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  4. What causes quantum uncertainty | Detectors are not the cause of collapse
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What causes quantum uncertainty | Detectors are not the cause of collapse

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Offline jeffreyH

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Re: What causes quantum uncertainty | Detectors are not the cause of collapse
« Reply #20 on: 07/08/2019 03:31:26 »
What about eigenvectors and eigenvalues? Maybe you have heard vaguely about linear algebra. If you don't know what I am talking about just stop embarrassing yourself.
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Offline pittsburghjoe (OP)

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Re: What causes quantum uncertainty | Detectors are not the cause of collapse
« Reply #21 on: 07/08/2019 03:40:32 »
"Lets say you and I go toe to toe on Bird Law and see who comes out the victor"
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Offline Colin2B

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Re: What causes quantum uncertainty | Detectors are not the cause of collapse
« Reply #22 on: 07/08/2019 06:39:49 »
Quote from: pittsburghjoe on 07/08/2019 03:40:32
"Lets say you and I go toe to toe on Bird Law and see who comes out the victor"
Let’s not get into more of your rubbish.
Also, you have been warned about posting false information and new theories in the Physics section of this forum. I sorry you decided to ignore our requests.
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Re: What causes quantum uncertainty | Detectors are not the cause of collapse
« Reply #23 on: 07/08/2019 07:00:25 »
Quote from: alancalverd on 06/08/2019 23:01:17
Not that indeterminacy has much to do with shaking anyway.
Alan is right and you (Pittsburgh) would do well to understand what he is saying, it is a point of common confusion.
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Offline alancalverd

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Re: What causes quantum uncertainty | Detectors are not the cause of collapse
« Reply #24 on: 07/08/2019 09:56:32 »
I've never had much time for Schrodinger's cat, so here's Calverd's penny, which I think is a lot closer to what we observe.

There's a coin in a box. It might be a head or a tail, and if you shake the box with enough amplitude to flip it, it may or may not change. Now open the box. Nearly all the time it will be in one or other state, but if it is a quantum penny, there's a very small probability that it has actually tunnelled out of the box altogether. It is obviously absurd to suggest that opening the box actually determined the state of the penny, but if your fortune (or at least the opportunity to bat first) depends on the discovered state of the penny, the act of observation has significant consequences for everything else.

So what? Here's what. The object of quantum mechanics is to provide a mathematical description of what we have observed, with sufficient generality that it can predict what we may observe in the future. Hence the collapsing wave function: it's a sufficient description of observed phenomena, with some predictive value (substitute a pair of dice for the penny, then use your wave functions to predict the most likely score) but not a necessary explanation of what actually happens.  The fun bit is that our best wave functions extend outside the box and predict tunnelling!
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Offline alancalverd

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Re: What causes quantum uncertainty | Detectors are not the cause of collapse
« Reply #25 on: 07/08/2019 12:11:48 »
As for what causes indeterminacy, the answer is it doesn't have a cause: it is a cause. Let's consider two models:

If you want to know the speed of a car, you have to measure how long it takes to travel between two points. That will give you the average speed between those points. If you move the points closer together, your calculation will approach the instantaneous speed at one point, but you can't actually measure that because the time taken to traverse an infinitesimal point is zero. However for large objects, we can state position and momentum with sufficient accuracy for practical purposes.

Now suppose you could measure the instantaneous position and momentum of an electron in a hydrogen atom, to an infinitesimal precision. That would give it the qualities of a macroscopic object  with a negative charge, close to another macroscopic  object with a positive charge. So either the electron would move directly towards the proton and the atom would collapse, or it would orbit like a planet round the sun. The atom plainly doesn't collapse, and an orbiting electron would radiate electromagnetic energy, which doesn't happen either.  So it seems that there is a fundamental limit to the determinacy of the product of position and velocity, and since it applies to all objects from electrons to planets,  we can generalise the statement by substituting momentum for velocity.

So much for the hypothesis. The fun begins when we discover that the same arbitrary constant h which describes the energy of a photon (E = hf) also limits the determinacy of the position and momentum of a particle (Δx.Δp = h) and is consistent with the observed diameter of a hydrogen atom. But these derivations are best left to textbooks, of which there are plenty.
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Offline yor_on

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Re: What causes quantum uncertainty | Detectors are not the cause of collapse
« Reply #26 on: 10/08/2019 01:55:41 »
Joe, there is quantum mechanics, relativity, and then there is 'common sense'. If we went by common sense only your computer shouldn't work. There is something called 'tunneling' that is used, 'Josephson junctions' if I remember right. I might be wrong there although I have some memory of it being used. http://www.w2agz.com/Library/Superconductivity/Anacker,%20IBM%20Josephson%20Project%20IBMJ.Res.Dev.24-2-107-112.pdf

Common sense change from generation to generation, but what lasts may be if you can define it as locally realistic. Cause and effect following what we normally expect around us. It doesn't quantum mechanically and as I see it neither in relativity.
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