Why Schrodinger's Cat Doesn't Work

[swivel]

I woke up this morning realizing that the famous Schrodinger's Cat experiment is deeply, deeply flawed and does not work.

If you don't know what this thought-experiment entails, a brief description won't help, but here is some history anyway:

It was actually Einstein's idea (not many people are aware of this). Einstein had deep problems with Quantum Mechanics, even though he helped start the field with his non-relativity papers. Quantum Mechanics was championed by Heisenberg, who is famous for his Uncertainty Principle. Heisenberg realized that the more precisely you determined a subatomic particle's Position, the less able you were to determine its momentum.

This isn't just a limitation of our experimental apparatus, this is really how the subatomic world behaves. Bell's theorem cinched this in the 50's when he found that particles which were separated by a great distance somehow "communicated" to one another. If you entangled these particles (so that they have similar properties like spin), measuring one particles would INSTANTANEOUSLY limit what you could measure from the other particle. This is 100% real. Lab-tested and guaranteed.

Einstein had big problems with this. After all, he was the guy that set up the speed limit signs all over the universe. Nothing could travel faster than the speed of light, not even information. (we now know he was wrong) So he was always coming up with thought-experiments to challenge Quantum Mechanics, and Bohr and Heisenberg were always debunking them. Schrodinger's Cat is one of those thought-experiments that Bohr and Heisenberg never debunked because they AGREED with the results.


A little more Quantum Mechanics simplified:

Until you measure a particle's position, it isn't defined. The particle is not "here" or "there", it has a probability of being everywhere all at once. Only, the probability of it being in the next galaxy is very, very slim and the probability of it being in the general neighborhood of where it was last is very, very likely. It isn't until you measure the particle's position that these probabilities "collapse" and it has definite location. And here is where we get the popular maxims that the "observer affects what is observed".

So Einstein wrote Schrodinger, another critic of QM, and said that he could build a bomb that was set off by radioactive decay, and the bomb would both go off and not go off. Schrodinger toyed with this idea and came up with his famous experiment:

In a box you have a Geiger-Counter which is reading the decay of some radioactive material. When the Geiger-Counter hits a certain reading, a hammer smashes a vial which releases a poison which kills a cat.

According to this experiment, until you open the box, the cat is both dead and alive. The probability function spreads out over both of these possibilities, and it isn't until you open the box that you find the cat in one or another of these states.

Now, if you don't really know what Quantum Mechanics is all about, you will reject this out-of-hand. But this experiment has really troubled physicists for 70 years because this seems to be how nature works. Bohr and Heisenberg agreed with this conclusion.

And they were all wrong.

The problem with the thought experiment is quite simple, Schrodinger (and Einstein) were confusing "observing" and "measuring". It is not when humans observe a measurement that the wave function collapses, it is when we take the measurement. By putting the Geiger-Counter in the box, they included a measuring device which will collapse the radioactive decay probability. Even worse, Schrodinger included an observer, the cat. But even Einstein's bomb would either go off or not, as soon as the Geinger-Counter made its measurement!

And this happens every day. Scientists set up experiments, complete with the recording devices which scratch out results on reams of paper (or nowadays records results as ones and zeros in a computer). It might be hours or even days before any human looks at the results of these experiments, and nobody thinks that THIS IS THE MOMENT when the results are solidified. They were determined when they were measured, not when the measurement was observed.

Problem solved. I'm sure Bohr would have found this flaw, except he didn't want to. It conformed to his prejudices so he never examined it. And if you think this is a small matter, look at the Wiki entry for Schrodinger's Cat, there are many interpretations that attempt to deal with what is a flawed thought-experiment.

[licata]

Interesting. I swear you're a genius Swivel. You scare me. :)

[I am Legend]

maybe im just retarded but:

why does it matter in reality? put a cat in a box with a bomb, and when the bomb goes off, the cat dies, no matter who does or doesnt see it! proof? wait 2 weeks and open the box................2 week old dead and decayed cat.

it seems to me like a mental exercise that isnt really worth much in the real world.

[Alphonsus di Ligouri]

Never thought of it that way. But you're right Swivel. Now where's your Nobel Prize?:present:

[CPL CHUD]

I think the thought experiment appeals (at least to me) more to the idea that according to quantum mechanics there is a possibility of particles existing in multiple states and these states on a micro level become much more confusing when dealing with larger objects and thinking on a macro level; such as the cat being both dead and alive. The possibility that its atoms (the cat's) have a probability of being both dead and alive at the same time on a micro level challenges our thinking about the states of larger objects; especially if you presuppose there is no way to observe or measure what's going on with the cat while the box is closed (something you've got to take for granted).

I think that's the best lesson we can pull from the experiment, so in a way I don't think there is really any way to solve the experiment without first outmoding Heisenberg uncertainty, which I think is what these guys had a real problem with.

[swivel]

maybe im just retarded but:

why does it matter in reality? put a cat in a box with a bomb, and when the bomb goes off, the cat dies, no matter who does or doesnt see it! proof? wait 2 weeks and open the box................2 week old dead and decayed cat.

it seems to me like a mental exercise that isnt really worth much in the real world.

But that is just it, you can't tell if the bomb has gone off or not until you measure the state of the decaying atomic nucleus. For most people, that means opening the box and looking inside. My complaint is that the Geiger counter, which is part of the apparatus, constitutes a check on the system, a measurement, which resolves the quantum state of the atom, without the box ever needing to be opened.

[Waldowas]

[TheMorningStar]

What about things that cannot be measured? Things such as beauty. Anything that is subjective requires an observer.
A friend can say, "You have to see this chick. She is a 10!". Then you see a picture of her (open the box) and she is an 8 tops.
So too, applying Schrodinger's Cat to things like asking someone for a date is quite appropriate. Before you ask the person out, the answer is both "yes" and "no". The answer cannot be known without opening the box a.k.a. asking the question.