joigus

A leading physicist today --Nima Arkani-Hamed-- pondering the contribution of Steven Weinberg to modern physics: https://www.quantamagazine.org/how-steven-weinberg-transformed-physics-and-physicists-20210811/?fbclid=IwAR27IwXxENuqp7AujdfZ0EZ6cJc0LdkIHXiK_XmhpsKVHjh9Vf8jpf9Uy5Y

My experience of meditation is very much like @Prometheus'. Don't try to fight your thoughts; it's futile. Don't let your thoughts run the show, that's all. Breathe low and become aware of your breath. Observe your thoughts. You can't control what you think, but you can take a sit and watch your thinking. Then, at some point, your thoughts become like fluff that's passing by in front of you. You get used to this feeling of watching your thinking like watching clouds going across the sky, one after another. Let go of any thought that stays there for two long (more than a couple of seconds). If it doesn't disappear, question it: Why this thought? Where did it come from? Where will it go after an hour? Questioning is very powerful. Generally.

Yes, the next line after the equation says exactly that: "where the dot means...". It should be, \[ \kappa = \dot{\psi} \] 'dot' to represent the derivative by the length of arc is traditional in differential geometry.

How can the paths be 'kept joined' if a Stern-Gerlach splitter is introduced? The whole point of the SG experiment is to introduce a correlation between spin projection and linear momentum --which gives you the path. Maybe there's something about your setup I don't understand. Perhaps you could make a drawing?

I can't give you references to something 'I have a feeling' of. So I suppose you mean the bit about 'information is physical'. Physical systems --whatever the theory we're considering-- have a way of measuring the total amount of information, which is called volume of phase space. Phase-space volume is a way of assigning a measure to the extension of all possible dynamical states accessible to a physical system. The definition can be applied to quantum systems as well as to classical (non-quantum) systems, thermodynamic systems, etc. Volume of phase space is synonymous to 'amount of information stored in the system': https://en.wikipedia.org/wiki/Phase_space Another formulation of the relationship between physics and information is Landauer's principle. If you erase one bit of information from a computer, you must do it at the expense of heating up the universe. On the different definitions of entropy: http://www.scholarpedia.org/article/Entropy

I'm not sure that state-of-the-art AI manages to replicate the adaptiveness of nervous tissue. I'm no expert on AI, but for AI to replicate that --adapting to slowly varying random environments-- it would have to be able to decide what abilities are worth developing. Maybe it's got to that point and I just don't know.

My glockenspiel has just sprung to life! Some superstrings now: Beauty and the beauty.

🤣 Linear momentum goes deeper than you think! And pressure is nothing more than a big system's parts not quite agreeing on one particular value of linear momentum. We both know we both know this. I will keep exploring your thinking until I find where exactly your dissatisfaction lies. The fault lines of one's thinking are the most interesting areas by far.

I meant deeply ingrained as a necessary condition, but not sufficient. I agree with you that the complexity part is needed. I've somehow implied it when I said, and elsewhere. I think I'm less of a reductionist than you picture me, @Eise. The very same way that microscopic variables give rise to pressure, temperature, etc., there must be microscopic variables that give rise to this --undeniably puzzling-- ongoing projection that we call consciousness. Linear momentum, charge, energy, and the like; to me; don't even start to suggest an analogue. The spinor mapping --that a space-time point is represented twice in an internal-variable space--, or the holographic principle, or some similar principle that strongly suggests some fundamental mirroring, bi-valued representation, etc, seem to me to be more likely candidates of this deeper level I'm talking about. x-posted with @Lan Todak

That's 100 % correct. M-theory is a theoretical framework, rather than a satisfactory theory of Nature.

They are not different; they are on a different category. M-theory is a generalisation of superstring theory; a theory about both the classes of geometries (Calabi-Yau manifolds) and fields (super-symmetric conformal fields) that make the two irreconcilable field theories we know (gravity and so-called Yang-Mills fields) compatible. Once you establish this very general context for field theories, you notice that there is huge freedom in the space of parameters (coupling constants) of the theory, as well as in the way the many dimensions of space-time that this meta-theory[?] suggests compactify (are reduced to tiny curled-up dimensions that we can't see). The multiverse is the proposal of a general context, within this M-theory, of how a universe like ours may have arisen from the enormously big freedom that M-theory allows. So M-theory gives you a plausible context for the physical laws as we know them to have arisen. Multiverse is an idea about how the particular universe that we know may have arisen within that context. I hope that helped. Hopefully also helpful:

Lovely, @Moontanman & @beecee. I've posted --another version of-- this before. For all those coffee lovers out there. J.S. Bach - Ei! Wie schmeckt from the 'Coffee Cantata' BWV 211 performed by Ensemble Échos Ah! How sweet coffee tastes! Sweeter than a thousand kisses. You must understand this comes from a time when Europe had just discovered coffee! To all my British friends: I'm working on finding another piece about tea of similar quality.

Cool.

My thoughts on torture --any kind of torture-- are: If a person has to ask another what their thoughts on torture are, something's really wrong with one of them. I'm sorry, but no nuances here.

Outstanding acting. Plus Patrick Stewart was Ahab himself too: https://www.imdb.com/title/tt0120756/?ref_=nm_flmg_act_93

Amazed at the length of your selfie stick. Colors are a bit more natural, if you ask me.

LMAO!

For a moment I thought you meant Association for Research in Vision and Ophthalmology. But Wolfram Alpha knows better: https://www.wolframalpha.com/input/?i=arvo&wal=header Well done, girls!

I read worrying news that the GBR is in danger.

Easy come, easy go. Thanks.

Thanks. I hadn't thought about that particular setup. It makes sense. If I understand you correctly, you've kept the correlation, while making it a perfect up-up correlation instead of an up-down correlation. There is no reason for the state to break the entanglement. The point I was trying to make was a disclaimer. I said something that could have been interpreted as 'flipping spins is never possible': And that's not what I wanted to say. What I wanted to say is that, for an entangled state, measuring one particle's spin does not flip the other particle's spin. But flipping spins is possible in general acting locally on one particle (magnetic fields for charged particles, polarisers for photons, etc.)

Just to correct myself. There are cases in which you can say an electron changes its spin, of course. But not for spin-entangled states. For example, you put an ion in an ion trap and subject it to a magnetic field. The ion will flip its spin. The devilish property of a maximally-entangled state is that you cannot say its spin has any particular value whatsoever. Yes, it's very much like that; they're initial correlations. The tricky part is that correlations are quantum. All hell breaks loose when correlations are quantum and you want to think about the gloves as actually possessing all these properties at a given time. Quantum mechanics embeds a different (non-classical) kind of logic when you express it in terms of properties you can measure. 'Quantum gloves' need to be able to occupy states that are neither right-handed, nor left-handed (superpositions); neither black nor white, etc. And we need to be able to measure several properties of the gloves. If we want to have properly quantum gloves and display all the 'trickery' of quantum entanglement, we would need: 1) Several measurable properties. Take three observables, say: handedness (H), colour (C), and material (M). 2) Measurements of any one of these properties (observables) completely mess up measurements of the other; and you can't measure (H,C), or (C,M), (H,M), at the same time. (Incompatible observables.) 3) (For simplicity) the observables have a discrete dichotomic spectrum (possible values when measured): H {left-handed, right-handed} C {black, white} M {natural, synthetic} 4) When the gloves are in a definite state of handedness, the H-incompatible properties C and M are maximally scrambled, or 'blurry': Equally likely to be black or white; equally likely to be natural or synthetic. The gloves simply don't have those C, M properties when H is well defined! If they had, it's not difficult to prove that, for many series of repeated experiments on a given glove: Probability(left-handed & white)+P(black & synthetic) greater or equal than Probability(left-handed & synthetic) This is called Bell's inequality, and it's just a consequence of the properties H, C, and M actually having a value. Quantum probabilities violate this inequality for certain choices of observables. But wait a minute. Didn't we say that properties H (handedness) and C (colour) are incompatible? How can I even make sense of Probability(left-handed & white)? I'm not supposed to be able to measure handedness and colour at the same time! (for the same glove). Yes, but the whole basis of this combined-probability setup is based on the assumption that when I measure, eg, H for one glove and the result is 'left-handed', I know with certainty that, were an experiment to be performed at the other glove's location, it would produce the result 'right-handed' with total certainty. And sure enough, it does, when I do so. So I'm counting 'left-handed' outputs for the other glove as 'right-handed' outputs for this glove. This is very important to keep in mind. So the gloves would have to be kinda schizoid. But the whole thing is local. In order to see that, let's go back to a pair of electrons. We take electrons from separate parts of the world, completely uncorrelated. We bring them together and have them interact. They reach a maximally entangled state called the singlet. This only happens because they've been proximal and interacting (local!!!). Now (and not before) they display perfect anti-correlation. If I perform my experiment on them when they're still next to each other, they display all the craziness that I've just described. Now the state decays (splits apart). I perform the same sequence of measurements. The perfect anti-correlation is still there. It hasn't changed. So it didn't come from me doing anything on one of the electrons and the other 'sensing' what I did. It came from the initial interaction that produced the anti-correlations. Murray Gell-Mann was very frustrated that people, decades after Bell, Clauser, Shimony, and all that saga, still called this 'non-locality'. Just as an indirect evidence of how much confusion this term 'non-local' has caused in physics, here's a quotation: (taken from a scientific forum.) Ooooooo-kay.

Yes. Methane really is the killer. There are vast amounts of it and release seems potentially very fast in geological terms.

Oh, it's... nothing.