Gabriel Syme

I was discussing Schrodinger's Cat with a friend at school, and I realized I don't really understand it. First of all, my friend brought up a seemingly valid point, why isn't the cat considered an observer to its own existence (If the cat doesn't die, doesn't the cat know this, and why doesn't this collapse the waveform). Also, do quantum theory and the superposition of binary states (did I just make that up?) make any testable predictions about the universe? It seems similar to me to a book I read called Permutation City, by Greg Egan, in which computer models of people live in virtual reality surroundings; only the objects they observe are actually rendered to save processor power, but they can never know this from within the program. The fact that the cat is alive and dead until someone sees it seems at best a distinction without a difference, and at worst a baseless complication. Would someone straighten me out?

--
Gabriel Syme
"You wish to abolish government?"
"To abolish God!"

Francois Tremblay

No, I agree completely.

Ernest Sparks

I like what Professors Murray Gell-Mann and Jim Hartle have to say about quantum principles. In a lecture at UCSB ITP in 1999, Gell-Mann said (something like): "When a horse race is ready to begin, nobody knows which horse is going to win. But when one of the horses actually comes in first place, nobody talks about a wave function collapsing."

Below is a link to an audio file of Gell-Mann's talk. NOTE: I get lost when he gets into fine and coarse grained histories and operators. But listen to the end of the session. It's fun!

<a href="http://online.itp.ucsb.edu/online/hartle_c99/gellmann/" target="_blank">Quantum Mechanics and the Familiar Quasiclassical World - Murray Gell-Mann, Santa Fe Institute</a>

Ernie

[ March 10, 2002: Message edited by: Ernest Sparks ]</p>

Bill

It is a thought experiment. Since it isn't a real cat, but only a hypothetical cat, it can't observe itself.....

This is the whole problem with trying to put some of the most confusing aspects of Quantum Mechanics into terms that an ordinary person might understand.....

== Bill

LeftCoast

Wasn't it Feynman who said something to the effect of "If you're not confused by Quantum Mechanics, you just don't understand it"?

LeftCoast

As Bill pointed out, the cat is just a thought experiment used to illustrate the concept of superposition of states; no reason why they have to be binary, however, a wave function can have many possible simultaneous solutions.

It's been a loooong time since my last QM course, but QM makes many testable predictions, since just about everything we understand about things like lasers, silicon chips, chemistry, the behavior of particles in the big accelerators is not understandable at all without quantum mechanics and it's derivatives.

Jesse

The theory of quantum mechanics says nothing about what the cat is "really" doing before you observe it. It just says that you should model the cat as being in a superposition of states if you want to get accurate predictions about what will happen when you make a measurement of the cat's state (this is assuming the cat is totally isolated from the external environment, which would actually be impossible in practice for such a large object).

Various interpretations of quantum mechanics try to imagine what's "really" going on in between measurements, but none of these interpretations are part of the "official" theory, nor do they make any new predictions (so they're all unfalsifiable). I ran through these interpretations on the thread <a href="http://iidb.org/cgi-bin/ultimatebb.cgi?ubb=get_topic&f=57&t=000110" target="_blank">Problems with quantum theory</a>, if you're interested.

Corwin

Now, I have to admit, I love physics in general.... but I have to ask....

Did anyone else just have flashbacks to Economics 101?

liquid

Quantum mechanics is actually the proud holder of the record for the best agreement between theory and experimental evidence ever found, so it is (quantitavely) the best model of our universe yet, and eminently falsifiable.

For more information, look at <a href="http://www.lassp.cornell.edu/sethna/Cracks/QED.html" target="_blank">this!</a>

Corey Hammer

Also, let's say for argument's sake, that QM is not falsifiable. Because it makes testable predications, it is still valid. Falsifiability is nice, but no longer necessary according to the philosophy of science.