The quantum challenge : explaining materialism

this talk is a harder one for me to get right and I've relied on the advice of Shaun Greenhalgh to check that what I'm saying is correct in this and I want to thank him for that I have been talking about classical materialism starting from Lucretius gradually working through Boltzmann etc now classical materialism had been based on the idea of the atom the indivisible atoms but in the 20th century it was discovered that atoms could be split what was the implication of this it was discovered that there were smaller particles inside atoms does this matter for matter does it matter if the atom turned out to be splittable if the atom turned out to have a nucleus with electrons going around it did it matter if the nucleus was - turned out to be made of neutrons and protons and did it matter if these in turn were discovered to be made up of smaller particles way back in 1905 same year that Einstein published his paper on the Brownian motion he published another paper on the photoelectric effect this is what he actually got his Nobel Prize for in his sent in essence what he did was he showed that the world what you might call atoms of light he showed that light was made up of particles the particles which we now call photons so to the question asked before does it matter if it turned out that the atoms were not indivisible no it doesn't matter because we're taking the word atom from Epicurus or not from Epicurus and in the nineteenth century these were mapped onto the chemical elements the atoms of the chemical elements and that is what the word now means but from the philosophical standpoint from the standpoint of the basic theory of materialism which Epicurus was putting forward it doesn't matter whether these indivisible particles these indivisible atoms were what we now call atoms or whether we regard these indivisible particles as being the photons quarks and electrons that we now regard as into this basic idea which persists from Epicurus is that there are fundamental particles of matter out of which other things are made exactly what we call these doesn't matter why then was quantum theory which developed at the same time as it was discovered that the atom was spreadable why was quantum theory seen as a challenge for materialism there appeared to be a number of challenges here first is that the quantum theory seems to involve non determinism it seemed to involve what was called a wave particle duality it involved the existence of non-local effects which seemed hard to reconcile with the view of materialism and it introduced or was made to seem to introduce an essential role for the observer the human observer in the world that was being observed well let's look first at this issue materialism versus non determinism the first point is that non determinism isn't new it was already dealt with in the statistical mechanics of Boltzmann which reasoned about probabilities of things occurring around certainties and has another level whether or not atomic motions a deterministic or probabilistic doesn't really matter for materialism and there is a further paradox here that the wave equations of quantum mechanics evolve deterministic lean linearly was Newtonian mechanics being nonlinear easily generates chaotic motion so that very small uncertainties in the motions of atoms treat as perfect billiard balls bouncing off one another rapidly generate complete uncertainty about the positions of atoms perhaps a harder problem is the wave particle duality classical materialism had been based entirely on the idea that things were made out of particles insofar as waves were recognized and they were began to be recognized in the 19th century for light and other electromagnetic effects materialism attempted to explain these in terms of the being a very thin medium and ether in which the light propagated but the the existence of this ether had been disproved in the early or late 19th early 20th century and had been dropped so the duality between particles and and light continued to be seen as a problem now the simplest form of interference effect is one that you get if you shine a laser through two slits you get a series of dots generated you don't just get one dot or two dots you get a row of dots generated by interference effects and if you hold up a CD for example to the light and you got a light source you will see multiple images if it's a small light source like an LED you'll see multiple images generated by reflection in the same way or as the multiple images you get in a screen from a diffraction slit so this is an easily observable phenomena which you can see with things which have readily available to you nowadays now what's happening here is the light is going through the slits and they are adding up and [Music] generating interference patterns on the far side you're all taught about this in in physics at school it's just classical optics but the odd thing is that this happens even if the light is so dim that only one photon at a time is being sent through so it's very hard to reconcile this with a particle view if the particle is passing through one slit how does it interfere with the light coming through the other slit so the first assumption one would make is maybe the particles don't exist maybe only the wave exists or you might say maybe the part of the eye she goes through both of them now if it was just light it wouldn't be so much of a problem but it was found that electrons behave the same way if you send an electron beam of the sort you have in an old-fashioned TV and you set it through pair of slits you would get a set of diffraction bands on the screen how could this be review reconciled with a materialist view of particles the standard view that's given of this is the Copenhagen interpretation summary of it is given in this quote from Bohr that in contrast ordinary mechanics the new quantum mechanics does not deal with a spacetime description of the movement of atomic particles the difficulties seem to require just that that renunciation of mechanical models in space and time which is so characteristic a feature of the new quantum mechanics so there in 1934 Bohr seems to be saying we have to chuck out materialism because of these effects because we can't give a definite position to the particles as they go through slits and another similar circumstances but in a sense this is just a recapitulation of Mark in this variant the photon has no definite position until it's observed but that's just a repetition of what what Mark said about scientific observation in general he said that all science is just about relationships between instrument readings relationships between observables that all science is doing in the end is constructing elaborate mathematical relationships between our sense impressions now Lenin objected to this and showing that in the end it reverted to the subjective idealism of Berkeley and ultimately to solipsism I'm referring to Lenin's criticism and materialism and imperial criticism now in the idealist account it's the observer who collapses the wavefunction collapses the wave and turns it into a particle bringing actuality bringing actuality to potentiality but the question is what is the observer the immediate intuition you're supposed to get from the reference to the observer if there's a human being that does this but if you consider the interference pattern you could say that the observer was the silver iodide on the film or the crystals of silver iodide which when they're hit by a photon turn black now suppose you just let a small number of photons through or exposed the film for a short period you'll only get a thin speckling of silver iodide crystals turning black have they really turned black until someone looks at the film is it the person looking at the film which collapses the wavefunction but since the crystals on the film are macroscopic objects objects which could be observed under a microscope or a magnifying glass if you wished it seems we've turned right back to naked Berkeley ISM where things only exist if a human looks at them objecting to this Einstein remarked you might as well say the moon doesn't exist when you're not looking at it it's an absurd position to take when you consider macroscopic objects like the moon but where does the the breaking point come why should a crystal of silver iodide be something which only exists if someone looks at it if you once accept the premise that things only exist when you look at them you might as well extend it to things of arbitrary size you might as well extend it to the back side of the Moon did it even exist before the first lunar lilyc probe took a photo of it let's take another example there's a lot of work going on now to develop quantum computers and one of the jobs that quantum computers are supposed to be very good at or in principle should be good at is factorizing prime numbers which is a hard hard mathematical job to do certainly if you took a hundred bit binary number and factorized it that would be something way beyond any human capabilities and would be very hard even for a conventional computer now there exists an algorithm which shows algorithm which you can use on a quantum computer to do this if we take the idealist school Copenhagen interpretation if a quantum computer runs this comes out with the factors of the hundred bit number the correct answer must be attributed to the observation of this by the human operator who looks at the answer on the screen now there is no way the human operator could actually work out the prime factors of a hundred bit number so here you'd be attributing to the human some kind of supernatural power a mystical power which enabled them to select the right prime number by some psychic ability so the idealistic interpretation that was the dominant quantum interpretation from the Copenhagen school leads to absurdities and dead ends but its dominance is a result of the dominance of the Marcus and positivist theory of science in European universities and physics departments at the time the people who became the leaders of quantum theory we're doing their original undergraduate training there was going right back to 1927 a perfectly coherent alternative to the idealist Copenhagen view which was that developed by de Broglie who developed a quantum theory of motion were by a quantum wave going through the slits exerts a force on particles that produces the interference effect he came up with equations of motions for particles in the wake of this quantum wave which has them following these Wiggly courses they seem absurd courses to us since we're used to things going in straight lines but what he was saying is that those additional forces exerted on tiny particles by the quantum waves and these quantum waves caused them to deviate from a straight-line path and the path that they end up in actually of the paths which give rise to the interference fringes on the film now this theory was further developed by Boehm in the 50s and there are now many textbooks on it I'm giving an example of Jean bricmont Spit textbook here in the bomb debris Glee Theory particles have definite determinate positions it's not like the idealist theory what particles have no position until we observed them any non-local effects come about through the interference of the waves which then act as forces moving the particles into the positions we see them here's another textbook quantum theory of motion the these theories are actually quite hard going because they rely heavily on fairly abstract forms of classical mechanics which if you haven't been taught them take quite a while to take in the actual development of this bomb theory was strongly influenced by Einstein who had been very critical of the elements of subjectivism that he saw in the Copenhagen interpretation in the start of the 1950's Bohm had written a standard textbook which was entirely within the framework of the Copenhagen interpretation Einstein read it Nast bombed to come and discuss it with him and over a series of conversations he persuaded bomb that this an idealist interpretation was wrong he taught me out of it I'm back where I was before I wrote the book said bomb after meeting Einstein a year later around the time you sacked from Princeton annex exile to Brazil for being a suspected communist he came up with a set of papers that built a new theory of mechanics an extension of the de Broglie theory it's not clear how much he knew of de Broglie in 1952 and how much it was an independent invention or how much it was just a recapitulation of de Broglie now this wouldn't matter if it were not for the fact that recent experiments have shown that you actually do get the trajectories projected by predicted by the de Broglie and Bohm theory this is a 2016 paper showing photon trajectories and you can see the in fact don't follow straight lines they follow the kind of curved paths that give rise to interference effects predicted by the de broglie-bohm theory so in conclusion what I'm saying is the apparent quantum challenge to materialism was just a dressing up of pre-given Markus prejudices which the physicists who first developed the quantum theory had been inculcated with during their training the same prejudices that initially caused physicists in Germany to reject Boltzmann's atomic theory since 1927 there has been a deterministic theory of motion the de Broglie theory this theory has led to fruitful results I'm not going to explain them at the moment but Bell the guy who invented bells inequality was a bohmian and from bells inequality has followed the harnessing of nonlocality to things like quantum encryption the rejection of bombs theory was not due to science but among other reasons the fellow physicists like Oppenheimer at Princeton said there were weren't interested in in bombs theory because he by that stage he was regarded as a Marxist a fellow traveller traitor to the USA in addition of course you have the fact that established professors would find it very hard to accept the paradigm shift if they had been lecturing for twenty years on the Copenhagen interpretation they were not going to enjoy someone coming up and saying well some of your basic assumptions are wrong

Channel: Paul Cockshott

Views: 3,248

Rating: 4.9200001 out of 5

Keywords: Einstein, Bohm, Mach, Quantum theory

Id: cOe-7GH83Us

Length: 22min 18sec (1338 seconds)

Published: Mon Jul 16 2018