If you can read this, either the style sheet didn't load or you have an older browser that doesn't support style sheets. Try clearing your browser cache and refreshing the page.

(Science Daily)   A physicist may have figured out if that damned cat is alive or dead. Or maybe not   (sciencedaily.com) divider line 77
    More: Interesting, Schrodinger, caterpillars, quantum superposition, quantum physics, physical review, quantum states, American Physical Society, University of Arkansas  
•       •       •

4141 clicks; posted to Geek » on 26 Aug 2013 at 6:02 PM (1 year ago)   |  Favorite    |   share:  Share on Twitter share via Email Share on Facebook   more»



77 Comments   (+0 »)
   
View Voting Results: Smartest and Funniest

First | « | 1 | 2 | » | Last | Show all
 
2013-08-26 10:27:19 PM  

Quantum Apostrophe: You're all a bunch of Luddites. Science is just a bunch of ideas and stuff, and computers got better and a scientist was wrong once, so anything is possible.

Go back to your caves.


I'm fairly sure that the cat was meant to illustrate how stupid he thought QM was
 
2013-08-26 11:22:39 PM  

Donnchadha: It's really easy to know if the cat is alive or dead -- you look in the damn box.




Cat killer!

Maybe.
 
2013-08-26 11:33:10 PM  
But if this issue gets resolved, the Big Bang Theory writers will lose the source for 30% of their jokes.
 
2013-08-27 01:37:55 AM  

Felgraf: Quantum Apostrophe: Felgraf: Quantum Apostrophe: ou're all a bunch of Luddites. Science is just a bunch of ideas and stuff, and computers got better and a scientist was wrong once, so anything is possible.

Please seek help, anti-space-sphere.

How dare you? Clearly this story will lead to teleportation, free food and colonizing the universe. Oh, and "anti-space-sphere "? Is your Haloperidol past its best-by date?

Nah, probably won't lead to that. But it might, since atoms don't age, so immortality.

And by "Anti-space-sphere", I mean... just that. You are like the evil universe version of the Space Sphere from portal 2. You are obsessed with not-going to space. To the point where you rant about it in unrelated threads like this one.


Usually I can predict when Quantum Antitechnologist will show up... Story about potential 1-way trip to Mars? yep, he'll be there... Any mention of 3D printers? he'll definitely be there... but physicists playing with thought experiments? Nope, I did not expect to see him in here.
 
2013-08-27 02:05:36 AM  

LemSkroob: But if this issue gets resolved, the Big Bang Theory writers will lose the source for 30% of their jokes.


Some of which evoke laughter, and some of which, contrary to experimental results in the writers' room, do not.
 
2013-08-27 02:08:23 AM  
What if the measurement is made on Caturday?
 
2013-08-27 03:59:25 AM  
Actually, a cat locked in a box will be in THREE Quantum states at the same time (which would be determined when the box is opened), these states being Alive, Dead and Bloody Furious And Not Going To Take It Anymore.
 
2013-08-27 04:44:06 AM  

way south: Donnchadha: It's really easy to know if the cat is alive or dead -- you look in the damn box.

THAT IS NOT ALLOWED!!


Fine, then you balance the box on a two-by-four and blast an airhorn.  If the box falls off, the cat is alive.  My high school teacher acknowledged this would probably work except it's really only a metaphor.  In which case it's not a very good metaphor.
 
2013-08-27 05:06:45 AM  
It`s been in the box since 1930 or so. The damn thing is dead already!
 
2013-08-27 05:41:32 AM  

Yes please: Fine, then you balance the box on a two-by-four and blast an airhorn.  If the box falls off, the cat is alive.  My high school teacher acknowledged this would probably work except it's really only a metaphor.  In which case it's not a very good metaphor.


That would be considered measuring the state of the cat. Therefore It would have to resolve to either an alive or dead state at that point.

Opening the box is just the easiest way to measure the cat's state.
 
2013-08-27 05:47:12 AM  

ParanoidAgnostic: Yes please: Fine, then you balance the box on a two-by-four and blast an airhorn.  If the box falls off, the cat is alive.  My high school teacher acknowledged this would probably work except it's really only a metaphor.  In which case it's not a very good metaphor.

That would be considered measuring the state of the cat. Therefore It would have to resolve to either an alive or dead state at that point.

Opening the box is just the easiest way to measure the cat's state.


Fine.  It's still a stupid thought experiment.  The real question is, what does it matter if the cat is alive or dead?
 
2013-08-27 06:10:53 AM  

Yes please: ParanoidAgnostic: Yes please: Fine, then you balance the box on a two-by-four and blast an airhorn.  If the box falls off, the cat is alive.  My high school teacher acknowledged this would probably work except it's really only a metaphor.  In which case it's not a very good metaphor.

That would be considered measuring the state of the cat. Therefore It would have to resolve to either an alive or dead state at that point.

Opening the box is just the easiest way to measure the cat's state.

Fine.  It's still a stupid thought experiment.  The real question is, what does it matter if the cat is alive or dead?


Measuring the state of the cat is not the AIM of the thought experiment! The aim of it is to illustrate that, without measurement by a human eye (or instrumentation which can be considered an eye in this situation) the cat is both alive AND dead at the same time (according to Quantum mechanics), and ONLY through observation can it be one or the other.

The act of observing the thing places the "thing" (in this thought experiment represented by the cat) in one of the 2 categories, and not before. Thus the act of observing the thing changes the thing from Possibility to Reality.
 
2013-08-27 06:10:59 AM  

Yes please: ParanoidAgnostic: Yes please: Fine, then you balance the box on a two-by-four and blast an airhorn.  If the box falls off, the cat is alive.  My high school teacher acknowledged this would probably work except it's really only a metaphor.  In which case it's not a very good metaphor.

That would be considered measuring the state of the cat. Therefore It would have to resolve to either an alive or dead state at that point.

Opening the box is just the easiest way to measure the cat's state.

Fine.  It's still a stupid thought experiment.  The real question is, what does it matter if the cat is alive or dead?


It doesn't matter whether the cat is alive or dead. The issue is whether it is actually in one of those states before you observe it.

The thought experiment was intended to demonstrate how problematic a certain part of quantum mechanics is. That is that subatomic particles exist, not in a single state, but in a probability distribution of possible states. It's only when you observe (measure) their state that they actually resolve to a single state.

The set up of the experiment is that a macroscopic effect is the result of a single subatomic event. The argument is that, until observed, the macroscopic effect will also exist as a probability distribution of states. In this case, the cat would be simultaneously alive and dead.

A great deal of discussion around the idea has been framed in the terms of this thought experiment. For example, what exactly does it mean to be observed? Can the cat be considered an observer?
 
2013-08-27 06:32:42 AM  
That phenomenon must be taken into account to resolve the measurement problem, he said. That means with Schrodinger's cat, the cat is no longer predicted to be both dead and alive. It is instead dead if the nucleus decays, and alive if the nucleus does not decay, just as one would expect.

That's exactly what I thought the first time I read about Schrodinger's Cat when I was 8.  Would be funny if it was that simple.
 
2013-08-27 08:43:07 AM  
Hobson has resolved nothing and the "Schroedinger's Cat" is terrible as an analogy.  I hope Schroedinger lived long enough to regret ever coming up with that woefully inadequate Gedankenexperiment.
 
2013-08-27 08:53:48 AM  

Yes please: way south: Donnchadha: It's really easy to know if the cat is alive or dead -- you look in the damn box.

THAT IS NOT ALLOWED!!

Fine, then you balance the box on a two-by-four and blast an airhorn.  If the box falls off, the cat is alive.  My high school teacher acknowledged this would probably work except it's really only a metaphor.  In which case it's not a very good metaphor.


You aren't allowed to move the box, or touch the box, or even sniff the box to see if there is a dead cat inside (well, it should be dead anyway*.  I don't think you can keep a cat in a box indefinitely and we've been arguing about this for decades without putting fresh water inside. The stink has probably worn off but you can safely presume it surpassed "free cat" a while back).

The point is that you need to be able to guess if there is or isn't (or wasn't) a live cat inside without knowing or checking if there is (or was) a cat. Once you know then you know, and guessing is no longer necessary, but its the guess that matters.
...I think.
Wait, I'm confused now.

/*I'm assuming we're talking about the same cat in the same box and not a new cat every time this experiment is brought up.
/Otherwise science begins to sound like a dystopian solution to a feral cat infestation.
 
2013-08-27 09:07:37 AM  

Felgraf: Aye, the really twisted thing about the experiment (if I recall corectly), is that the only thing it *really* disproved was local hidden variable theory.

Which means, technically, one could still have a 'hidden variable' theory... but it would have to be a *non local* hidden variable, and trying to figure out how that would work makes my head hurt and there is a REASON I am an experimentalist, and not a theorist.


Absolutely. Many people overstate the implications of Bell as ruling out all hidden variable theories.

I suppose you could also retain locality and give up on realism, but I have even less of a mental picture of how that would work...

However, I think it is fair to say that whichever one you give up, it's clear that the world is definitely not classical (for any reasonable value of "classical").
 
2013-08-27 09:18:22 AM  

albatros183: I'm fairly sure that the cat was meant to illustrate how stupid he thought QM was


Almost. It was meant to remind his colleagues that the Copenhagen interpretation was only supposed to be a place holder for a profoundly difficult problem that would have to wait until they had sorted out some more fundamental problems, such as why the energy for the electron kept coming out wrong, and why there were two possible electron orbits instead of just one.

In other words, "we'll get back to you on the whole Explaining the Entire Universe thing after we've solved some more basic problems, like the existence of hydrogen atoms, and are more confident that we're on some sort of right track".

And then somehow, this placeholder got elevated to dogma even though everybody involved knew it couldn't possibly be more than an approximation that worked really well when neither theory nor experiment could probe the region between "a handful of particles" and the macroscopic world.
 
2013-08-27 09:48:16 AM  

czetie: Felgraf: Aye, the really twisted thing about the experiment (if I recall corectly), is that the only thing it *really* disproved was local hidden variable theory.

Which means, technically, one could still have a 'hidden variable' theory... but it would have to be a *non local* hidden variable, and trying to figure out how that would work makes my head hurt and there is a REASON I am an experimentalist, and not a theorist.

Absolutely. Many people overstate the implications of Bell as ruling out all hidden variable theories.

I suppose you could also retain locality and give up on realism, but I have even less of a mental picture of how that would work...

However, I think it is fair to say that whichever one you give up, it's clear that the world is definitely not classical (for any reasonable value of "classical").


And people say science removes the wonder from the world. I've always felt Physics helped me appreciated how truly flipping amazing and strange the universe is.

Then again, I am the kind of person that, undrugged, occasionally looks at the tendons on the back of my hand with mild amazement, because, just, holy shiat.


Yeaaaaahhh I'm probably a bit cracked in the head.

Though, I'm a physicist, so I suspect that's a given.
 
2013-08-27 09:59:42 AM  

ParanoidAgnostic: Yes please: ParanoidAgnostic: Yes please: Fine, then you balance the box on a two-by-four and blast an airhorn.  If the box falls off, the cat is alive.  My high school teacher acknowledged this would probably work except it's really only a metaphor.  In which case it's not a very good metaphor.

That would be considered measuring the state of the cat. Therefore It would have to resolve to either an alive or dead state at that point.

Opening the box is just the easiest way to measure the cat's state.

Fine.  It's still a stupid thought experiment.  The real question is, what does it matter if the cat is alive or dead?

It doesn't matter whether the cat is alive or dead. The issue is whether it is actually in one of those states before you observe it.

The thought experiment was intended to demonstrate how problematic a certain part of quantum mechanics is. That is that subatomic particles exist, not in a single state, but in a probability distribution of possible states. It's only when you observe (measure) their state that they actually resolve to a single state.

The set up of the experiment is that a macroscopic effect is the result of a single subatomic event. The argument is that, until observed, the macroscopic effect will also exist as a probability distribution of states. In this case, the cat would be simultaneously alive and dead.

A great deal of discussion around the idea has been framed in the terms of this thought experiment. For example, what exactly does it mean to be observed? Can the cat be considered an observer?


There are several reasons it's a bad analogy. One is that it defines the entire system based on the state of a single particle. Another is that it's actually not true, even from a quantum physics perspective. The cat isn't both dead and alive. There exists a probability that the cat it's dead and a probability that the cat is alive, and it's those probabilities that really define the system.
 
2013-08-27 10:22:26 AM  

SansNeural: Hobson has resolved nothing and the "Schroedinger's Cat" is terrible as an analogy.  I hope Schroedinger lived long enough to regret ever coming up with that woefully inadequate Gedankenexperiment.


You do realize that the point of  Schroedinger's Catwas to poke fun at the craziness it caused?  It wasn't trying to prove anything other than the absurdity of one particular interpretation of quantum physics.

He was very successful!
 
2013-08-27 10:53:45 AM  
The thought experiment only works if the box is sealed, so depending on how long you leave the cat in there, the cat is in a superposition of two different kinds of dead.
 
2013-08-27 12:43:11 PM  
Yes please, it's not an analogy, it's a thought experiment.  All the cat does is provide a macroscopic indicator or a quantum level event.
My favorite of the two Bell's Theorems isn't his inequality, which suggests that any hidden variables are non-local, but the Bell Kochen-Specker theorem which suggests that hidden variables are non-contextual. The reason I like it is because in 1994 I read the paper by N. David Mermin: Hidden Variables and the two theorems of John Bell, as well as the John Conway proof of the Kochen-Specker theorem and my mind was blown.  Love that stuff.
 
2013-08-27 12:44:45 PM  
http://www.science20.com/hammock_physicist/quantum_casino_less_zero_c h ance-95615
I haven't seen this approach.  Negative probability is a very odd concept.
 
2013-08-27 05:45:33 PM  
Does the cat continue to consume half of it's normal food and water per day while in the box until you open it up at which point it eats all or none of it?
 
2013-08-27 08:50:46 PM  

Yes please: One is that it defines the entire system based on the state of a single particle


That was the point.

It's saying:

1) If a subatomic particle has no real state until observed
2) And a situation is created in which a macroscopic state is the result of only the state of that particle
3) Then the macroscopic state is also not resolved until observed.

The argument was that 3 is ridiculous and a (rather impractical) method is described to satisfy 2. Therefore 1 is wrong.

It didn't quite win the argument but became a useful way to frame some further arguments about 1... at least in the absence of lots of maths.
 
2013-08-28 03:20:34 AM  

czetie: There's no getting away from the weirdness of QM, regardless of what interpretation you prefer. It just does things that have no classical analogy. If you're looking for a satisfying resolution to the underlying weirdness, well, you will have to get used to disappointment.


"The theory of quantum electrodynamics describes Nature as absurd from the point of view of common sense. And it agrees fully with experiment. So I hope you can accept Nature as She is - absurd."
 
Displayed 27 of 77 comments

First | « | 1 | 2 | » | Last | Show all

View Voting Results: Smartest and Funniest


This thread is closed to new comments.

Continue Farking
Submit a Link »
On Twitter





In Other Media


  1. Links are submitted by members of the Fark community.

  2. When community members submit a link, they also write a custom headline for the story.

  3. Other Farkers comment on the links. This is the number of comments. Click here to read them.

  4. Click here to submit a link.

Report