Comment by drdeca | Hacker News Reader

Comment by drdeca | Hacker News Reader

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Asking what it “is made of” seems like a somewhat ambiguous question to me. Still, the answer would not be “mathematical abstractions that fit the data”, but “these mathematical abstractions”. (And, there is a lot of meaning behind these “abstractions”. For example, there is a close correspondence between the Higgs mechanism for mass and superconductivity.)

Really, what possible answer could you ask for that wouldn’t be of this form?

When you describe an idea sufficiently precisely, you do mathematics; that’s almost what mathematics is.

It feels to me like complaints like yours tend to derive from an unwillingness to believe that things aren’t at their core made of solid objects or fluids or other stuff which behaves like macroscopic objects we have everyday experience with.

Can you describe an explanation that wouldn’t be like that but which (if it were true) you would find satisfying?

If you can’t describe how an explanation could (if it were true) satisfy you without being like that, then, if the universe isn’t like that, you have to be disappointed. And, in that case, again, I have to say, take it up with God.

On the other hand, if you can describe how an explanation (if it were true) could possibly satisfy you without saying “at its core, the universe works based on [behavior that you have plenty of physical intuition for based on your everyday interactions with macroscopic stuff]”, I would very much like to hear it.

I think probably in the past what one might have expected to find is akin to something like a magical material that couldn't be further probed. That would have been satisfying in a sense because it brings a wonder back into it while connecting you to the fundamental "thing".

What we have now is not that, it's still very much a mechanistic explanation where the "magic" is hidden within abstractions that make no sense to anyone, i.e abstract fields with properties but no material realty, instantaneous wave function "collapse", wave-particle duality, virtual particles etc. The reality of these things is glossed over.

But my point is that if that's what we've been driven to, why are we still engaged in this enterprise? We're just receding further into these abstractions. What are we going to find next year or next decade? A better mathematical model to fit the data? The mission has gone from finding out what the universe is made of to finding a better abstract model. Particles aren't real, they're excitations in a field, etc. It's an engineering enterprise now. So we're not going get a satisfying answer, were just going to get better lasers or whatever the next tech is.

That makes little sense to me. “Can’t be further probed”?

A thing behaves in some way. If you do things, things happen.

One can do certain measurements about how things behave, and then record these measurements.

What would it even mean for a material everything is based in to be magical? If there was some exceptional material that is unlike other things, following different rules, I can understand calling that “magical”. But, the only meaning I can think of for a material underlying everything to be “magical” is that either everyone just, declines to study it, or its behaviors like, depend on the intent of those studying it or something like that.

I also don’t get your statement that “brings a wonder back into it”. Like, do you not experience wonder when contemplating the nature of fundamental fields?

Like, if we set aside the “magical” part, it kinda sounds like your objection is that fields aren’t a substance/material. But, if you just generalize your notion of “material” a bit, why don’t quantum fields satisfy all your requirements? And, if they do, don’t you want to understand how this “magical material” behaves??

You decry these things as “abstractions”, and say that they “make no sense to anyone”. They can certainly be confusing, but they aren’t beyond comprehension, and I don’t see them as any less “material reality”? Macroscopic things just behave differently.

I don’t think I agree with “particles aren’t real” either. Electrons being excitations in the electron field, doesn’t make them “not real” any more than an apple being made of atoms makes it not real, or sound being vibrations in a medium makes sound not real.

Like, buckyballs are clearly “real” (they can act like little cages with something else contained inside), but they also clearly are “particles” like protons are (you can do a double slit experiment with them and get an interference pattern).

Also, I don’t think I’d say the enterprise was ever “What is the universe made of?” so much as “How does the universe work?” ? It is a drive to understand! It is asking “How do initial conditions relate to final conditions?”. The tech is ancillary to this!

science still cannot predict the path of a particle through a double slit. they cannot explain why this is the case. its claimed that the particle bounces of vacuum fluctuations, yet the energy predicted by these fluctuations is way bigger than what we measure.... how is that satisfactory to you?

I don’t expect the particle has a one single path it takes. This is just an example of reality telling us our assumptions (“each particle has a single well-defined path it takes”) were mistaken.

“It’s claimed that the particle bounces off of vacuum fluctuations” : hm? Like some kind of classical particle bouncing off of something?

“ yet the energy predicted by these fluctuations is way bigger than what we measure” : This is indeed a mystery, one which people are working to resolve. You spoke earlier of wonder. Is this not something to wonder about?

> Is this not something to wonder about?

no, i dont wonder about it, i worry about it. it means the theory is wrong - works most of the time like newtons, but cant explain these weird edge cases... highly likely to not be the full story. odds are on my side for that statement.

> This is just an example of reality telling us our assumptions (“each particle has a single well-defined path it takes”) were mistaken.

this is just a copout to explain the path integral. it acts AS IF it takes every path, but it cannot possibly take every path in an instant. mass creates gravity, so where were these gravitational effects? cannot be found. so this particle taking every path did it without mass somehow. little details like this conveniently without explanation in your theory.

Hm, I think you are taking the language “takes every path” too literally. Like, set aside the “infinitely many paths” issue for a moment, and consider just two paths. A quantum superposition of two paths doesn’t mean “it took this path and also it took that path”. A quantum superposition is a different kind of thing from that. A quantum superposition is a linear combination.

A path integral involves an integral of e^{i S/hbar} where S is the action for a given path, with the integral being over the path, and evaluates to the amplitude from the starting state to the ending state.

(Of course, there are some difficulties defining integration over paths, especially if you want to get into QFT. Still.)

If you want to incorporate gravity into this, you probably need to do so within the path integral, with it being incorporated into the action.

But, of course, quantum gravity hasn’t been resolved, so to see why the issue you point to isn’t actually an issue, let me point out that the point you propose applies equally to electromagnetism: say we have an electron, and it goes from one point to another, and nearby we have a positively charged balloon. Replace “mass” with “electric charge” and “gravity” with “electromagnetic force” in your point, and we obtain an argument of the same form. But, QED works extremely well, and doesn’t predict an infinite electric charge in a region when an electron travels from one point to another (for the reason I said: the electromagnetic interaction between the electron and the balloon will appear within the action).

> Hm, I think you are taking the language “takes every path” too literally.

im taking it as literally as Feynmann took it. people seem to think because their theory is probabilistic, that the world is. theyre mistaken

https://www.youtube.com/watch?v=XcY3ZtgYis0

I'm not interested really in how something behaves, that's an accounting or record keeping task. I am interested in why it behaves a certain way, or what it is. Why does the earth go around the sun? We're told it's because of space time curvature. Curvature of what? Where is space time and what it is made of that it has a shape or geometry? There is no ether, space is not made of anything. Yet it has a shape, or at least there is some accounting going on somewhere that keeps everything moving like it's supposed to. Where is that, what's the mechanism? What we have is a mathematical model that fits the data, but doesn't explain anything. Yes, A behaves in a certain way when B is in a certain position relative to A, we can model that and we call that relativity or whatever, but what is the mechanism? That's where the abstraction is. Are we satisfied with modelling an alien system that we can't understand in any other way? To me that's not that interesting, it just leads to getting lost in abstractions. Maybe relativity will be replaced by a more complicated model that covers more edge cases, but that doesn't tell you what it is. It just tells you how it behaves, as you said. It's like if what you thought was your dog meowed and liked to climb trees instead of barking and chasing squirrels. You don't know what it is anymore, it's not a cat it's not a dog, you don't know what it is but you can model it's behavior. That's what you're forced into. The familiarity is gone. Acting like that's some big accomplishment or achievement is a cop out. We found out the universe is not amenable to our knowing it with any familiarity. Is that something to celebrate? No, it's like finding out your parents were androids. So what are we left with, just accounting rules and accounting models. All they'll give us are ways to make better tools.

Your concept of “explains” seems like nonsense to me.

“what’s the mechanism?”? “[…] but that doesn't tell you what it is. It just tells you how it behaves […]”? A thing is what it does. C.f. the Yoneda lemma.

Again, your complaints sound like dissatisfaction with the fact that the world doesn’t run on stuff that fundamentally resembles substances we have everyday familiarity with.

You speak of “fitting the data”. I say “is compatible with the evidence”.

Also, asking where spacetime is, is a goofy question.

Oh, I see, you are expecting intrinsic curvature to derive from extrinsic curvature? There is no need for that. You could posit a larger (flat) space to allow that, but there is no reason to, as it would be indistinguishable from the simpler alternative.

“ We found out the universe is not amenable to our knowing it with any familiarity.” : You have to remember: it all adds up to normality. Any part of how the world works that seems “weird”, was already like that before you learned of it, and is, in fact, normal.

When I said “take it up with God”, that wasn’t just a figure of speech. Isiah 55:8-9 : “ “For my thoughts are not your thoughts, neither are your ways my ways,” declares the Lord. “As the heavens are higher than the earth, so are my ways higher than your ways and my thoughts than your thoughts.”

God’s thoughts, God’s designs, are greater than our own. If how the universe functions offends our sensibilities, it is our sensibilities that need to change.

At the same time, Philippians 4:8 : “ Finally, brothers and sisters, whatever is true, whatever is noble, whatever is right, whatever is pure, whatever is lovely, whatever is admirable—if anything is excellent or praiseworthy—think about such things.”

You say “ All they'll give us are ways to make better tools.” , but, better tools? This is certainly not my motivation! My motivation is to know truth! And, there is much that is both lovely and true in what you dismiss as “models that fit the data”.

> When I said “take it up with God”, that wasn’t just a figure of speech. Isiah 55:8-9

how come our lord and saviour only seemed to do magic tricks around 2000 years ago? has he lost mana or something?

You seem to be asking about “divine hiddenness”. I don’t know why God doesn’t make His existence more obvious to those that don’t seek Him. Like I quoted above, his ways are above our ways. That’s not to say that the reason is definitely beyond what I can comprehend, just that it is beyond what I do comprehend.

(On the off chance that you were being sincere in your question about mana: no.)

The point I was trying to make by quoting that passage was the necessity of humility. The way the world works doesn’t need our approval. It is above us.

> I don’t know why God doesn’t make His existence more obvious to those that don’t seek Him

i didnt ask that and you know it. why doesnt he do headline magic tricks like feeding the five thousand or sending beasts down from heaven or raising zombie jesus from the dead? is it because those stories arent true?

> Like I quoted above, his ways are above our ways.

youre religion does calim to know however... how do they claim to such privileged knowledge? what do they know that we dont?

> Again, your complaints sound like dissatisfaction with the fact that the world doesn’t run on stuff that fundamentally resembles substances we have everyday familiarity with.

Ok, so you tell me, what does it run on? Intrinsic curvature and virtual particles, or what?

I wouldn’t say it “runs on” virtual particles per se. I think the virtual particle terms are more tracking the interactions between different fields. I would say it runs on quantum fields on a curved spacetime, yeah. And, as for what precisely a quantum field is, this is somewhat mysterious, but generally it is a quantum version of a classical field, where there is a value (e.g. “value of the electromagnetic field”) at each point in spacetime. For quantum fields, instead of each point having a definite value, for any region there is an observable for the total value in that region.

As for how the curvature of spacetime fits with all that, that is an open question that has yet to be resolved. Well, constructing a quantum field theory within a given curved spacetime is fine, but we don’t know how exactly GR and QFT fit together.

I expect that your response is going to be to call these “abstractions” or something, as if this does anything more to discredit them than complaining that any idea is “just an idea”. But these are measurable things. That which can be measured is a real thing.

"That which can be measured is a real thing."

But this is just mystifying measurement. It's a convention that's been adopted because we've had to regress on the question of what is a real thing. It's not something you can look at or hold in your hand, it's not even something with material reality necessarily, it's just something that can be measured, or rather something that can be inferred to exist given the measured behavior of other things - i.e. gravity. You make it sound like it's a given, but this definition is a position that's been arrived at by progressive regression.

"And, as for what precisely a quantum field is, this is somewhat mysterious, but generally it is a quantum version of a classical field, where there is a value (e.g. “value of the electromagnetic field”) at each point in spacetime."

But what does this mean concretely? Do you believe there is a real field out there with a value at each point in space time? What's it made of, what is the value a value of? If there no real field where is the accounting done and by what? I understand that when we run it through our models that assume a field like thing we get the right predictions, but what's the mechanism out there?

Something which I found surprising is that it appears that a Gaussian random field in more than one dimension apparently has to be distribution valued, such that with probability 1 one can’t really evaluate it a particular point.

Even setting that aside, I wouldn’t expect the state to be an eigenstate for that even if the “value of the field at this location” was an actual observable rather than a like, operator valued measure, so, even then I wouldn’t expect the value to be determinate, no.

If spacetime turns out to be discrete, that would resolve the “the distribution over the values for the field are distribution valued, not valued in genuine functions” issue, (and the other reason for it not having a determinate value is actually normal) but it is hard to see how this would fit with our non-observation of violations of Lorentz invariance.

I don’t know what you are asking for when you ask about a mechanism. Do you mean a classical mechanism? Nature isn’t classical.

Sounds like you might have gotten lost in abstractions. It's a simple question. There is a box. I cannot see inside. I can model the output based on my input to it. Is that enough to tell me everything I want to know about the box? If that is all we can know about it, if we can never see inside, or there is no inside, then what do we know? Is that enough to satisfy everything you want to know about the nature of the universe?

I believe I answered the question? You asked whether these quantum fields have values at points. I believe there is a field-of-sorts, but that unless spacetime is discrete, the value of it at an individual point isn’t really a meaningful question, and even if spacetime is discrete, while the question becomes meaningful (as in, it is an observable), typically it will not have a determinate answer.

If there is no inside to a box, then knowing everything about how the box interacts with things outside the box, is pretty much everything there is to know about the box, yeah.

The study of physics concerns only that which we can observe/measure. Now, like I implied before, I’m not a scientific materialist, and I don’t claim that all-that-there-is is amenable to understanding through the lens of physics. So, like, I guess the answer is “No, I don’t expect physics to tell us everything I want to know about the nature of the universe, just all of it that is accessible to experiment.”.

> If there is no inside to a box, then knowing everything about how the box interacts with things outside the box, is pretty much everything there is to know about the box, yeah.

Yeah, that's kind of a biggie. And kind of the point. It's not just some box somewhere, it's the thing we've been trying to figure out since the beginning. If physics can't tell us the fundamental nature of the universe, then what is it doing?

no answer to that question lol. they normally say "well the predictions are correct arent they!?"

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