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Anyone hear of "Schroedinger's Cat"?


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#1 of 31 Ted Lee

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Posted November 26 2002 - 05:52 AM

are there any quantum physics people here?

if so, please explain this to me. i've done searches on google and read some good articles, but i still think i'm missing something.

okay, i get the experiment. you put some atomic material, a geiger counter rigged to a hammer, some poison in a glass container, and a cat in a box. if the atomic material decays, the geiger counter senses this and makes the hammer break the glass thereby killing the cat.

what's confusing me is the whole part about whether the cat is really alive or dead and how we don't know until we open the box? or is the cat in a parallel existence?

i think this whole experiment was originally designed to debunk the whole quantum physics thing, so maybe i'm not getting it because i'm not supposed to?

hmmm...

ps - i saw some cartoon on disney with a cat whose name was schroedinger. i thought that was pretty cool. Posted Image
 

#2 of 31 Patrick Sun

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Posted November 26 2002 - 06:04 AM

Isn't this the cat who walks through walls?
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#3 of 31 Ted Lee

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Posted November 26 2002 - 06:30 AM

hey patrick -

no...this has something to do with whether the cat really exists if we can't see it. again, i'm not real clear on the whole thing. :b

a quote from the following website: http://www.galactic-...icles/8R56.html

Quote:
....and the theories that go along with it, you can not determine what will happen, only the probability of a certain event occurring. Strangely, this event does not actually happen until you observe it.


so what i'm thinking is that the cat is neither alive nor dead until you *open* the box. that's what's kickin' my ass.

i think it's one of those "can you hear a tree fall if no one is there?" type of scenarios.
 

#4 of 31 Danny R

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Posted November 26 2002 - 07:01 AM

so what i'm thinking is that the cat is neither alive nor dead until you *open* the box. that's what's kickin' my ass.

Schroedinger originally included a hypothetical one paragraph example of his famous cat in the box in a paper describing the present state of Quantum Mechanics as of 1983.

The paragraph in question is as follows:
Quote:
One can even set up quite ridiculous cases. A cat is penned up in a steel chamber, along with the following device (which must be secured against direct interference by the cat): in a Geiger counter there is a tiny bit of radioactive substance, so small, that perhaps in the course of the hour one of the atoms decays, but also, with equal probability, perhaps none; if it happens, the counter tube discharges and through a relay releases a hammer which shatters a small flask of hydrocyanic acid. If one has left this entire system to itself for an hour, one would say that the cat still lives if meanwhile no atom has decayed. The psi-function of the entire system would express this by having in it the living and dead cat (pardon the expression) mixed or smeared out in equal parts.
The whole point of the mind experiment is to illustrate that the indeterminate and unknown state of the cat can be expressed with a single equation. The purpose of such equations is to describe the also unknown and indeterminate state of things like electron positions, which can't be accurately measured, but like the cat's predicament, can be described using equations. A lot has been made of Schroedinger's cat, but really other than this you are putting more into it than intended.
They found my psych results fit a certain profile. A certain "Moral flexibility" would be the best way to describe it....

#5 of 31 Joseph DeMartino

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Posted November 26 2002 - 07:03 AM

Quote:
so what i'm thinking is that the cat is neither alive nor dead until you *open* the box.

Rather, the cat is both alive and dead. Both probabilities exist until they collapse into a single outcome when the obeserver opens the box and sees the result. I don't pretend to understand this either, but that is the way it was explained to me. Posted Image This is connected to Heisenberg's uncertainty principle, and the notion that the observer always affects the object being observed, that the very act of observing is an event that affects the outcome. Schroedinger's thought experiment says that there is no outcome without the act of observation - both probabilities remain equally true until the box is opened.

I'm going to take an aspirin and lie down now. Posted Image

Regards,

Joe

#6 of 31 Ted Lee

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Posted November 26 2002 - 07:08 AM

ahh...thx joeseph. that actually sort-of-kind-of cleared it up - if you can believe that.

i did read that this was a cursory statement and has been pretty much blown way out of proportion, but it still piqued my curiosity.

guess i need to get the heisenberg compensator off the enterprise. Posted Image
 

#7 of 31 Joseph DeMartino

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Posted November 26 2002 - 07:32 AM

Quote:
ahh...thx joeseph. that actually sort-of-kind-of cleared it up - if you can believe that.


It did? I'm not sure which of us I'm most worried about. Posted Image

Regards,

Joe

#8 of 31 Phillip Larrabure

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Posted November 26 2002 - 08:13 AM

Quote:
...the notion that the observer always affects the object being observed, that the very act of observing is an event that affects the outcome.


If anyone is interested, check out this page. It discusses the "quantum eraser" experiment. It speaks directly to Joe's point. Very interesting experiment.

http://www.biols.sus....in/quantum.htm

#9 of 31 Ted Lee

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Posted November 26 2002 - 08:32 AM

cool read phillip -

i like that test with the photon light particles.

Quote:
It tunnelled through the barrier faster than the speed of light, in less than 3.6 femtoseconds. As the researchers put it, "it is as though the particle 'skipped' the bulk of the barrier". But don't ask them, or anyone else, what it means -- in the words of Richard Feynman, "nobody understands quantum mechanics"


Posted Image
 

#10 of 31 John Miles

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Posted November 26 2002 - 08:36 AM

(IBTL, before Jack Briggs locks the thread on grounds of probabilistic cruelty to cats)

#11 of 31 Vince Maskeeper

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Posted November 26 2002 - 09:03 AM

aaaaaaaaaaaarrrrrrrrrrrrrrrrggggggggggghhhhhhhhhhh ... high school physics. run away!

-thanks for the horrible memory.

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#12 of 31 Ted Lee

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Posted November 26 2002 - 09:09 AM

Posted Image [insert evil laugh here...] Posted Image
 

#13 of 31 Phillip Larrabure

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Posted November 26 2002 - 11:33 AM

Ted-

The "Faster than light" experiment is definitely cool. As I understand it, the result is undergoing further study. Until quantum mechanics is fully understood, the day I grow a third butt, gaining wide-spread acceptance requires a line of concurring results.

This experiment definitely tweaks the noggin. Does the particle speed up? Does it disintegrate and reappear? Does the medium alter the position's probability density which results in the accelerated time of arrival? In the quantum world, the first two questions probably make no sense. My mind can't help but be deterministic. Damn you Heisenberg.

I can determine one thing though. It makes me wish I was back in college.

Phil

#14 of 31 Joseph DeMartino

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Posted November 26 2002 - 11:51 AM

Here's another interesting article (that is way over my head. Posted Image)

Physicist throws Einstein for a loop

Regards,

Joe

#15 of 31 EricW

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Posted November 26 2002 - 06:06 PM

when i first saw the title of this thread, i was reminded of an issue of the comic book ANIMAL MAN by Grant Morrison i read years and years ago. i still remember it cuz it was pretty interesting. the example had to do with the cat in a box or something, and you don't know if it's alive or dead, but the act of opening the box would also either kill it or set it free. so when you don't know (box closed) the cat could be alive or dead, but the act of finding out also affects its fate.

that's how i remember it anyways Posted Image
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#16 of 31 Mark R O

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Posted November 26 2002 - 08:55 PM

Thanks for the links everyone. The article on event-enabling and cause/effect was great. The rather casual mention of String Theory was a serious flaw, but then the focus was on Quantum Mech's so benefit of the doubt goes to the author.
String Theory is moving us towards new forms of perception so profound that it may usher an evolution in mankind on the order cognitive thought. The math involved in unification is so far beyond my understanding that I'll never envision the mechanics. But isn't unification basically the answer that makes there be no such thing as a question? (ouch, that hurts my head every time..) Relativity and Quantum Theory are both attempts to write the one unifying equation aren't they? That's the best way I have to express it :b . Each one works until applied to the other, then glitches show up. Finally, both accept light as the universal speed limit. If it proves not to be, than it's all a bunch of bulls**t! Anyway, String Theory avoids all this. Worthwhile reading. Posted Image
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#17 of 31 Danny R

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Posted November 27 2002 - 12:37 AM

String Theory is moving us towards new forms of perception so profound that it may usher an evolution in mankind on the order cognitive thought.

The problem with string theory is that it is not background independent. Also while it unifies known fundamental physics, it has failed at Planck scale physics.

An alternate theory that doesn't have those limits is loop quantum gravity. Loop quantum gravity provides a vigorous explaination of physics at the Planck scale.

I'm betting however that both theories will merge, or one will be found to be a subset of the other.
They found my psych results fit a certain profile. A certain "Moral flexibility" would be the best way to describe it....

#18 of 31 Joe Szott

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Posted November 27 2002 - 06:22 AM

Ted,

I took some Quantum in college, and by no means understand it fully (and if anyone here says they do 99.999% chance they are lying Posted Image), but here is what I understood from S's cat:

As Ted said above, it is basically an equation about whether the cat is alive or dead. If we never open the box and there is a 50/50 chance each hour the cat will die, we can only ever estimate it's current state. For example:

hour 1 : alive 50%, dead 50%
hour 2: alive 25%, dead 75%
hour 3: alive 12.5%, dead 87.5%
hour 4: alive 6.25%, dead 93.75%
hour ...

So if we pop the top on the box at end of hour 4 and the cat is dead, we know for sure that it is now dead but we can never know exactly when it died. In hour 1, 2, 3, or 4? All we can do is formulate the % chance that it was alive/dead at any time, we can never know for sure exactly when it died (cuz the box was closed.)

If someone walked up to you and asked if the cat is alive or dead while the box is closed, what would you say (if 'I don't know' wasn't allowed)? You would have to say that there is a 6.25% chance it is alive and a 93.75% chance it is dead (if it was during hour 4). The cat isn't in a parallel universe or anything, but you can only give it's chances at any given time, you can't really confirm if it alive or dead without opening the box.

I know it seems a little silly, but with electrons it is like always having the cat in the box (or having a box that you cannot open.) You never know where exactly the elecron is, but you can assign % to each of it's possible states (or locations) and make a guess based on different situations.



#19 of 31 Ted Lee

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Posted November 27 2002 - 06:38 AM

that's a great example joe.

i didn't get any of how the forumla stuff was supposed to work, so that helped tremendously.

thx! Posted Image
 

#20 of 31 Alex Spindler

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Posted November 27 2002 - 06:51 AM

The part that I could never get was how this wasn't solvable empirically.

I "get" (read accept, but probably don't really understand) how the particle may or may not be decayed. I also "get" that the act of observation changes the result. But, doesn't the Geiger counter count as observation. By detecting decay, aren't you observing the side effect of the particle's state, and therefore determining its true state. Kind of just like opening the box and looking at the particle?

Also, by using a cat, you have a whole host of empirical data to determine what really happened. If you open the box and find the cat dead, you could check and see how long it was dead. The cat could also be talking and letting you know what its state was (alive or dead).

I think, distilled down, I just don't understand how the Geiger counter doesn't count as observing and thereby robbing the quantum particle's flexibility to be several things at once. Anyone able to help?


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