I recently read a book all about the double slit experiment. I understood the book but I still don't understand the double slit experiment. I haven't understood it for about twenty years. If you don't know what I'm talking about its explained pretty well in this YouTube for high school kids. (At 4.00 the real weirdness begins.)
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31 comments:
Quantum physics is way over my head, I can't even begin to explain why the reaction happens. The video did make it interesting though.
Glenna
Well I get it but I dont understand it...if that makes any sense.
Oh, man. Why did you do this?
I read Six Easy Pieces last year and had headaches for a week.
I am obsessed with physics but I just can't get a handle on it. Dr Brian Cox (ex-keyboard player of D:Ream) does some brilliant shows for the BBC on astrophysics. I think SBS show some of them over here
How can an electron know its being observed?
Does this mean that all matter reacts differently when watched? if you expect it to do one thing it will do the other. Petulant electrons? hmmm
Heehee! that's great. I'm reading a book about a ghost that I don't really like right now - neither the ghost (hackneyed) nor the book (a bit contrived).
Thanks, it's awesome. Will ask my son about it when he gets home as well, so doubled my money today on your excellent blog.
I know this is the kind of thing that only really naive people say, but I somehow feel convinced that there will someday turn out to be a relatively simple and completely different explanation.
Its funny that we were just talking about matter in this discussion group I go to tonight. One guy said the root of the word matter is 'mother'. But one of the leaders talked about the work of a French philosopher who wrote about the transition in human life from the forest to the city and said that matter actually comes form materia, the hard inner wood of a tree. Apparently matter is also dual in origin, then, which makes a kind of sense.
rob
about a third of the books i read are on physics i love this stuff, but i dont have a handle on a lot of it.
frankie
that is the question...how can the electron know it is being observed?
gen
i just finished a bad ghost story myself ....sarah waters the little stranger. that was pretty disappointing because i like her.
seana
i hope im around to see it because this thing has been puzzling me for two decades.
Well, remember the tiger and the lion debate and keep yourself fit.
Oh, yeah, here's another unanswered question that caught my eye yesterday.
I don't think it's physics, but it might be.
I loved the Little Stranger although discussions afterwards as to the nature of the ghost lessened it slightly.
I thought the scene where the mother was locked in the nursery was terrifying.
Ghosts are explained by physics I think.
Seana
In Wind Sand and Stars they kept walking miles through the desert and ending up back where they started.
Rob
Way too slow for me.
Was it blindfolds, or sandstorms?
Rob, I think physics might be right. I'm not highly susceptible to ghosts, but I don't discount the phenomenon. There was one incident that might have been physics when I was back in Illinois, and my sisters and I were back with my at that time very young nephew. My sister came up, surprised to see my nephew sitting in the living room, and said, but I just saw him go running around the house. In the circumstance, there was no way that could actually have happened, but apparently it had. I think something did happen then, not spooky, exactly, but unexplained.
I love this stuff, totally mind blowing. Quantum Enigma is a good book on the same subject, showing that if you observe a particle in one place it instaneously determines the the state of a particle someplace else and vice versa, so "the properties of objects in our world have an observation-created reality or that there exists a universal connectedness, or both." Got it. Pretty simple.
If it's weird you're after, try 'spooky action at a distance' ...
http://en.wikipedia.org/wiki/Quantum_entanglement
The apparently lunatic chaos of quantum mechanics will have pretty simple explanation, as Seana says, but only if we discover that the universe is a self-regulating organism (conscious or otherwise).
Big if, though ...
Cheers, Dec
Seana
I think it was the sandstorms. Poor chaps kept ending back at the crashed plane.
Dennis
Yeah I love that stuff too. I like the idea of the observation created reality and I like the idea that that observation can move forwards and backwards along the arrow of time.
Dec
I wrote this kids book once called The Lighthouse Keepers where I tried to explain Spooky Action At A Distance thus: at the point of observation the second entangled particle doesnt change instantly violating the theory of relativity...no what actually happens is that at the point of observation, the information from the observation travels backwards along the arrow of time letting the second particle know what has just happened in the future.
This I think is a boon to novelists who want events from the future to somehow leak into the present....
I think that people get too hung up on the consciousness aspect of observation. What we need to remember is that observation changes the state of the electron. That is, the electron has to have some sort of interaction with the detector (otherwise the detector doesn't detect anything), which changes the state of the system. So when you have that interaction, you collapse the wave state into a particle.
I can't find a reference right now, but I remember reading somewhere that someone did the experiment with very low-energy detectors, and they got the interference pattern. But I could be misremembering.
Btw, that's not to diminish the weirdness of the whole wave-particle duality thing, which is still one of the coolest things in physics, I think.
I just don't like the mysticism that is sometimes attached to the idea of "observation."
Oooh Gavin has sorted a few things out for me there.
Gav
But if you were to put a dummy camera on the electron it would know and the wave form wouldnt collapse, but it does with a real camera. If you put a camera on the electron that works but you dont plug it in or include a photographic plate the wave form also doesnt collapse. How?
Gav
But yeah I hate the new age bullshit you read in the Huffington Post - quantum physics proves afterlife, etc.
In either case does the shutter fire? Obviously camera shutters make a sound and vibration?
I guess my question would be, what is observation? And what does it mean to say the electron 'knows'?
I still haven't read Wind, Sand and Stars, and meant to have by now.
Adrian,
My non-physics major understanding is something like this:
First, I think talking about a camera is mis-leading, in that a camera doesn't need to interfere with objects to see them (*). We're really talking about electron detectors, which do interact with the electrons.
So if the electron detector isn't turned on, and it doesn't interfere with the electron, then it's not doing anything to the system.
The same goes for the photographic plate. At some point, putting in a photographic plate doesn't change the experiment, because otherwise we'd never see the interference pattern (the whole thing is registered on a photographic plate).
I'm not going to try to talk about the quantum eraser, because I'm just not smart enough.
Again, all this isn't to diminish the weirdness of the wave/particle collapse thing. The idea that measuring a particle gives particle-like results and measuring a wave gives wave-like results weird me out big-time.
(*) That's not really true, either. A camera only seems passive, but it works by a bunch of photons hitting something and then coming into the camera; but cameras are looking at macro-level things that don't get affected by photons.
Gav
Brian Greene's been on the Guardian science blog pedaling the idea that the collapse of the wave function actually represents the creation of a new universe, the old many worlds idea. I find that thesis very unattractive.
Adrian,
Agreed. I think that the idea is really horrendous as anything other than an analytical abstraction.
I think Greene is a really lucid writer, and one of the best things about that is that I can easily find where I disagree with him.
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