Schrodinger's Cat

Schrodinger's cat


Schrödinger's cat is a famous illustration of the principle in quantum theory of superposition , proposed by Erwin Schrödinger in 1935. Schrödinger's cat serves to demonstrate the apparent conflict between what quantum theory tells us is true about the nature and behavior of matter on the microscopic level and what we observe to be true about the nature and behavior of matter on the macroscopic level.

Here's Schrödinger's (theoretical) experiment: We place a living cat into a steel chamber, along with a device containing a vial of hydrocyanic acid. There is, in the chamber, a very small amount of a radioactive substance. If even a single atom of the substance decays during the test period, a relay mechanism will trip a hammer, which will, in turn, break the vial and kill the cat. The observer cannot know whether or not an atom of the substance has decayed, and consequently, cannot know whether the vial has been broken, the hydrocyanic acid released, and the cat killed. Since we cannot know, the cat is both dead and alive according to quantum law, in a superposition of states. It is only when we break open the box and learn the condition of the cat that the superposition is lost, and the cat becomes one or the other (dead or alive). This situation is sometimes called quantum indeterminacy or the observer's paradox : the observation or measurement itself affects an outcome, so that the outcome as such does not exist unless the measurement is made. (That is, there is no single outcome unless it is observed.)

We know that superposition actually occurs at the subatomic level, because there are observable effects of interference, in which a single particle is demonstrated to be in multiple locations simultaneously. What that fact implies about the nature of reality on the observable level (cats, for example, as opposed to electrons) is one of the stickiest areas of quantum physics. Schrödinger himself is rumored to have said, later in life, that he wished he had never met that cat.
~Courtesy of techtarget.com

I love this paradox. What do you guys think of it?

 

Never been totally sure that there is much of a paradox here. There is nothing inconsistent going on here other than our incorrect perception of reality. We always assume that an event had an outcome even if we don't know what it was. What we now know that matter has a wave like nature we can have a superposition of states until a measurement forces the object to have a definite state. The measurement problem is definitely a problem, ive never been totally convinced its a paradox.

 

Well using common sense and the reality of life, we know the cat cannot be both dead and alive simultaneously. Although what you stated "What we now know that matter has a wave like nature we can have a superposition of states until a measurement forces the object to have a definite state" is very relevant in all cases making objective observation and measurement subjective, as Heisenberg's Uncertainty Principle states.

Our observation of the experiment might force the cat to pick a state of living or dead, but how do you not see the paradox and flaw of quantum mechanics when applied on a macroscopic level? QM says the cat will be both dead a alive simultaneously, and it is made more interesting by the thought that the cat may or may not be conscious.

The original version of this thought-experiment contained a keg a gunpowder, which would be forced to explode when the geiger counter picked up radiation. QM said that the gunpowder after a while will contain both exploded and unexploded parts simultaneously.

Schrodinger decided to add another kick to it, instead of gunpowder being forced to explode or remain in stable condition, he added a living thing that may or may not be conscious, and force it to choose a condition of living or dead.

Of course the problem would painstakingly dumb if a human replaced the cat, but its the fact mentioned in the above paragraph that makes is so intriguing.

I guess this problem will not be solved until we fully understand consciousness and its connection to nature and the physical world.

 

Using common sense we think the cat can't be dead and alive simultaneously, I think would be a more correct statement. I think the biggest problem when this problem is explained is that the emphasis goes in the wrong place. The superposition is a natural consequence of the wave like nature of matter, far removed from our perceptions but perfectly explicable none the less. The interesting part of the question is two fold firstly how do these superpositions collapse and how does this lead to a macroscopic world on the large scale.

The first part is more philosophical and the second part is more physics in my opinion although both contain plenty of both. There is no answer and the debate has been raging for years. My favorite explanation for the border between classical and quantum is something called quantum decoherence which at is most basic level is where a wavefunction interacts with with its surroundings. This is interesting because it can give the appearance of wavefunction collapse.

 

So you're attempting to justify that the cat, who I must stress may be conscious or not, could in fact be both dead and alive at the same time because of the wave-like nature of matter?

I'm telling you, that would perfectly explain the experiment if it wasnt a cat in the box. You would be famous for solving this paradox already. But just the fact that the cat may or may not be conscious makes your theory flawed. Even without the oustide observer, the cat would know if its dying or not.

 

Ok. Every particle (or system) can be described by a wavefunction. This wavefunction can be expanded to be a sum of all physically allowed states for that particle. In a similar way to how a water wave can be expresssed as a sum of sin and cosine waves. The important point here is that when the particle is un measured its described as as a sum of all possible states. Only when a measurement is performed will it 'collapse' to a particular state. In the case of Schrodingers cat the 'box' is representing something region in which we have complete ignorance of its content, as such the wavefunction exists as a superposition of all physically allowed states. Some these states will involve a dead cat, some will involve a living cat. It is worth noting that some properties cannot be defined at the same time (wiki: quark mixing, and neutrino mixing).

If people choose not to like subjective superposition (that is where only a conscious observer collapses the wavefunction) there are alternatives. Many worlds, dechoerence and a objective collapse, where some physical variables causes collapse. I find many worlds a bit over indulgent, decoherence I quite like but it only gives the appearance of collapse. Objective ones are quite interesting dont know much about them. While im nervous about putting life on a pedistal for those that like beauty in maths. I have always thought that the diea of the universe being this huge immensly complex wavefunction evolving through time only ever existing as a combination of everything else, until life came along and wrecked it by measuring it, though atheists do have to explain the first measurement.

 

I must agree with this post. Atleast to some degree.

Just beautiful poetry to my ears, or eyes in this case. If the universe is a huge wavefunction, and it probably is according to string theory and m-theory, then there is a possibility to unite all the forces and all the matter into a grand Theory Of Everything. The final Theory!

I completely disagree, if we didnt come along and start speculating these questions, then all of it would be meaningless. I believe our purpose and challenge in life is to try understand the universe, and our purpose in death is to become one with it.

 

How naive it is for humans to think that by viewing a situation they can ACTUALLY collapse a waveform.

If we are to understand the difference between wave-form universe and discrete state universe, we must understand the difference between things existing, and us being aware of their existance.

The wave-form NEVER collapses. Instead, when we observe the world, we take a sample of it, and this sample is one specific state of the universe.

By using maths, we try to predict other states of the universe. We compute one state and according to our understanding of the universe, we predict some state will exist after it.

In the case of the cat in the box, the can does not EXIST as being alive or dead. it is merely that as human beings, our ability to calculate whether the cat lives or dies is absent. That is to say, there is NO reason for us to have faith in either case.

What we write on a page does not represent reality but it represents reality as it is relative to us. Thus, when we calculate that something both exists and doesnt exist, or exists to a certain degree but siuultaneously doesnt exist (eg with the dynamite), that just means that as far as we are concerned, we can have different degrees of faith that either states are true.

But I believe the world exists as a set of discrete states, and the waveform represents the fact that we cant have enough information to determine the universe definately. instead we calculate it as a range of possibilities with different magnitudes.

Other people believe the waveform exists, and discrete states are an illusion created by the mechanics of observation (the brain).


but anyone that believes actually opening the door might kill the cat is suffering delusions of grandeur. The cat dies or lives when the vial breaks and the chemical enters the atmosphere. We just cant determine what is in the box without looking inside it. that fact is obvious and trivial.

 

The measuring device would collapse the wave function before anything. The chain reaction would just be a result of the collapsed wave. Even then, the cat would be an observer on his own. How egotistical to think that only a human can be an observer. Anything that can react is an observer.

On a lighter note:

I have been reading of Schroedinger's cat
But none of my cats are at all like that.
This unusual animal (so it is said)
Is simultaneously live and dead!
What I don't understand is just why he
Can't be one or other, unquestionably.
My future now hangs in between eigenstates.
In one I'm enlightened, the other I ain't.
If you understand, then show me the way
And rescue my psyche from quantum decay.
But if this queer thing has perplexed even you,
Then I will and won't see you in Schroedinger's zoo.

 

Indeed, the cat would be an observer. But you can replace the cat with a plant or something.
either way it doesnt matter if theres an observer or not. nothing actually does anything to the waveform. it always exists, but it also never exists because all possible states cannot be realised. only one.

 

Well, I don't know--the first I ever heard of this was on a recent episode of The Big Bang Theory--but personally, it sounds like a sick experiment to me! Paradox or not, Erwin Schrodinger should have been charged with animal abuse!

 

the way i think about it is like this: the cat/box scenario isn't whether the cat is actually dead or alive, it represents that we cannot know if it's alive or dead (current state) until we open the box (measure it), thereby causing that state to occur (if we open the box before it's dead our 'measurement' is forced to be "living cat", if it's dead when the box is opened, our 'measurement' is forced to be "dead cat"). If we don't open the box, we are forced to say the cat is both alive and dead, because we can't know until the box is opened. This is in analogy to our measurement of an object's state and the possible states it could be in until we measure it. It sounds somewhat redundant, but represents the math and physics behind it all (waveforms and such), and the cat scenario is more of a thought experiment.

 

I don't care if it was a thought experiment--just the mere fact that people are capable of even entertaining such thoughts makes me sick!

 

what if instead of traditional cardboard, the box was made of plexiglass.

 

This thought experiment is basically a manifestation of Heisenberg's Uncertainty Principle, that observation affects measurements.

then it wouldnt be a paradox at all.. the premise of the paradox is that since we cant see the cat die or remain alive, then QM predicts that the cat will be in both states simultaneously.

 

I am not sure if I completely get this. Just to clarify, the whole raidoactiveness and the hammer is just a way to make the of the cat completely random, right? I mean would it basically be any different if there was a with a random detonation program?

 

I don't know if you're jokin'...
but if you not, I have to let you know, that this experiment is theoretical. It never took place.

 

In response to your post, DelxPez--no, I'm not joking--I don't kid around when it comes to animals and issues relating to them! And yes, I'm sure that the experiment was theoretical--but like I said in my previous post, just the fact that people can even entertain such sick and twisted thoughts makes me want to throw up! Theory or not, I still maintain he should have been charged with animal abuse--just because he never went through with the experiment, the mere fact that he thought about it would be grounds enough for me!

 

ok, don't get me wrong, I love all animals (including humans) but ... charge him cause he just thought about it? I don't know...

"...just because he never went through with the experiment,.." well, he never had an intent to go through with that experiment,
because practically it would be useless.
It's like "if I kill that man, will he go to heaven? Will I go to hell?"
There's no point to proceed with that experiment, because then again the question would not be answered.
But it makes you think things like "is he good or bad man?", "is there heaven and hell?",etc.
Now, should I charged with murder for thinking something like that?

 

boy would u love to live in a communist police state, huh?