h2g2 The Hitchhiker's Guide to the Galaxy: Earth Edition

Your entry begins:

"If a tree falls in the forest
and no one's there to hear it,
does it make a sound?"

That is the gist of this experiment once you strip it
of all its contrivances. Erwin Shrödinger's original
intention in creating this puzzle was to point out
the absurdity of quantum physics, namely that the
state of a particle is dependant on whether anyone
is watching it or not.

Regardless of Schrödinger's intention, it has always been my understanding that this is the nub of quantum mechanics. Counter-intuitive though it may be, the cat in the thought experiment really *is* in a state that is neither life nor death, but somewhere in between.

The cat emerges from this in-between state only when it is observed and the probability function collapses. Only then does it assume a more intuitive state: alive or dead.

I acknowledge the similarity with the noise made by the unobserved tree falling, but I think this is a side issue by comparison.

Oddly enough, although the alive-AND-dead state seems counter-intuitive, it's not as odd as you might think. [Bear with me for a paragraph or two; I hope what I'm getting at will become clear.]

Assumption: *objective* perception is impossible for a human being.

Therefore, although we can easily formulate objective hypotheses, we have no means to (objectively) confirm their correctness (or not). The pursuit of *objective* knowledge is therefore pointless for a human being - we can never verify it. [The pursuit of *knowledge* is not at all pointless, IMO.]

Our perceptions are unavoidably subjective - so there is a probability that any given human perception is objectively accurate. When I see the famous slogan "Don't panic", my perception that it is rendered in large friendly pink letters has a probability (somewhere between zero and one) of being correct.

Back to the cat: if you remember, it spends most of the experiment in the alive-AND-dead state. That is, there is a probability (somewhere between zero and one) that it is alive.

The two situations are not identical, I concede, but you can see the similarity, can't you?

Food for thought, courtesy of the Pattern-chaser.

Assumption: *objective* perception is impossible for a human being.

I agree. Everything a person experiences is unique to that person--DNA said something like that in "Mostly Harmless" didn't he?

Personally, I think the tree and the cat are remarkable similar problems. Schrödinger was trying to proove that it was ridiculous for the particular universe to behave in accordance to who was watching. To him, an electron was an electron and therefore had a defined, mathematical way of acting that in no way involved all that mucking about with human intervention. The cat should, he reasoned, die or live regardless of whether it was alone or not.

Now, back to the tree.
If it falls, does it make a sound? Well, it depends on how you define the universe. If the universe is everything that exsists and the sum total of all its reactions, there is no reason to believe that it behaves any differently without an observer.

That's what Schrödiger would say.

The other interpretation is that the universe is the sum total of a person's five (ok, some say six) senses and everythign they've learned--everything that affects them, and everything they know. Therefore, becasue the tree crashing to the ground didn't affect the person because they didn't experience it and didn't know it fell, in which case, it didn't make a sound.

That would be what, say, Richard Feynman would say.

Maybe I'm missing something (and feel free to post a rebuttal) but I see the two circumstances as exact parallels as far as either thought experiement is concerned. Tree, cat, whatever. They're saying, at least to me, the same thing.

Please elucidate your point, I'm quite curious as to what you mean.

Triv

Triv said "Please elucidate your point, I'm quite curious as to what you mean", but I thought I just did!

I acknowledge the similarity you observe between the cat and the tree. I wanted to discuss the quantum-derived aliveANDdead state, which I find fascinating. And I did/have. That's it. I'm unsure *what* to elucidate. Sorry.

Pattern-chaser

Ok, let me try this again.

The 'nub of quantum physics' as you put it, has little to do with the cat, really. The purpose of the cat is subsidiary to the behavior of the electron that kills or spares it. We can't SEE electrons under normal circumstances, therefore we must make it effect (or not) something else so we can see how the electron
behaves.

Electrons are indecisive little buggers.

We can see a cat. So, by observing whether the cat is alive or dead, we can deduce where the electron was inside the box. Until we take a blowtorch to the chamber, the cat is 50% alive and 50%dead, but all this really means is that the electron has even odds of being in one side of the box or another.

this superposition of states is the part that defies common sense and yet WORKS as the basis for quantum physics, and is what interested you, as far as I can tell.

Ok. But it's the rest of your post that I didn't understand. The chance of the electron being in one side of the box as opposed to the other is almost exactly 50%--it's actually very slightly less; there's the probability that the electron won't be in the room or the box at all, that it will appear somewhere else in the universe, but it's so unlikely that it doesn't factor into the experiment much. the experiment isn't subjective at all--it's not designed to be. if it were objective it'd never end because, as you say, we don't view anything from an objective standpoint and we'd never be able to open the box. Or rather, if we DID open it from a position of aboslute objectiviity the electron would never decide whether to kill the cat or not.

Ok, is it me, or did I just agree with you? I'm a little confused...

Triv

Note: there has been a potential resolution of this thing...

the idea is that waveforms spontaneously collapse. but it's very unlikely, per proton.

However, when a large object, like a human, observes (IE, is effected by) something, then the large number of photons in our bodies ensure that it collapses very fast.

In which case, the cat would beeither alive, or dead, but not both - the wave would collapse very fast, since cats are large.

Now, how does this tie into quantum physics? I'm extremely iffy here... any reccommended reading? I'm just getting into a book by Feynman.

Recommended reading. Yes. Go get ANYTHING by Brian Greene, and "Schrödinger's Kittens and the Search for Reality" by John Gribbin.

The kittens will be the subject of another guide entry rather soon, I think...it puts an interesting spin on the problem.

Triv

"The kittens will be the subject of another guide entry rather soon, I think...it puts an interesting spin on the problem."

Ooooh, do tell, Master of Sacred Signposts.

Pattern-chaser

Ok. Here we go. I appologize for the delay but I've had to organize this.

So. You take a cylinder and design it much in the same way as you designed the box with the electron trapped in it in the previous experiment--there's a partition that drops down the center and makes the probability of the electron being in either half of the tube 50/50. There is a chamber at each end of the cylinder, separated from the tube by another door, and in each chamber there is...a cat. In EACH chamber is a diabolical device that will kill the cat if it detects the electron. Tada.

This entire contraption is a satellite in orbit of the earth. The satellite is designed so that, once the central partition is dropped, it can seperate in half creating two satellites, each with a diablical device and a cat. One of the two satellites has an electron and the ultimate end of the life of one of the cats.

So, the experiment progesses like this: The doors at either end of the cylinder start the experiment closed, isolating the electron from the cats. The partition is dropped, creating the famous 50/50 shot. The doors isolating the chambers from the electrons are opened. The satellite is seperated into two independant satellites.

Ok. So using some for of engine, we send these two satellites to, say, opposite sides of the universe at near light speed. Where they end up is immaterial, provided they are a significant distance from each other.

Let's say one of the capsules is discovered by an advanced race and they open up the capsule and find a live cat. That means that other cat MUST be in the opposite state (dead) and its waveform, on the opposite side of the galaxy, collapses at exactly the same instant in time.

That means that whatever impulse was carried form one cat to the other happened instantaneously. According to Einstein there are NO instantenious cause/effect relationships in the universe and that therefore the impulse must have travelled FASTER THAN THE SPEED OF LIGHT.



I thnk it's a cute illustration and brings up some interesting questions about locality/nonlocality. Feel free to pick it apart.

Triv

A similar experiment has been done, although it involved determining the polarity of photon pairs instead of killing cats. ASCPA and all. The upshot of the expriment? The universe appears to be non-local. Cheers!

You realize what this means, eh? Non-locality means that we can send information from one place to another faster than light speed.

This doesn't help a lot right now, but wait until we send a space probe beyond our solar system.

See, even commanding the Mars probe is quite slow. There's a delay of several seconds, since it takes that long for the light-speed radio signals to travel to Mars. Also, the radio signal gets a bit of interference as well.

The way to use instantaneous waveform collapse is by pairing electrons this way. If one splits an atom (it's been done) and separates the electrons from that same atom (it's been done), and changes the spin on one atom (by collapsing the waveform of its spin by measuring the spin, then somehow changing the spin -- I'm not a physicist [yet]; I don't know how), the other electron's spin will switch as well (yes, that has been done).

The tricky part is making it cheap, or at least not the expensive universities-and-governments-and-big-honking-corporations-only operation it is now. Splitting the atoms and changing the electron spins, that is.

Anyone want to put this in an entry?

Everything living is technically aliveANDdead at all times, with cells constantly dying and being born. Add to this fact that all our known physical laws completely break down and fail on the sub-atomic level and the whole argument becomes a moot point at best.

I'd also like to add an anarchists view to the Schroedingers cat and if a tree falls argument. Drop a five ton weight on the box, then burn the tree and chuck the flattened box on top of it.
~S

Just thought you guys'd like to know--according to the guys over at slashdot, IBM has developed a Quantum computer.

The article's here:

[Broken link removed by Moderator]

Have fun with it.

Triv