Comment by albatross79 | Hacker News Reader

Comment by albatross79 | Hacker News Reader

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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”.

> 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.

"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!?"

"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.

> 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?

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