The Heisenberg Uncertainty Principle

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  • #1
Whitestar
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The Heisenberg Uncertainty Principle tells us that while it is possible to measure the position and velocity with reasonable accuracy, we cannot measure both an atom's position and velocity at the same time. The reason for this is simple. For instance, to find the position of an atom, we must shine a beam of light which come in small packets, or quanta, also known as photons. The individual photons of each wavelength have an energy inversely related to their wavelength.


The greater the resolution we want, the smaller the wavelength of light we must use. But the smaller the wavelength, the larger the energy of the packets. If we bombard an atom with a high-energy photon in order to observe it, we may ascertain exactly where the atom was when the photon hit it, but the observation process itself, that is, hitting the atom with the photon will clearly transfer significant energy to the atom, thus changing its speed and direction of motion by some amount. That is the case with our current 'scanning systems'.


1) But what if we invented new scanning systems which wouldn't cause the same problem, that is, without probing particles with other particles?


2) What if we could measure an atom's position and velocity at the same time with something that has no energy at all? Is it possible in theory?


3) Also, if future new physics are introduced, would the Heisenberg Uncertainty Principle be broken, disproved, modified or overcomed?


4) What about freezing up the atoms prior to measuring the atom/molecule's position and velocity at the same time?


5) Would that do the trick, if not, why?


Whitestar
 

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  • #2
James R
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Bear in mind that the Hiesenberg principle is not JUST about measurement. It is about how accurately position and momentum can be defined. In other words, beyond the limits specified by the principle it actually makes little sense to talk about exact positions or momenta.

Keeping that in mind, let's think about your questions:

1) But what if we invented new scanning systems which wouldn't cause the same problem, that is, without probing particles with other particles?

Can you think of any way to do that?

2) What if we could measure an atom's position and velocity at the same time with something that has no energy at all? Is it possible in theory?

Only if you can find something with no energy, which I think is impossible.

3) Also, if future new physics are introduced, would the Heisenberg Uncertainty Principle be broken, disproved, modified or overcomed?

Who knows? Future physics may overturn everything we think we know. This is looking into a crystal ball.

4) What about freezing up the atoms prior to measuring the atom/molecule's position and velocity at the same time?

Freezing them up would change their velocities, wouldn't it?
 
  • #3
Whitestar
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James R said:
Freezing them up would change their velocities, wouldn't it?


But how does freezing an atom or molecule changes their velocity? If you can freeze an atom/molecule to absolute zero, shouldn't it freeze an atom/molecule in place?


Whitestar
 
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  • #4
James R
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If you can freeze an atom/molecule to absolute zero, shouldn't it freeze an atom/molecule in place?

Sorry, I misunderstood what you were saying.

The problem with freezing an atom to absolute zero is simply that it can't be done. If it could be, then we could violate the uncertainty principle.
 
  • #5
Whitestar
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James R said:
Sorry, I misunderstood what you were saying.

The problem with freezing an atom to absolute zero is simply that it can't be done. If it could be, then we could violate the uncertainty principle.


Yes, but why can't we reach absolute zero?


Whitestar
 
  • #6
James R
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Yes, but why can't we reach absolute zero?

Because doing so would violate the uncertainty principle!

Circular, I know, but that's the way the universe seems to work.
 
  • #7
edro
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The third law of thermodynamics:
It is impossible by any procedure, no matter how idealized, to reduce any system to the absolute zero of temperature (0 K/−273.15°C/−459.67°F) in a finite number of operations.

They can come close... but not absolute.
 
  • #8
DaveC426913
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Atoms, when reduced to abs zero, form what is called a Bose-Einsteinian Condensate - in effect, they stop becoming individual atoms and form an amorphous blob - defeating an attempt to measure them.

An atom reduced - even theoretically - to abs zero will still not freeze its electrons and protons. It does not literally stop in place and become a well-behaved hard ball.


"if future new physics are introduced, would the Heisenberg Uncertainty Principle be broken, disproved, modified or overcomed?"

It is possible, but it is important to be aware that it is not simply a matter of getting better at measuring. For HUP to be overturned would require a radical new understanding of our universe, not simply better measuring techniques.
 
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  • #9
James R
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Even a Bose-Einstein condensate has a temperature greater than zero.
 
  • #10
Chaos' lil bro Order
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i like whitestar's idea

If you cooled atoms down to say 1 degree Kelvin, clearly their oscillations and jittering would slow down as well. That said, if you then bombarded them with high energy photons, wouldn't it make measuring the 'cooled' atoms position and velocity much easier, that say, firing photons at hotter atoms?

Surely, Heisenberg's Principle would not be violated, but in effect, the limit to how precisely one could know the exat position and velocity of the 'cooled' atom's electron(s) would be more refined and accurate.

What do you think?
 
  • #11
DaveC426913
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James R said:
Even a Bose-Einstein condensate has a temperature greater than zero.
Yes, I did not mean to imply otherwise. I merely meant to point out that, even before you reach abs zero, the effect happens and their position/velocity can't be measured.
 
  • #12
DaveC426913
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Chaos' lil bro Order said:
If you cooled atoms down to say 1 degree Kelvin, clearly their oscillations and jittering would slow down as well. That said, if you then bombarded them with high energy photons, wouldn't it make measuring the 'cooled' atoms position and velocity much easier, that say, firing photons at hotter atoms?

Surely, Heisenberg's Principle would not be violated, but in effect, the limit to how precisely one could know the exat position and velocity of the 'cooled' atom's electron(s) would be more refined and accurate.

What do you think?

It is not merely a matter of a round, hard ball coming to a stop. Atoms actually lose their identity as individuals - each one physically "spreads out" and blurs, until the properties of position and velocity no longer apply.
 
  • #13
Whitestar
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DaveC426913 said:
It is not merely a matter of a round, hard ball coming to a stop. Atoms actually lose their identity as individuals - each one physically "spreads out" and blurs, until the properties of position and velocity no longer apply.


1) Are you saying that atoms "spreads out" or becomes blurry once they reach absolute zero, or before they reach absolute zero?

2) Could some extremely advance technology overcome this in the far future?


Whitestar
 
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  • #14
Math Is Hard
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DaveC426913 said:
Atoms, when reduced to abs zero, form what is called a Bose-Einsteinian Condensate - in effect, they stop becoming individual atoms and form an amorphous blob - defeating an attempt to measure them.
Just curious - is this Bose-Einsteinian Condensate considered a state of matter? How close to abs zero does the temperature have to get for this effect to occur?
 
  • #15
Chaos' lil bro Order
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dave, So then what becomes of the electrons at 0 degrees kelvin? Can you site experiments or data to back up your claims?
 
  • #16
Chaos' lil bro Order
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dave, Do the quarks comprising the atom blur out and flatten too? What actually happens here?

Please don't answer with an analogy unless its scientific in nature, ty.
 
  • #17
James R
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A BEC is a state of matter. It occurs when the particles get close enough together for their quantum wavepackets to start to overlap sufficiently.

In practice, BECs in dilute atomic vapours, occur at about 1 nK above absolute zero (thats 0.000 000 001 degree about absolute zero).
 
  • #18
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James R said:
A BEC is a state of matter. It occurs when the particles get close enough together for their quantum wavepackets to start to overlap sufficiently.

In practice, BECs in dilute atomic vapours, occur at about 1 nK above absolute zero (thats 0.000 000 001 degree about absolute zero).

Thanks. :smile: I had no idea.
 
  • #19
gurkhawarhorse
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this thread is reminding of eistein/bohr argument on this same principle. it is a joke.:rofl: but exaggarated :redface:
but i found its first half in the book 'einstein's cosms' by dr. kaku! don't know if it is true :confused:

einstein=oh! cmmon god doesn't play dice.
bohr=stop god telling what to do. :devil:
e=cmmon :uhh:
b=stop telling me what to do. :tongue2:
e= :cry:

gurkha-war-horse
 
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  • #21
OnTheCuttingEdge2005
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I believe BEC Matter under its condensed condition is where the Molecules of the Atomic structure loose their electron valence identities and the vector spaces between atoms begin to shrink, as the Atoms approach 0 K they share their most inner electron orbits with each other, This is probably being caused by internal field collapse which allows the Atoms to become more dense in nature, It is probable that if the Atoms did reach absolute 0 K that Atoms would in fact become a singularity type particle function and behave like a singularity.

I have seen Gold Atoms up close in an electron microscope and I can say they look like cotton balls or cumulous clouds.

Gerald L. Blakley
 

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  • #22
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James R said:
The problem with freezing an atom to absolute zero is simply that it can't be done. If it could be, then we could violate the uncertainty principle.

Why? The momentum and position operators would still not commute.
 
  • #23
James R
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You could simultaneously know the velocity of the atom (zero) and its exact position (plenty of time to determine that since the atom isn't moving), which would violate the uncertainty principle.
 
  • #24
selfAdjoint
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James R said:
You could simultaneously know the velocity of the atom (zero) and its exact position (plenty of time to determine that since the atom isn't moving), which would violate the uncertainty principle.

On the contrary, the particle isn't a little ball or speck that has a position whether we observe it or not. You can onlly get a position for it by an observation that collapses the function to one of the eigenvalues of the observation operator. And the working of the uncertainty principle is that if you knew the momentum exactly, there would BE no definite eigenvalues to collapse to; you would be unable to get a measurement of position at all.
 
  • #25
OnTheCuttingEdge2005
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In my above posting of the Gold Atoms.

1.Atoms are not uniformed, They're irregular in shape.
2.The Atomic Clouds move with a whispy type TO and FRO irregular movement in XYZ, Although the Atom stays in it captured position it will have irregular whispy type movements in its position.
3.Atoms are foggy Clouds, You cannot see the Nucleus, With the fundimental knowledge that Atoms move in very small irregular XYZ positions this would indicate that the Nucleus is also moving internally with an irregular XYZ type movement caused by internal electron field inductions (Moving Field).
4.If one was small enough to stand on the Nucleus of an Atom, It would look like you were standing on a very cloudy planet with the forcast of eternal Overcast.
5.The Atomic clouds share their electrons, this causes Atoms to form Chainmail type structures Atomically.
6.When an Atom approaches 0 K the Chainmail type spaces begin to disapear and the Atoms begin to form what appears to be a solid structure with no spaces inbetween Atoms.

With knowing all this, uncertainty principle still holds true.

Gerald L. Blakley
 
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  • #26
James R
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selfAdjoint:

Yes. I was using a counterfactual example. If the atom could be cooled to absolute zero, then ...
 
  • #27
selfAdjoint
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The counterfactual bit has nothing to do with my post. It was your misunderstanding of what QM says.
 
  • #28
Math Is Hard
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OnTheCuttingEdge2005 said:
I have seen Gold Atoms up close in an electron microscope and I can say they look like cotton balls or cumulous clouds.

That picture is fascinating. Is there a place where I could see more?
 
  • #29
Draya22
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OnTheCuttingEdge2005 said:
In my above posting of the Gold Atoms.

1.Atoms are not uniformed, They're irregular in shape.
2.The Atomic Clouds move with a whispy type TO and FRO irregular movement in XYZ, Although the Atom stays in it captured position it will have irregular whispy type movements in its position.
3.Atoms are foggy Clouds, You cannot see the Nucleus, With the fundimental knowledge that Atoms move in very small irregular XYZ positions this would indicate that the Nucleus is also moving internally with an irregular XYZ type movement caused by internal electron field inductions (Moving Field).
4.If one was small enough to stand on the Nucleus of an Atom, It would look like you were standing on a very cloudy planet with the forcast of eternal Overcast.
5.The Atomic clouds share their electrons, this causes Atoms to form Chainmail type structures Atomically.
6.When an Atom approaches 0 K the Chainmail type spaces begin to disapear and the Atoms begin to form what appears to be a solid structure with no spaces inbetween Atoms.

With knowing all this, uncertainty principle still holds true.

Gerald L. Blakley


What would happen if you took an atom that was cooled as close to abs zero that it could get, and fired negative energy at it? What would happen? What if it wasn't just one atom, what if it was a group, that was cooled to become a BEC, and then negative energy was fired at it? What would happen?
 
  • #30
metacristi
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selfAdjoint said:
On the contrary, the particle isn't a little ball or speck that has a position whether we observe it or not. You can onlly get a position for it by an observation that collapses the function to one of the eigenvalues of the observation operator. And the working of the uncertainty principle is that if you knew the momentum exactly, there would BE no definite eigenvalues to collapse to; you would be unable to get a measurement of position at all.

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.
 
  • #31
selfAdjoint
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metacristi said:
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.
 
  • #32
metacristi
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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.
 
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  • #33
selfAdjoint
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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?
 
  • #34
metacristi
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selfAdjoint said:
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.
 
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  • #35
Chaos' lil bro Order
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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
 

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