Sixty Symbols should explain more physics ideas using Ed Copeland analogies.

"Are you alright darling?" "I'm being maintained annoyed in some regions of space" "oh"

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Level 5 Multiverse: Multiverse that doesn't have any math or physics but runs on something completely unknown to us. Alien concepts, logic and types of things..

Don't fuck with Ed

Can Numberphile do a video on different types of mathematical structures? I think I get what the level 4 means, but I'm not quite sure. It would be helpful if you guys can expand on that a bit. Also, can you guys do a video on decoherence? That would be really interesting as well, thanks a bunch.

Quote from the Wikipedia article on the Mathematical Universe hypothesis: "in those worlds complex enough to contain self-aware substructures they will subjectively perceive themselves as existing in a physically 'real' world" This absolutely blew my mind.

Level 4 multiverse makes my imagination go wild.

You should do a video on Boltzmann Brains.

About that 'seeing circles in the sky ' thing... it seems strange, coz if it is an actual contact between two universes, then what set of definitions are we using to distinguish them as 'different' ? If they can meet, they have a common interface of space and hence they are essentially a part of the same physics domain. Also, during impact, don't they influence or interact with each other?

Ed being riled up: **no footage found**

Right when he said "Well they're right on top of each other but there's no way to communicate between them" audio from another browser tab started playing in my headphones at the same time as him talking and my mind exploded

I listened to an audiobook a few years ago that mentioned something that I've not heard mentioned elsewhere. The idea was that the Pauli Exclusion Principle means that if the universe is above a certain size that every possible combination of quantum states would be present, and the exclusion principle would mean that the universe would have to begin to repeat. It was an interesting idea, and I'd really like to hear more about it.

everytime i watch this video i get more curious about what Prof. Copeland is like when he''s angry

Haven't seen Dr Tony in awhile. Thanks for the video and keep going! It's great to see theory and it makes everyone better for seeing these types of videos. Thank you!!!

Fantastic video Brady and fantastic explanations! What a great teacher. The amount of silly speculation on multiverses on the webs has been ridiculous lately, now I finally have a solid starting point to bring the discussion back to reality! Once again proving why you're one of the best producers on KZfaq. Keep up the good work :)

I like the forth type. Radical thinking is the only thing thats gonna take us forward from this point.

level 4 are in there own continuum. according to max tegmark the level 4 multiverse dont exist in spacetime but spacetime exists (the universes that have space and time instead of other unique math or equations) in them. so they exist in a completely different physically really reality. its hard to imagine. those realities have the right to be called universes of there own. even though nothing there will never effect whats happening here and vice versa. but they are physically out there. they could look like anything you can imagine and even cant imagine. my brain really hurts trying to imagine level 4 multiverses but whichever universes in the level 4 multiverse can have self aware entities they are just as real as we are. according to tegmark also theres literally no way of ever comprehending or knowing if such a mathematial set of physically real realms is possible or real as like i said there nothing from there or here can effect each other no matter how godlike one can become. its almost as if they are real but at the same time not real for us and for them ours isnt real either. but they exist physically somehow somewhere but its almost a paradox. because the level 4 dont exist in a space but in a hypothetical unreachable existent containing our reality that contains space with other realities and universes that perhaps dont have space or time but wholly alien concepts and colors and rules and nature.

Hey Brady, thanks for the video! You should do a numberphile on different mathematical systems, that sounds really interessting!

Very well explained Dr. Padilla.

Level 5: They could all be true. Or would that be included in level 4? Come to think of it that is probably the case...

Can someone tell me what exactly is in between the parallel universes in the second level? It is obviously not space..do we have a clear understanding of the all pervading medium ?

Awesome video guys!! Great topic and even better explanation.

amazing... and amazingly explained by Dr Padilla!

So does this mean that somewhere in a level 4 multiverse, Bitcoins might be physical entities?

Is Dr Padilla using Professor Copeland as an example just to rile him up? =p

Great explanation! Loved it.

Love the "maths is reality" theory, the one thing that permeates all the universes. So someone in a different universe could study the maths of our universe, see that it checks out and think "damn that'd be weird"

I have my own hypothesis for a multiverse. First of all, considering the notion of higher dimensions, we have no experience of them and so could not have a clue what or how they are, we can however look at the dimensions we do have, and work up from 1D to 2D and so on such that we can repeat the difference for higher dimensions. From 1D to 2D you find that 2D can be described as an infinite amount of 1 dimensions put together in a dimension- so you have the same dimension over and over, each varying from the others, being further on in the new dimension, the same goes for 2D to 3D. Also the two dimensions in 2D are exactly the same, in fact the only difference is perspective. Now let's apply this to 3D, we have an infinite amount of 3 dimensions put together, varying across the new dimension, this actually describes time pretty well, however, from our perspective, we only experience 1 position of "time", whereas we can experience multiple in the lower 3 dimensions, hence the differences. Although, from before, going along with this hypothesis, we also have that "time" is exactly the same as distance, it's just a matter of perspective. Anyway, we now have 4D, a "line" of an infinite amount of 3 dimensions, containing all variations of those 3 dimensions, lets do it one more, now we have a plane of these infinite amount of dimensions in 5D, an infinite amount of "variations in the timeline" so these would be alternative universes. Now let me clarify that when I say variation, a different arrangement of particles. Anyway you could continue to do this, I loose all grasp of what I'm trying to comprehend at 7 dimensions though if I'm honest. However the point that all dimensions are the same and perspective is the only thing that makes them seem different is the idea, this would also mean particles can travel through the dimensions, and that could be a good explanation for quantum probabilities- there will be structures across the higher dimensions because forces in this dimension (and others) attract particles, meaning cross dimensional structures would compliment the structures within the dimensions and vice versa so it wouldn't interfere with the mechanics we know in our 3 dimensions (and a half- time). Let me also say that I'm not saying that the 4th dimension is time, or that time is like distance, but however, the 4th dimension we experience (they're all arbitrarily similar) that is exactly the same as distance is experienced by us as time, and if we somehow changed our perspectives through dimensions, we could walk through what we call time. Also since we move with respect to a dimension that we only exist at one point on, the notion of motion is meaningless when looking at all the dimensions, and really everything is more of a multidimensional image- we experience movement because the particle arrangement at each later point of the "4th" dimension is such a way that our brains contain memories from the previous points. But I'm not saying we're not moving, just that moving is unique to particular perspectives of dimensions. Sorry for the long ramble- I had so much to say and it's hard to put this kind of thought into a youtube comment and it didn't quite turn into a particularly great explanation, it's only an idea I've thought up which I think is at least self consistent and would make sense with what we see in our universe. I'm not sure anyone will read it though ._.

Ah. The observable universe iS ginormous.

one of their best videos

Thumbs up not only because all Sixty Symbols videos are great, but in particular because Dr Padilla actually uses the word "Ginormous"!

I like the theory of a fractal universe. One where there is a universe inside every black hole. With black holes inside the universe that's inside a black hole. It could go on forever. In a singularity there is no time any space but a portal into the next universe. That could be the theoretical wall.

3 Doesn't need to create a whole universe for every collapse that's just a convenient way to think about it. I always pictured that every possible universe was created all at once and every time you have what we call a collapse one of the infinite number of them diverge from the rest of the pack that are still in sync. So still probabilistic but accounting for every probability being played out somewhere without some magic universe spawning every time you flip a coin.

Yes, more with Padilla!

I'm really looking forward to advances in research on Ed Theory.

I can't help but feel like Dr Padilla doesn't quite understand what the Many-Worlds interpretation really means. And to be fair, I very well may not either, and I'll admit that Dr Padilla knows several orders of magnitude more about physics than I do. But I did want to clarify a few things, as I understand them: One "world" refers to a "blob" of the wavefunction where the amplitude is greater than zero (and therefore, according to Born's rule, the probability of finding ourselves there is greater than zero). Two worlds would refer to two seperate such blobs. There is no need to have a specific moment in time at which two worlds split. To understand this, it may help to look at a function over the real numbers: Imagine a function g(n)(x), which is just a normal distribution with the mean at n. (So it pretty much looks like the blob I referred to). Now we can imagine that the wavefunction at time t is g(t)(x)+g(-t)(x). (I'm not choosing this example to represent anything meaningful, just to see what it would look like when a world splits up.) At time t=0 it would just be a normal distribution, because the two terms in the wavefunction are g(0)(x). But at time t=100 there would be two seperate normal distributions, or blobs, one at x=100 and one at x=-100. There wasn't any specific point t when these two blobs split up. I'm not sure what he means by increasing the size of the state of the quantum system. As far as I know, the evolution of the wave function is unitary, _unless_ you incorporate a collapse postulate which states that all but one point of the wavefunction suddenly goes to zero. Decoherence is, in a way, synonymous with Many-Worlds. Two decoherent "blobs" in the wavefunction correspond to two seperate worlds. This all means that the Many-Worlds interpretation is the natural conclusion one can draw from looking at the wavefunction. Anything else would require to add additional information, which goes against Occam's Razor. Also, every law so far in physics is deterministic, which suggests that it's likely that physical laws in general are deterministic.

The 4th one bothers me. I can understand this as being an extension of the 2nd option, where instead of merely altering constants we alter the fundamental equations, but it strikes me as mathematical mysticism.

@10:12 The splits occur at all times. It's why the many worlds theory is so fascinating, because literally every moment is an infinity of possible moments coming into existence.

The reason I like many worlds is it explains quantum superpositioning and waveform collapse of a particle as it entangling itself with our universe creating many with different positions in different universes or whatnot

If Tegmark can prove that reality is Godel complete, I'll accept his walking off the firmament of physics and grasping onto a stairway to the Platonic ideal.

Last I heard there are five types and what he describes as level fours are what I've heard described as level fives and the real level fours that he skipped over are called Daughter Universes. These daughter universes explain away the grandfather paradox. Basically there's a different universe for every possible outcome of every event. Imagine Schrodinger's cat. After you open the box a new daughter universe is created so there's a universe where the cat is dead and one where it's alive. So if you go back in time to kill your own grandfather, once you arrive in the past you instantly create a new daughter universe since you didn't exist in the past of your original universe so you can kill your grandfather in that daughter universe without threatening your own existence because in the past of your original universe your grandfather is still alive and well. The catch is you may never be able to get back to your original universe even if you travel forward in time again you'd likely just wind up in the future of the new daughter universe you created by going back in time in the first place.

Well done! Love your video!

''The universe could be absolutely ginormous'' It's not like that now? :O :D

I think a level 4 multiverse is actually the only thing that really makes sense. Everything that can exist, does exist. That, or nothing at all. But since we exist, it has to be the former. *Edit* I just thought about it again and changed my mind. Copied from a comment below: If all of the possible universes are just manifest without any kind of probability distribution attached to them and assuming that it is possible to construct at least a countable number of contradiction-free mathematical systems to any given base set of contradiction-free axioms by just adding stuff, this means that Occam's razor goes right out the window. Since this clearly does not correspond to our observations, it's reasonable to assume that any given universe has a higher probability of having a small set of rules than a large one.

Guys, bare in mind that all of this is theory. Don't go about your day now believing that any one of these IS the way the universe is because the fact of the matter is that it's highly unlikely that we'll ever be able to even attempt to prove these theories. Instead, go about your day understanding that all of these could possibly be the way reality is.

I like this guy... He managed to ''explain'' something so unfathomable... awesome

MIND BLOWN

I have a problem with the type 4 multiverse. It just seems like navelgazing, to me. Mathematics isn't a component of reality, but a way, a language, to describe it. A language that we have invented. If that language had indeed concluded that one plus one equals three, or "scrubbeildupe", or "licorice wrinkle", it would still just be subjective descriptions of a constant. Isn't it the same thing with other realities? In one of these universes, even if one plus one can seem to equal three, from our point of view and lingual context, isn't that is just a failure of ours to detach ourselves from our own universe, from our own circumstances?

This guy was high in cosmology class.

Multiverses are possibilities that converge to resolve into a perceived "reality". We live in a multiverse of possibilities. Rather, our existence is projected onto a canvas of multiverses of possibilities.

Awesome! I was missing Sixty Symbols!

Well, that would answer the pesky question of whether Mathematics is invented or discovered...

Quantum mechanics is likely only probabilistic due to the inability of precisely measuring all variables involved, and not due to some true randomness in nature. Randomness has no logic to it, so I am weary of thinking of it as real, therefore I only take deterministic interpretations of quantum mechanics seriously. I recommend Max Tegmark's book. I do like his Mathematical Universe Hypothesis. What he says makes a lot of sense.

I am quite interested with that 3rd degree universe. is there a chance for us to hear more about each universe in its own separate video? The way I see that 3rd type of universe is a bit like time having one or possibly more dimentions to it. like you can go bacwards and forward in time (toward and away from big bang) and you kinda ride this shockwave that is present radiating away from the center and stretching yourself out, getting more and more fuzzy so there is not really a split but a cone (unless you start at the big bang)

One interesting point Max Tegmark mentioned in his book when talking about L3 multiverse is that if the universe is infinite (or even just colossally huge) a level 3 multiverse can be interchangable with a level 1 multiverse. So in a L3, from each point, you have all possible quantum states that become a reality. In a L1 multiverse, assuming it's again, infinite-ish, the combinations of matter will repeat themselves in such a way that there is another pocket universe where those alternate universes DO exist. Not necessarily as a direct result of causality from your current point of view, but none the less just as real.

Level 4 begs for the questioning of reality. If a universe has faulty mathematics, meaning that it can't exist, does that mean that it doesn't exist? Or has it tried to exist but it failed? How can we know if those universes are real, if our eyes aren't real ;)?

#4: everything exists. there's a real universe somewhere, right now, that looks like a cartoon. one where light is 10x as fast. one where every KZfaqr is required by law to like this comment. mind blowing

I think of the Many World hypothesis as follows: There is just one universe at a time, andeach instance wouldn't manifest itself immediatly but over time. When this universe is dying (it doesn't matter if big bounce, heat death, big rip or any other) all the fundamental blocks would be shuffled and a new universe with new properties and/or outcomes will be formed. I'm thinking of the microwave backgroudn radiation of a unique fingerprint and in this prior described scenario we will have a new fingerprint. Over time and probability every possible outcome could manifest by itself and we're just lucky to life right now in this universe with this specific fingerprint. The next universer will have a new fingerprint and a certain cointoss will be tails instead of heads and nothing else changes. In general i just think, there is no need for more than one universe when thinking about repeating itself indefinetifly with always new properties.

I am sorry if this question is stupid, but do Sixty Symbols have a video related to Hyperdimension? I got really into this lately and since I don't follow Sixty Symbols from the beginning I can not tell if there is one that I am not able to find on google. KZfaq is full of ~amateur~ content on this and I think it would be a great topic for Sixty Symbols to do a video or even a series on.

Love these videos. Keep up the great work. Really well described for the lay person as always

Question: Would it theoretically be possible to measure the gravitational force on an object near the border of the observable universe that it gets from an object outside of the observable universe?

Brilliant - thanks

@tony.p since the constant are different can there be a collision such that a universe of dark matter collides with universe of normal matter. Note dark universe is 5x large as ours

Birdkeeper Toby brought me here. This is intense stuff and I find it EXTREMELY interesting.

a video on the different interpretations of Quantum Mechanics would be good

Interesting stuff

I'd really love to see arguments for each of these theories. It seems (without seeing any arguments) that choosing to believe one or the other is just arbitrary. I really hope to see an expansion on this video!

I found this a nice subject to think about,I also don't find any of them hard to imagine but these theories are what really get my mind to think and play many other thing are not as in the lack of the better expression as interesting

This is nice to listen to while high. Amazing trip.

How about a video on the relationship between quantum decoherence (which Tony was talking about here) and the thermodynamic arrow of time which Sean Carroll talked about before? Are there two separate arrows of time, one from wave function collapse, and one from thermodynamics? Or are they somehow equivalent?

Man, Tony was on fire for this one! Thanks for your good work, Brady.

I think of Godel's incompleteness: "Any axiomatic theory recursively enumerable and capable of expressing some basic truths of arithmetic can not be both complete and consistent at the same time. That is, there is always in a consistent theory true propositions that can neither be demonstrated nor denied. " "A theory, recursively enumerable and capable of expressing basic truths of arithmetic and some statements of proof theory, can prove its own consistency if and only if it is inconsistent." In my modest opinion nonlocal and even tridimensional aporetic statements couldn't be mathematically described.If they do so, it will never be proved.

Good, I was hoping for a bit more extensive coverage on various multiverses.

I loved the reference to Ed. I'd have to agree, he is a pretty cool guy ;)

will the gravitation const also change ??

Hm, would the following make sense for the many-worlds-when-does-it-split: we can assume a plank-time, the shortest-possible duration between two events, or the time required for light to travel plank-length (is this even possible?). Or think it as the shortest possible time we can assume between two measurements. If we can assume a plank-time, we could say that a universe splits at each plank-tick, between two plank ticks there is only uncertainty. That might sound a bit esoteric but this is only because of my low layman level :) Thoughts?

Sometimes, when thinking about multiverses, I wonder whether our universe actually exists. Maybe the whole universe is some sort generator that would "play" our universe if the right generation seed was supplied, until then we just exist in some probability space outside of what the reality actually is. Like with the Library of Babel website where you can find any book you could possibly write. But are these books a thing until you open them and generate them? Or is that a part of the mathematical universe theory?

The idea of Ed becombing an inflaton and blowing up on random walks is pretty scarey. Don't think I want to live in that universe...

Nice video !

I like the idea of the type 3 universe. I've been wondering about this sort of stuff for years (and still do), and I believe that there are no splits, but all these universes already exist. They just share the beginning of their timeline. (And there's at least an uncountably infinite amount of them) I think this fits with the idea of backwards time travel nicely, universes in which a paradox would happen simply don't exist. If backwards time travel is possible, it won't actually happen if it would result in a paradox in that universe.

Physical constants are the same everywhere and -when in our universe, right?. However, for level two multiverse, somehow it really feels awkward, as you might have a new universe "contained" within ours but has different constants. Would you please give me some answer?

Tegmark's level 3 multiverse is not based on the assumption of solving the probablistic model. It was, rather similar to the string theory, based on something much simpler and later interpretted as a level 3 multiverse. The assumption was: what if wave function doesn't collapse (no decoherence).

9:20 Correction, according Max Tegmark’s Many Worlds in Context a split doesn’t occur at the time of an event as described in this video. According to him I believe all many-worlds configurations have existed since always similar to how I also believe common scientific consensus holds that spacetime exists as a static eternal infinite Minkowski spacetime or whatever the appropriate description is so an event wouldn’t actually cause this controversial mysterious explosive birth of multiverses which many have issues with. Others may disagree though.

Good job on that coin flip visualization ;p

A lot of these concepts (like hierarchical universes) can be explained much more clearly using analogies with computer simulations, virtualisation, emulation, etc., and even things like superscalar CPUs and speculative execution (modern CPUs can start executing code that depends on some test _before_ knowing the result of that test - they start executing the most likely outcome, or in some cases both possible outcomes, and then kill the branch that turned out to be unnecessary once the result of the test arrives). It's a problem (or a lost opportunity) that becomes more and more apparent as different fields become more specialised - the people in one area don't necessarily know much about other areas, and fail to notice important parallels (which might actually be connected in some cases, but, even if they're not, can be used to get some ideas across more clearly). For example, a lot of algorithms used to compress audio and video have strong parallels with the way the human brain processes vision and hearing, and while codec writers do take some psychovisual / psychoacoustic elements into consideration (especially for lossy codecs, that try to preserve _perceptible information_, rather than hard data), I have a feeling that very few neurologists have ever bothered to look at how JPEG or MPEG work. If they did, they'd probably find some clues that could guide their own research, and they'd definitely find some parallels that would make it easier for them to _explain_ their research to other people. Even purely "mathematical" algorithms like LZW / LZ77 have some interesting parallels with human memory.

Please do a video on Boltzmann Brains!

If the 4th level "physically exists" doesn't that mean that it's testable? Or is the term "physical" used in a different way here? I could say that the moon physically exists because astronauts landed on it. Similarly, could I say mathematical universes physically exist because we it? Another great video on the subject, I'm loving these.

Could it be possible for there to be a universe in which maths doesn't exist at all, as in there is no such thing as quantities (like numbers) or operations to do to quantities (like addition, subtraction, etc...)? What about a universe with no space and no time, and it just operates in a completely different way that's entirely separate from dimensions. Maybe an extremely simplistic universe, where there's just this one eternal state? All I seem to be able to see when I try to picture this, is a universe where there's just one solid colour, that's always there, except not really because a term like "always" is irrelevant because time doesn't exist. Obviously the concept of colour couldn't possibly exist in such a universe, because colour requires light and everything. but that's the only thing left that my mind seems to be able to picture, when things like space, and therefore shapes, are taken away. Human language is very restrictive when it comes to this kind of thing because it's evolved only needing to describe how things are in this universe, with our laws of physics. What about a universe that's not so different to ours, where space and motion and things are allowed, and say maths works in the same way, but when it comes to physics, different mathematical formulae govern things? Suppose F=m/a in this universe instead of F=ma, as I believe someone else in this comment section said. How would that work? The way that motion behaves in this universe would have to coherently conform to that formula no matter what, in much the same way as motion in this universe always conforms to F=ma, and I try to picture how that would work but I just can't.

Level 2: bubble within a bubble due to different constant values, the expansion of the inner bubble does not necessarily imply the expansion of the outer bubble. the inner bubble can expand and it's total interior volume becomes greater than it's exterior volume so it continues to occupy the same space in the exterior bubble which remains unchanged in both interior and exterior volume.

One question, it might be silly though, from the entropy point of view in our universe, dS/dt >=0 at all times. Increasing the number of states would thus increase entropy which matches our universe (this could very well only happen in our universe). However, if we assume this happens in the multiverse space, increasing the number of universes wouldn't also match the principle? (Many worlds interpretation).

Tony is my favorite physicist. Please more videos with him!

Great video :-)

Imagine entering a universe where the speed of light is a walking pace...

I really like Tegmarks Book about it. Highly recommend it. .

Level 4 is the closest anser to a deeper, more fundamental question: Why is there something instead of nothing? It does not answer it, but comes as close as you can get.

I can 100% guarantee you the universe is exactly absolutely ginormous.

Could the inside bubble be larger than the outside bubble because of changes in physical constants? e.g.scales

Great video! Cool! :)

There's a fine line between genius and madness, and I have the feeling that some physicists have jumped right across that line.