Physics Challenge! Explain "entangled particles" to me

by AlmostAtheist 41 Replies latest jw friends

  • iggy_the_fish
    iggy_the_fish

    Hello again, try this link. It's the same experiment, but with a better description possibly. The experiment works because there's a difference between a wave that's reflected, and a wave that's just passed through the half silvered mirror. The way they have the experiment set up, they have the waves going towards detector 1 interfering constructively, and those going toward detector 2 interfering destructively.

    They're assuming you have prior knowledge of something called the Mach-Zehnder interferometer, an interesting looking piece of kit, designed to monkey about with the phase of the incident light in such a way that you get light at detector 1, and no light at detector 2. I've just been reading about in here

    http://www.upscale.utoronto.ca/GeneralInterest/Harrison/MachZehnder/MachZehnder.html

    I'd never heard of it before! I think the point they're making is that, assuming you buy that the experiment works with a beam of light, it also works with a single photon, which is weird in the same way that the slit experiment with one photon is weird.

    Something even weirder: the delayed choice experiment, devised by one Prof Wheeler.

    ig.

  • AlmostAtheist
    AlmostAtheist

    >> You can't really KNOW a watch by gazing at and
    >> speculating on smashed and disarranged smithereens.
    >> (Not without having experienced a functioning
    >> watch before the smash.)

    I think I understand what you're getting at, Terry, but let me offer a change to your analogy. Imagine that watches are extremely durable, virtually indestrutible. Also imagine that they are very tiny, much smaller than you can see. And to make matters worse, they stick to each other. So the only time you come across a watch, it is hopelessly glommed together with trillions of other watches. In their glommed-together state, they take on properties that you can see. In one arrangement, they look like Gold. In another, they look like Lead. It would likely take you centuries of looking at gold and lead to even realize the things you see as two substances might actually be the same substances arranged differently.

    So you start smashing gold and smashing lead under more and more strenuous circumstances until you manage to get one individual watch out of each substance. It is at this point that you can begin to examine the watch itself, rather than just the properties that emerge from it when it gets together with other watches.

    As I understand it, they aren't smashing the watch, they are extracting it. Once extracted, they can study it on its own.

    As an aside, you'll enjoy a point made in one of the articles. It said that if you have a particle A and I have a particle B, and the two particles are precisely the same, they can reasonably be said to be the same particle, just existing at two different points. I read that and thought, "No, they are two identical particles." But the author seemed very comfortable with the idea that they were the "same particle".

    Dave

  • AlmostAtheist
    AlmostAtheist

    >> Hello again, try this link. It's the same experiment,
    >> but with a better description possibly.

    Wow, MUCH better description. Thank you, Fishman! It makes alot more sense. Not that I understand it, but at least it makes sense.

    Dave

  • Elsewhere
    Elsewhere

    The problem with understanding this experiment is that the illustrations used are not detailed enough.

    The Half Silvered mirrors reflect on one side only, not both sides as suggested by the the illustrations being used. The first Half Silvered mirror is silvered on the side facing the laser source and the second Half Silvered mirror is silvered on the side facing Detector 2.

    Basically what is happening is the photon is traveling both paths at the same time, but in one path it is put 180 degrees out of phase. The second path keeps the photon in its normal phase.

    When the photon meets itself (REMEBER we are watching one photon take two paths as the same time, NOT two photons) at the second Half Silvered mirror, on one side of the mirror it is in phase but on the other side it is out of phase, which causes the photon to cancel itself out on the reflective side of the second Half Silvered mirror.

    Bottom line: You could not understand the illustration you have been looking at because it was dumbed down far too much which caused it to loose its meaning.

    A much better illustration if this is here (It also gives a "step by step" explanation of what is going on:

    http://www.upscale.utoronto.ca/GeneralInterest/Harrison/MachZehnder/MachZehnder.html

    Edited to add: Oops! Sorry! I did not notice that someone already posted the same link!

  • iggy_the_fish
    iggy_the_fish

    Great minds think alike!

  • Mac
    Mac

    *edited for too much silliness within an enoyable thread

    mac, that's a first class

    *edited again to add a "j"...place it where you feel it's needed

  • Terry
    Terry
    I think I understand what you're getting at, Terry, but let me offer a change to your analogy. Imagine that watches are extremely durable, virtually indestrutible. Also imagine that they are very tiny, much smaller than you can see. And to make matters worse, they stick to each other. So the only time you come across a watch, it is hopelessly glommed together with trillions of other watches. In their glommed-together state, they take on properties that you can see. In one arrangement, they look like Gold. In another, they look like Lead. It would likely take you centuries of looking at gold and lead to even realize the things you see as two substances might actually be the same substances arranged differently.

    While staring at the Period Table of the Elements I had an epiphany one day. As you go to the highest numbers and start removing properties you get the next lower number. Not much of an epiphany for a Physics professor, but, for me it was quite illuminating.

    I thought of it like looking at a bunch of letters of the alphabet tossed out randomly on a table. You might find a stretch of letters such as INARTICULATE. Wow! You can remove certain letters and get: IN ART LATE ATE, etc.

    But, note: there is no "meaning" attached. It is just random possible combinations of letter that you must IMPUTE meaning to because you have these patterns assigned to meaning already.

    Hold that thought.

    The Bible Code had a similar inherent illogic to it that gave people a thrill because they attached SIGNIFICANCE to the fact scripture was involved. Randomly (non)organized letters in certain sequences had the appearance of names, places, etc. Michael Drosnin imputed "meaning" and the world took a sharp breath and went gah-gah.

    We cannot escape this possibility in Physicas as well.

    Notice in your question to me (in the box above) a watch is already a watch. The concept arrives in your "what if" as a given. That is a huge given for the sake of the point you really want to make. But, by smuggling in (unawares) a hidden concept (The Watch exists as a timepiece rather than as a puzzling unknown) you color the outcome.

    Sometimes random letters may appear to spell something. But, a word is only a true WORD if there is meaning attached by intention.

    A sidebar:

    (This is what Creationists want to do with everything. When they see a random pattern which they recognize (already a given) they jump to IMPUTE meaning and intention. They fool themselves with this smuggled concept and call it proof. It is not proof. It is a possible premise and nothing more.)

    Or, to put my point simply: what a thing is.....is according to its nature. We are the ones insisting that the nature MEANS this and that in order to fit it into an overall pattern. That pattern is often (mostly?) (always?) an artificial construct for the purpose of understanding it.

    I am NOT saying what Immanuel Kant said. Nature is not impossible for us to understand because it can be misunderstood. We must simply take care to wipe the equations already on the blackboard off before we begin the new set of numbers.

    I'm not even sure I've made any point now that I re-read the above. Try this: When we disturb the nature of anything in order to discover what it MIGHT BE we risk only seeing what it has become now that it is disturbed and then extrapolating and imputing MEANING.

    Terry

  • iggy_the_fish
    iggy_the_fish

    I read a good passage in a book by James Gleick (spelling?) about quantum theory, and what we actually understand about life (<-- you see that, I'm anthropomorphising already!) at the quantum level. I have to declare an interest at this point, being a physicist myself I'm all in favour of smashing atoms to bits and extrapolating "meaning" from the experimental results - it's fun!

    He (James Gleick) talked about oxygen, and how it has eight electrons orbiting its nucleus, which immediately fills the mind with an image a bit like a tiny solar system. However, what's actually going on in the oxygen atom is absolutely nothing like that, and quite what it is like, I'm sure any physicist would tell you is perhaps outside our human imagining at the moment. That's the trouble with being the sort of beast optimised by evolution to run away from animals with big teeth, hit large docile animals on the head with clubs and eat them, and shag. When you're suddenly called upon to understand the world of the very small, words understandably fail.

    Sorry, went off the track a bit there! Back to James Gleick. He was making the point that the best we can really say about oxygen is that it has a certain "eightness" about it. In terms of its mass it has a certain "15.9994ness" about it (according to www.webelements.com). In chemical composition with other elements it has a certain "sixness" about it, so that when it combines with hydrogen (which has a certain "oneness" about it) we get two hydrogens to one oxygen, giving a combined "molecule" we'll call it (well, we have to call it something don't we?) with again a certain "eightness" about it. We also know from experiment that when "molecules" attain a state of "eightness" they seem more stable. However we code this into language with words like "orbit", otherwise a conversation between two chemists about oxygen might take quite some time!

    It seems to me, physicists (and scientists in general) in my experience are pretty good at understanding the limits of their understanding of nature, and are pretty good at not over-deducing from experiments. Unfortunately I think sometimes the language that physicists use gives the impression that they think they understand what their experiments "mean". I think if you questioned any scientist hard enough they'd eventually admit that all they could really do would be to predict the result of a given experiment to a certain degree of accuracy. But that's extremely useful, and it's enabling us all to use the computers we're using at the moment..

    God I'm rambling now! I'm not sure of the point I was making! I'll post anyway...

    ig.

  • Elsewhere
    Elsewhere
    He (James Gleick) talked about oxygen, and how it has eight electrons orbiting its nucleus, which immediately fills the mind with an image a bit like a tiny solar system. However, what's actually going on in the oxygen atom is absolutely nothing like that

    Yup... a better way to visualize an atom is with a wave that is going around the nucleus. What is very interesting is that because the electron has a certain wavelength it can only exist at certain distances from the nucleus and in certain numbers, otherwise the wave would interfere with itself.

    With the illustration below you can see that the total circumference of the electron's orbit divided by the wavelength of the electron must be a whole number. This is what forces the electrons to settle into very specific distances with very specific numbers of electrons in any given orbital distance.

  • frankiespeakin
    frankiespeakin

    Igi,

    I like your explanation, I've read Glick's book on Chaos,,and found it fasinating,,I'm just a layman when it comes to physics so I had to read some parts a couple of times and I'm sure I missed alot of information in his book do to my lack of education in that area.

    Have you read the book "The Non-Local Universe" and a universal mind,,I think that was the title it was writen by 2 men they might both have been physists if I remember correctly. They talked about the Bell theorim and instant comunication between photons experiments. I think the book pointed to the fact(?) that all space time is an illusion and that there is really no distance between everything. Which seem to me intuitively atleast correct.

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