Schrödinger's mental experiment

chevy

chevy

Marvelous Da Vinci
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Schrödinger's mental experiment is based on quantum physics.

A theory in quantum physics sais that some undefined states become defined only once it's observed.

Example: if such a state is black or white, it will be either black or white when observed, but as long it is not observed it is only in a potential between black and white. This is true for the state and for any consequence of this state. This state applies to very small bit of material like a photon or an electron. But consequences of such states can be much bigger.

Schrödinger's mental experiment is the following (he was not cruel enough to make it real).
Let's have a box than can be hermeticaly closed. In this box we install a cat with enough food an air to live without any interaction with the exterior of the box. If we close the box and then open it, the cat is still alive.
Now let's add in the box a closed bottle of lethal poison which opening is controlled by a random quantum mecanism as described above.

Wait.

According to the quantum theory, the cat is not dead or alive but in a state between live and death until we open the door.

Do you have any better explaination ?
 
Schrödinger's theory is an experiment of the mind only.

Exact equation is : ??(x) + (2m/h^2 [E- V(x)] ?(x) = 0, when x is a vectorial and when h is h/2?.

Now if you need the exact details of it, I'll have to ask my girlfriend, she's far more smarter than me in physics and maths :p

Photons may go through inclinated glass, just as they may not go through it. Hence, until you ask the photon (ie. test its luminance), you cannot know if it has gotten through the glass.

So you put a vampire into a room and close the door behind you. At midday, the sun might have changed him into ashes. Or may have not. The only way to know is to open the door :p - that's a simpler version of Schr.'s theory.

You can add something to it: if you open the door and the vampire's alive, you're virtually dead. Therefore, at midday, yourself are either dead or alive when you open the door and...

etc. etc.

In electronics, a quantic bit is not 0 or 1, but is excited: he's both at a time. That's what is interesting in Schr.'s theory applied to computers: you're out of a binary system, you can compose a byte with 0, 1 and (e) (for Excited bit).

Infinite combinations of bits thus give infinite power of calculus, infinite storage, etc. But that's all in your head :D !
 
Argh ! vB forums do not allow all ASCII chars ! My math symbols did not get right in previous post... Too bad.
 
Originally posted by toast

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Photons may go through inclinated glass, just as they may not go through it. Hence, until you ask the photon (ie. test its luminance), you cannot know if it has gotten through the glass.
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I don't need the equation here.

I'm not sure your description shows the problem/paradox. The paradox lies in the fact that the state of the photon (or other quantum element) is defined by the measurement instrument (or by the observer). The state is only potential as long as it is not measured. Somewhere, the state did not exist before it was mesured, and indeed if you try an interaction with the quantum element, the interaction will be relative to its state probability, not to its final state. Which demonstrates that the final state was not set before.

Schrödinger's Jaguar in half dead, half alive. Try to touch it...
 
Originally posted by chevy
I'm not sure your description shows the problem/paradox. The paradox lies in the fact that the state of the photon (or other quantum element) is defined by the measurement instrument (or by the observer).
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There is no paradox, be careful. Schrödinger's theory is a theoreme at the very basis. It is an abus de langage to say it's a paradox, as his equation does verify itself without any contradiction in quantic physics.

Originally posted by chevy
The state is only potential as long as it is not measured. Somewhere, the state did not exist before it was mesured, and indeed if you try an interaction with the quantum element, the interaction will be relative to its state probability, not to its final state. Which demonstrates that the final state was not set before.
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The state is not potential ! :D Watch your vocabulary: the state is impotent, it has no power, no characteristics, except that it exists (ie. it is excited).

The state exists before you measure it. If it didn't quantic physics would be a science about nothing. The problem is: it exists but cannot be reached. Just like Kant's real world, hidden behind appearances: metaphysics are based on the same idea.
 
Surely the device that releases the poison is in fact making an "observation" in order to effect its random behaviour. Likewise, with the vampire example, the inclinated glass is performing an "observation" when it comes into contact with the light.

Just because there is no human observer in the system, doesn't make any difference to the way the system behaves.

The problem with the Schrodinger's cat experiment is that it takes a far too literal meaning for an "observed event". Any event that must resolve to a state represents an observation. But Schrodinger misread the theory as meaning the observation must be made by a human observer.
 
gosh, anybody who watches CSI should be able to answer this one. the cat is dead when the cat is dead . period. although no one percieved it at the time, an autopsy will provide all the observable evidence needed to know approximately when the cat died. while not a physicist by any means or loose description, it seems that the 'state' of certain molecules and their particles changes at the point of death and acts in a predictable manner.
 
Slight correction, the cat is NOT in an in between state, the cat only has two states. The beauty of quantum physics says that the cat is indeed in both states (or neither, can't remember now which) until an observation forces one or the other state to become the observed state.

Symphonix, I always thought that Schrodinger was simply making a generalzation, not that he was necessarily implying that a human MUST be involved. This is esp. true since these quantum effects do not occur at such a macro level as a cat, so trying to tie quantum level effects to macro level occurances is purely a mind game (disclosure, IANAP).
 
Jason's Superdonut Experiment:

Buy a box of donuts. Eat them all without looking. Then close the box.
Until you open the box, you cannot know if there are donuts inside. In fact, the donuts are in a super-state.
If you open the box and the donuts are there, then you're onto a really good application of quantum mechanics.
If the donuts aren't there, you can blame whoever was watching you eat them with your eyes closed.
 
Slight correction, the cat is NOT in an in between state, the cat only has two states.
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Exactly. Why do you think that quantum physics is called quantum. It is because states have distinct levels in certain circumstances. In the cat's case, alive or dead.

Remember also that Quantum theory is not actually what happens, it is simply a mathematical model that describes what we perceive in the physical world. The same with Newton's laws of mechanics - good enough for macroscopic applications, but only a model, not actually what happens.

It is sometimes easier to consider it in terms of probabilities. It is not actually what happens, but it is an easier model to think about. Before the box is opened, there is a probability that the cat is alive, and a probability that the cat is dead. When we open the box, we know which state the cat is. However what is harder to show/understand with this scenario is that before the box is opened, the cat ACTS as the percentage probability of being both alive and dead. i.e. if you were to pick up the box and shake it, if the chance of the cat being alive was 90% then you would expect some response. However if the chance of the cat being alive was 30%, then when you shook it, you would expect less response. This is assuming that the illness of the cat is due to it being not all alive, and defining alive as being 100% healthy.

One example of this has been shown by experiment. Quantum theory was developed because light didn't always behave as a wave, which classic theory predicts. The experiment was to shine a monochromatic laser light through a diffraction grating. A diffration pattern appeared. Now reduce the intensity of the laser until it was possible to measure individual photons. Individual photons were detected, but they still, over a period of time, formed a diffraction pattern. This means that whilst going through the grating, a photon must have been exhibiting behaviour as a wave, but we know that it also behaves as a particle (at detection).

In my experience, it is better not to bother trying to visualise these physics models but to rely on the maths. otherwise you get a headache quite quickly.
 
If I put a blue ball in a black box, is the ball still blue? No, there is no light reaching the ball to be absorbed or reflected. Then again, you have to assume that the light you would shine on the ball once it is out of the box is white light. If you shined light on the ball that was missing all the blue light in the spectrum the ball would appear black. But then again, is the ball really blue, or is this a phenomenon of the surface chemistry and physics of the ball and light source?
 
Originally posted by chemistry_geek
If I put a blue ball in a black box, is the ball still blue? No, there is no light reaching the ball to be absorbed or reflected. Then again, you have to assume that the light you would shine on the ball once it is out of the box is white light. If you shined light on the ball that was missing all the blue light in the spectrum the ball would appear black. But then again, is the ball really blue, or is this a phenomenon of the surface chemistry and physics of the ball and light source?
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You're arguing definitions not physics. If your definition of "blue" is that a person looking at it would see it as blue, then the answer varies depending on the conditions you specified. If your definition of "blue" is that the surface of the ball will respond in a particular way to various wavelengths of light before/during/after being in the box, then yes, it stays "blue" all the time.

This is similar to the old "if a tree falls in the woods ...." argument. If your definition of "noise or sound" is the reception of moving air waves via a human ear, then no it doesn't make a "sound". However, if it's simply that the waves are generated then the answer is yes.
 
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