Schrödinger's Cat

[Qfwfq]

Many times the implications of quantum mechanics creep into discussions here in Hypography. Quite often there is disagreement about certain implications, or some posters are less informed on the topic and want explantions.

 

These are often discussed on the spot but it might be a good idea to have a chat here. A good thing to start the snowball rolling might be the famous Gedankenexperiment:

 

A box contains a sample of a radioisotope and a suitable detector, possibly such that external radioctivity is negligible and things can be adjusted to have an average of a couple of counts an hour from the detector, which can also be turned on and off from outside the box. The detector is rigged to trigger a device that will release cyanide into the air inside the box, enough to kill a cat that is placed inside the closed box. If the detector is then left switched on for an hour and then switched off, the chance of the cat being killed is about 50-50.

 

After the detector has been switched off, and before the box is opened to see if the cat has been killed, how does the cat feel?

[Anomalistic Thought]

The cat is both dead and alive, it shows the quantum property of superposition. This being true, I guess the cat would either feel both dead and alive. Though do cats understand the concept of death? Of course if they did, then they would be aware of their state, and cause fluctuations in the experiment, similar to how temputure and heat affect actual particals in superposition. The property I much prefer is quantum tunneling. I beleive this is when a partical passes through a barier that normaly would stop it.

[lindagarrette]

Couldn't we talk about something besides that poor tortured cat? I wish Schrodinger had used a different example because I get sad whenever the poor little helpless thing is mentioned. Maybe that's why I don't agree with the observer influence concept.

[Qfwfq]

Neither do I agree with the conscious observer influence concept, but I'd be of the same opinion if it were a cockroach in the box!!! :Alien:

 

P. S. I believe it wasn't Schrödinger that chose the cat.

[Rincewind]

From a list of famous (?!) quotes:

 

"What have you done to the cat? It looks half dead!"

---Schrödinger's wife.

[paultrr]

Many times the implications of quantum mechanics creep into discussions here in Hypography.

 

It tends to creep in because its the background of the macroworld, which seems so ordered as a whole, and yet, down at that scale everything seems unordered.

 

I'd suggest the cat feels exactly alive if it is alive and feels nothing if it is dead, at least from a scientific point of view since by being dead all capacity to feel would be gone. :Alien:

[paultrr]

The cat is both dead and alive, it shows the quantum property of superposition. This being true, I guess the cat would either feel both dead and alive. Though do cats understand the concept of death? Of course if they did, then they would be aware of their state, and cause fluctuations in the experiment, similar to how temputure and heat affect actual particals in superposition. The property I much prefer is quantum tunneling. I beleive this is when a partical passes through a barier that normaly would stop it.

 

Who's to say a cat would not perform the same position of an observe and have influence via fluctuations in the experiment. I've often thought that old cat in the box overlooked that one a bit.

[Qfwfq]

I've often thought that old cat in the box overlooked that one a bit.

It wasn't overlooked for long, that's where Wigner's friend came in! :Alien:

[Eduffy80911]

I'm no expert, so please correct me if I'm wrong, but I think the implication in the cat experiment is that probability = reality. It's like saying that if you flip a coin and it falls where nobody can see it, it is both heads and tails until someone actually observes it. I believe truth and reality are objective and don't need human confirmation to exist, therefore the cat is either dead or alive, but not both, and whether anyone ever checks on the cat's health or not will not affect which it is.

[Buffy]

I'm no expert, so please correct me if I'm wrong, but I think the implication in the cat experiment is that probability = reality. It's like saying that if you flip a coin and it falls where nobody can see it, it is both heads and tails until someone actually observes it. I believe truth and reality are objective and don't need human confirmation to exist, therefore the cat is either dead or alive, but not both, and whether anyone ever checks on the cat's health or not will not affect which it is.

Most people misunderstand what point Erwin Schrodinger was actually trying to make. His point was that the indeterminancy which is dominant at the quantum level (e.g. Heisenberg's Uncertainty Principle) does *not* translate well into the macroscopic world. That's not to say that quantum uncertainty does not have macroscopic effects, but that the observational issues really don't apply directly.

 

Cheers,

Buffy

[paultrr]

It wasn't overlooked for long, that's where Wigner's friend came in! :circle:

 

Yes,true.

[paultrr]

Most people misunderstand what point Erwin Schrodinger was actually trying to make. His point was that the indeterminancy which is dominant at the quantum level (e.g. Heisenberg's Uncertainty Principle) does *not* translate well into the macroscopic world. That's not to say that quantum uncertainty does not have macroscopic effects, but that the observational issues really don't apply directly.

 

Cheers,

Buffy

 

True. On a quantum level, irrespective of weither we look or not the cat(wavefunction) appears to be in more than one state at the same time. By the act of looking what one is doing with examining one slice or event, in which case the wavefunction(cat) appears in one state or another(Dead or alive). But the act of looking is not what actually decides which state it is in. All one did by looking was examine and define a certain event as witnessed. The mind has really little to do with the actual event itself, except as a witness to such. The Double Slit experiments in themselves show how the wavefunction has the ability at times to have no solid defined path and yet, under other conditions it can display such. This all runs counter to the macroworld where everything is far more shall we say, without causing an arguement, deterministic and more exact. Somehow these two worlds unite. Somehow the random manages to generate the less random.

[lindagarrette]

Most people misunderstand what point Erwin Schrodinger was actually trying to make. His point was that the indeterminancy which is dominant at the quantum level (e.g. Heisenberg's Uncertainty Principle) does *not* translate well into the macroscopic world. That's not to say that quantum uncertainty does not have macroscopic effects, but that the observational issues really don't apply directly.

 

Cheers,

Buffy

Good statement. And probability is a good way to describe such events since there is no known way to find all the variables that can occur when it happens. It can only be extimated.

[Qfwfq]

Most people misunderstand what point Erwin Schrodinger was actually trying to make. His point was that the indeterminancy which is dominant at the quantum level (e.g. Heisenberg's Uncertainty Principle) does *not* translate well into the macroscopic world.

True that this is what the Gedankenexperiment was meant to imply, but I'm not so sure it was Erwin himself that proposed the cat trick. Somewhat to the contrary, Schrödinger for some time strongly believed in the waves being something very real.

[Qfwfq]

This all runs counter to the macroworld where everything is far more shall we say, without causing an arguement, deterministic and more exact.

Without causeing an argument, the macroworld is far more exact in proportion to the values of q and p. It would be practically impossible to measure the position and momentum of the centre of mass of a pool ball with a precision anything like that of the Heisenberg limitation, let alone more precisely if this were possible. Aside from practical feasibility, the limitation is the same and tresspassing would imply the possibility of observations leading to the contradictory conclusions.

 

Somehow the random manages to generate the less random.

The random in this Gedankenexperiment: the dacays from which the detector may pick up an emitted particle.

 

The less random: ?

 

Is "whether the detector triggers and give an outut pulse" less random? How much less random?

 

Corrollary: Is "whether the will be dead when the box is opened" less random? How much less random? :circle:

[Qfwfq]

It's like saying that if you flip a coin and it falls where nobody can see it, it is both heads and tails until someone actually observes it.

Right, when you talk about flipping the coin. A lot more tricky when you talk about the outcome of systems that started in a given QM state.

 

Suppose you have just measured the momentum of a particle very well, you can't have simultaneously measured it's momentum very well. Before things have had time to change much, you then measure it's momentum very well. According to the coin-flipping notion of not having yet made the measurement, one could draw conclusions about the value of momentum before that measurement and, in some contrivable cases, Heisenberg would be violated and, hence, so would the savage contradictions be let loose.

 

I believe truth and reality are objective and don't need human confirmation to exist, therefore the cat is either dead or alive, but not both, and whether anyone ever checks on the cat's health or not will not affect which it is.

The conscious observer is no longer speculated to play a role in determining the outcome, there's a newfangled idea about it.

 

What might this idea be? How might the state, starting out as something like a|u> + b|v> become either dead or alive, rather than something like a|dead> + b|alive>????

[sanctus]

There are also some funny interpretations of the superposition of a dead and alive cat: it takes into account other dimensions/universes and states that the cat is alive for example here and dead elsewhere. Same thing with the macroscopic detectors....