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just wanted to formerly introduce myself.. .
i've been hanging out here lately.. didn't want anyone to think i was barging in.. i got so excited about all of the normal people here.. and seem to have lost my manners!
At this point, I don't know what I believe.. I just know what I DON'T Believe...
Hey that's pretty cool, knowing what you don't believe.
And thanks to my globe (which lives on my desk) I now know where South Carolina is. It seems to be just below North Carolina. Hoodathunkit? Next time we're visiting the Mother-in-law in Cornwall, I'll have a look out across the Atlantic, see if I can see your island!
ig.
i never thought to check before i re-signed up again for jwd whether my old alias was still active...i just wanted to write this post to see how long ago i signed up originally...frog
My login saw something....
.
just wanted to formerly introduce myself.. .
i've been hanging out here lately.. didn't want anyone to think i was barging in.. i got so excited about all of the normal people here.. and seem to have lost my manners!
Welcome,
I do like a delicious hog roast. Where's me apple sauce....
ig
hey all,.
i'm totally fascinated by the concept of entangled particles.
as i understand it, you take a proton (or something tiny like that), split it apart, but don't observe the resulting particles.
Great minds think alike!
hey all,.
i'm totally fascinated by the concept of entangled particles.
as i understand it, you take a proton (or something tiny like that), split it apart, but don't observe the resulting particles.
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.
hey all,.
i'm totally fascinated by the concept of entangled particles.
as i understand it, you take a proton (or something tiny like that), split it apart, but don't observe the resulting particles.
humm, I'll have a think about the mirrors. In the meantime, if you want to blow your head apart even further, have a read about the Copenhagen interpretation of quantum mechanics, and the transactional interpretation of quantum mechanics. There's also the many worlds interpretation, but that's a bit weird, even for quantum mechanics!
The transactional one is interesting because it talks about the emitter and the absorber setting up a standing wave between them, one going forward in time and the other going backward in time! Spooky. Don't quite understand it yet, still looking for a sufficiently dumbed down description on the internet...
Right, back to the mirrors....
ig.
hey all,.
i'm totally fascinated by the concept of entangled particles.
as i understand it, you take a proton (or something tiny like that), split it apart, but don't observe the resulting particles.
So here's our particle, existing all over the room like a bubble extending from the emitter. Then one of my observational particles (light, death rays, something) impacts the particle. Where does it do that? For lack of any understanding of it, I'll say I send out a stream of observation particles and the first one to touch the bubble causes it to collapse to a single particle. No impact, no particle. Does the particle "appear" at the point where my observation particle impacted the bubble? Or can it appear anywhere? It doesn't make sense that it would appear just anywhere, or my observation particle wouldn't have impacted with it. But then at the quantum level some things are caused by their own effect, right? Something all backward like that?
Right - with nothing up my sleeve, and without the aid of a safety net, I'll try to answer this! I have to put a disclaimer on my answer - I'm not an expert in this field, but I'll give you the best answer I've got. If there's any real physicists out there, feel free to chip in, fill in the holes in my argument.
Yes, the particle evolves from the emitter, like a bubble if you like, although it's probably better to think of it as a spreading ripple, like when you drop a stone at the edge of a pond. It's the next bit of your question that's not quite right. You see, your observational particle is also spreading out from its own emitter in the same ripple like way. So now you've got to imagine dropping two pebbles into your pond, at different points on the pond's perimeter, and the result is a combined ripple field accross the surface of your pond, or in our experimental chamber, two "superposed" ripple fields of our particles. This combined ripple field now gives us the probability of finding the particle at any given point.
Well, now I start to get a bit hand-wavey, because I don't understand this bit myself (see my earlier post). How does the system decide where it ends up finding the particle?
Have you read anything about string theory? The basic idea is that all fundamental particles can be thought of as different modes of vibration on very small loops of string, and that therefore the whole of the natural world is a gigantic symphony played by the great universal chamber orchestra. To simplify a bit, imagine a guitar string. Without putting your fingers on the fretboard, there are a restricted number of notes you can get out of it, corresponding to what's known as the normal modes of the string (harmonics to you and me). So, if we think of our two particle system as like a vibrating system, there are only a certain number of "harmonics" the system can settle to.
If we do our two particle experiment (emitted particle and detector particle) 1000 times, we get 1000 different answers. What made each experiment settle to the particular quantum "note" it did? Who knows? Not me that's for sure as mustard! Just remember though that the wavefunction of the detector particle is coupled to a whole load of detection equipment. There's lots of stuff on the internet talking about things like: once a system gets sufficiently complex (lots of vibrational fields interacting with each other) it forces the original system to choose which note it's singing.
Maybe it's a bit like, when you're uncertain about something (where to go on holiday? France or America this year? Decisions, decisions...) and you talk to enough people about it, eventually you have enough information to make up your mind, and then your probabilities collapse into definite certainties. Perhaps the emitted particle chats to the detector particle, the detector particle talks to the particles in the detector, the particles in the detector talk to the particles in the wiring and computer part of the detector, and when the system becomes complex enough (probably just in the detector bit) our probability waves collapse into a definite "note" which the system "sings", which is then measured by the detector somehow.
Why is the answer different every time? That I don't know.
Hope this helps! I know I'm more confused than ever now...
ig.
hey all,.
i'm totally fascinated by the concept of entangled particles.
as i understand it, you take a proton (or something tiny like that), split it apart, but don't observe the resulting particles.
Goodness, this thread has woken me up a bit! To misquote Richard Feynman,
I think it is safe to say that no one understands Quantum Mechanics.
AA - You've heard of Richard Feynman right? He was smarter than God, and what he didn't know about quantum theory wasn't worth knowing, and even he didn't understand it! I did mathematical physics at university, and that single electron slit experiment really freaked me out, and continues to freak me out really.
Here's as far as I got with the problem.
I'm reasonably happy with the particle "existing" as a probability wave between the emitter and the detector, and I can even just about stretch my brain to thinking about that probability wave going through two gaps simultaneously and continuing on thereafter to the detector screen, creating on its way the interference pattern that eventually describes that banded detection pattern you get out of the experiment.
It's the mechanism of the detection bit that I continue not to understand. If memory serves, it's the collapse of the wavefunction (the thing that controls the probability distribution) into a certain state. Let's remove the slits for a minute, we have an emitter and a detection screen that's giving us definite locations of collisions of electrons with the screen. So, the way my poor human brain imagines it, the wavefunction of the electron evolves as waves do, and then starts interacting with the detector screen (which also has a wavefunction, which is much more complicated than the single electron of course) when it reaches the screen. Then, these two wavefunctions do some sort of funky mojo, which is like some kind of quantum committee meeting, where they decide whether the emitter is happy for the electron to have been emitted in the first place, and then if this is OK, the electron and the detector discuss where the electron would like to be detected (anywhere the electron wavefunction was non-zero when it hit the screen would be OK).
What are the exact mechanics of this collapse of probabilities into certainties? I don't know, and unless some kind of amazing breakthrough has happened in the last 10 years since I was at university, physicists don't really know either. I'll have a google, see what I find...
ig.
Meet the new boss... same as the old boss...
(duuuuurrrrrrrrrrr, dur dur)
i contend that we are both atheists, i just believe in one less god than you do.
when you understand why you dismiss all other possible gods, then you will know why i dismiss yours.
- stephen f. roberts.
"Before you judge someone, you should walk a mile in their shoes. That way, when you judge them, you're a mile away from them, and you've got their shoes!!"
No idea who came up with that originally...
ig.
