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PsiSeeker

The Uncertainty Principle

15 posts in this topic

From Wikipedia

Intuitively, the principle can be understood by considering a typical measurement of a particle. It is impossible to determine both momentum and position by means of the same measurement, as indicated by Born above. Assume that its initial momentum has been accurately calculated by measuring its mass, the force applied to it, and the length of time it was subjected to that force. Then to measure its position after it is no longer being accelerated would require another measurement to be done by scattering light or other particles off of it. But each such interaction will alter its momentum by an unknown and indeterminable increment, degrading our knowledge of its momentum while augmenting our knowledge of its position. So Heisenberg argues that every measurement destroys part of our knowledge of the system that was obtained by previous measurements.[3] The uncertainty principle states a fundamental property of quantum systems, and is not a statement about the observational success of current technology.[2]

Can someone please help clarify why this is a fundamental property of quantum systems? >.< I don't see how to read this in any other way bar the observational success of current technology.

I'm trying to figure out if objective determinism or objective probability exists.

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do you want an explaination of the uncertainty principle ?

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Posted (edited)



I know this doesn't really answer your question, but anytime you you hear Feynman talk you get smarter. Even with auto tune. Edited by Imaginarynumber1

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Posted (edited)

this is the reason einstein hated quantum physics.

if you take two properties of a particle , say momentum and where it is , posistion. ..These both cant be known at the same time. The more preciesly you measure one the less preciesly you can measure the other one..

I suppose a good way to think of it would be

Imagine sitting in your car and you were traveling so fast that the outside world was a blur , You can look at the speedo and see how fast you are traveling , but you cant preciesly know where you are in the world .

Max Born wrote this

..To measure space coordinates and instants of time, rigid measuring rods and clocks are required. On the other hand, to measure momenta and energies, devices are necessary with movable parts to absorb the impact of the test object and to indicate the size of its momentum. Paying regard to the fact that quantum mechanics is competent for dealing with the interaction of object and apparatus, it is seen that no arrangement is possible that will fulfill both requirements simultaneously

Edited by danydandan

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The reason for this being that subatomic components will sometimes behave as waves. Did some farther searching on this. I just found it difficult to understand why they say "it is unknowable" when the problem appeared to be the instruments used to measure, not the particles themselves.

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Its just that , . There are no insttruments to measure both at the same time.

I recommend , a book called Quantum by Manjit Kumar , its easy to understand if your just jumping into the quantum world....

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Posted (edited)

The reason for this being that subatomic components will sometimes behave as waves. Did some farther searching on this. I just found it difficult to understand why they say "it is unknowable" when the problem appeared to be the instruments used to measure, not the particles themselves.

Which is wrong, and why the Wiki article attempts (poorly, imo) to clarify.

The issue is not the instruments, but that the energies that have to be used to measure quantum properties are significant when compared to the energy of the quantum system itself. This is what disrupts the measurement and leads to the uncertainty - not the instrumentation, or the actual observation.

Edited by Leonardo

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I agree that going into the wave-particle duality theory might help to understand. It is another fundamental property of quanta.

The uncertainty principle and wave-particle duality as much as I understand them make it impossible for physicists to precisely predict how a quantum is going to behave in the future. Scientists like Einstein "hated" this idea. Beeing a profound chistian, he refused to even think that "God plays dice with the universe". That is an example on how some beleifs might restrict our own minds from seeing things as they really are.

First time I got into this and uncertainty I just got mind-blown beyond beleif.

And that's when I started to beleive even more that consciousness might have a major role in all that. The deeper I go into quantum theories (strings, dimensions, multiverse etc.) the more I find major sense into it.

God I love it.

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To the OP: In most interpretations of quantum mechanics, the uncertainty principle is a fundamental theoretical limit.

To try to explain qualitatively: a wave can be thought of as an infinite superposition of (virtual) particles, and conversely a particle can be thought of as an infinite superposition of (virtual) waves. (This is basically just a Fourier transform; a sequence of positions can be represented by a summation of frequencies, and a sequence of frequencies can be represented by a summation of positions.) When you perform a position measurement, a wave will spontaneously change into one of those particles (now a real particle). Conversely, once you perform a momentum measurement, a particle will spontaneously change into one of those waves (again, now a real wave). This means that all the information encoded onto those other (virtual) particles or waves is now lost.

So conventionally, objective determinism does not exist. However there are many different interpretations of quantum mechanics, some of which allow determinism. See the long wiki article for more.

The issue is not the instruments, but that the energies that have to be used to measure quantum properties are significant when compared to the energy of the quantum system itself. This is what disrupts the measurement and leads to the uncertainty - not the instrumentation, or the actual observation.

I agree with the first sentence, but in my mind that still implies an instrumental effect.

In contrast, the uncertainty principle is conventionally encoded into the mathematics of the system (PX - XP = i hbar, for example), which imply that even in the limit of an ideal non-perturbative measurement there will still be wave function collapse.

I am curious, Leo, do you think that uncertainty is innate to a quantum system (i.e. wave function collapse is true at all levels), or that is simply a consequence of finite resolution measuring tools (i.e. you can't use less than a single photon to look at the position of an electron)?

There are certainly good arguments for many different interpretations of quantum mechanics, I'm just curious what your take is.

First time I got into this and uncertainty I just got mind-blown beyond beleif.And that's when I started to beleive even more that consciousness might have a major role in all that. The deeper I go into quantum theories (strings, dimensions, multiverse etc.) the more I find major sense into it.God I love it.

It has been experimentally demonstrated that wave function collapse occurs regardless of whether or not a conscious mind is observing the outcome of the collapse.

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It has been experimentally demonstrated that wave function collapse occurs regardless of whether or not a conscious mind is observing the outcome of the collapse.

Yep, you are right.

I did not mean that conscious observers collapse the wave-function. Just that consciousness, in my opinion, has a very important and fundamental role in the existence of the universe. That could mean a lot of things. :)

Peace.

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I am curious, Leo, do you think that uncertainty is innate to a quantum system (i.e. wave function collapse is true at all levels), or that is simply a consequence of finite resolution measuring tools (i.e. you can't use less than a single photon to look at the position of an electron)?

You answered your question yourself, Sepulchrave, when you said "you can't use less than a single photon to look at the position of an electron".

I don't view quantum uncertainty as being a consequence of instrumentation, but a consequence of that the universe is a quantum universe. If it wasn't, then theoretically we could determine all properties of any system with the same measurement.

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Beeing a profound chistian, he (Einstein) refused to even think that "God plays dice with the universe". That is an example on how some beleifs might restrict our own minds from seeing things as they really are.

I've never heard of Einstein saying he was a Christian.

I believe in Spinoza's God who reveals himself in the orderly harmony of what exists, not in a God who concerns himself with the fates and actions of human beings. (Albert Einstein)

http://www.spaceandmotion.com/albert-einstein-god-religion-theology.htm

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From Wikipedia

Can someone please help clarify why this is a fundamental property of quantum systems? >.< I don't see how to read this in any other way bar the observational success of current technology.

I'm trying to figure out if objective determinism or objective probability exists.

At the quantum level the world is undeterministic

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Thank-you everyone :). After looking into a bit more I realized that the explanation would lie in the duality of the particle and wave phenomenon. (Especially well put by sepulchrave) But yeah, the way things were worded definitely made it seem like fundamentally instrumental errors >.>...

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I've never heard of Einstein saying he was a Christian.

http://www.spaceandmotion.com/albert-einstein-god-religion-theology.htm

Hummm, you are actually right.

My bad.

But the quote is quite right though.

From Wikipedia:

"Albert Einstein's religious views have been studied due to his sometimes apparently ambiguous statements and writings on the subject. He believed in the God of Baruch Spinoza, but not in a personal god, a belief which he criticized. He also called himself an agnostic, and criticized atheism, preferring he said "an attitude of humility"

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