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(All Voices)   Scientists cast doubt on infallibility of Heisenberg's Uncertainty Principle, which holds that it is impossible to measure anything, since the act of measurement disturbs the object and thus, the measurement   (allvoices.com) divider line 74
    More: Interesting, Heisenberg, doubts, quantum mechanics, quantum cryptography, physics, relativity, Physical Review Letters  
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3591 clicks; posted to Geek » on 08 Sep 2012 at 3:09 PM (2 years ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



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2012-09-08 12:10:48 PM
which holds that it is impossible to measure anything

That's certainly true. I tried to measure something today with a yardstick; but as I got the yardstick near, it fell over and broke. Quantum mechanics works in mysterious ways.
 
2012-09-08 12:16:01 PM
From Schrodinger's Cat (an epic poem):

Shine light on electrons,
You'll cause them to swerve!
The act of observing,
Disturbs the observed!
 
2012-09-08 12:29:37 PM
I concur with this. I tried to measure the diameter of my penis with a set of calipers and disturbed/pinched the hell out of it!
 
2012-09-08 12:39:56 PM
I know I get disturbed when I'm measured, especially when they put the tape in your crotch to get the inseam.
 
2012-09-08 12:42:15 PM
Say my name.
 
2012-09-08 01:05:05 PM
That article is stupid. Anyone have a better explanation of what was actually done?
 
2012-09-08 01:09:14 PM

Marcus Aurelius: I know I get disturbed when I'm measured, especially when they put the tape in your crotch to get the inseam.


Yeah, that's how they measure them inseam. IN PRISON
 
2012-09-08 01:23:18 PM
Submitter - you have used the partial classical explanation of the uncertainty principle. The one we use to explain it to children.

It's really about the relationship between momentum and wavelength.

In short. Don't.
 
2012-09-08 01:51:52 PM

Tigger: It's really about the relationship between momentum and wavelength.


That's what they always say to the little guys.
 
2012-09-08 01:52:12 PM
Uh subby? *reads comments* never mind Tigger covered it.
 
2012-09-08 02:08:51 PM

Tigger: Submitter - you have used the partial classical explanation of the uncertainty principle. The one we use to explain it to children.

It's really about the relationship between momentum and wavelength.

In short. Don't.


I'm a layman here, but I'm guessing that the paper just challenges certain assumptions about the principle. No matter (ha!) what, you still have to rely on some kind of interaction to make the measurement, which is always a two-way street, right? And that the precision is still limited to the wavelength involved, and the higher the precision you want, the shorter the wavelength and therefore the more energetic of an interaction. Yeah, this headline is a bad explanation - the measurement doesn't disturb itself, it's just that by measuring part of the state information of a particle you have to disturb the rest of it. Am I getting even close?

Wish I had access to the actual paper.
 
2012-09-08 02:16:48 PM

Dafodude: Tigger: Submitter - you have used the partial classical explanation of the uncertainty principle. The one we use to explain it to children.

It's really about the relationship between momentum and wavelength.

In short. Don't.

I'm a layman here, but I'm guessing that the paper just challenges certain assumptions about the principle. No matter (ha!) what, you still have to rely on some kind of interaction to make the measurement, which is always a two-way street, right? And that the precision is still limited to the wavelength involved, and the higher the precision you want, the shorter the wavelength and therefore the more energetic of an interaction. Yeah, this headline is a bad explanation - the measurement doesn't disturb itself, it's just that by measuring part of the state information of a particle you have to disturb the rest of it. Am I getting even close?

Wish I had access to the actual paper.

Not very close no! The Heisenberg uncertainly principle doesn't state that you can't measure it because you'll disturb the measurement. It states that there is a limit to what is functionally knowable about the position of a particle in the universe because that particle has a waveform. As a result it is not in any particular place it is merely an uncollapsed probability function before you measure it.

If you actually are interested I would recommend "How to Teach Quantum Mechanics to Your Dog" as an excellent book that doesn't require any specialist knowledge.
 
2012-09-08 02:44:09 PM

Tigger: Dafodude: Tigger: ...

Not very close no! The Heisenberg uncertainly principle doesn't state that you can't measure it because you'll disturb the measurement. It states that there is a limit to what is functionally knowable about the position of a particle in the universe because that particle has a waveform. As a result it is not in any particular place it is merely an uncollapsed probability function before you measure it.

If you actually are interested I would recommend "How to Teach Quantum Mechanics to Your Dog" as an excellent book that doesn't require any specialist knowledge.


Yeah, that's way more correct and I guess I subconsciously knew that. My explanation was a thing that I keep forgetting to "un-learn" as being the basis of it. It's a pretty crazy field of study and I find it fascinating but I know I'll never have a Ph.D. in Theoretical Physics. Could never get my head around all of it at once. Once you mentioned the above I was like "oh duh, probability. Sum-over-histories and quantum foam and all that jazz..." but stuff like entanglement and even the double-slit experiment still REALLY blow my mind. Plus I hate doing even calculus so LOL nope. I have read a few pretty cool books on the subject, but not that one, I'll have to check it out.
 
2012-09-08 03:18:59 PM
Are they certain about this?
 
2012-09-08 03:20:47 PM
This is lame. They had this on BBC the other day and they made it sound like Heisenberg's ideas were finally proven wrong by some modern geniuses. But no mention was made of the actual experiment or its details.
 
2012-09-08 03:23:53 PM
Heisenberg was driving down the highway and was pulled over by a police officer. Heisenberg rolls down his window and the officer asks him, "Do you have any idea how fast you were going?!"

Heisenberg responds, "No, but I know exactly where I am!"
 
2012-09-08 03:24:51 PM
Subby seems a bit uncertain about the principle.
 
2012-09-08 03:28:21 PM

r1chard3: Are they certain about this?


lol
 
2012-09-08 03:33:17 PM
I HATE SCIENCE "JOURNALISM".

Here's a wonderful example: this study provides experimental support for the HUP. That's right- this study demonstrates that the Heisenberg Uncertainty Principle does exactly what we think it does, but instead, everybody's running around going, "OMG! It's not uncertain at all!"

Once upon a time, there was this thought that it was the act of measurement that caused uncertainty. Since measuring a particle requires interacting with it, and interacting with it changes its state, this makes intuitive sense. Like most intuitive ideas in QM, it's also wrong. It's been proven wrong mathematically for decades, but this provides experimental evidence that the measurement disturbance relationship is not the cause of uncertainty.
 
2012-09-08 03:33:36 PM
Click through to TFA linked by TFA. It's not questioning the "true" uncertainty principle, the one bounded by Planck's constant. It's just challenging the limits of the "measurement-disturbance relationship," where uncertainty beyond the physical minimum is introduced by the act of measurement. The only reason Heisenberg's name came up is because, and I did not realize this, Heisenberg himself had initially proposed such a relationship as the reason for the uncertainty that now bears his name.
 
2012-09-08 03:43:27 PM

Olympic Trolling Judge: The only reason Heisenberg's name came up is because, and I did not realize this, Heisenberg himself had initially proposed such a relationship as the reason for the uncertainty that now bears his name.


Yep. Sometimes it seems like schools still teach QM in the order it was figured out, rather than going straight to how its now understood, which means people get taught a lot of confusing bad ideas that they later have to discard.

Even something as simple as the double slit experiment is often taught "semi-classically", leading people to confuse probability waves with waves in physical space.
 
2012-09-08 03:43:58 PM

Olympic Trolling Judge: Click through to TFA linked by TFA. It's not questioning the "true" uncertainty principle, the one bounded by Planck's constant. It's just challenging the limits of the "measurement-disturbance relationship," where uncertainty beyond the physical minimum is introduced by the act of measurement. The only reason Heisenberg's name came up is because, and I did not realize this, Heisenberg himself had initially proposed such a relationship as the reason for the uncertainty that now bears his name.


and that is why they named a blimp after him
 
2012-09-08 03:51:38 PM
They are disputing something called an uncertainty principle. It seems odd.
 
2012-09-08 03:52:35 PM
ih2.redbubble.net

Wanted for questioning.
 
2012-09-08 03:58:33 PM
your observation is only as good as your tool and definition.


particle
wave
field?
 
2012-09-08 04:05:04 PM
Heisenberg's Principal has nothing to do with disturbing the thing that's being measured. It' just describes an intrinsic feature of sub-atomic particles. You can't know both their position and momentum.
 
2012-09-08 04:12:28 PM

whatshisname: Heisenberg's Principal


That's true, he worked as a high school chemistry teacher.

i948.photobucket.com
 
2012-09-08 04:14:02 PM

oldfarthenry: I concur with this. I tried to measure the diameter of my penis with a set of calipers and disturbed/pinched the hell out of it!


The diameter is the most sensitive part.
 
2012-09-08 04:17:45 PM

whatshisname: You can't know both their position and momentum.


Close: you can't know both momentum and position to an arbitrary precision. The amount of uncertainty in the measurement has a floor- there will always be a minimal level of uncertainty. That level is ħ / 2 (ħ being planck's constant). You can know both position and momentum, but only to a point- at some point you have to sacrifice precision.
 
2012-09-08 04:24:07 PM

t3knomanser: You can know both position and momentum, but only to a point- at some point you have to sacrifice precision.


And the more you know about one, the less you know about the other. Hence you can't know both at once.
 
2012-09-08 04:31:05 PM

kevinboehm: [ih2.redbubble.net image 375x360]

Wanted for questioning.


25.media.tumblr.com
 
2012-09-08 04:40:27 PM
So we may someday be able to construct a Heisenberg... compensator?
 
2012-09-08 04:44:29 PM

whatshisname: Hence you can't know both at once.


Yes you can. But only to a certain limit of precision. Which is true of every measurement; every measurement has a finite precision. That's why the concept of "significant figures" exists. No measurement can ever be said to be 100% accurate- it's accurate to a certain level of precision. HUP just sets some lower bounds on how precise a specific pair of measurements can be.
 
2012-09-08 04:52:02 PM

whatshisname: t3knomanser: You can know both position and momentum, but only to a point- at some point you have to sacrifice precision.

And the more you know about one, the less you know about the other. Hence you can't know both at once.


And this all comes from the wave nature of particles. Only an infinitely long wave is composed of a single wavelength. A truncated wave is composed of waves of many different wavelengths. However that is not what the experiment is about. Here is the paper that inspired the experiment.  I don't believe I have ever looked at, let alone read Heisenberg's original paper (or a translation) but apparently in it he described a measurement disturbance relationship which is the topic of the experiment.
 
2012-09-08 05:23:19 PM
i.imgur.com
 
2012-09-08 05:43:31 PM
imgs.xkcd.com

The real truth is that Heisenberg's Uncertainty Principle doesn't say what most people think it says. Subby showed that eloquently in the stupid headline.
 
2012-09-08 05:45:46 PM
I once attended a lecture by Heisenberg, so I'm getting a kick out of this.

/It was in 26-100, I was sitting in about the 8th row a little to the right of center in, I don't know, '72 or '73 - something like that.
 
2012-09-08 05:57:21 PM
Even a weak measurement that has a large error term must sometimes be correct, and since the experiment involves a summation of weak measurements, sometimes one of these measurements is not weak because it is accidentally very accurate, error happened to be zero. In which case the results would have to be sometimes incorrect, so, there is still uncertainty maybe less of it. I'm still not convinced anything was proven yet.
 
2012-09-08 06:13:03 PM

Sliding Carp: I once attended a lecture by Heisenberg, so I'm getting a kick out of this.

/It was in 26-100, I was sitting in about the 8th row a little to the right of center in, I don't know, '72 or '73 - something like that.


My first reaction was "that can't possibly be right", but it turns out he died in 1976. Huh.
 
2012-09-08 06:43:35 PM

dramboxf: Say my name.


Ok. My name.
 
2012-09-08 06:53:37 PM

Tigger: Submitter - you have used the partial classical explanation of the uncertainty principle. The one we use to explain it to children.

It's really about the relationship between momentum and wavelength.

In short. Don't.


You nailed it. Subby's explanation is exactly how it was told to us by my 5th grade teacher. I guess the thinking is, "the reality is too weird for them to understand, so we'll just make something up that sounds like it makes sense even though it isn't true."
 
2012-09-08 06:56:08 PM

nobody seems to bother to click through links.

From Synopsis: The Certainty of Uncertainty

... If the observer affects the observed, how can one even make such a measurement of the disturbance of a measurement? Rozema et al. use a procedure called "weak" quantum measurement: if one can probe a quantum system by means of a vanishingly small interaction, information about the initial state can be squeezed out with little or no disturbance. The authors use this approach to characterize the precision and disturbance of a measurement of the polarizations of entangled photons. By comparing the initial and final states, they find that the disturbance induced by the measurement is less than Heisenberg's precision-disturbance relation would require. ...
 
2012-09-08 07:02:11 PM

Aye Carumba: Even a weak measurement that has a large error term must sometimes be correct


False. I know it sounds right, but it isn't. For any continuous value, like velocity, momentum, mass, etc., you can represent it as a real number. Every real number is an infinite number of digits long. There is no 1, there's only a 1.0000... (with the 0 repeated an infinite number of times).

So let's say I measure momentum out to 1000 significant figures. What is the probability that the 1001th is not zero? The 1002nd? And so on- the odds of me hitting the right number bang on are infinitely small. So yes, technically, it could happen, but because it's so vanishingly unlikely, we use terms like "significant figures" to describe how accurate we're certain we are.
 
2012-09-08 07:12:44 PM
It annoys me when everyone gets all "Heisenberg's Uncertainty Principle means you can't really know everything!" and applies it to all fields of knowledge.

Screw that. Godel's Incompleteness Proof is all over that. Use that instead. It's cooler.
 
2012-09-08 07:13:28 PM

HairBolus: nobody seems to bother to click through links.


If we wasted our time clicking on articles, somebody else might make our snarky comment before us, and then we'd have to just quote them and oh wait..
 
2012-09-08 07:18:53 PM
There are 46 posts to this point
 
2012-09-08 07:27:04 PM
This seems like the year of "Important principles of physics are WRONG" followed by "never mind" a few months later.
 
2012-09-08 07:30:17 PM
Years ago, I had a university professor claim that the term "Uncertainty" was a bad translation in to english, and that "Indeterminably" better described the nature of the principle. It's not so much that we don't know, it's that we can't know. 

And quite different from the observer effect.
 
2012-09-08 07:31:53 PM
*Indeterminability

FTFM.
 
2012-09-08 07:33:31 PM

ko_kyi: This seems like the year of "Important principles of physics are WRONG" followed by "never mind" a few months later.


EXCEPT THIS ISN'T EVEN THAT. The articles are casting this in entirely the wrong light. The results of this experiment are exactly what we would expect because the Uncertainty principle is correct.
 
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