patrick.net

See this old post.

Executive Summary

The Heisenberg Uncertainty Principle says that the value of any property of a quantum object cannot be know with zero error, i.e., there is always some uncertainty in in actual value. The Heisenberg Uncertainty Formulas are

Δx Δp > h / 2
Δx is the change in a particle's position or displacement.
Δp is the change in the particle's momentum.
h is the Planck constant, 6.62606957 x 10^-34 J s

All this formula says is that the product of the change in displacement and the change in momentum is greater than a certain constant value, which implies if you try to measure either the displacement or the momentum, you can only do so within a certain error.

The Copenhagen Interpretation is a philosophical, not physics, school of thought that says because the value of the property can only be estimated to within a range (the maximum error), the property actually assumes all values within that range.

The Schrödinger's Cat thought experiment refutes the Copenhagen Interpretation by showing how ridiculous it is when applied to the real world. It takes a binary property, whether or not a radioactive particle has decayed, and converts it into a macroscopic property, whether a cat is dead or alive. If the quantum property actually can take on both states at once, so two must the cat, but that's impossible and ridiculous and no one would believe it.

Advocates of the Copenhagen Interpretation tried to bullshit their way out of this by saying that as soon as the radioactive decay is observed by the sensor, the quantum property "collapses" to one specific value. But if that actually did happen in the physical world, the Copenhagen Interpretation would be meaningless anyway as it could never have any affect on anything.

freak80 says

Wasn't it just a "thought experiment" and not a real experiment?

Only because it would be unethical to run the experiment in real life. Newton's two bricks falling at the same time was a thought experiment as well. Thought experiments serve to show flows in logic and reasoning.

Dan Simmons' excellent "Hyperion" series uses a narrator who is stuck in a Schroedinger "cat box" and sentenced to die when a particle decays and the cyanide is released.

freak80 says

Wait wasn't this topic already discussed ad nauseam in another thread?

It was discussed in another thread. Heraclitusstudent proposed the subject, even though it was off topic, and seemed to disagree with Dan's comment:

Heraclitusstudent says

The MWI states there are 2 overlapping quantum states that encompass the entire cat, both have an objective reality, and that is what we are talking about: the quantum properties extend to macro objects... The only thing that is asserted and that can be empirically verified is that if you open the box, then, to you as an observer, it will appear like the dice is thrown and either the cat is alive or the cat is dead. What you think happened in-between (or after) is just interpretations not physics.

It is the topic of this thread, so as far as I'm concerned, others more knowledgeable than I can have at it. So far, I think Dan's interpretation more persuasive, i.e. the point of the thought experiment is to reduce to absurdity the Copenhagen Interpretation.

That a particle can exist in 2 states is the only way to explain certain observations.
But whether the cat can be in 2 states is just an interpretation that has no practical consequence. By the time it reaches someone's brain, the dice is cast one way or the other. This is just philosophy.

If you consider science an ever expanding reservoir of knowledge on the world around us - and consequently the remaining unknowns and superstitions an ever shrinking knowledge gap - it's very reassuring but it assumes that there is a tangible world around us that is independent of the observer. Unfortunately quantum mechanics puts you in the uncomfortable situation where the result of an experiment depends on what is measured. An observation 'collapses' a wave function. From there, some will jump to say human consciousness 'creates' the world, something that evokes Hindu mythology. That can't go very far because of the randomness of results, but in a way they have a right to raise the issue.

There is an interpretation that doesn't require a collapse of the wave function. If the 2 states exist in whatever is impacted. That extends to the observer's eyes and neurons. Then the observer's brain itself will exist in 2 states. And we are just one of these states and we observe only 1 branch. In some other state of the world the observer sees something else. So it sweeps under the carpet the uncomfortable notion of observer dependency.

It remains that science can only be based on observation and speculating on the existence of other states that we can't observe is not science. As far as science goes, observation causes collapse. And observation is always decided by a human being. You're left with a probability. And that's all there is to it.

Heraclitusstudent says

You're left with a probability. And that's all there is to it.

I hope there's more to it than that. As my statistics professor used to say: "Ultimately, all probabilities resolve to either zero or one, because something either happens or it doesn't." To posit a universe of macro-level uncertainty, or even a multi-verse, goes in the opposite direction of Occam's razor. I understand that the MWI can't currently be disproved, but I question whether things are in fact that complicated, with an infinite number of cats in an infinite number of boxes, and an infinite number of brains each embodying a slightly different collection of thoughts and every other possibility.

If you buy a lottery ticket, MWI would suggest that in an infinite number of universes you bought a losing ticket, yet in an infinite (and yet paradoxically smaller) number of universes you bought the winning ticket. Somehow, in this universe, most people find out within a few days that they lost, i.e. their probability of winning resolved from a small number to zero.

curious2 says

the MWI can't currently be disproved

Neither can the theory that we're all living in a computer simulation (like in The Matrix movie).

Such an idea is "not even wrong."

curious2 says

To posit a universe of macro-level uncertainty, or even a multi-verse, goes in the opposite direction of Occam's razor.

The uncertainty is there for sure for a particle decay. If you make the life of a cat depend on it, then you have the same uncertainty for the life of the cat. So there you have uncertainty at the macro level.
Logically that can't be avoided.

Heraclitusstudent says

From there, some will jump to say human consciousness 'creates' the world, something that evokes Hindu mythology.

Uh oh...I detect me some Quantum Woo...

Heraclitusstudent says

The uncertainty is there for sure for a particle decay. If you make the life of a cat depend on it, then you have the same uncertainty for the life of the cat.

One of my favorite professors is Paul Hewitt, whom I've only ever seen on TV and YouTube, and read. He taught Conceptual Physics, literally wrote the book on it, which made him quite wealthy, though he continued teaching at CCSF. In addition, he opined about philosophy, and one of my favorite observations was how he described past theories that seem, in retrospect, stupid. The people who developed those theories were not stupid, to the contrary they were brilliant, but they lacked the right framework on which to build their ideas. They lacked a tool that might have enabled them to see better, e.g. a telescope, or a community with a more accurate intellectual understanding. As Newton said, "If I have seen further it is by standing on the shoulders of Giants."

I love the Antikythera mechanism, attributed to Archimides, because it produced such an accurate depiction of the moon and sun and observable planets, despite the now disproved assumption of a geocentric solar system. Someday, the Copenhagen Interpretation and the philosophy of string theory may seem like geocentrism, we just can't see how yet.

Dan8267 says

See this old post.

Executive Summary

Dan8267 says

Advocates of the Copenhagen Interpretation tried to bullshit their way out of this by saying that as soon as the radioactive decay is observed by the sensor, the quantum property "collapses" to one specific value. But if that actually did happen in the physical world, the Copenhagen Interpretation would be meaningless anyway as it could never have any affect on anything.

Thanks for that (everyone else too). So, basically Schroedinger was trying to show how Copenhagen was wrong by using the cat in this Rube Goldberg type experiment to show them the error?

And that everyone who quotes it nowadays is probably quoting it wrongly, most likely due to their professors misquoting it and so on?

That would explain why every time I tried to wrap my head around it, it always came up lacking something.

I bet if you were to bounce Schroedinger's dead cat, when it came to it's final resting place. It would jump up and say "Ta-dah!".

More details on the Copenhagen interpretation here:
http://en.wikipedia.org
/wiki/Copenhagen_interpretation#Consequences

There are different variations of it, but basically they all include a notion of wave function collapse caused by a measurement. As such it gives central importance to the measurement process but fails to define it clearly or to explain its effects.

There is a spectrum of what people will accept as measurement, whether it's just interaction with an other particle or a larger apparatus or only human consciousness, thereby raising Schrödinger's question. But we can only register a measurement if we eventually become aware of the result, so eventually it all comes down to human knowledge, and at that point the transition from the possible to the actual has been done. And so the description works in that way.

In general the interpretation denies that the wave function is anything more than a mathematical abstraction that describes our knowledge of something, rather than a 'real' entity. (By itself I find this distinction suspect since all equations in physics represent knowledge, and knowledge of the world is self-evidently not the same as the real world or objects in the real world.)

In any case this interpretation remains one of the most widely accepted among physicists. One alternative being the 'Many Worlds Interpretation' which gets rid of the need of a collapse by including the observer in the experiment.

All this illustrates we can't ultimately separate a description of the world from a description of the nature of our knowledge of this world - considering we are part of this world.

The thought experiment is a method of explaining the behavior of unfamiliar quantum objects, using a familiar macro object as a metaphor. Of course it is absurd for a cat to simultaneously exist as alive AND dead. I've always understood Shroedinger's Cat as a way of explaining the strange observed behavior of quanta. Like most metaphors, this falls apart if you try to take it literally.

AF's cat

Bop69's cat

odi ergo sum

If a blind person doesn't know whether it's light or dark, is the cat alive or dead?

nothing exists until it is observed. so the cat is neither dead nor alive.

the moment someone looks at it, then it is either dead or alive. there is nothing wrong with it.

Mark D says

nothing exists until it is observed.

I can't see you. Are you there?

Don't worry: the NSA has Total Information Awareness, ensuring that everything in the multiverse is carefully observed and recorded, and therefore exists. Your tax dollars at work, securing your existence, now and for all time.

Mark D says

it is either dead or alive. there is nothing wrong with it.

Veterinarian: Your cat is dead. There is nothing wrong with your cat.
Customer: What should we feed our cat?

Meow!

Wow this is sure making my head spin, too much pussy science for one night!

Antonia's cat's name is See See.

Schrödinger's cat's name is Bill.

Actually dude that is Bill the Cat from Bloom County. I like this one better:

And you forgot the crazy Penguin too

SJ says

And you forgot the crazy Penguin too

I could never forget Opus! He just isn't a cat. This is a cat thread, so he is off topic.

Start a thread about penguins if you want to comment about Opus.

Maybe Schrodingers cat is making realtards rich like this:

Or making SD's cat is taking a dump on the taxpayers?

Steve Dallas is the realtard shown above and Bill (S's cat) is screwing the people with high RBA home prices!

@Patrick, spam link no longer shows. Threw some spam in ad hom.