of the Schroedinger's cat.

Matt, you’re awesome at making me think about things I already know about in a completely different way, or introduce aspects of concepts I didn’t know existed at all. Thank you!

It's been a while since y'all put out such a thought provoking episode

Such wonderful content, thank you! Gravitational Decoherence makes a lot of sense to a layman like myself, but as always this video has raised several questions that I'll be pondering all weekend :)

This is amazing! Why isn't everybody talking about objective models more?! With such explanatory power, this could be a theory of everything. It's deterministic, no more quantum mambo jambo, it may connect gravity to the other forces. I got excited watching this, after so many years of frustration trying to understand the world.

Am I the only one who had a major mind blown moment by his definition of the wave function collapse in 1:16?

This channel has fed my curiosity of space so much that now im taking every possible science class in my high school and hopefully going to Boston university for a degree in planetary biology or astronomy to become a astronomer or astrobiologist

Man, this channel is the beast!!! just amazing guys keep goinglike that

I love this! I never really liked the ideas of many worlds or quantum gravity. This feels more intuitively right. Can't wait to hear how the testing goes. It's crazy that we can even test some of these theories.

So, wait... If we assume that the mutual gravitation of particles leads to collapse, then how are we able to maintain superpositions here in the Earth's gravity well? Wouldn't the environment inside a quantum computer be subject to the same superposition-collapsing effect as the rest of the macroscopic Earth? Wouldn't this be testable by measuring the error-rate of a QC device at various altitudes?

00:00 / 04:21 I paused it here to appreciate the depth and detail of that introduction to 'the interpretation of quantum mechanics'. Wonderful

Brilliant, a great show of our cutting edge knowledge of "what is this place called the universe and what is this stuff doing, and how does it do it!" I freaking love this channel!!! And Matt the narrator, seemingly brilliant, I mean genius level!!! And yet the humble, good willed teacher, who just wants to share his deep understanding with us curious and yet less informed neophytes , who (at least me, anyway) sometimes struggle to fully grasp the concepts, but are utterly fascinated with these subjects!!! Bravo, great job!!! And thanks!!! And Matt , you're a rock star brother!!! All the best!!!

I've been watching this channel for about a year, and it's starting to pay off. I'm actually starting to understand at least 30% of these videos. I'll keep watching till it's 100% 😁

So exciting to learn about this stuff! Feels like we're on the brink of understanding reality

This is now my favorite interpretation/explanation for the collapse of the wave function!

Just discovered this channel, got a lot to catch up on. Thank you for the very understandable explanations of complicated ideas.

"Instead of gravity being quantized, Penrose theory predicts that Quantum Mechanics will be gravitized" Penrose's way of thinking just fascinates me.

Another truly fascinating episode which branches into Objective Collapse Theories. There's nothing better than being surrounded by a whole slew of science magazines and periodicals while interspersing between the articles videos such as this. ✌️

Even though I've watched this episode 3 times... Our Pre-Deterministic Universe keeps me guessing

This episode was fire!! I really love the idea of being able to test things there experimentally. Cheers!

I think it's one of your best videos in the past year. It's sad you're getting so few views, I really hope it won't discourage you from making more in the same vein.

10:05 (image reference) I still think wave function is somehow tied to 4th dimensional shapes and objects. We are only seeing a fraction or shadow version of most objects, passing through our field of 3 dimensional view. And when it's in our window of view, we say the wave collapsed so that's where it is for real. But maybe it is in more places than we can tell. Things can be both inside and outside our window of view. And the part outside our view, we call a "wave of potential". The image of the planet moving through the gravitational wave at 10:05 in the video, is a good example of a 4th or 5th dimensional object moving through space/time. We cannot see the shape in it's entirety. Only the portion within our 3D view but, we can slightly detect there is or was more to it. So we call that the wave collapsing

I love listening to you Matt. Absolutely fascinating stuff. Mind-blowing....Now just understanding anything at all,all the time...now that therein is the problem...😁

Knowing that there are actual experiments we can do to test these is quite exciting!

Love this program, value what it contributes to our collective curiosity, and since I've not yet commented I thought it might be time. For whatever reason--and I'll have to think more deeply about why--this was my favorite episode yet. Cheers!

It's fascinating that the two biggest mysteries of our time both have powerful (but fringe) solutions from Roger Penrose. Wave function collapse being one, and the Big bang being the other (via his CCC). Penrose's imagination and independence of thought is truly remarkable. Also notable: his theories actually make predictions, unlike some other popular theories we don't need to mention...

Matt: The 'Temple Equation' describes Causality. e^mean*lambda=cos(mean)+lambda*sin(mean). You need to see the model sooner than later.

Loved this chapter, it explained so many things to me.

In music theory the more basic the harmony is, the more potential connections it has The more vague you are, the more avenues you can take But as soon as you bring in more notes, you collapse any avenues that are no longer possible As you drag it through time, it becomes narrower to maintain a strong structure Apart of this is a natural inclination to do so but also lives within our expectation Maybe the two theories could work simultaneously, maybe potentials exist in the physically world and interacts with the observer aswell similar to how notes parallel to each other aren’t harmonious but are apart of a parallel stream that connects at some point They go in opposite directions, but it doesn’t feel that way as it feels forward but in a minor equivalent But if you try to compare both perspectives, you see an opposing forces, that are not compatible unless you go with the flow or limit your perspective/expectation Chords consists of a series of notes, but these notes are not married to the chord It shares homes with many, many other chords That you may not be able to hear at the moment Maybe superposition is the process of sharing particles Maybe the observer part of us is connected to the universe in a physical sense The thing that seems the most disconnected yet the most harmonious I feel this would connect with how they say there’s an opposite universe going backwards in time Maybe they’re the inverses perspective on everything Viewing the same but opposite particles from the same but different angle Making backwards feel forwards

I like this explanation. Makes more sense to me than anything else I've heard.

As somebody who's been to the ICTP in Trieste, it warms my heart every time I hear the name "Gran Sasso" :)

I always think of the wave function as a formula that describes how to cook every variation of every type of food, in every type of oven, in every possible container, with every possible visual presentation in every possible kitchen in every possible place a kitchen could be. Only, we aren't talking about food, we're talking about the matter and forces of the universe.

I wish I was smart enough to understand the total depth of everything he said. That being said he's one of the best communicators for physics related topics.

4:40 - I have always had an issue when physicists say the waveform collapses when it is "measured" or "observed." Please mention that when someone measures or observes the collapse they do it by interrupting the waveform with matter, and the result is the observation. So instead, say that the waveform collapses when it interacts with matter (or whatever else), not when it is observed, because it would still collapse if we weren't paying attention to the results. Saying it this way removes any human agency in the phenomenon.

i really really appreciate two things about this channel: consistently impressive educational animations, and Matt and co having FAR more humility and open-mindedness than many other professional science communicators that engage in Internet drama and topics way outside their expertise. Refreshing to not have any hints of whiny clickbait from certain public intellectuals buddying up with greaseballs like Jordan Peterson or JK Rowling and talking about science and politics they barely understand beyond skimming pop-sci and wikipedia to get that sweet sweet short term engagement boost and publicity. Always hollering about how all the OTHER scientists are the problem. Just plain good science education for YEARS on SpaceTime. Matt (and Gabe) and perhaps Brian Cox are the true successors to Carl Sagan.

Matt O’Dowd is the very best explicator of quantum scale phenomena, dynamics and plausibilities, by an indeterminate but visceral certainty. You illuminate and clarify my window on the world, Matt! Thanks for your sequential, genuinely delivered logic.

Interesting. I'd been thinking the collapse was a result of interaction with other objects, and the more interactions, the more likely the collapse, which was why they tended to collapse when measured, as that required subjecting it to more interactions.

I’ve been watching Sir Roger Penrose’s career for 20 years. He’s got so many cutting edge ideas on quantum mechanics, consciousness and cosmology which make intuitive sense to me. It’s amazing to watch the scientific community come around to agreement with his theories. I believe History will regard him as an intellectual giant on par with Einstein. There is a whole episode of material around one point this video left out: Penrose doesn’t think consciousness causes the collapse of a wavefunction, he thinks the collapse of a large enough complex wave function IS consciousness.

Awesome work as always Matt. Great to hear a down under twang bro.

I'd definitely like to learn about white holes. I know nearly nothing about them, but the concept is so interesting.

So, I had an initial question, and it cascaded into other questions as I was typing. I don't really expect anyone to answer the entire train of thought. But I really hope that Matt would address at least some part of it. His beard always looks so good. Grow it out, Matt. Anyway.... If gravity collapses the wave function, that's binary, right? It's either collapsed or it isn't. Is that absolute? Does any amount of gravity at all cause the collapse? Or is chance of collapse increased with higher gravity? There's still *some* gravity in deep space. Galaxies affect each other's velocities. Is it enough that there is *some* amount of gravity felt at the barycenter between the Milky Way and Andromeda? Or is space there "more quantum" due to the extremely small pull? If that's still sufficient gravity, would you then need to go deep into the voids between threads of the galactic web to find a region of space that's fully quantum? Wouldn't it then collapse from the signal used to measure it? And if gravity collapses the wave function, what does that mean for the role of an observer in descriptions and explanations of quantum mechanics? There's certainly gravity in the box with Schrödinger's cat. And assuming gravity collapses the waveforms of each particle that that feel it's force, that would make all particles that we experiment on permanently collapsed, wouldn't it? That seems to imply the pilot wave theory to me. That even is we can't know a particle's absolute physical properties, they do *have* absolute values, but the measurementitself perturbs them according to the Heisenberg principle.

Wow, this is a really amazing theory. I hadn't heard of objective collapse theories before this!

This may be the most useful chapter in the Space-Time series. I keep wondering about the stark differences between Quantum activity and the real world we all live in. The approach laid out here starts to tug at the fact that the 2 systems are, and will forever be, distinct from each other even though they interact together.

Absolutely loved this week's episode!! Really exciting stuff!!

I love these videos on the quantum wave function. Thank you for another fascinating one. It's exciting to have some actual testable theories on the table!! Stay well out there everybody, and God bless you, friends. :)

"But maybe that is our mistake: maybe there are no particle positions and velocities, but only waves. It is just that we try to fit the waves to our preconceived ideas of positions and velocities. The resulting mismatch is the cause of the apparent unpredictability." (Stephen Hawking, 1988) spaceandmotion

When I was watching The Launch Pad LIVE, one person suggested me about your channel. Found Great Channel !

This is some quality content here. Thanks PBS!

The universe is like a giant sudoku puzzle. The more restircted the squares possible values have the closer you get to a single answer to the Sudoku. Just my way of thinking about the quantum.

I already had this question, and this episode reminded me of it. as sir Penrose has proven that according to GR there is a singularity at the center of a black hole, would the uncertainty principle affect the black hole?

Ok, i don't have any bucket list like thing. But now I think I do! I would love to spend a weekend with Matt, talking about spacetime, with him answering my questions (an ideal Matt, where he'd have time, be in my vicinity, and would enjoy and want to talk about spacetime to me). I would soooooo love that. I just feel such a fascination with the nature of reality we live in. And I would just love to sit and ponder, ask, listen, and ponder some more, meanwhile looking at some nice trees. Listen to beautiful music in between questions:). There, that's my dream!

Matt is so cool. This show rocks!

I greatly like the new ideas although I doubt that they are due to gravity in anyway ... perhaps 'Collapse' and Gravity have something more fundamental in common?

Also, objective collapse theory introduces an arrow of time independent of entropy.

What a wonderful video to supplement my quantum mechanics exam I had today

This is one of the coolest episodes of this show ever

Sounds like forgetting that the model is a model... the wave function gives you the distribution of possible outcomes, if you run the experiment over and over, you will see outcomes consistent with what the wave function predicts. But the universe isn't run over and over... the present moment isn't hypothetical, it isn't a probability... but also, not everything can be "well defined", like the position of a hurricane, you can see it on a satellite picture, you can point to it, but it doesn't have well defined edges... it's an effect that drops off with distance, it is a set of behaviours that interact in such a way as to perpetuate its existence, but it's not "a thing", and any description of it as "a thing" in "a place" is necessarily incomplete, but still useful.

Those new theories and interpetations of QM are a necessary step to the real question. What exacty is the wave function? The physical aspects of it. With every new theory we take data and try to find which ideas could fullfill these data....!! One thing that really is overlooked is that the schrodinger dif equation is a lot alike the light dispersion dif equation.

Great video I was looking for it 3 days ago and now it’s here lol

This is one of the most important areas of physics study I can imagine. Unifying quantum and Newtonian mechanics in the same universe is a rationale I’ve been wondering about for 40 years.

It sounds like a great theory that explains a lot, but I’m wondering why the curvature of spacetime itself cannot be in a superposition. From an earlier spacetime video, I understood that mass/energy causes time dilation, which in turn makes masses attract (gravity), and that this is what “curved spacetime” is. Is that the reason why it cannot be in superposition? Because if it could, time could be running at different speeds in the same reference frame, which I imagine would break causality and give us some spicy paradoxes.

Hang ten! Surfing the waves through the wormholes! Tasty waves, crunchy tunes.. exciting! Gratitude to everyone that create this revolutionary new theories and scientific advancement! Congratulations peeps! Keep on rocking!

Great episode. THANKS PBS SPACETIME!

Great show as usual ! The concept of small things can stay quantum , but the chance of collapse to classicality increases with size is interesting . The concept of consciousness could not exist in a « quantum existence » since conscious need a precise wave function collapsing to make sense of anything logical at all ( ie: principle of causality?) .

Wow: a Kugelblitz! Never come across this concept before, but it makes sense as E=mc². Black holes from focussed gravitational waves or light? Mind blown! Thanks for another great episode. 👍🏼

I love the Wren promotion with the bird taking a poop mid-flight. 😁

Wow. A very useful intro to objective collapse theories. The description of the Diosi-Penrose model was helpful in understanding some of Penrose's thinking about consciousness and quantum-gravitonic microtubules. I still think Penrose is off-base about conscious experience, but I am now less dismissive than I used to be. I hope you can compare objective collapse theories to superdeterminism, like the ideas of Tim Palmer and Sabine Hossenfelder? What's staistical independence got to do with it, is it just a second hand emotion? Quantum 2.0 wants to know.

The simple explanation is, particles are manifestations of energy in a wave function that exist in a field. The trick is defining the wave function and the field.

Very interesting. To me, this make sense and gets the 'mysticism' out of quantum mechanics. Looking forward to seeing what the experimental evidence can tell us. Oh yes, never full trust a physicist with taking care of a cat. We're looking at you Matt!

I recommend watching Arvin Arsh's short video "Why there is no diffraction of tennis balls" - because there are simply too many atoms involved in the experiment.

8:42 I hadn't heard about this Diósi & Penrose idea before, but I have to say, this is the one that makes by far the most sense. Landau & Lifshitz's volume on Quantum Mechanics (first published in 1948) explains wavefunction collapse in terms of interactions between quantum and classical particles forcing the quantum particle to lose some of its wave-like properties. They didn't provide any math for this, but they also frequenctly emphasize that classical mechanics is the "short de Broglie wavelength limit" of quantum mechanics, so it does make sense as an explanation. Diósi & Penrose's theory is essentially a theory on the physical mechanism of why classical particles force quantum particles to act classically rather than the other way around: They have a larger mass, and gravity is what forces quantum particles to become 'classical' in the first place. Excellent stuff!

Oh though I find myself struggling to fully comprehend these theories I am great full of this work. Thank you and keep up with the great work.