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June 4, 2008 11:40 PM   Subscribe

The Reality Tests. "A team of physicists in Vienna has devised experiments that may answer one of the enduring riddles of science: Do we create the world just by looking at it?"
posted by homunculus (82 comments total) 19 users marked this as a favorite

 
Atmospheric (ooh! adjectives!) , but weak article: this took a long time to hum and haah about polarization experiments which were not explained properly (16 orders of magnitude! 80 orders of magnitude!), to come up with the money shot

Late last year Brukner and Kofler showed that it does not matter how many particles are around, or how large an object is, quantum mechanics always holds true. The reason we see our world as we do is because of what we use to observe it. The human body is a just barely adequate measuring device.


It's not just the body: its the nature of measurement itself.

We've known this for years from the earliest interpretations of QM.

De broglie hypothesis states: wavelength * momentum = plancks constant.

Plancks constant is a tiny number. A component of the momentum=mass.

Hence: if mass is big (i.e. bigger than a molecule of a few dozen carbon atoms), the wavelength (and hence the quantum mechanical effect) is small. Really small, smaller than than the planck distance, 10^-34m. In order to see QM properties, we must assume the wavelength correponds to a physically measurable size. <1>plenty of evidence for it.

Zelinger and his optics may have discovered something new about QM, but it's not explained by this article. .......They should still hire the philosopher though.
posted by lalochezia at 12:45 AM on June 5, 2008 [7 favorites]


Stupid HTML....grrr ignore everything after "plenty of evidence for it."

it should read

The Planck distance is not a physically measurable size : there are no processes we can use to interrogate space that small. Some hypothesize that the planck distance is the minimal quantal unit for space itself. Wavelengthplenty of evidence for it.

Zelinger and his optics may have discovered something new about QM, but it's not explained by this article. .......They should still hire the philosopher though.

posted by lalochezia at 12:52 AM on June 5, 2008 [1 favorite]


Mods: link button is broken and scrambling my posts! Grr!
posted by lalochezia at 12:54 AM on June 5, 2008


This lavishly touches on something that has always bothered me. The idea that observing something changes(creates) it -- isn't this due to the fact that observing something on a (sub)atomic scale requires the physical interjection of a measuring device? -- i.e. shooting a proton at an electron to see what it will do?

This seems like a weakness of our ability to investigate and not much more.
posted by undule at 1:02 AM on June 5, 2008


Is it just me, or is it pretty cool to live in our little post-QM, post-modern, post-traditionalist society? A quantum foam right in front of our eyes, that we can't parse without changing? Beats the hell out of Daddy God in the Sky if you ask me.
posted by farishta at 1:20 AM on June 5, 2008 [6 favorites]


This was a bad article, and I'm convinced the author didn't actually understand what he was writing about. But not only that, even the basic grammar is confusing. For example
The data is tested against two theories: one that preserved realism but allowed strange effects from anywhere out there in the universe, and quantum mechanics.
Does that mean theory A is "one" (unnamed theory) that "allowed strange effects from anywhere out there in the universe" and theory B is the theory named (but not capitalized) "quantum mechanics"?

Or does it mean theory A is "one" unnamed theory that allowed strange effects from "anywhere out there" and also allowed strange effects from quantum mechanics? and theory B is simply not specified?

I'm assuming the first, but that's some serious non-parallel construction going on. Also, the article completely fails to explain just how the experiment actually works. I'm assuming it's some variation on the double slit experiment?
posted by delmoi at 1:22 AM on June 5, 2008


God does not play dice with the Universe; God is the dice.
posted by loquacious at 1:48 AM on June 5, 2008 [8 favorites]


I'm blind.
posted by Flex1970 at 1:52 AM on June 5, 2008 [1 favorite]


God does not play dice with the Universe; God is the dice.

So, God is a dead cat. At least some of the time.
posted by stavrogin at 1:56 AM on June 5, 2008 [1 favorite]


So, God is a dead cat. At least some of the time.

Only when you're not looking.

Also, the dice talk to each other, there's an infinite number of them and they keep changing how many sides they have for some reason.

And it's turtles all the way down.
posted by loquacious at 2:03 AM on June 5, 2008 [3 favorites]


I still think it is language that creates the world.
posted by acrobat at 2:40 AM on June 5, 2008 [3 favorites]


Good god, we just can't get off the anthrocentrism, can we?
posted by Pope Guilty at 2:51 AM on June 5, 2008 [5 favorites]


Anthrocenterism is an a read of things that is cause by what "observer" implies to people writing about quantum physics. But consciousness causes collapse is only one potential explanation of what is going on. It can also be argued that I represent a superimposed state where I finish this post or where I say, “I got nothing”, turn off the computer and get ready for work and that these two states won't sort themselves out until it really matters and that I'll be none the wiser of any of the time I spent in this indeterminate position.

To put this another way, for any given chunk the universe behaves as if the average of all potential events have happened until it matters what has specifically happened. I like this as a mental model because it implies that God is trying to free up clock cycles by making the physics engine only resolve what it absolutely has to and implies that the afterlife will begin with a song by Jonathan Coulton.

Someday I really ought to get off my ass and get that Schroedinger Wave Equation tribal armband tattoo that I've wanted since p-chem.
posted by Kid Charlemagne at 4:09 AM on June 5, 2008 [3 favorites]


Can some one point to an actual description of the experiments. Cause that article was a total let down.
posted by afu at 4:12 AM on June 5, 2008


God does not play dice with the Universe; God is the dice.

Also, the dice talk to each other, there's an infinite number of them and they keep changing how many sides they have for some reason.

That's just the way God rolls.
posted by Sparx at 4:29 AM on June 5, 2008 [1 favorite]


God does not play dice with the Universe;
God does not play dice with the Universe; He plays an ineffable game of his own devising, which might be compared, from the perspective of any of the other players*, to being involved in an obscure and complex version of poker in a pitch-dark room, with blank cards, for infinite stakes, with a Dealer who won't tell you the rules, and who smiles all the time.

*i.e., everybody
-- Neil Gaiman & Terry Pratchett, Good Omens
posted by eriko at 4:34 AM on June 5, 2008 [7 favorites]


I too pondered the question "Do we create the world just by looking at it?" a while ago. I remember vividly how suddenly the answer came to me, as my head smashed into the windshield of the car that didn't much care that I was looking the other way.
posted by JeNeSaisQuoi at 4:38 AM on June 5, 2008 [1 favorite]


Ahh, it's good to know for sure that none of you actually exist. Re-LIEF!
posted by not_on_display at 4:39 AM on June 5, 2008


How'd he know my couch was blue!
posted by From Bklyn at 4:50 AM on June 5, 2008


I'm not going to RTFA; therefore it doesn't exist.
posted by yhbc at 4:52 AM on June 5, 2008 [1 favorite]


Your eyes may not have observed that windshield, but your head certainly did.

And it observed your head.
posted by Flunkie at 6:07 AM on June 5, 2008


Your eyes may not have observed that windshield, but your head certainly did.



A 'head' does not have consciousness, nor does a windshield, as far as we know. It therfore cannot 'observe' anything. Which is the point. Our 'consciousness' may change or define our 'understanding' of our universe, but a baseball bat to the kneecap has nothing to do with is independent of our consciousness. Whether we consciously know it happened via pain, the kneecap will shatter. Of course, now we are back to Schroedinger's Cat. But the point about 'observation' stands.
posted by spicynuts at 6:34 AM on June 5, 2008


i like science, in theory.
posted by fuzzypantalones at 6:37 AM on June 5, 2008


The author of the article tries to talk up the experiment for more than it is. It is another test of Bell's inequality. Basically it asks the question, "Can quantum mechanics be explained by local hidden variables?" All previous experiments have said "no," but left some room that a more exotic experiment might just allow for it. This experiment ruled out another loophole, but essentially pointed in the same direction as all previous Bell test's: QM does not allow for local "realism."
posted by justkevin at 7:00 AM on June 5, 2008


> A 'head' does not have consciousness, nor does a windshield, as far as we know. It therfore cannot 'observe' anything.

Are the speedometer in your car or the thermostat in your house conscious too?
posted by xbonesgt at 7:59 AM on June 5, 2008


windshield of the car that didn't much care that I was looking the other way

Other people can observe too. You don't have to ascribe consciousness to inanimate objects.
posted by RockCorpse at 8:25 AM on June 5, 2008


consciousness has nothing to to with quantum mechanics. QM is about measurement. I think this confusion with consciousness began with those new age physics books in the 70's.
posted by bhnyc at 8:29 AM on June 5, 2008


While I, too, loathe hippie physics and agree that QM is indeed about measurement, I must ask: if a ruler is next to an object, is it being measured? Or is it measured when I look at the ruler?

And how might we be able to devise an experiment to tell the difference between measuring equipment merely being in the proximity of a subject and the observation of the measurement process?
posted by adipocere at 8:48 AM on June 5, 2008


"Observe" is a terrible word in this context, since it implies a conscious observer and causes this sort of confusion, but we're stuck with it by now. "Measure" or "interact" would've been a better choice.

Wikipedia actually has a pretty good rundown of the various current interpretations of QM; in most of them, consciousness isn't considered relevant at all: any two particles "observe" one another when they interact.
posted by ook at 8:57 AM on June 5, 2008


Journalists try to explain things that they themselves don't understand. Nowhere is the folly of this more apparent than when the press covers Quantum Mechanics. In other branches of science it's often possible for journalists to successfully convey a sense of how the world works without actually understanding the underlying principles. But Quantum Mechanics is the perfect storm of journalistic incompetence.

What makes QM special in this regard? I'm not sure, but I have a couple of guesses. First, unlike other areas of study, QM is deeply, deeply counter-intuitive. Your intuition about how matter behaves in the quantum realm will lead you astray every time. I'm told this goes for many physicists, too -- they have to intentionally ignore their own intuition, abandon hope of having an intuitive mental model, and focus on the math. Journalists don't stand a chance.

Second, it's not possible to understand QM laws, experiments, or experimental results without a solid grounding in the mathematics of probability. You can understand gravitation, astronomy, basic chemistry and biology, and many other sciences without probability. But QM? You can't even get started.

Finally, like the vast majority of people, journalists lack the tools to reason about uncertainty. The modes of reasoning we employ in our everyday life break down in the quantum realm. So journalists find themselves unable to draw conclusions about any aspect of the quantum world. Of course, they don't let that stop them.

I can only speak for the English-speaking Western world, but science reporting in general is terrible, and QM reporting is always completely useless. The entire news industry should be ashamed of its complete and utter failure in this regard.
posted by sdodd at 9:02 AM on June 5, 2008 [2 favorites]


an "observer" is just something that records a measurement. it can be mechanical. (we are in essence a complicated machine)

a ruler just lying there isn't recording anything.
posted by bhnyc at 9:06 AM on June 5, 2008


a ruler just lying there isn't recording anything.

I think you're oversimplifying, bhnyc. Measurement does require an observer. If the observer is a second machine that simply records the measurements of the first measuring instrument, you haven't measured anything--you've just created a more complicated measuring apparatus. It still takes a conscious observer to observe the result of the secondary set of measurements before they become "measurements"--otherwise it's all just "some stuff that happened," not a measurement.

I'm not an expert on the subject by any stretch, but just because it's true that many new-age claims about the theoretical problems in QM tend to distort the science and draw all sorts of specious conclusions, that doesn't make the underlying theoretical problems disappear. And as I understand it, there are still some problematic experimental results that seem to favor QM interpretations in which a conscious observer does play a role.
posted by saulgoodman at 9:23 AM on June 5, 2008


I too pondered the question "Do we create the world just by looking at it?" a while ago.

I confirm it thus. (*kicks rock*)
posted by newmoistness at 9:25 AM on June 5, 2008


I can only speak for the English-speaking Western world, but science reporting in general is terrible, and QM reporting is always completely useless.

What I can't understand is why there aren't any science journalists out there that have a background in physics. There are quite a few physics undergrads and not all that many positions out there for physicists. Why aren't a few of them becoming science journalists? Is the pay that bad? I'm pretty sure that anyone who spent four years studying physics and can string together a readable sentence could do better than this.
posted by ssg at 9:27 AM on June 5, 2008


Measurement does require an observer [...] It still takes a conscious observer to observe the result of the secondary set of measurements before they become "measurements"--otherwise it's all just "some stuff that happened," not a measurement.

Measurement might mean something entirely different to you than it does in the context of QM. If you want to discuss QM, you are going to have to put aside your common-sense definition of measurement.
posted by ssg at 9:38 AM on June 5, 2008


Measurement does require an observer -saulgoodman-

we agree on this, but the observer can be anything. see ook's comment above.
posted by bhnyc at 9:40 AM on June 5, 2008


an "observer" is just something that records a measurement... a ruler just lying there isn't recording anything.

Likewise...a head just hitting a windshield is not recording anything either. Unless you count the resulting fracture a record.

Other people can observe too. You don't have to ascribe consciousness to inanimate objects.

If you drive into a telephone pole on a deserted highway in the middle of the night after falling asleep at the wheel and there is no one around to see it, would your head still get fractured etc etc etc...

My point was, as someone stated above, that 'observe' is a horrible word for this.
posted by spicynuts at 9:42 AM on June 5, 2008


If the observer is a second machine that simply records the measurements of the first measuring instrument, you haven't measured anything--you've just created a more complicated measuring apparatus.

This is not considered true in the current paradigmatic account of quantum theory. An observer can be a machine or object; the only restriction is that it be a classical object rather than a quantum one.
posted by voltairemodern at 9:52 AM on June 5, 2008


Measurement might mean something entirely different to you than it does in the context of QM. If you want to discuss QM, you are going to have to put aside your common-sense definition of measurement.

well, I don't think it's just bad journalism that gives this understanding of "measurement". Einstein apparently understood it this way. It seems as if some portion of scientists have interpreted observation to include specifically conscious observation. Which certainly seems bizarre from a classical standpoint, but that's exactly why everyone got so riled up over QM to begin with. If you just mean it's "measured" because there is something interacting with it, then isn't the term more or less meaningless? Then everything is always "measured", isn't it?
posted by mdn at 9:53 AM on June 5, 2008


Okay, grab your standard issue Edmund Scientific's Schroedinger/Bonsai Cat Box and take it out of its packaging without opening.

Place that box in a larger box, along with a scientist who, five minutes after opening the Schroedinger/Bonsai Cat Box will record the experiment down on a slip of paper, which says "ALIVE" or "DEAD," then rap on the wall of the box.

Interestingly, although the waveform of the Schroedinger/Bonsai Cat Box has collapsed for the trapped scientist, it has not for you, nor has the state of the slip of paper - at least, not until you hear the rap and open the box. Thus, waveform collapse is relative to and dependent on the ... observer? recording device? to as many levels as you like.

We used to toss this idea around in QM, but does suggest that you are the end point in the chain, not the recording device which is an intermediary.
posted by adipocere at 9:57 AM on June 5, 2008 [1 favorite]


What I can't understand is why there aren't any science journalists out there that have a background in physics. There are quite a few physics undergrads and not all that many positions out there for physicists. Why aren't a few of them becoming science journalists? Is the pay that bad? I'm pretty sure that anyone who spent four years studying physics and can string together a readable sentence could do better than this.-ssg

Partially because decent journalism is about more than "stringing together a readable sentence". Scientists (especially theoretical ones) that I've known have been lacking in certain journalistic basics such as being engaging, writing for non-scientists, and meeting deadlines.
Anyone who can do these things and has an understanding of QM, for example, will make scads more writing a text book or an introductory text for the layman than some silly old article.
It is frustrating for anyone who wants a good article about science but there you go, it's two very different skill sets that rarely overlap, combined with the limited distribution, and therefore budgets, of science mags.
posted by mikoroshi at 10:01 AM on June 5, 2008


Do we create the world just by looking at it?
Damn. I came in here looking for a discussion of old-fashioned idealism, but all I find is talk of quantum mechanics. Berkeley, anyone? Shopenhauer?
posted by dilettanti at 10:06 AM on June 5, 2008


If you just mean it's "measured" because there is something interacting with it, then isn't the term more or less meaningless? Then everything is always "measured", isn't it?

That's what I was trying to get at, mdn.
posted by saulgoodman at 10:07 AM on June 5, 2008


but does suggest that you are the end point in the chain, not the recording device which is an intermediary

But couldn't one argue that the "you" in this story is just an instrument? Yes a special kind of recording device, one made of organic cells and formed through millions (if not more) years of natural selection etc. We tend to give words like "I" and "You" special status (and "we" as well.) Yet, consciousness (or what is being taken as the final observer in a chain of interactions) could well be a function of purely physical interactions - that is, not "special" or different from any other physical interactions.

"Observe" is too loaded a word, because it presumes there is something non-physical about consciousness (or at least that it is some kind of end point.)
posted by elwoodwiles at 10:22 AM on June 5, 2008 [1 favorite]


This is not considered true in the current paradigmatic account of quantum theory. An observer can be a machine or object; the only restriction is that it be a classical object rather than a quantum one.

Weird. Then what is the significance of the observer at all, then? Everything that has a relative spatial extension is a sort of measuring stick against which other things, by this definition, are measured. In other words, any two random objects of different spatial extensions laying side by side are, in this sense, 'measuring' each other as much as an object designed to be used as a ruler laying next to either one of those object is.

"Observe" is too loaded a word, because it presumes there is something non-physical about consciousness (or at least that it is some kind of end point.)

You could argue "physical" is too loaded a word because there aren't any irreducible, atomic particles to speak of, and matter is just energy excited to particular wave-lengths, isn't it?
posted by saulgoodman at 10:27 AM on June 5, 2008


It still takes a conscious observer to observe the result of the secondary set of measurements before they become "measurements"--otherwise it's all just "some stuff that happened," not a measurement.

I'm not sure that's the case. We're assigning artificially important status to consciousness, when it definitely doesn't take a consciousness to cause quantum collapses. Just a measurement does it, even if the measurement device has no consciousness itself.

And what's a measurement? It's an interaction; the interaction forces the quantum state to collapse and the matter it constitutes to become 'real'.

I suspect that most of the Universe is probably 'observing' most of the rest of the universe at any given time; the ruler lying on the table isn't actively measuring anything for a human, but it is nonetheless forcing a quantum collapse of the atoms it's interacting with, holding it off the floor. It will continue to do so, with or without a human observer there to see it.

As alluded upthread, I really wonder if this isn't pointing to some kind of simulation. That sounds a lot like a 'lazy' algorithm that only figures out things it needs to figure out.
posted by Malor at 10:27 AM on June 5, 2008 [1 favorite]


Okay, grab your standard issue Edmund Scientific's Schroedinger/Bonsai Cat Box and take it out of its packaging without opening.

Please keep that damn cat out of this. Discussing a cat in a box when you are really talking about very small particles does nothing but confuse the issue. Metaphors do not behave in exactly the same way as the things they are metaphors for so conducting a thought experiment on the metaphor doesn't tell you anything about the behaviour of the underlying objects.
posted by ssg at 10:28 AM on June 5, 2008


You could argue "physical" is too loaded a word because there aren't any irreducible, atomic particles to speak of, and matter is just energy excited to particular wave-lengths, isn't it?

But we don't have to reduce things to physical particles - reducing them to "energy excited to particular wave-lengths" does the same job.

And what Malor said.
posted by elwoodwiles at 10:40 AM on June 5, 2008


That Damn Cat is quite a handy way of discussing the situation. Otherwise, I would need to spend a great deal of time:

Introducing the idea of a Very Very Very Small nanoscale random number generator, specifying that we are using a truly random physical process, rather than an algorithmic method which can, after all, only create pseudo-random numbers,

Creating another receptor for the randomly-generated number, which feeds into an irreversible decision-making machine which makes a binary choice based solely on the output of such a generator,

Specifying a permanent and incorruptible register for this data,

Surrounding the apparatus with some kind of lattice of atoms constructing a "wall" through which we cannot observe, etc., while applying hinges to it so we might eventually peer in at the register, all while making sure this lattice does not interfere with the apparatus within,

Extending a probe into the apparatus at a later time to read the register,

Having a debate on whether or not the several thousand atoms of this entire package is so large that it tips us into the macro scale,

And, at last, dealing with the inevitable questions from the people who ask, "Can we even build such a thing so tiny?"

Now, you'll pardon me for my extreme laziness, but I'd rather just say "cat in a box" than type that out every. single. time this discussion occurs. We all know what it means.
posted by adipocere at 10:42 AM on June 5, 2008


We used to toss this idea around in QM, but does suggest that you are the end point in the chain, not the recording device which is an intermediary.

End point?
posted by ook at 10:45 AM on June 5, 2008


All this bull because of the wrong choice of words. Sigh.

Unless you want to believe that dinosaurs sprung into existence the moment the first human laid eyes on a fossil, somehow sending a signal back in time that it was OK for that particular dinosaur to live and die...the entire conscious observer thing is worse than wrong. It's worse than string theory.

At least string theory advances math.
posted by effugas at 10:55 AM on June 5, 2008


the kneecap will shatter

The kneecap is a construct of the mind. Whatever is *really* there, it's only a kneecap because it is defined that way.
posted by owhydididoit at 10:56 AM on June 5, 2008


Introducing the idea of a Very Very Very Small nanoscale random number generator [...]

Why would you do this? We aren't discussing the behaviour of random number generators, etc. You don't need to construct another metaphor.

Why not talk about something real that we can actually experiment on? For example, if you reframe your cats-and-scientists-in-boxes example in terms of a beam of silver atoms and some Stern-Gerlach devices, you might find that your conclusions will look quite different.
posted by ssg at 10:56 AM on June 5, 2008


> We used to toss this idea around in QM, but does suggest that you are the end point in the chain, not the recording device which is an intermediary.

I don't see how that suggests anything, except what you'd already shown - the waveform is collapsed for you, but not for anything that might be monitoring you.
Let's say I invent a machine that can read your mind without you knowing it. I point my machine at you and scan your brain, and write down whatever it was that you saw on your slip of paper. How does your being a conscious observer (of the original event) affect the result I get from my machine?
posted by xbonesgt at 10:57 AM on June 5, 2008


And what's a measurement? It's an interaction; the interaction forces the quantum state to collapse and the matter it constitutes to become 'real'.

Well, that's what I mean: If measurement is just a trivially special category of physical interaction, then 'measurement' is a pretty terrible word for it, too.
posted by saulgoodman at 11:09 AM on June 5, 2008


Unless you want to believe that dinosaurs sprung into existence the moment the first human laid eyes on a fossil, somehow sending a signal back in time that it was OK for that particular dinosaur to live and die...the entire conscious observer thing is worse than wrong. It's worse than string theory.

Right - this was exactly Einstein's problem with QM! And he argued with the top QM scientists of his day, so I don't think it was just bad journalism. The problem is that the claim seems deeply counterintuitive, and yet the theory is that at the quantum level it works this way, and it somehow just is "balanced out" (or decohered) once we get back to middle-size objects. I don't even know if this is explicated on a temporal level.

But the basic intuitive problem (is the moon not there if you don't look at it?) is what Einstein had a problem with and what David Bohm was trying to solve with his theory. These guys are saying they have further evidence that Bohm's view isn't the way to go, that we have to accept the "ideal" interpretation at the quantum level, although I didn't understand what the proof consisted in (just that experiments matched math - but that detail wasn't explained).

Damn. I came in here looking for a discussion of old-fashioned idealism, but all I find is talk of quantum mechanics. Berkeley, anyone? Shopenhauer?

Ain't that different. (though QM is more like Kantian idealism, at this stage)
posted by mdn at 11:22 AM on June 5, 2008


You know I have to say, that was a really weak article. WTF is up with the long digression about the facade of the building in the 2nd graf? Do we really need that much? Where is the editor?

Get to the point, writer. Not to go on, but the subject is difficult enough and writing this circuitous further complicates things . . .
posted by matthewstopheles at 11:26 AM on June 5, 2008


In terms of the article itself - it is pretty poor. But I've always found Seed Magazine wanting.
posted by elwoodwiles at 11:34 AM on June 5, 2008


xbonesqt, I brought up the multi-layered box because it's not immediately obvious to some that the collapse is strictly relative.

ssq, the random-number generator is not a metaphor. We need a non-deterministic event in there, an unknown. It is a requisite part of the experiment. That's why we have radiation in the original metaphor - decays are random. Because you seem to dislike metaphor, I brought up a very literal alternative. NOTICE THAT IT IS WORDY AND SUCKS. That's why we use silly metaphors - so we don't spend time deciding the precise mechanism we will use to specify randomness. Just imagine if, instead of That Damn Cat, I sent you CAD drawings and specifications of a potential apparatus. That'd be a real timesucker.

And while I agree that a metaphor does not prove anything, they are quite useful. You might recall the original thought experiment behind the development of special relativity - I am not supposing that Einstein was considering riding, literally, upon a beam of light. It was a metaphor. It disregards the quagmire of mundane details of the apparatus, and raises questions rather than providing answers.

Science, even maths such as geometry, would progress very, very slowly sans metaphor. We get fuzzy ideas and explore them a bit in our minds. We visualize a rubber sheet for general relativity, ignoring the fact that the rubber would have to have more than two dimensions, and that there is no rubber there. If you have a problem with people mistaking the map for the territory, that is the problem of the person making the mistake, not a problem with maps.
posted by adipocere at 11:36 AM on June 5, 2008


What I can't understand is why there aren't any science journalists out there that have a background in physics.

You are allowed to pine for this, but only after we've finally gotten an acceptable substitute for Martin Gardner's Mathematical Recreations columns. (holding the torch aloft)
posted by JHarris at 12:07 PM on June 5, 2008


In the end your either a Monte Carlo kind of person or a manybody wavefuntion kind of person.
posted by ozomatli at 12:08 PM on June 5, 2008


Everytime I read "Austrian physics" I know there's Zeilinger inside. That guy is just annoying. I root for whomever will debunk him.
posted by dhoe at 12:12 PM on June 5, 2008


adipocere, we don't need a metaphor in this case, because we can discuss the actual subject at hand. We can talk about electrons and all kinds of other things that actually exist. These are real things, upon which we can do real experiments. Metaphors can be a useful way to explain something, but you can't conduct an experiment on a metaphor.

If you have a problem with people mistaking the map for the territory, that is the problem of the person making the mistake, not a problem with maps.

This is exactly the problem. You are trying to prove your point with talk about cats in boxes (i.e. the map) and ignoring the real subject.
posted by ssg at 12:13 PM on June 5, 2008


Metaphors aren't just for explanation, they're also for communication. Again, please specify your apparatus with a nice CAD drawing.

What do you think the real subject is? Because when I point at the map and it says "St. Louis," I know I'm talking about St. Louis, not about a piece of paper. Do you know I'm talking about St. Louis? When I say, "I'm going to drive over there" and move my finger a few inches to the left, do you assume that I am going to hop in my car, plow it into my living room, up the stairs, and try to park it on the physical map? Of course not.

I'm not really talking about cats in boxes. I know that. Do you know that I am not talking about cats in boxes? If yes, then why bring it up? If no, then ... grant me enough intellectual sophistication (available to any seven year old) to understand that I am dealing with metaphor for the purposes of abstraction and compact communication.

How would you specify what I'm talking about, in an easily communicable manner?
posted by adipocere at 12:43 PM on June 5, 2008


I'm not really talking about cats in boxes. I know that. Do you know that I am not talking about cats in boxes?

What are you talking about? For what is your double box w/ scientist and cat a metaphor? To what does it correspond on a scale with observable quantum effects? What are you trying to communicate?
posted by ssg at 1:07 PM on June 5, 2008


I am trying to communicate exactly what I said before, "... waveform collapse is relative to and dependent on the ... observer? recording device? to as many levels as you like."

How would you have gone about making a multilevel illustration of the phenomenon in a manner familiar to everyone? I keep asking this part, and I keep not getting an answer. If you've got a critique, come up with a replacement, don't just hammer the buzzer (another metaphor) and yell "WRONG!"
posted by adipocere at 1:18 PM on June 5, 2008


I am trying to communicate exactly what I said before, "... waveform collapse is relative to and dependent on the ... observer? recording device? to as many levels as you like."

That's fine, but since your claim is quite different from the standard interpretation of QM, you'll have to provide a lot more than a metaphor about cats to back it up.

How would you have gone about making a multilevel illustration of the phenomenon in a manner familiar to everyone?

I have no need to do so, because I see no reason to believe the phenomenon that you are talking about is real.
posted by ssg at 1:32 PM on June 5, 2008


Uh, now it's been awhile since I got my degree, but I do not recollect a standardization of interpretations in recent history.

That would mean that you believe that wavefunction collapse occurs for everyone, simultaneously. Is that what you mean to state?

I keep asking, and all I am getting in response is "No, that's not it either." Why don't you tell me what you think it is? Is this a guessing game? Is it smaller than a breadbox? How about a breadbox with a kitten in it and a vial of poisonous gas whose opening is triggered by radioactive decay?
posted by adipocere at 1:49 PM on June 5, 2008


That would mean that you believe that wavefunction collapse occurs for everyone, simultaneously.

I would reject your assumption that consciousness has something to do with it ("everyone").
posted by ssg at 2:40 PM on June 5, 2008


So wait, we're dismission the Schroedinger's Cat think as metaphore but buying into the trancendental hypothysis "electrons" as undenyably real? Swell. Because I've always wanted a real world understanding of spin +1/2 -1/2 without a lot of vague hand waving.
posted by Kid Charlemagne at 2:43 PM on June 5, 2008


Do we create the world just by looking at it?

Mine would have many more soft, voluptuous curves.
posted by turgid dahlia at 2:48 PM on June 5, 2008


That would mean that you believe that wavefunction collapse occurs for everyone, simultaneously.

"Wavefunction collapse" is a concept that is itself from a particular interpretation of QM, or at least it's present only in a subset of interpretations.
posted by XMLicious at 2:53 PM on June 5, 2008


ssq, I am hearing "I would reject" a lot. Do you have anything to state in the positive? I've gone through a number of contortions trying to find this out.
posted by adipocere at 3:00 PM on June 5, 2008


adipocere, to my understanding, your assertion (that the waveform collapse is local to each observer) is supported by some interpretations of QM, and contradicted by others. (If I'm reading you right, you're describing the Wigner's Friend thought experiment.) I'm not clear on whether you believe that the observer must be conscious or if you accept the idea that any particle interaction counts; either way you're still supported by some interpretations and contradicted by others (though my impression is that the conscious observer interpretations are falling out of favor).

I don't understand what you mean by the "endpoint" of the observational chain; short of lapsing into a solipsistic There Can Only Be One True Observer, I can't imagine how there could be any endpoint, just lots of observers observing one another.

I don't know what ssg's point is, other than that he doesn't like metaphors.

I guess my point is that since what you're discussing is still an open question, it might not be worth getting too hot under the collar about it.


All of which is pretty much irrelevant to the experiment described in this article, which if I'm reading through the purple prose correctly, was an attempt to disprove QM altogether: it was testing whether an observable property of light was set by a waveform collapse, or if it existed (was "real") before observation. And, as it turned out, QM was not disproven. (surprise!)

Could've been a much shorter article: "Quantum Mechanics Still Not Wrong!"
posted by ook at 3:32 PM on June 5, 2008


was set by a waveform collapse the act of observation
posted by ook at 3:34 PM on June 5, 2008


ssq, I am hearing "I would reject" a lot. Do you have anything to state in the positive? I've gone through a number of contortions trying to find this out.

No, I don't. I don't think you and I are talking about the same thing, so I don't really see the point.

I don't think it is a good idea to state as fact particular facets of relatively unpopular QM interpretations that you happen to believe. I wish we could discuss these issues in terms of observables instead of hypothetical cats, because I think the metaphor in this case tends to muddy the issues. I've tried to discuss similar issues in past threads while sticking to the cat metaphor and it hasn't gone well. I guess MeFi is probably not the place for these discussions.
posted by ssg at 4:10 PM on June 5, 2008


If there was voting about it, I would vote against the hypothetical cats too. I hate their hypothetical pantsuits and their hypothetical controversial Reverend.

But seriously, I agree with ssg. Schrodinger's cat is more of a metaphor for pop misunderstandings of QM to me, rather than a consistent or useful metaphor for anything in physics.

As far as the meaning of the experiment I think lalochezia had it right up at the top, that non-realism is present regardless of scale. Which, as ook says, basically just means "Quantum Mechanics Still Not Wrong" - well put, BTW.
posted by XMLicious at 4:47 PM on June 5, 2008


People say they don't follow or "believe" in QM referring to Einstein's famous protest, but then they buy lottery tickets all month long.
It's not the wavefunction that determines much, it's the square of the wavefunction. Which always turns out to be some observable event. (Because even negative numbers square to positives.)

And:
Do we create the world just by looking at it?

Mine would have many more soft, voluptuous curves.


Try the Andes.

QM wasn't discovered until people started looking at very small events unobservable without complicated apparatii. Equations were postulated. Many people were repelled by the implications. Attempts to disprove the resulting conclusions have been spotty at best. So it's still the best we have. Sorry, and see you in Vegas.
posted by telstar at 11:28 PM on June 5, 2008


Mods: link button is broken and scrambling my posts! Grr!

[insert clever joke that ties scrambling of posts to uncertainty principle here]
posted by davejay at 12:42 AM on June 6, 2008


Does that mean the link button just entangles the strings?

Sorry, I'll leave now.
posted by Talanvor at 4:04 AM on June 6, 2008


Nature is not 100% repeatable; every part of Nature is unique, and not exactly like any other part. But there are patterns, and these show up as probability distributions, given sufficient numbers of measurements of similar experiments.

QM is a system for modelling these probability distributions up front. It's well tested - the probability distributions it generates mathematically are the same, to a very high degree of precision, as those generated by statistics based on real experimental measurements.

If you were to run the Schroedinger's Cat scenario ten thousand times, QM would be able to predict up front what percentage of dead cats and live cats you'd see in the boxes after opening them, and it would be right. And this will be so, regardless of the fact that it will not tell you, until you open the box, whether any given cat is alive or dead.

The collapse of the wave function has no effect on the real world, which just does what it does regardless of what some experimenter using QM to model it believes it might be about to do. The collapse of the wave function occurs when the probabilistic information derived from that function is superseded by hard information derived from the actual experiment, and the consciousness responsible for causing the collapse is the same consciousness that cared about the wave function in the first place.

There is no deep mystery here. The wave function is a feature of the map, not the territory. Any given cat will be either dead or not dead at any instant. The fact that some experimenter finds it useful to treat any particular cat's state as a probabilistic superposition of dead and not dead is absolutely irrelevant to the cat. This is why so many people write the cat thing off as a stupid, misleading waste of time.

What feels like deep mystery derives from the clash between the demonstrable fact that Nature is not repeatable on the smallest scales, and our intuition that it ought to be. We simply have no way of knowing what it's up to between measurements, and the natural tendency is to make shit up and then get confused when our best models don't look anything at all like what our intuition says they should.

We're so accustomed to physical theories that tell us how stuff works that we're intuitively ill-equipped to deal with one that doesn't do that. QM says nothing at all about what's going on "under the hood". All it says is: here are some initial observables; here's a model you can apply to those; and here's the distribution of results you're going to see when you run this experiment ten thousand times.

We don't know what happens to the electron between the time we know it's emitted from the cathode and the time it hits the plate on the far side of the double slits. We don't even know if an electron exists, in any cat-like sense, between those times. The only things we can reasonably say about it are things we find it quite unreasonable to say about a cat - like, it exists as a superposition of this and that quantum state to such and such a degree of probability, as dictated by the wave function we're using to model it.

The useful part of the Schroedinger's Cat scenario is to highlight the necessary disconnect between our idea of a cat - which it seems paradoxical and nonsensical to consider as being in a superposition of alive and dead states, because we're familiar with cats and know that they're generally one or the other - and our idea of an electron, which we will tend to think of as being akin to a tiny little cat unless we're very careful not to.

How many times have you heard people talk about the electron "going through both slits at once"? Poppycock! We don't and apparently can't know that it does any such thing. All we know is that if you set up an electron source over there, and put two slits here, you get a pattern like this on that photographic plate there, and here's a mathematical model that predicts accurately what that pattern is going to look like. And that model includes wave functions for the electron in flight, and the only description of the in-flight electron is a probability distribution that predicts your chance of encountering an electron at location X if you were to put a detector at X instead of waiting for one to hit the plate.

QM puts limits on what it is meaningful to say about the systems it's good for modelling, and assumes limits on what we can know about those systems. So far, those assumptions are well borne out by the success of QM's models.

But they are only models. They're in our heads and on our scratchpads and in our computers. The map is not the territory. The collapse of the wave function occurs in the model, not in what's modelled, and it's really not necessary to go as far as thinking about Wigner's Friend to work that out. All it needs is a little intellectual humility, so we can let go of the need to think of QM as revealing some underlying truth. It's a probabilistic theory, and it doesn't do that.

It remains to be seen whether any theory that does purport to reveal an underlying truth can actually be tested. Personally, I'm hopeful but skeptical.
posted by flabdablet at 8:50 AM on June 6, 2008 [5 favorites]


It is tautological that the universe doesn't exist without us. I'm not sure what these physicists are getting at. If we weren't here, this new thing would be a different universe, no? Measurement is us as part of the universe. Or, as Parmenides, a pre-Socratic philosopher put it:
"Reality itself is a thinking thing, and the object of its own
thinking."
posted by Mental Wimp at 1:27 PM on June 6, 2008


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