[HN Gopher] Why this universe? New calculation suggests our cosm...
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Why this universe? New calculation suggests our cosmos is typical
Author : rbanffy
Score : 88 points
Date : 2022-11-18 12:53 UTC (10 hours ago)
(HTM) web link (www.quantamagazine.org)
(TXT) w3m dump (www.quantamagazine.org)
| jl6 wrote:
| How confident can we be about what other potential universes
| might be like with different fundamental constants? Maybe if we
| pick one constant and vary it slightly, we can reason that there
| would be less carbon, but how do we know that some other
| combination of parameters wouldn't create some other phenomenon,
| unknown in our universe, that could act as the substrate of life?
|
| Especially considering we may not know what all the parameters
| are.
| [deleted]
| [deleted]
| Garlef wrote:
| There could also be a bias here.
|
| Maybe cognition that develops in a cosmos and is able to reason
| about cosmoi is more likely to develop models of cosmoi that make
| their/its own cosmos very typical.
| julienreszka wrote:
| Yes it's called the Anthropic principle
| optimalsolver wrote:
| https://en.wikipedia.org/wiki/Anthropic_principle
| jessermeyer wrote:
| I don't know how much bias the fine structure constant has on
| the function of cognition, but I think we can all agree that
| constats incompatible with higher level biological function
| like cognition would never produce arguments in favor of their
| typicality.
| sigmoid10 wrote:
| The answer is: A lot. When looking at fusion processes that
| create carbon, if the strength of the electric force
| (quantifiable as the fine structure constant) were just 4%
| different, our universe would never have produced enough
| carbon to create life as we know it. The limit is even
| tighter for the strong nuclear force - less than one percent.
| If you pick arbitrary constants, you'd very likely just end
| up in a universe that contains only protons and no higher
| elements. And it gets _even_ weirder when you start looking
| at gravity, because most universes should actually have
| collapsed again long ago or expanded so fast that no elements
| could form. Some of these fine tuning problems can even be
| looked at in the absence of intelligent life, because even
| for a liveable universe they seem ridiculously fine tuned to
| support what we actually see in the sky.
| jessermeyer wrote:
| I carefully chose my word "function" instead of
| "existence".
|
| Give me two different universes where cognition exists but
| where the fundamental constants differ. Would you expect
| the ability to perform syllogism would be fundamentally
| biased to reflect the constants which brought about their
| existence?
| sigmoid10 wrote:
| Easy. I present you two universes, one with our
| cosmological constant and one with a slightly smaller but
| still nonzero one. The differences would only become
| apparent over distances greater than a few billion light
| years or so. Out planet, solar system or even the entire
| galaxy would be virtually indistinguishable. But
| inhabitants of both would wonder how the cosmological
| constant got cancelled out so precisely against the QFT
| vacuum over so many orders of magnitude when studying the
| sky. No bias required.
| [deleted]
| [deleted]
| malfist wrote:
| Well, I checked all my samples and every single universe I've
| ever seen is identical. Right down the the atoms.
|
| I think I need to be published!
| nsxwolf wrote:
| This comment should not be downvoted. It is entirely correct.
| Matches my own observations - this universe is exactly the same
| as all the universes that are known to exist.
| bilsbie wrote:
| Perhaps we're overdoing the copernican principle at this point?
| It's weird how researchers internalize that to the point they
| can't even fathom that anything about existence is special.
|
| IMO that well is dry and our future breakthroughs will come from
| focusing on the observers of the universe.
|
| (Thanks for attending my Ted talk)
| layer8 wrote:
| Specialness requires explanation, or alternatively it's just a
| fluke. The latter is unsatisfactory, so we're looking for
| explanations, and if there are none, or they again require
| special assumptions, then the natural conclusion is that there
| is no specialness.
| wongarsu wrote:
| Some amount of specialness is normal. If our place in the
| multiverse can be described by 1000 random normal-distributed
| variables, you would expect 50 of those values to be at least
| two standard deviations away from the mean, and 3 variables
| to be three standard deviations off.
|
| Of course we don't know which ones, so assuming any one thing
| to be normal is the best approach. But looking at the big
| picture, there are bound to be flukes. Not having any would
| be an even bigger fluke
| _Algernon_ wrote:
| Seems silly to try to calculate probabilities from a sample size
| of 1, but what do I know.
| diegoperini wrote:
| British may think otherwise.
|
| https://en.wikipedia.org/wiki/German_tank_problem#Historical...
| _Algernon_ wrote:
| I'm missing where they estimate anything from a sample size
| of 1. Care to enlighten me?
| diegoperini wrote:
| It was a joke, they didn't but the problem has a formula to
| estimate the total number from a sample size of one tank,
| explained in the wiki article under "One Tank" section.
| vehemenz wrote:
| It's theoretical physics. Metaphysically and experimentally,
| the question may be absurd, but the exercise of calculating
| entropy for potential universes could still yield novel
| understandings about the actual universe.
| samatman wrote:
| Silly is an excellent word to use when describing a category
| error, agreed.
| layer8 wrote:
| If you have two competing theories, one requiring fine-tuned
| parameters and the other not, then the latter seems more
| plausible, because it requires less assumptions. Our universe
| being "typical" in the context of some theory just means that
| it requires less fine-tuning, and therefore the theory arguably
| has more merit.
| zwkrt wrote:
| But the problem is that we have no evidence to suggest that
| our universe is typical in the first place. For all we know
| there are a trillion trillion universes and ours is the only
| one with gravity by some fluke, and we are actually living in
| the least likely possible universe.
|
| And that's the issue is this model is trying to 'work
| backward' and justify our universe and it's constants as
| being mathematically harmonious and 'typical' without having
| any understanding of what the actual value of 'typical' is.
| layer8 wrote:
| What I tried to explain is that this is not really about
| other universes. The logic applies even if our universe is
| the only one. It is about the amount of seemingly arbitrary
| assumptions we have to make for the theory to explain our
| universe.
| zwkrt wrote:
| But we end up having to make other arbitrary assumptions
| about what happened at the very beginning of the big bang
| or about multiverses that we have no scientific
| justification in making. Calling the observed physical
| constants 'arbitrary' is a very mathemetician-like move.
| It is true that they are free variables in the sense that
| they cannot currently be derived--mathematical models of
| the universe must include these constants as hard-coded
| values. But the word arbitrary implies that they could
| have been something else, and we really don't have
| justification for that.
|
| We write the modeling program and somewhere we write
| FINE_STRUCTURE_CONSTANT=1/137;
|
| It is very tempting to instead write
| ./my_universe.sh --fst=0.007 ...
|
| The code does the same thing, but as far as we know that
| constant is as invariable and intrinsic to what it means
| to be a universe as PI is to what it means to be a
| circle.
|
| It is fun to think about but it can't produce scientific
| results. It's epicycles, coming up with more complicated
| stories that over-fit for a singular observation.
| layer8 wrote:
| > But the word arbitrary implies that they could have
| been something else, and we really don't have
| justification for that.
|
| Well, we're looking for a reasoning that would support
| that they couldn't have been something else, and the
| article is about one way of coming closer to that.
|
| There are really only two possibilities: Either there's a
| reason why they are what they are, then we want to find
| that reason, or there is no reason, then in other words
| they are arbitrary.
| teolandon wrote:
| Both theories are assuming that the parameters are tunable.
| Why would we assume that?
| layer8 wrote:
| The parameters are "tunable" because we know of nothing
| that would prevent the parameters from having a different
| value. The particular values they have aren't a logical
| consequence of other known facts, and hence appear to be
| arbitrary. They are tunable in the sense that if they were
| different, no logical contradiction would arise. There is
| nothing that compels them to have the particular values we
| observe them to have. This means we have no explanation of
| why they have those values.
|
| But one goal of science is to provide explanations of why
| the world is how it is. If we can somehow reduce the
| apparent arbitrariness of a parameter, or remove it
| completely (by having it be a mere logical consequence of
| something else we know), then that increases what we can
| explain about the universe.
| _Algernon_ wrote:
| How do you know that the parameters are fine tuned from a
| single observation? Occam's razor still needs multiple
| observations to create the model.
| layer8 wrote:
| They are fine-tuned in the sense that we have to postulate
| them as axioms, due to lack of any further reasons or
| causes of why they are how they are. The more we can
| constrain the value space from which the parameters could
| conceivably have been chosen, the more "typical" the actual
| values we observe become, and the less remains unexplained.
| nsxwolf wrote:
| It's typical. Typical of all the other cosmoses out there.
| Animats wrote:
| So the most likely universe has "no appreciable curvature and
| just a touch of dark energy. Weirder types of cosmos are
| vanishingly rare." OK.
|
| This doesn't seem to be an answer to why the fundamental
| constants are set for an interesting universe with stars and
| atoms that do chemistry. Not ones full of dispersed hydrogen, or
| one big mass, or ones with uninteresting chemistry where nothing
| happens. See "fine-tuned universe".[1] Still, it's a step
| forward.
|
| [1] https://en.wikipedia.org/wiki/Fine-tuned_universe
| Barrin92 wrote:
| Never really understood why that requires an explanation. A
| universe full of life is 'interesting' from the perspective of
| life but that's a subjective sentiment. If the universe was
| only full of rocks it'd be 'fine-tuned' for rocks. If you were
| one big mass you'd probably think this universe is tuned
| awfully wrong. 'Carbon chauvinism' of the wiki page alludes to
| this but I think you could even generalize it to 'life
| chauvinism'.
|
| Or alternatively you could ask, why isn't it fine-tuned even
| harder, with life in every corner? After all it's astonishingly
| empty in most places.
| zwkrt wrote:
| The fine-tuned universe is not a scientific concept though. The
| only hypothesis at a high level is that the constants or
| initial conditions of our only observable universe could have
| been different. However we have no data or reason to believe
| this is the case. We have no other universes to observe. We
| have no statistics about the distribution of possible
| constants. There are no experiments we could run.
|
| Even the headline of this article smells bad, right? Typical as
| opposed to what? When I see an albino squirrel, I know that it
| is atypical. I have seen thousands of squirrels, and other
| mammals, and I have good reason to believe that an all-white
| squirrel with red eyes is out of the ordinary. I can calculate
| how many of them there are out of the population and get a
| ratio to operationalize my definition of "atypical". I can
| learn more about genetics and biology and melanin and
| understand an underlying cause for the condition and make
| predictions about albino-ness in other animals that is
| falsifiable through further investigation.
|
| In this case though we just have an untestable mathematical
| model for 'possible universes' (whatever that means) that puts
| our universe near the top of some abstract bell curve. I
| understand that smart people made it and that it is very
| technical and fancy, but I also know that it is made outside of
| the scientific process becuase I know that we have never
| observed another universe, we don't have an understanding of
| how universes are made, we don't know what the possible bounds
| are for the constants of nature (because they
| are...constant...). So I consider this to be like a very
| technical art project.
|
| The argument that god created the universe is also a fine
| tuning argument, but no one seems to give that one much
| credence.
| deltarholamda wrote:
| >becuase I know that we have never observed another universe
|
| You should hang around people who do a lot of mushrooms, they
| can clue you in to the others, duuuuuude.
| technothrasher wrote:
| When I asked a Jehovah's Witness who was proposing the fine
| tuning argument to me, "So what would a non-designed universe
| look like?" He just stared for a second and then said, "Are
| you like, a scientist or something?"
| nxmnxm99 wrote:
| That's not as clever an answer as you seem to think
| kulahan wrote:
| I'd probably get thrown off by such a basic question too.
|
| "Look, these cards are only standing because they were so
| carefully placed!" "So what would it look like if they
| weren't?"
| pixl97 wrote:
| That's easy
|
| "Entropy"
| TEP_Kim_Il_Sung wrote:
| Brownian motion and the Casimir effect in the early universe
| should be enough to jumpstart accretion.
| GuB-42 wrote:
| You have the anthropic principle: you can only observe a
| universe that produces observers. More specifically, if a
| universe existed that is full of dispersed hydrogen, we
| wouldn't be there to observe it. The universe _must_ be fine
| tuned in some way, not just the constants but the very laws of
| physics. But this is an undecidable and therefore unscientific
| problem.
|
| The reason scientists want our universe to be "typical" is that
| the more we can generalize our findings, the more we can make
| predictions. For example if we can find an equation that gives
| us the cosmological constant exactly, we can get rid of it as a
| free parameter. Not only it is philosophically satisfying, but
| we may also use that equation to find something else, like a
| new particle, maybe even a practical application.
| machina_ex_deus wrote:
| Just as a hypothetical thought experiment, suppose the entire
| description of our universe laws of physics and initial
| conditions can be described with a bits string of size X. Add a
| few more bits to describe a specific location and time, and a few
| more bits to decode whatever it is that humans wrote at some
| time.
|
| Then everything humanity will ever reach or know has Kolmogorov
| complexity no larger than this X. My intuition is that if you
| take X to be too small, the general "nothing's special about the
| universe and it's all extremely typical" argument and you must
| surely reach a contradiction. Surely not everything is so
| incredibly compressible, is it?
|
| Physicists keep crying about fine tuning and what not, but
| honestly, I would be even more surprised if the initial
| conditions and the laws of physics were extremely small. Because
| we already know the laws of physics are relatively simple, I
| would put my bets on the initial conditions having most of the
| entropy.
| jakeinspace wrote:
| Either that, or reality is inherently quantum and the entropy
| of an evolving unitary wave function (well, the entropy of any
| given amplitude) basically goes to infinity.
| BurningFrog wrote:
| Does this assume the/a universe is deterministic?
| otabdeveloper4 wrote:
| > Then everything humanity will ever reach or know has
| Kolmogorov complexity no larger than this X
|
| No. Information complexity does not obey conservation laws. The
| initial rule for generating the Universe is simple, but as time
| goes on information complexity only increases exponentially.
| It's a singularity of information complexity and we are at the
| center of it.
|
| (This is the real reason, by the way, why aliens don't exist
| and Fermi's "paradox" isn't really.)
| canjobear wrote:
| What do you mean by "information complexity"?
|
| Quantity of information absolutely does follow conservation
| laws, at least in quantum mechanics.
| otabdeveloper4 wrote:
| Same thing as the Kolmogorov complexity the original poster
| mentioned. It corresponds to entropy somehow, so I don't
| think quantum mechanics is on topic here.
| constantcrying wrote:
| >Then everything humanity will ever reach or know has
| Kolmogorov complexity no larger than this X.
|
| Only if it is deterministic, which certainly seems not very
| plausible. (You could say everything is a probability
| distribution, but to me it seems to get extremely complex after
| that, collapse?)
|
| >Because we already know the laws of physics are relatively
| simple, I would put my bets on the initial conditions having
| most of the entropy.
|
| Just because the laws are simply _expressible_ does not imply
| they are simple. A variational minimization problem can be very
| easy to state (certainly that seems a good candidate for a
| "true" law of nature), but it can easily be as hard as a PDE!
| machina_ex_deus wrote:
| The point about determinism is correct, but since
| wavefunction evolution is unitary, the universe is fully
| deterministic. Only if you take some interpretation that
| there's real physical process of measurement which we don't
| understand and is indeterministic you can get randomness.
|
| But maybe if you subscribe to multiple worlds interpretation
| then the hardest part might be specifying which universe
| you're in, which would require number of bits proportional to
| the time since the big bang.
| mistermann wrote:
| > The point about determinism is correct, but since
| wavefunction evolution is unitary, the universe is fully
| deterministic.
|
| A problem: if you consider _the contents of_ the universe
| (and the precise state of the contents at a given snapshot
| in time) to be part of "the universe", you have the hard
| problem of consciousness to tend with (in that humans are a
| part of the universe, and they rearrange its contents on a
| regular basis).
|
| > Only if you take some interpretation that there's real
| physical process of measurement which we don't understand
| and is indeterministic you can get randomness.
|
| Randomness is not the only means to achieve a non-
| deterministic universe, there is also the possibility of
| non-deterministic forces being in play, like human
| activity.
|
| Of course, one can _assert that_ human cognition is
| deterministic (no other option may even be available in
| some cases!), but science strongly suggests that simply
| asserting something to be true does not necessarily cause
| it to be true (though it does often cause it to appear to
| be true _to pre-trained instances of_ human consciousness,
| a phenomenon which science has well demonstrated).
|
| Abstractly(!), humans seem to be in a very similar
| cognitive state as they were when they ran on sub-
| perceptual religious axioms.
|
| https://ell.stackexchange.com/questions/155593/meaning-of-
| th...
| d_tr wrote:
| > Only if it is deterministic, which certainly seems not very
| plausible.
|
| A collapsing quantum state is so far the only proposed
| process which would result in a nondeterministic universe.
| The problem is that absolutely nothing is known about it, and
| everything around it is fishy.
|
| I personally think that the concept of the universal
| wavefunction makes more sense.
| PartiallyTyped wrote:
| It's also possible that our __models__ are simple, but the
| underlying reality is not, so as long as there exists some
| error after sufficient evaluations it is safe to say that our
| model's complexity is less than the universe's.
| constantcrying wrote:
| Yes, I agree. It is definitely possible that the underlying
| laws are extremely complex and there is absolutely no
| simple way to state them.
|
| But what I think is really interesting that this extreme
| complexity can only be found in extremely large and small
| scales. E.g. Newtons laws are phenomenal at predicting the
| universe at "human scales". The systems which can arise in
| Newtonian physics can be extremely complex, but their
| descriptions are usually very simple. Deviations from
| Newtonian predictions either are very small or arise only
| at large/small scales.
| PartiallyTyped wrote:
| > Newtonian physics can be extremely complex, but their
| descriptions are usually very simple
|
| IIRC Constructor theory builds on this, in a way, it
| defines some very basic and simple building blocks out of
| which the rest of the laws that govern our universe.
|
| https://en.wikipedia.org/wiki/Constructor_theory
| ninkendo wrote:
| The universe appears chaotic, in that outcomes have sensitive
| dependence on its initial conditions. Even if all laws of
| physics are deterministic.
|
| So for there to be a wide range of possible things happening
| from the initial starting point (including you and I having
| this conversation right now), IMO it follows that a _complete_
| description of the initial conditions would have to be absurdly
| (infinitely?) large to cause the universe to replay to this
| exact moment if you started it all over again.
|
| In other words, the size of X would have to be extremely
| large... so I think I agree with you.
|
| (Edited once I realized that myself and OP are likely in
| agreement.)
| layer8 wrote:
| We don't know that the universe is discrete, hence a
| description in a finite number of bits, and Kolmogorov
| complexity, may be inapplicable.
| robertlagrant wrote:
| > My intuition is that if you take X to be too small, the
| general "nothing's special about the universe and it's all
| extremely typical" argument and you must surely reach a
| contradiction. Surely not everything is so incredibly
| compressible, is it?
|
| This sounds similar to saying, "This photograph can be
| expressed in this small number of bits, therefore it's not
| special." Why does one imply the other?
| ardel95 wrote:
| This line of reasoning assumes that all physical processes are
| deterministic. If they are not (as is the current mainstream
| belief) then I don't think that line of reasoning would stand.
| Instead, the current state is the result of that initial set of
| inputs, and countless other nob-deterministic dice rolls.
| jondeval wrote:
| > Surely not everything is so incredibly compressible, is it?
|
| I like your line of thinking and I'm actually quite excited
| about this recent shift in physics to a more information-
| theoretic line of inquiry.
|
| Is it fair to state a corollary of your question this way?
| Given a complete description of some hypothesized
| universe/multiverse generator (essentially the next layer down
| that we are actively trying to discover), the Kolmogorov
| complexity (or some variation of K-Complexity) of this
| description must be greater than the K-complexity of any
| generated universe.
|
| In my view, it would be very weird if this were not true. And
| (to me) it would be even weirder if this K-complexity was some
| large number but still less than infinity.
| wongarsu wrote:
| You could have an incredibly simple universe generator that
| just produces universes with random laws of physics and
| random initial conditions. From our human point of view
| that's indistinguishable from a highly sophisticated universe
| generator, since we can only observe the successes (or rather
| only one, that by our definition is a success)
| pfortuny wrote:
| Also keep in mind that everything assumes the equations are
| Lipschitz in order to guarantee uniqueness of the solution
| given specific initial conditions. But this is too optimistic.
|
| y'=y^(1/3)
|
| with y(0) = 0
|
| has an infinite number of solutions.
| constantcrying wrote:
| It gets far worse if it is not an ODE, but a PDE, there a
| uniqueness criteria is somewhere between "for this PDE in
| this extremely special case with these extra assumptions ..."
| up to "?????".
| voxl wrote:
| There is an easy counter model. The universe is _literally_ a
| real number machine, i.e. even a particular point is only
| describable to us in the approximate. The laws of physics get
| to be finite, but you can't talk about a particular location or
| place in time without infinite information, or you talk about
| it in the approximate.
| Mtinie wrote:
| Am I correctly summarizing this statement, for my own
| understanding?
|
| "All values in the cosmos are integers. Decimals exist to
| help humans make comparisons between objects."
| empyrrhicist wrote:
| I mean, they seem to be saying the exact opposite of that
| based on the usual way people talk about the "reals".
| Blackthorn wrote:
| No. They're talking about real numbers; even decimal
| numbers (rationals) are isomorphic to integers. The reals
| are different.
| visarga wrote:
| You could put all the human knowledge in a single real number
| and still have infinite room left.
| vlovich123 wrote:
| There exists an abstract mathematical mapping, sure.
| However, finding the spot in the real number where that's
| the case may require infinite storage (you need to store
| the pointer) or infinite time (you start searching through
| the number to find what you want). It also has a halting
| problem where you don't actually know how you'll know when
| you find that data.
| civilized wrote:
| > The universe is _literally_ a real number machine
|
| I am wary of this. Just because you have a good predictive
| model based on math, and the math can be made rigorous using
| ZFC / Cauchy sequences / infinite decimals / etc., doesn't
| mean that any of those rigorous mathematical concepts are
| literally running the real universe.
|
| Personally I don't think there's any reason to believe that
| any numbers, even zero and one, have any existence outside of
| being concepts in our heads.
| oezi wrote:
| I don't get what you say in the last paragraph. Isn't the
| mapping of zero and one to nothing and something kind of
| the easiest thing (e.g. one photon or no photon)?
|
| For the first paragraph it is my understanding that the
| universe is discrete/quantizied and it is not running on
| 'real numbers'.
| civilized wrote:
| > I don't get what you say in the last paragraph. Isn't
| the mapping of zero and one to nothing and something kind
| of the easiest thing (e.g. one photon or no photon)?
|
| You can map and mapping is useful, but the map lives in
| your head and isn't the territory.
|
| > For the first paragraph it is my understanding that the
| universe is discrete/quantizied and it is not running on
| 'real numbers'.
|
| This is a widely believed folk myth among software
| engineers, but it isn't supported by evidence. There are
| some speculative theories that try to solve some problems
| in physics by quantizing space, but right now they are no
| more empirically supported than other speculations.
| lo_zamoyski wrote:
| Worth a read:
|
| 1. "Russell's No Man's Land" [0]
|
| 2. "The hollow universe of modern physics" [1]
|
| [0] https://edwardfeser.blogspot.com/2020/08/russells-no-
| mans-la...
|
| [1] https://edwardfeser.blogspot.com/2022/05/the-hollow-
| universe...
| czbond wrote:
| Wouldn't a probability model also suggest our universe, galaxies,
| and solar system are all probably.... typical?
|
| The probabilities of trillions of galaxies suggest it is more
| likely we are 1 of many, rather than 1 of 1.
|
| Just because, for example, an ancient tribe in Europe lived in
| the north and might never see others because they're 100's of
| miles away - doesn't mean the tribe is 1 of 1.
| optimalsolver wrote:
| Our star system isn't typical. Most stars are red dwarfs.
| wongarsu wrote:
| Some models suggest we might be fairly early, probably
| somewhere in the first 10-25% of space faring species.
|
| Maybe we are special, for example space around our solar system
| is emptier than usual, maybe due to a super nova blasting stuff
| away. But chances are we are not all that special, just in an
| early part of the game where nobody expanded into our
| neighborhood yet
| InvisibleCities wrote:
| >Some models suggest we might be fairly early, probably
| somewhere in the first 10-25% of space faring species.
|
| I'd like to see some sources for this, because this sounds
| like unscientific, unprovable drivel.
| wongarsu wrote:
| [1] is the first paper Google spewed out, though I think
| there is newer work. I'm on mobile though, so can't check.
| The basic idea is to figured out how many stars that may
| support space faring civilizations have formed, and how
| many will form in the future. Add in some delay for planets
| and life to form, and account for the death of the star,
| and you can estimate how many such species should spawn
| over time, and thus tell if we are early or late to the
| party (assuming all assumptions are somewhat right)
|
| 1: https://ouci.dntb.gov.ua/en/works/7PgprAO9/
| https://arxiv.org/pdf/1606.08448v2.pdf
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