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Comment author: cousin_it 21 May 2017 08:57:17AM *  0 points [-]

This kind of "stuff gets cheaper, everyone benefits" advocacy is why I wrote that comment to begin with. The free market can't be always pushing down the price of all goods (measured in other goods), that's a logical impossibility. There's no magic force acting on one conveniently chosen side of each transaction. Why isn't the same force pushing down the price of labor then, making labor cheap in terms of bread, instead of making bread cheap in terms of labor? Oh wait, maybe it is. Maybe all these forces are acting at once and going into weird feedback loops and there's no reason why the end result would be moral in any way. That's my point.

Comment author: RolfAndreassen 22 May 2017 02:39:21AM *  0 points [-]

The free market can't be always pushing down the price of all goods (measured in other goods), that's a logical impossibility.

And yet that seems to be precisely what has happened.

However, supposing we hold tech progress and capital investment constant, then yes, we'll reach a steady state in which prices as a whole cannot fall further. But that still does not demonstrate that it is possible to maintain the sort of high-value-extraction transactions you outline for any great length of time. If the profit of bread is high then it will fall as people enter the market; this will, yes, slightly raise the profit of all other occupations, holding technology and capital steady. But the eventual equilibrium has all the profit rates being the same. Otherwise investment flows from the low-profit ones to the high-profit ones.

Comment author: cousin_it 16 May 2017 04:32:25PM *  2 points [-]

There's a free market idea that the market rewards those who provide value to society. I think I've found a simple counterexample.

Imagine a loaf of bread is worth 1 dollar to consumers. If you make 100 loaves and sell them for 99 cents each, you've provided 1 dollar of value to society, but made 99 dollars for yourself. If you make 100 loaves and give them away to those who can't afford it, you've provided 100 dollars of value to society, but made zero for yourself. Since the relationship is inverted, we see that the market doesn't reward those who provide value. Instead it rewards those who provide value to those who provide value! It's recursive, like PageRank!

That's the main reason why we have so much inequality. Recursive systems will have attractors that concentrate stuff. That's also why you can't blame people for having no jobs. They are willing to provide value, but they can't survive by providing to non-providers, and only the best can provide to providers.

Comment author: RolfAndreassen 20 May 2017 09:10:30PM 3 points [-]

It seems like you have just reinvented the criticism "if you can extract almost all the value from each transaction (aka 'exploitation'), you will shortly be rich". Well, yes, but the point is that a market with competition generally prevents you from doing that. As someone pointed out, if you make 100 loaves then you have created 100 dollars of value; the question is how those 100 dollars are distributed. You construct an example where the baker is able to capture 99% of the value he created; good for him, but it relies on your construction of the price. Seeing the baker get rich, won't a bunch of other people decide that bread-making can't be that hard, make some loaves, and sell them for 98 cents? And so on until the price of bread is equal to the cost of production plus the smallest profit anyone is willing to live with, which in your example seems to be a penny.

Comment author: Pimgd 20 April 2017 10:50:16AM 0 points [-]

What's Chesterton's Fence for "Don't play with your food"?

I did some thinking and googling and found that...

  • The food might get cold
  • The food might go places it shouldn't go, making things dirty (or you might get dirty hands by playing with your food and then things get dirty that way)
  • It's disrespectful to the chef (table manners)
  • It's annoying to the other people who are eating so please just stop
  • Touching the food might not be very hygienic

What reasons am I missing? If you're eating food that doesn't go cold on your own, is playing with your food bad?

Comment author: RolfAndreassen 24 April 2017 01:34:02AM 1 point [-]

It's disrespectful to people who don't have any food to eat, much less play with. Food is important, and this fact is easily forgotten.

Comment author: RolfAndreassen 04 March 2017 04:48:53AM 1 point [-]

Idea 2 seems very vague. Can you give an example of how I would use it?

Comment author: gjm 13 February 2017 01:56:36AM 0 points [-]

you are the one who suggested that entropy could be calculated in a non-arbitrary way

All I actually said was "not-so-arbitrary". I think that's pretty much all one can say about anything, which is why I asked what if anything you would consider non-arbitrary.

It conflicts with the notion that entropy is a good way to consider the problem; entropy is a non-full-information heuristic that doesn't appear in the actual laws of physics.

I don't see the connection between the two halves of that sentence. There seems to be some implicit premise along these lines: "When contemplating the 'arrow of time' we should not consider anything that doesn't explicitly appear in the laws of physics." but I don't see any reason to accept such a premise.

an intuitive understanding is sufficient to get a grasp of how a microlevel asymmetry can become macrolevel

If you mean that that's enough to appreciate that in principle something of that sort is not entirely ruled out -- yeah, I agree. If you mean that your intuition tells you that weak parity violation really is the reason why we can fry eggs but not un-fry them then, well, I'm afraid I don't trust your intuition as much as you might.

If I talked to a bunch of theoretical physicists -- a group whose intuition in such things I think we should probably trust more than that of either experimentalists like you or pure mathematicians like me -- would you expect them to agree with you, to say "yes, of course, weak parity violation is probably the cause of the familiar macroscopic time-asymmetries we see in the world"? My impression -- which I admit is not based on actually finding lots of theoretical physicists and asking them -- is that they mostly would not say any such thing.

As one example, I'll cite Sean Carroll again; although he is an author of pop-science books he is also a working scientist and this is pretty much in his field of expertise. And he says: Time reversal violation is not the arrow of time.

Comment author: RolfAndreassen 15 February 2017 04:03:22AM 0 points [-]

There seems to be some implicit premise along these lines: "When contemplating the 'arrow of time' we should not consider anything that doesn't explicitly appear in the laws of physics." but I don't see any reason to accept such a premise.

I would say "explicitly or implicitly", and then it seems to me that we have every reason to accept that premise, because where the Devil else are you going to look? Noting that entropy does not appear in the laws of physics even implicitly; it's a heuristic, not a derived quantity.

If I talked to a bunch of theoretical physicists -- a group whose intuition in such things I think we should probably trust more than that of either experimentalists like you or pure mathematicians like me [...]

I would rather phrase it as "micro-level time violation is the cause"; we're talking about weak parity violation only because that's much more easily measured, and implies time violation. That aside, yes, I would expect a poll of theorists to find at least a sizable minority who think micro-level time violation is the cause of macro-scale time asymmetry.

Comment author: gjm 11 February 2017 03:55:56PM 0 points [-]

I don't understand how your suggested calculation is non-arbitrary; you still seem to be picking some criterion and then doing math.

I don't understand what, if anything, you would consider non-arbitrary.

the laws of physics [...] just apply the exact laws of motion to the exact particle locations at every time step.

And why does that conflict with what anyone says about the "arrow of time"?

with high-energy intermediate states, you can get weak particles in your electric interactions; and then you get time asymmetry.

So you actually are suggesting that weak-interaction parity violation is responsible for the asymmetry between frying and un-frying eggs. OK, then. Do you have any actual evidence that it's so? It seems awfully implausible on the face of it, to me, but since (1) neither of us is a quantum field theorist and (2) so far as I know no one knows how to do the QFT calculations on anything like the scale required to understand what's happening when you fry an egg, I'm not sure that either my intuition or yours is to be trusted. So, I dunno: has anyone done the back-of-envelope calculations to figure out whether this works in some sort of toy model? have any actual quantum field theory experts given opinions on how plausible this is?

Comment author: RolfAndreassen 12 February 2017 03:24:54AM 0 points [-]

I don't understand what, if anything, you would consider non-arbitrary.

I'm not sure this is actually an important disagreement; I'm ok with dropping it if you want. However, you are the one who suggested that entropy could be calculated in a non-arbitrary way; but I don't think you've offered an example of such a calculation.

And why does that conflict with what anyone says about the "arrow of time"?

It conflicts with the notion that entropy is a good way to consider the problem; entropy is a non-full-information heuristic that doesn't appear in the actual laws of physics.

neither of us is a quantum field theorist

Well, I'm not a theorist, no. I do have a PhD in experimental particle physics. I will admit that the QFT classes tended to fry my brain like an egg, which is one reason I went experimental.

so far as I know no one knows how to do the QFT calculations on anything like the scale required to understand what's happening when you fry an egg

That's true. I do think, however, that an intuitive understanding is sufficient to get a grasp of how a microlevel asymmetry can become macrolevel.

Do you have any actual evidence that it's so?

It seems that such evidence would have to be in the form of simulations or calculations, since you can't very well turn off the weak interaction and see what happens when you fry an egg without it. I am not aware of any such calculation, no. But, again, there's such a thing as a qualitative insight.

Comment author: gjm 09 February 2017 01:45:46PM 1 point [-]

why bother with entropy as such?

Because it's one of the more obvious descriptive statistics to look at and it shows the difference nice and clearly. If we just say "the initial conditions need explaining" (or: the differences between initial and final) then the obvious question is what about the initial conditions, and part of the answer to that is going to be the entropy. (Or maybe some other thing that's essentially equivalent.)

Also, because it's a statistic that not only is different between the distant past and the distant future, but also varies in a consistent way at present.

I do not understand how these two paragraphs are a response to what I said. Can you elucidate?

I can try, but if they aren't then my best guess is that I didn't correctly understand what you were saying (which was less than 100% clear to me). So I'll be brief about the elucidation, and then whichever of us turns out to have been misunderstood first can do the next round of elucidating :-).

It looked to me as if you were saying, more or less, that entropy is a silly thing to be looking at at all, because it describes only our state of ignorance and not the actual universe; that when we say "the universe seems to be evolving from a low-entropy state to a high-entropy state" all we really mean is something like "we know a lot more about the past of the universe than about its future".

I, on the other hand, think that is a wrong (i.e., a less than maximally useful) way to look at it. Yes, a notion of entropy depends on some state of knowledge and observational ability. But that doesn't mean it depends on picking ours in particular, and there are not-so-arbitrary ways to do it.

Electroweak unification.

Noun phrase!

Would you like to make your argument a little more explicit? Do you think that weak parity violation is responsible for the familiar macro-scale time asymmetries everyone notices?

Well, then, that solves the problem

Only in so far as it's plausible that the asymmetry-in-the-laws that we found actually causes the asymmetry-in-our-observations that we're trying to explain. I don't see that it is plausible, but perhaps the words "electroweak unification" should have enlightened me?

Comment author: RolfAndreassen 11 February 2017 06:46:27AM 0 points [-]

Yes, a notion of entropy depends on some state of knowledge and observational ability. But that doesn't mean it depends on picking ours in particular, and there are not-so-arbitrary ways to do it.

I don't understand how your suggested calculation is non-arbitrary; you still seem to be picking some criterion and then doing math. My point is that the laws of physics don't do any such thing; they just apply the exact laws of motion to the exact particle locations at every time step. Picking a different criterion for the entropy doesn't help - it's still not going to be what actually happens.

Would you like to make your argument a little more explicit? Do you think that weak parity violation is responsible for the familiar macro-scale time asymmetries everyone notices?

Sorry, I will try to be less brief. The known CP violation occurs, as you point out, in the weak force. (Side note: There is also a large source of CP violation somewhere else in the laws of physics, otherwise we wouldn't observe the matter/antimatter asymmetry we do. But that doesn't change the argument since it must occur at high energies.) When you fry an egg, the interactions are basically electric.

At high energies, the electric and weak force unite into the electroweak force. Now, when you do the quantum-field-theory math encapsulated in Feynman diagrams, you are integrating over all the possible paths from initial to final state; including ones with extremely energetic particles in the intermediate states. (This appears to violate the conservation of energy; the usual explanation given to students is that you can do this because of a Heisenberg uncertainty relation between energy and time. If the time is sufficiently short, "the universe is not aware" that energy conservation was violated. Personally I find this explanation immensely unsatisfying, but I don't understand the underlying math; so I'm taking this on faith. Anyway it's the same phenomenon that causes Hawking radiation around black holes.) Well, with high-energy intermediate states, you can get weak particles in your electric interactions; and then you get time asymmetry. To be sure this is a third-order effect; but then, frying an egg takes several seconds, which is an immense amount of time relative to the characteristic timescale of the weak force. (Which is only 'weak' by comparison to the strong nuclear force.)

Comment author: gjm 07 February 2017 11:24:22AM 1 point [-]

You keep coming back to entropy, but I think this is the wrong way to look at it.

I keep coming back to entropy because the asymmetry in entropy is one of the things that needs explaining, and because some of the other things that need explaining seem to be explicable in terms of entropy.

[...] when we don't have all the information; but the universe does

Given any criterion for distinguishing macrostates, you can (in principle) compute entropy relative to that criterion. E.g., if you care only about macroscopic thermodynamic parameters when distinguishing macrostates, you get the classical Boltzmann entropy. These parameters presumably stop making sense when you consider the early enough universe, but we can still say that the thermodynamic entropy of the universe appears to be surprisingly small early on and much larger later on.

(If the universe is infinite in extent, there are some technical difficulties here. I don't know exactly how they are addressed, but I note that cosmologists who accept the possibility that the universe may be infinite don't thereupon seem to stop talking about entropy, and I infer that the current best way of addressing them doesn't make the time asymmetry of entropy go away. If there are experts in the field reading this who would like to enlighten me further, I'm all ears.)

once you have identified a microlevel asymmetry [...] there is no need to go through the tedious steps of finding how it produces a macrolevel asymmetry.

I'm pretty sure this is just plain wrong, unless you have already established that the microlevel asymmetry is responsible for the macrolevel asymmetry. So far as I am aware, there is no reason to think that weak parity violation is responsible for the familiar macro-scale time asymmetries everyone notices.

Comment author: RolfAndreassen 09 February 2017 05:57:02AM 0 points [-]

I keep coming back to entropy because the asymmetry in entropy is one of the things that needs explaining

Again, why bother with entropy as such? Just say "the initial conditions need explaining" and be done.

Given any criterion for distinguishing macrostates, you can (in principle) compute entropy relative to that criterion.

I do not understand how these two paragraphs are a response to what I said. Can you elucidate?

So far as I am aware, there is no reason to think that weak parity violation is responsible for the familiar macro-scale time asymmetries everyone notices.

Electroweak unification. That aside, the original problem was "there is no asymmetry in the laws of physics that can cause [macrolevel asymmetry]; Newton's and Maxwell's (and Einstein's) laws are the same in either time direction". And then we realised that yes, there is an asymmetry in the laws of physics. Well then, that solves the problem; what more do you want, unfried egg in your barley-that-used-to-be-beer?

Comment author: gjm 07 February 2017 12:45:16AM 0 points [-]

I agree that this definition is fuzzy. (So does Carroll, as he makes clear in the text immediately following the bit I quoted.) But no, I don't think it's moving the goalposts, though it may not be putting them where you would prefer them to be.

I take the basic arrow-of-time problem to be something like this: The universe appears to be dramatically asymmetric in time: it is expanding in one time direction and contracting in the other; if we trace its evolution in the direction we call "past" according to our best understanding of the physics, we find a "big bang"; if we go in the direction we call "future" we find a "big freeze". These are distinguished not only by density/scale but also by entropy: the big bang is a much lower-entropy state than the big freeze. Furthermore, we see a similar dramatic asymmetry in our everyday lives: it's easy to break an egg or fry one, not so easy to put it together or turn it raw again. But in the fundamental laws of physics as we currently know them, we find nothing to explain any of this. Weak interactions do indeed show a slight violation of CP-symmetry, hence of T-symmetry, but frying eggs doesn't appear to have much to do with weak interactions; CPT-symmetry would appear to turn our universe into one that "looks just the same" but has time running "the other way"; and nothing in all of this shows any sign of explaining why (the history of) the universe should be so dramatically asymmetric in time.

If weak parity violation really explains anything here, I don't see what. Do you have any grounds for suspecting that weak parity violation explains why we see a very dense low-entropy universe in one direction and a very sparse high-entropy universe in the other? Do you have any grounds for suspecting that weak parity violation explains why smashing an egg is easier than putting it together?

Is there a criterion other than "Sean Carroll thinks so"?

I'm not sure whether this question is really directed at Sean Carroll (complaining that the passage I quoted is vague) or at me (complaining that I'm treating him as some sort of authority). If it's directed at him, the answer he gives is that what you choose to call time-symmetry is up to you and is just a question of terminology, and what really matters is what symmetries the universe actually has. (And, I think he implicitly says, questions about the "arrow of time" remain whatever definitions you choose to adopt.) If it's directed at me, then (1) I endorse his answer and (2) no, I was not using him as an authority, I was using his book as an example of the sort of thing people are usually concerned about in this area.

Comment author: RolfAndreassen 07 February 2017 05:19:14AM 0 points [-]

If weak parity violation really explains anything here, I don't see what. Do you have any grounds for suspecting that weak parity violation explains why we see a very dense low-entropy universe in one direction and a very sparse high-entropy universe in the other? Do you have any grounds for suspecting that weak parity violation explains why smashing an egg is easier than putting it together?

So first let me note that the weak parity violations cannot explain the observed matter/antimatter asymmetry; it follows that there is a source of CP violation that we don't know about, and hence also a large T violation.

You keep coming back to entropy, but I think this is the wrong way to look at it. Entropy is a probabilistic framework using multiple states of the same energy, that we apply when we don't have all the information; but the universe does, and is deterministically evolving from one specific state of high density, to another specific state of low density. Humans look at the final state and say "there are a lot of hypothetical states with different specific arrangements, which look a lot like this one; therefore it is high entropy"; but so what? You can't get there from the actual initial conditions; inaccessible states can have no physical effect, and ought to have no philosophical one either. Asking for an explanation of "the evolution from low to high entropy" is meaningless; better to ask for an explanation of where the initial conditions come from.

As for "what does that have to do with frying eggs", I opine that once you have identified a microlevel asymmetry, your work is done; there is no need to go through the tedious steps of finding how it produces a macrolevel asymmetry.

Comment author: entirelyuseless 05 February 2017 04:22:08PM 2 points [-]

Reversed spatial particles look the same to us as unreversed; and the names "matter" and "anti-matter" are arbitrary. So those differences are not helpful in explaining an arrow of time. They will not make any large scale difference in how the universe evolves.

Comment author: RolfAndreassen 06 February 2017 06:22:48AM 1 point [-]

Reversed spatial particles look the same to us as unreversed

No they don't; the neutrinos would change their handedness. (So would our amino acids, but that wouldn't affect their functioning, so far as I know, since everything else would as well.) And chiral-reversed neutrinos don't interact with anything. The laws of physics are in fact just about as P-violating as they can possibly be!

and the names "matter" and "anti-matter" are arbitrary

The names are arbitrary, but the functions aren't; matter consists of particles favoured by the CP asymmetry in the laws. Flip everything to antimatter and after a sufficiently long time you have matter again.

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