That first paragraph is not a simple one. I think it helps to separate the apparatus of quantum mechanics (which we all agree upon) from its interpretation. The theory doesn't really say much about the source of the probabilities, just that they exist. We can see that the defining aspects of quantum mechanics manifest themselves only in a measurement. We have two mutually-incompatible laws of evolution in quantum mechanics: 1. a perfectly deterministic, causal evolution equations (unitary in math terms), and 2. a probabilistic, acausal (non-unitary) wavefunction collapse. These two are opposite to each other. It's not a simple statement that the probabilities are intrinsic and not just an effect of measurement. For all we know, probabilities have no place in any part of quantum mechanics other than in a measurement.
Connecting measurement to consciousness is okay, maybe. But it doesn't tell us much. Consciousness is a material phenomena, whatever it is, it's still "made of" particles that should obey quantum mechanics. It's yet another interaction obeying the Schrödinger (or Heisenberg) equation; where does the collapse come from? We cannot dismiss the defining property and problem of quantum mechanics this way. At least not until we have a complete (even conceptual) model of how this works.
Regarding causality and probability, I don't feel like I can say anything useful at the moment, so I'm gonna leave it where it is.
About spacetime, I was not referring to the symmetry of the metric tensor (in Einsteins relativity, the metric tensor is always symmetric). I was referring to the Lorentzian signature of spacetime (the temporal component of the metric has an opposite sign to the spatial components of the metric). This is just math for "time only goes forward", kind of. So the preservation of causality is baked into relativity. That's what I meant by space and time are not perfectly symmetric. It's not simply a 4 dimensional thing. It's more of a 3+1 dimensional thing, one of them has a distinct character from the other three.
@Pat You said to reply only after the poll is complete.
Why does "any treatment of explicit non-locality necessarily implies temporal non-causality"? Space and time are still not perfectly symmetric in relativity.
Very interesting. I'd like to make three points regarding this.
1. The Schrödinger equation is perfectly deterministic. The "wavefunction" evolves causally, including interactions. Indeterminacy appears only in the act of measurement, which then forces a probabilistic interpretation of the wavefunction. If measurement is not involved, quantum evolution is as deterministic as a classical one.
2. Shouldn't measurement be nothing more than an interaction? Measuring devices, scientists operating measuring devices are all made of matter that obeys QM. So if the equation of motion (describing interactions) is deterministic, where do probabilities come from? This is the most frustrating property of QM. But even in a measurement, we don't simply lose all traces of causality. The outcomes of a measurement still depend on the way the system is prepared. We get a random outcome *from a set of allowed outcomes*. This set is determined by the way the system is prepared and how the measurement is made. So, causality is still present, but in a more relaxed sense, maybe.
3. Can science, or any organized thought for that matter, be done without a temporal order of events? If causality is macroscopic only, how did we manage to still make sense of the microscopic world if there is no temporal pattern to begin with? It seems to me that causality (maybe in a broad sense) is inescapable.
Thanks for your post!
It sounds really good. I have no experience with virtual amps whatsoever but it was relatively simple to get a pretty good sound out of it. I have a tiny sample here https://threeammo.neocities.org/muselog-4-guitar-sound-1/
Thanks. Yeah I'm on 5.13 and it's working fine so far. I just get carried away with the music then check the screen after a while to find the xruns count to be 6 or something, I don't even notice when they happen. I am thinking about fast storage, but that will have to wait for now.
Muselog #3 - Project Roam
Resources I used to setup Linux for audio and JACK settings. There are some xruns that I can't figure out, but it's fine so far.
Project: trying to recreate a Metallica song at home, using a guitar, a midi cintroller and #ardour on #linux. Let's see how that goes.
@freemo At this point I think we are in agreement. We just have different words.
I’m not sure about your philosophical conclusions from that. Actually I’m not even sure about mine. But, for the time being, I have settled on “reality exists, but we have no access to it except through our mental models”. I can’t say the speed of light “in reality” is so and so, I can just create a theory/model and decide that c is constant in it, what I call a postulate and you a convention. In fact, the way I think of the principle of relativity is that it is not a physical theory at all, it is a requirement on science: the fundamental laws cannot change from one person to another, at least not without a dictionary. Of course, there’s more to be said, but I don’t think it belongs to social media post.
Thanks for the interesting conversation!
@freemo Okay, this discussion is getting a little bit out of hand for me.
We have already established that we both agree we can have consistent descriptions of our measurements with anisotropic speed of light. This is not the issue.
What I am saying is that we are not allowed to make statements like "In reality, c is anistropic, but whenever we measure it it looks like everything is symmetric". That statement is not forbidden because we have an experiment that contradicts it (we already established that it's compatible with measurements), but because it's logically incompatible with the framework we already chose. Why is logically incompatible? Because it asserts that there is a fundamentally anisotropic physical effect, without a theory behind it. If we decide to put a theory behind it, then that theory will have to conform to the symmetry *because we said so*. If it does, then it will have some isotoropic signal.
If we allow arbitrary, UNDETECTABLE effects to enter the theory but have a way of canceling them out at measurement, then this more than just "making the math difficult". This is adopting a different theory, which gives us a different view of reality. Again, I am fine with that, but I wouldn't call it a mere "convention".
I think I understand your points. I don't think I can explain mine better.
@freemo As I said, to keep the symmetry of space with asymmetric light, you have to have some theory to *explain* the asymmetry of light, just like out current theory explains the asymmetry of sound. In THAT theory, we must have a signal of some sort, that signal must be postulated to have constant speed in all directions: a de facto "new light".
@freemo Yeah it's not about acceptance. I wanna do it myself to really see what assumptions will I be forced to make. There's always something to learn playing in the mud.
@freemo I don't like to refer people to books online. I'm not trying to be pretentious or imply that you haven't read the book.
That said, if you check the first chapter of Landau & Lifshitz Mechanics, in the first few pages you will see his argument for the homogeneity and isotropy of space. Although I admittedly make more radical statements, this is what I have in mind when I insist on these kinds of symmetries and why I claim that we can't have science without them.
Also I have not seen this argument in any other mechanics book, that's why I like to recommend this one in particular.
@freemo Like I said, I'm not sure how that works. I have no reply until I actually carry out the construction of spacetime that way.
@freemo I agree with both points, but you’re replying to things I’m not saying.
Maybe I’m not clear. I’m not referring to the cosmological principle, nor am I saying the symmetry (short for homogeneity and isotropy) of space relies on the constancy of c.
What I am saying is this: Given free space and no interaction between the observer and the light prior to the detection (both are reasonable assumptions), why would light behave differently moving towards an observer than away from them? A statement of this sort says something about the asymmetry of free space. Why? Because this is not really about light or sound or similar things, it’s about establishing a way to measure things in general, we must send signals to interact with distant objects. If light was like sound, the postulate would be “the speed of signaling is constant everywhere”.
Why do we want space symmetry? Like I said, this is NOT about the cosmological principle and our large scale observations. It about our assertion that there must be a “reason” to differentiate one point or one direction in space from another. If that was not the case, then science (or even any communication) wouldn’t exist because simply being in a different place means there are different “laws” of physics, Of course, it’s not even a law of it changes every time we move.
And the above paragraph is NOT about the measurement of the round-trip of light that will remain the same. You can’t even make that statement, let alone make a measurement, if the laws are different in each point in space without reason. So what is the reason? It’s any space dependent interaction. We start with completely symmetric clean slate, then add non-symmetric objects as space-dependent Lagrangian or whatever you choose to represent physics. It’s the first law of Newton “Things are the same (symmetric) unless there is a reason (force)”. Now, if you assert that light has different speeds in different directions (keeping round-trip measurements constant), then you have provide a reason, that is, some interaction theory. Fine, in THAT theory, you will have to assert the existence of a signal that propagates with symmetric speed: what we call light.
Locality is another reason we have all this, in addition to the symmetry of space.
You see, this is not really about light or measurements. You can’t measure anything without having a framework for interpreting such measurement. This is really deeper than just accounting for the constancy of the round-trip speed of light.
@freemo But the general constancy in the speed of light is about more than making the math easier. As we discussed earlier here: https://qoto.org/@3ammo/105963064680177147, the "isotropy" of the speed of light is also directly related to our notions of space symmetry (among other things). This a statement about the world.
On the other hand, I'm not sure how will gravity look like then, since the theory we use relies on spacetime being a 4D-space, that assertion needs Lorentz transformation to be the same everywhere in all directions (constant c). Again, if you wanna call all of that "just making the math easier", I can also agree because I'm fine with the idea, fundamentally, theories are choices of the way to see the world. But I'm assuming that you don't want that.
@freemo Yes. Postulates are definitions. That’s what I keep trying to say. The speed is light constant “because we say so”. I repeated that multiple times. It is a definition, we don’t use the word “convention” for this kind definition, we use “postulate”. And that has nothing to do with any assertion about reality. Reality exists, but you can only see it through the lens of some model/theory. If you want a lens that says “in reality, the speed of light is different in different directions”, you can do that, and your measurements will agree with my lens that says “the speed of light is constant in general”. Reality doesn’t care about our definitions of space, time, velocities and how we communicate times and clocks. This is us, not the world.
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