The Heisenberg Uncertainty Principle

[selfAdjoint]

This is the copenhagenist version of HUP, interpretation laden, the minimal interpretation of HUP merely says that that we cannot know simultaneously the values of complementary variables/observables with infinite precision, see also this. Thus James R's explanation is fully valid, after all Hawking himself use something similar in 'A brief history of time' to show that the empty space fields cannot be 0 for in this case we would know with infinite precision both the value of the field and its rate of change.

On the contrary my criticism was not based on any interpretation but on the mathematical formulism for calculating results, which all schools of thought agree upon. As for your link, it has so many errors I don't know where to begin. One big one is your misunderstanding of Born's theory. It is not statistical (properies of many unseen things en masse) but probabilitistic; it asserts the squared wave function, suitably normalized, gives the probability of observing the position (or momentum or other quantum observable depending on the experiment). Your notion that this cannot be applied to single particles is just wrong. If you want to replace QM with a theory based on statistical ensembles, be advised that it's been tried, and it failed to account for the phenomena the experimenters see.

In general your reasoning is based on popular descriptions of QM not on the real thing with its mathematical description. This is not a sufficient base for valid criticism or original thought about QM.

 

[metacristi]

Your knowldge has too many gaps, I do not want to polemize with you, you're definitely not accustomed with the subtleties involved by the interpretations of QM and HUP as presented by modern philosophy of science (try to read Popper's criticism of the assumption that we can deduce HUP from the axioms of QM-I have it in a romanian translation of his 'Logic of scientific discovery'-and what means the minimal interpretation of HUP). As for the problem of whether QM is statistical or not well I'd argue that the 'frequentist' interpretation of probabilities involved require statistically relevant samples of (supposed identical and identically prepared) quantum particles, otherwise I don't see how Born's rule is compatible with frequentism.

 

[selfAdjoint]

Perhaps you might look at this critique of Popper's critique from a philosopher, or in your egotism do you suppose he is unacquanted with subtle arguments too?

 

[metacristi]

Perhaps you might look at this critique of Popper's critique from a philosopher, or in your egotism do you suppose he is unacquanted with subtle arguments too?

What's your point? I still do support Popper's view of a concept of 'knowledge without authority', the author fails to convince us that a general inductive method (probabilistic or not) has enough justification to force us to adopt strong ontological commitments. Anyway this does not change the fact that your version of HUP is compatible only with copenhagenism and related views (advocating intrinsic indeterminism). Or that Born's interpretation of the wavefunction has a probabilistico-statistical nature. Or that there are still problems with the frequentist interpretation of probabilities adopted (mathematical or empirical) in spite of the fact that we use currently in practice many types of relevance tests (inductive in nature). Or whatever other alternative interpretation of probabilities.

Bohm's causal interpretation of QM is enough for the moment to discourage us to make too strong commitments regarding HUP. Currently at least there is no good reason to think (there is genuine underdetermination at the quantum level) that the only correct interpretation of HUP is one which states that 'there are no quantum states which have both a definite momentum and a definite position'. A certain form of causal determinism cannot be ruled out, the actual indeterministic program has at most a fallible epistemological privilege, QM can still be seen as a measure of our ignorance (in Bohm's account for example quantum events are a special type of chaotic processes with the final distribution tending at limit to |PSI|²). Even Hawking, probably, recognize this thing for he talks in terms of the 'weak' interpretation of HUP (we cannot reject yet a pilot wave solution a la Bohm-deBroglie, not even a 'pure wave' one, seeked by Schrodinger in the 1920, both causal in nature).

Besides even accepting at limit that the uncertainty relations can be derived from the axioms of QM (and that HUP is a basic postulate) it can be easily argued that this means only that HUP is coherent with the axioms of QM, this fact does not raise its probability of holding for every imaginable experiment. HUP should be hold as being fallible, as a matter of fact fallibilism should never be dropped.

Your 'authoritarian' style is pretty silly (for me it is also a form of dogmatism) and can only expose your manifest ignorance of some important philosophical problems in science. Try reading, for example, James T. Cushing 'Philosophical [concepts] in physics' and you'll see that the allegedly huge number of 'errors' you 'spotted' in what I wrote will 'melt away' till disappearance.

 

[Chaos' lil bro Order]

OnThe CuttingEdge2005,

First off thanks for the great replies, Self and Christi are being somewhat snobby as to who is smarter and are not really helping us learn about BECs like you are.

Secondly, please help me understand BECs further...As the electron jittering slows to nearly zero, nuclei can get so close that they actually touch? If so, does the electron cloud surrounding a single nucleus basically recede into the nucleus altogether?

Also, I am having difficulty understanding how an atom's electron can be shared with other atoms unless it is sigma or pi bonded. Say we had 5 atoms of the same shape and element all in a row and they were cooled to just above 0K. Would the atom at either end of the line have less electron density than the middle atom, since the middle atom has two neighbours vs. one neighbour for the outermost atoms?

What I am trying to ask is, how are the electrons shared between adjacent nuclei?

Sorry if my questions are poorly worded, it simply reflects my confusion.

ty

 

[Rade]

I have what is most likely a simple minded question. Suppose it was possible to build a quantum machine that could measure (observe) itself internally for both position and momentum at different times. In this case, would such an entity also be able to measure both position and momentum simultaneously and thus violate the HUP ? It seems to me that all historical thinking on the HUP deals with the predicted outcome of an "external" observer viewing some object, and not an "internal" observer viewing itself...but I may be incorrect, that is why I ask.

 

[cozzmikjoker]

I have what is most likely a simple minded question. Suppose it was possible to build a quantum machine that could measure (observe) itself internally for both position and momentum at different times. In this case, would such an entity also be able to measure both position and momentum simultaneously and thus violate the HUP ? It seems to me that all historical thinking on the HUP deals with the predicted outcome of an "external" observer viewing some object, and not an "internal" observer viewing itself...but I may be incorrect, that is why I ask.

Seeing through the eyes of a quantum particle. I've wondered what that would be like for a long time.
Would it be like determining the state of a quantum cat? Maybe it would see things so weird, the information would be lost in translation. What do you think?

 

[invincible_me]

1) But what if we invented new scanning systems which wouldn't cause the same problem, that is, without probing particles with other particles?
...the major probs of misconception are, we try to see things much in same respective we are thriving in...imaginination...scanning is to get the information of a subject ..which are then trasformed into digital signals...and are intepreted on other end by other hardware<<like comp>>..now the best way to get information of an object is through light...the same way our vision works...but when we goo deep in side a new world...i.e. when we are somewhere near atomic dimensions ...the concept of measuring ...throu light,,laser,,magnetic fluctu,,potential reader..all precise ways are one or other for of energyand if they will interact with that small masss object..will make a good mount of difference...i.e. i would measure a jet liner with a object whose lenth relativly measurable to it...for eg..1 jet liner = 2 big bus...not like 1 jet liner = 1000000000000 ants...so if we wana measure position of elctron we want a light beam of small wavelength...so we get the position...but small wavelenth light is of high energy and would add up k.e...thus change its velocity...so ne way we could measure it prisicely...

<<<<ABSOLUTE ZERO>>>>ACC to me in absolute zero we will absorb all of its energy and will end up in neutral atom...obviously when we ccool objects their energy is absorbed there by reducing its vibration...

 

[werner heisenberg]

Tthe matter is not that if we want to measure the exact velocity we must accept an inexact position, the problem is that the electron BECOMES bigger. (as James R put it *it actually makes little sense to talk about exact positions or momenta*)

What is very interesting in this subject is Bohr's complementarity principle. He claimed in it that the reason of the uncertainty are the choice of one of the side of the wave-particle duality to measure the fenomenon.
Neither position and velocity nor energy and time can be measured with arbitrary precision. For Bohr that proved his point of view. A particle is often decrived in terms of its velocity and energy while a wave often is descrived with the space-time parameters, that is, position and time. So when you choose (and you have to) to measure either the particle side or the wave side you must accept some uncertainty in from the side you have not choosen.

 

[cozzmikjoker]

Dr. kaku will be on Art Bell Sunday Jan. 22

What can I say but IT'S ABOUT TIME!
I hope to call in and nail doc about his claims that a black hole cannot be created without the power of the sun.
Cern just might be getting there.

Condoloences to Art on the recent tragedy but glad to see him come back. Especially with Dr. Kaku now!

 

[Manchot]

Hey, here's something that I'm wondering. Say you measure the position of a particle. The particle's wavefunction then collapses to that position eigenstate, temporarily forming a delta function with a standard deviation of zero. Doesn't this violate the uncertainty principle? Or, since the particle's momentum's standard deviation is then infinite, does the infinity "cancel" out the zero?

 

[profilexis]

I think that when any particle reaches 0° K, this happens:
the superstring creating the particular particle stops vibrating, therefore forms an infinite line and the particle created by these vibrations ceases to exist.

 

[DaveC426913]

Correct me if I'm wrong, but here is an (admittedly simplistic) rationalization of why you can't cool anything to absolute zero: *how* would you do it?

A particle can only lose heat by transferring its kinetic energy to another particle (since that's what heat is). That energy can only be transferred in discrete quanta. Once you have an electron at its lowest level, it is still bouncing off the walls of your container - albeit with little energy. Since any counter-force is also quantized, there just isn't any way to bleed that last little bit of energy off the particle.

 

[cozzmikjoker]

"A particle can only lose heat by transferring its kinetic energy to another particle (since that's what heat is)."

So does this mean if a particle could wander like into a field of nothing but dark matter or some kind of vacuum, then it could not lose its heat? Or would the argument be that "virtual particles" are everywhere, so there would always be particles around to transfer heat to...


"Since any counter-force is also quantized, there just isn't any way to bleed that last little bit of energy off the particle."

The movie "Hard To Kill" comes to mind.

 

[Mace Williams]

Scientists and engineers are trying to figure out how to build Quantum Computers. If I understand correctly, one intriguing by product of that effort is observing pairs of photons 'entangling' with each other and thereafter whatever happens to the one seems to simultaneously happen in the other, no matter their subsequent position or state relative to each other.

Perhaps this suggests future applications where velocity can be measured in one entangled photon and position in the other. But then, wouldn't the phenomena that occurs during the entangling permanently skew the data?

The overall problem with this whole line of questioning is the 'fact' we'll eventually be forced to face: everything is happening everywhere all at once, and everything affects everything else. Eternity is now. Everywhere is here.