Hes referring to a different video further up the thread.
Apologies. I see that now.
Very neat post and a very clear description of the text book version.
What of the all missing area above h and below the curve?
I’ll have you know I didn’t refer to any text books … text and diagrams are my own
The area above h and below the curve disappears in the limit as Δx goes to zero. That’s, uh, how calculus works! On the other hand, the space between the circle and your infinity of turned-in square corners doesn’t go to zero. Limits are a tricky thing.
In reality, does it all really “disappear”?
Does it every really ever get to 0?
Yes, I’ll acknowledge that.
Its due to my writing style. I jot down a few sentences then flesh them out as I go.
Sometimes odds and ends are left untied.
Ok, i’m confused now.
Are you familiar with the DCQE experiements?
If I can discuss in simple terms - a drop of water for a wave, an ice cube for a particle pattern.
If a squirt of water is split in two (down phased) and dropped down 2 drains both will have the same ‘outcome’ - a splash/wave/water pattern if unobserved/uncollapsed and a particle, icecube pattern if observed/collapsed.
As both drops of water are ‘linked’ they will both produce the same pattern.
If one drain is shorter than the other - say 1m and 10m, then the shorter drain will produce a pattern first.
However in the second drain there is an apparatus which either heats or freezes the water and is not visible to humans. So it could come out as water or ice independent of how it went it and make a splashy wave pattern or a ‘chunky’ icecube pattern. This is beyond the observers control or vision and is random.
As the first drain is only 1m long it produces a pattern in say 1 second.
The second drain is 10m and produces a pattern in 10 seconds.
However, as both drops of water are linked they must both produce the same pattern - and they do - 100% of the time.
So the first 1m drain must ‘know’ what will happen in the second 10m drain a fews seconds before it happens or the second drain follows its random path, and produces a ice/water pattern and then retroactively the pattern in drain 1 changes to match it.
This simplified example works 100% of the time whether the 2 drains are side by side or on differnent sides of the universe… so the ‘cosmic speed’ for transmission of information between the two drains is broken or even reversed. Perhaps the point you were trying to make is that information states are not physical and can travel ftl?
If so, we are into the nature of ‘information’ and the what (or who ) is doing the knowing?
(ps - again, I wrote piecemeal and stitched together - apologies in advance)
The quantum eraser experiment is interesting…
Yes, “in the limit”. Calculus has been around for hundreds of years and it demonstrably works, but the underlying concepts were only put on a truly rigorous footing in the last sixty using nonstandard analysis.
Also, I think this “tree in the forest” thing is a pretty obvious line of thought for people. Certainly I can remember thinking along those lines independently around age 9 or 10, and realising that I would’t know the difference if everything I saw and perceived stopped existing when I stopped looking, i.e. all some sort of projection/simulation/whatever for my benefit.
I didn’t actually think that was the case, but I realised that I wouldn’t really know the difference.
(I think I’m more with yourself ps200306 on this thread)
Yes, I’m familiar with it. Unfortunately I find your water / ice cube analogy way more confusing than the real thing. The description diverges in essential ways from real world experiments.
First of all, you’ve got a hidden variable mechanism – the apparatus in drain two – which is ruled out in the real quantum world. Secondly, real experiments do not show 100% correlations, for two reasons. Detectors are never 100% efficient. But more fundamentally, the outcome of a measurement is affected by the choice of measurement basis. This is what is actually used in real-world experiments that prove the non-existence of local hidden variables. Bell-type inequality tests show that the amount of correlation is categorically different from what is classically expected.
But let’s go with your analogy. The correlation between your drain one and two is just that – a correlation, not a prediction of what any particular outcome will be. You say " the first 1m drain must ‘know’ what will happen in the second 10m drain a fews seconds before it happens". By using loose language here you may have missed the point. Drains don’t “know” stuff. You haven’t made a measurement in drain one, by definition, otherwise the relevant states would not be in their superposition. The wave function would be already collapsed.
The only way you can show a correlation is by measurement after you have made the detection in drain two. The difference between a correlation and an actual measurement outcome is at the heart of the issue here. It’s why we can say that the mechanism is non-local but does not violate causality or FTL travel. There is no way you can use the correlation to send information.
(Look, for example, at any description of quantum communication envisaged for use in Internet security. It is limited to sending encryption keys. It guarantees that two parties can have a shared key that no eavesdropper can intercept. But the two parties only know that they share a random string. It’s not a case of one party saying “here’s my random string and I am now going to send it to the other party”. They don’t know in advance what the string will be, only that when they perform their respective measurements that they will be correlated).
Let’s get back to your fundamental mistake. You are assuming that something going on in drain one has a definite value, and that something that happens later in drain two reaches back into the past to change that value. This contradicts the very essence of quantum physics. Drain one does not have a definite state until after a measurement is made. If you insert an additional mechanism to measure drain one before drain two, then the two drains are no longer correlated. Your analogy fails on the same grounds as any classical imagery is prone to do – it has nothing analogous to the superposition of states which is a pure quantum phenomenon.
You can find an excellent article explaining all this and more (better than I could, and including the hard maths if you’re interested) here:
P.S. Apropos our earlier disagreement about the role of human consciousness – have a look at the video that Diana posted above. It’s the usual excellent PBS Spacetime standard. Listen to 1:51:
“To head off any wild metaphysical giddiness I want to point out right now that there’s absolutely no reason to believe that observation by a physicist is any better at collapsing wave functions than observation by an electronic detector … or a house plant, for that matter”.
Ok, I was trying to keep the discussion within parameters that those unfamiiliar with the experiments might undersatand; I was writing with an ear for an audience who may not have background.
If you didnt understand it, this was the silvered mirror apparatus, whereby there was a 50% chance of a down-phased photon passing through one path or the other leaving its path untraceable, unknowable and unreconstructable.
But the Dougals have invaded the thread, projectign their own insecurities so I’ll continue without reference to their ignorance, without care for their opsition if that is what you want.
If snide arses like https://thepropertypin.com/u/owenm want to post shite, perhaps they should read https://phys.org/news/2017-07-physicists-retrocausal-quantum-theory-future.html before they do.
Just look how fucking confused this article is.
It can, yet it cant.
It doesnt, yet it does.
It can, yet it cannot.
It isnt, yet it is.
Welcome to Physics, folks, the science that an intelligent study of your own chosen cultural scriptures would have told you 1000 years ago; expressed in mathematical hieroglyphics that excludes you.
Like Latin or Aramaic Greek excluded you 1500 or 1000 or 500 years ago.
Theres the scam; avoid high priests and their prognostications, promulgations and prohibitions.
When a small sect says only they can interpret the meaning of life, the sacred texts, the hieroglyphics, the equations and you are excluded, then you know the lie is iin play.
An army of monkeys like @owenm will hail them too; look at the fool!
Is this not obvious to those who read?
Steady on there Whimsy. I’m sure owenm was just havin’ a larf. I thought it was quite funny.
Anyway, now I understand what your apparatus in drain two was supposed to represent. I did warn you the analogy was more confusing than the real thing. You confused me when you said that drain one changed to match the pattern in drain two 100% of the time. In the DCQE experiment, the screen either registers an interference pattern or not, and the which-way detector either detects which-way information or not.
Anyway, let’s assume that we understand each other now. My objection still stands. You don’t actually know whether you got an interference pattern or not until after the which-way detector fires. That’s because you have to find out which photons at the screen match which photons in the which-way detector, which you do with a correlation counter.
There is no “reaching back into the past”. The two photons are in a superposition of states. If the which-way detector fires, then the wave function is collapsed for both photons, the first photon is localised to one of the slits, and there is no interference. If it doesn’t fire, then the wave function remains in a superposition of states, allowing interference. It’s weird, and it’s non-local … but it’s not retrocausal.
I also refer you to another PBS Spacetime vid on entanglement below. At 10:04 :
“It’s only possible to see the influence between the entangled partners after measurements have been made and those measurements are compared, just as we saw with the delayed choice quantum eraser. The universe seems to conspire to avoid the paradox of information travelling faster than light or backwards in time.”
Sometimes even ostensibly scientific presentations can’t help themselves introducing a “woo” factor. I mean over and above the real “woo” of quantum physics – that reality is described by waves which are not the spatial distribution of some quantity, but probability amplitude waves describing the likelihood of some measurement outcome.
With that in mind, here are two insanely brilliant videos that boil it down to essentials but don’t skip the fundamental concepts. If you’ve never encountered quantum physics before this is for you.The first video introduces quantum probabilities by way of polarisation measurements. It goes on to describe entanglement and explains Bell’s inequality in a way I think anybody can understand, using those Venn diagrams you learned in junior school. Along the way you get to actually see wave function collapse courtesy of sets of interposed polarisation filters.
The second video covers classical waves in the context of Maxwell’s equations. One concept which is often assigned its own “woo” factor is superposition. This is really a pure mathematical concept which says that any two solutions to a linear equation can be summed to give a third solution. Waves are described in terms of linear equations so you’ll see how this applies to classical waves, not just quantum wave functions. The actual “woo” arrives because of the way these superpositions apply to quantum probabilities.
The second video is supposed to give you a more mathematical introduction to the concepts. The maths is no more complicated than Leaving Cert higher level. However it gets a bit more abstract than a Leaving Cert student might be comfortable with, and Dirac’s bra-ket notation is only briefly explored without getting into vector inner products. Also, it skips over how quantum probabilities apply to quantities which are (assumed to be) continuous such as position – Born’s rule for probability densities flashes up once but isn’t mentioned.
In any case, even if you gloss over the maths there are more concepts in this second video that are well worth hearing. My own experience is that by the time you have gone into the level of detail given in a university level course, you are so bamboozled that the awesomeness of the basic concepts is lost on you. Can’t recommend these two vids highly enough for the fabled “interested layperson”. I have to mention also, the respective youtube channels – minutephysics and 3blue1brown – are what I’d like to be paying my TV license for instead of reruns of Eastenders.
I agree with Owen that theoretical physics gets very confusing, and happily so, but am enjoying seeing the debate In 1919, when asked whether it was true that only three people in the world understood the theory of general relativity, apparently Eddington asked “Who’s the third?"
I’ve heard that Eddington story many times. Apparently Eddington himself told it to Chandrasekhar, but I reckon there’s a good chance he was just joking. By 1919 there were a lot more than three people who understood General Relativity. Even within Einstein’s own circle there was his longtime friend Marcel Grossmann who coached Einstein on the Riemannian geometry and tensor calculus he needed, and who co-authored the first tentative paper on GR. There was Tullio Levi-Civita who was also a pioneer of differential geometry who found and corrected errors in Einstein’s maths, and who corresponded with Einstein from 1915-1917.
Then there was Max von Laue who popularised Special Relativity and who Einstein references in the aforementioned GR introductory paper. Laue himself won the Nobel physics prize in 1914 and was a professor of theoretical physics at Berlin where he organised a physics colloquium at which he rubbed shoulders weekly with Einstein. Also there was Willem de Sitter who actually introduced Eddington to General Relativity. He went on to develop the de Sitter model of the universe, a solution of the GR equations for an empty universe which was indepedently derived by Levi-Civita.
Even earlier we have Karl Schwarzschild who derived the first solution to GR, for a single spherical mass. He was dead by 1919, having died at the Russian front in WW1. There were undoubtedly many others within the German physics community, which was really the centre of the universe as far as early 20th century physics was concerned. In fact, the reason why Eddington was relatively late to the party was the unpopularity of such a “German theory” in the course and near aftermath of WW1 in English speaking circles.
But it’s still a good story.
Ok, lets take a breather here… there are no ‘insanely brilliant’ anythings involved here - only repeatable observations.
Again, I object to the ‘woo’ term.
Its a snide term designed to undermine explanations others produce that adhere to the evidence but disagree with your conclusions. Like ‘conspiracy theory’ if you dont think all government action is above board and innocent.
Is akin to saying 'even if you gloss over the explanation in Japanese; which I do.
I I explain my point to you in Portuguese would it make it any more valid?
Do let me know - I have a Portuguese friend who is willing to help; he can break it down to ‘simple’ Portuguese if you require some glossing over. Alas, the conclusions will remain the same but you wont be able to argue against them.
I will endeavour to watch the videos, but as you suggest, the evidence is king; wave function collapse occurs only under human ‘which-path’ observation.
There can be - and is - no doubt about this.
I would add that people such as Roger Penrose accept this so much as FACT that they have moved on to seeking the mechanism by which Human consciousness achieves this.
Whimsy, your points are either nitpicking or wrong. I already presented copious evidence of this. No point in covering that ground again. Maybe you’d like to present your side of the argument / evidence that only human consciousness collapses the wave function? Include a description of what you understand by decoherence.
C’mon, its not my argument, its not even an argument.
The wave function shows ‘collapse’ only when apprehended by human agency; thats the whole root of the problem. (I’ll concede that perhaps cows or parrots also cause it but you’ll have to research that yourself…)
The experiment was repeated when ‘measurements’ or ‘observations’ were taken and recorded by computer.
Those resultant records were passed in a binary fashion (yes/no) to a 2nd computer.
The records on the 1st computer - the actual measurements - were irrevocably deleted.
The result was a wave pattern, even though an ‘observation’ or ‘measurement’ was made and recorded by laboratory apparatus.
A wave pattern - as you know - indicates no measurement was made.
The experiments proved that the wave function collapsed only when a human had ‘which-path’ information.
The DCQE experiments went further with very simple theories tested on very complicated apparatus.
As you know this was designed to obfuscate the which-path information randomly and it too has proven that whatever happens only happens under conditions of human apprehension of which path info.
It throws up a huge level of complexity re retrocausality and non-local FTL shenanigans… but there it is.
Somehow something seems to be passing information in a non-local or FTL fashion and only doing so when humans are conscious of it. This is less of a measurement problem, even an observation problem - its an observer problem. Thus, in our current comprehension it must be one of