quinta-feira, março 29, 2018

Follow-up on ∂S/∂t + H = 0: "Reality Is Not What It Seems" by Carlo Rovelli



"The world of quantum mechanics is not a world of objects: it is a world of events".

In "Reality Is Not What It Seems" by Carlo Rovelli


"Experimentation and transformation in both art and science spring from the same root - to understand, to encapsulate the world. This is why I've ever found reductionism (and scientism) drearily limiting and worthily pompous - that utilitarian speculation over what art 'is for', that misapprehension of art as a kind of elaborate trickery, only readable in the light of neuroscience or physics. The best writers of fiction, artists, composers and scientists are, I've long felt, the ones who see the 'divide' as porous, and are open to findings in both great spheres of endeavour and experimentation."

In "Incognito: The Secret Lives of the Brain" by David Eagleman


Rovelli is more than right to rail against the schism of art and science. Theoretical physics in some sense is the poetry of science; and science in its great evolution from the classical era on was intertwined with art (Galileo was a musician, Leonardo an anatomist and technological innovator; Piero was a geometer, while painters have ever worked at the edge of physics (light properties) and materials science (pigments and chemical properties), and so on). I have come across this author's work before and have found him to possess a really enlightening, critical yet accessible style. The work of his that I read and still stays with me is his "The First Scientist: Anaximander". It is a brilliant evaluation of the 'Earth as floating stone' thesis of the Greeks.

Just remembered the Hamilton-Jacobi equation ∂S/∂t + H = 0 is another way of describing a classical system. From which you can wiggle your way to the Schrodinger equation. I think particularly interesting is in a paper by Hiley, and de Gosson where they say, Schrodinger was led to his equation from his knowledge of the classical Hamilton-Jacobi approach which has a close connection with the eikonal of classical wave theory. They go on to derive the Schrodinger equation from classical mechanics using a very deep group and operator approach. The Hamilton-Jacobi equation is indeed a good motivation to get to the Schrödinger equation (and is already very similar to it).  Whichever way, you are motivated by classical mechanics, but you can't avoid the mathematical complexity of quantum mechanics. Classical mechanics is a good approximation in some regimes, but overall it's wrong and there's no "going back to classical" in physics.

This time around, I'm also struck that superdeterminist physicists think of correlations between widely separated points as "vacuum correlations", which are well-known to decay faster than exponentially at space-like separation. It seems better to consider correlations that are observed in experiments at widely separated points to be a consequence of experimenters taking months or years to set up and debug and tune their state preparation and measurement apparatus (which, moreover, is often constrained to an effectively 1-dimensional space of light guides or collimated matter or laser beams, so that the 3+1-dimensional vacuum is kept as far away as possible). Full of nonsense as usual, I am. Hey ho.

I think about the work of people like Einstein, Maxwell, Dirac, Heisenberg, Pauli, Fermi. The list is very long. Such as those could pull the physics right out of the math and make either predictions that can be measured or better yet people used the principles to make things like AM/FM radio, transistors, and more recently GPS from good old Einstein; the list is almost endless as I said. But some theoretical work seems very difficult to solidify. Maybe a 1927 style Solvay conference is needed to help the general audience understand where the focus is going on Quantum Mechanics, cosmology, particle physics, the hunt for dark matter, etc. Lots of great work is being done right now in condensed matter physics that may bring great practical applications but the money spent on the LHC thus far seems to be a dud. Other than the technology that went into it is remarkable but nothing truly remarkable came out yet (the Higgs boson; bah!).

I think Rovelli is closer than t'Hooft as Rovelli focuses on something that seems philosophically important to me. He talked about velocity as though it is meaningless to a particle unless it is measured in relation to another object. It implies that motion isn't a property as much as an observation. Space is relational and not substantival according to what I understood from Rovelli. I would argue that it is neither, but that might seem to "unscientific" to some, I'd imagine.

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