Well, golly gee! Other forums on this board *do* exist! (And I realize this thread's a few days old, but I was Summoned, and I find the subject interesting, so anyone who's done with it don't mind me...)
[disclaimer] IANAQP [/disclaimer]
Abunai! wrote:
I've heard that it is that an atom has a chance to be somewhere else at the same time. But I've also heard that it is simaltaneously there, and not there. Leading to a debate about another physicist's cat. Damn all these cats.
Heh. I wouldn't take Schroedinger's cat analogy too seriously. I don't know of any physicists who do. Besides, the cat is observing itself anyway :)
Basically, in quantum physics you can determine the *probability* of certain things happening (to a high degree of certainty, in fact) but never know for sure ahead of time which possibility will come true (I'm simplifying, I know, but this gives the general gist). So if I have a photon cannon that shoots out a single photon, it will most likely continue in a straight line until it hits the wall. There is also a small possibility that it will fly off in an unlikely direction, go back in time, or do loop-the-loops. The probability of that is miniscule enough that you can be pretty sure your flashlight beam is never going to do a U-turn and shine back in your face.
To my knowledge, there are two main (competing) interpretations of quantum uncertainty. The usual one, known as the Copenhagen interpretation, basically says that that state of a system is indeterminate until observed, at which point the wave function collapses and one of the possible states of the system becomes manifest (with the probability of which state it will be well understood ahead of time). This version may make the math come out right, but I've always found it annoyingly solipsistic in nature. The interpretation I prefer myself is the so-called "many-worlds" version, in which *every* possibility becomes manifest, just in a different quantum universe. (Good FAQ on it
here). In most cases, the various interpretations come out to looking the same from our point of view, but there are some subtle differences that may lead the way to determining which is the "correct" one.
Abunai! wrote:
Before quantum theory, everything was deteriminist. Meaning, every action had only one logical reaction that could follow, if you knew everything involved. For instance, you let go of a ball. Assuming no outside forces were involved, it drops pretty much straight to the ground. But with quantum randomness, there is a very tiny chance that all it's atoms could appear somewhere else.
While it's true that there's a slim chance that some of its individual atoms could take a less-likely path and end up somewhere else, the chance of *all* of the ball's atoms doing so at once are so miniscule that I'm pretty sure such an event would be unprecedented in the history of the universe. In other words, if you throw a ball to someone and it goes wide, it's your own damn fault :)
While we're on the subject, I'd like to note, for Pratchett fans, that his books are full of references to quantum mechanics, particularly where the high-energy magic department of the Unseen University is involved. I remember seeing a direct reference to the many-worlds theorem in the one where Granny Weatherwax is talking to the Dean. Hell, my current sig is a reference to quantum uncertainty (I'm curious- how many of you got that? I'm thinking about changing it...)
Abunai! wrote:
Argh, my physics knowledge is too small. Wandering Idiot, come here and tell us about particle theory and fluid theory, and all those fun things!
I know nothing about fluid theory except that the math is nasty, so it's best left to computers to figure out. And that you can use simplified versions of the equations to make cool Winamp visualizations.
IcyMonkey wrote:
I assume what creeps you out about determinism is the "no free will" thing. But Quantum Physics doesn't actually solve the problem of free will. I mean, a slot machine has no more free will than a clock. The output the brain produces is dependent on two things: a) the input, and b) random quantum chance. I don't see where free will enters into this.
[snip]
Free will, to me, seems like way too metaphysical a concept to be included in any scientific discussion of the world. Of course, we still need to pretend free will exists. After all, our entire society is based on the idea of responsibility and blame, and without the idea of free will these concepts are empty.
Heck, If you want to be *really* pedantic about it, the input, i.e. the outside world, is also determined by random chance, so there's really only one value to worry about (although one could argue about interference from "outside the system" like god(s), advanced aliens entities from other universes, etc.) Of course, this gets into cosmology, which is a decidedly speculative field.
The way I've always liked to think about it is, even in a deterministic universe, the future may be set, but it's our actions which choose what that future is. Semantics, sure, but arguably, I had no choice but to type that just now :P
Abunai! wrote:
I guess it boils down to a definition of the fuzzy term, "consciousness." It is a meaningless bullshit term, but that doesn't preclude something like it existing.
It's not a meaningless term, but it is a bit fuzzy. Consciousness is an emergent property of certain very complex systems (i.e., the brain, or a very advanced hypothetical computer program). Now, if you understood a complete working model of a human brain and nervous system, down to the neuron level, there would be no need for a high-level term like "consciousness". You would understand all the workings of the brain, and the various neurological feedback loops that underlie what we call "consciousness" at the base level. The problem is that such a model is simply impossible for a human mind to comprehend fully, by definition. You can't fully understand a fine-grained model of your own brain, because that gets you into a nasty Godelian loop where your brain has to be bigger than itself. So we come up with a term like "conscious" to describe a certain class of phenomena, which gains in practicality what it loses in exactness. I imagine a superintelligence (alien, future computer, god, take your pick) would be able to comprehend fine-grained models of human brains just fine, and would thus have a far better idea of the actual neurological processes involved. Note that this means that humans are not fully conscious, since we can't understand the working of our own minds (In fact, I don't see how *any* intelligence, no matter how advanced, could be, since a more complex intelligence would still be susceptible to the same Godelian loop). As a final note, I regard it as a mistake to classify entities simply as "conscious" or not- there are varying levels of consciousness. Think of it in terms of a linear progression. At one end are rocks, gases, etc. Further along are things which react to the world via simple feedback mechanisms, like plants which bend towards the light. Then the lower animals, like tapeworms, continuing up through the higher vertebrates, with humans at the farthest end, and any hypothetical super-conscious superintelligences beyond them. I regard this more/less consciousness continuum, as I like to call it, as a useful tool for ethical analysis, since we'll probably be dealing with sentient AI's and such before too long.
The best book I've ever read on the subject of "what is consciousness?" is Douglas Hofstadter's
Gödel, Escher, Bach. You are all hereby ordered to read it (and nevermind the somewhat dull bit of typographical manipulation in the first chapter, which Amazon inexplicably chose for their sample pages).
To make a comment on the *original* topic (poor Unum, thread hijacked at the second post...) I believe people believe in luck for the same reason people believe in a lot of things- they're trying to make sense of the world. Pattern-finding and grouping are some of the deepest and most-used capabilities of our brains, and are vastly important, but using them has its drawbacks. Just as we use the term "consciousness" to denote a phenomenon that is too complex to really understand, so some people use the term "luck" to talk about sets of statistically unlikely occurrences. The problem comes when you "confuse the map and the territory", so to speak, and think of the shorthand concept as being divorced from its more complex true nature. When I use the term "consciousness", I do so with the awareness that it's merely a handy identifier for a complex system based on the interaction of billions of neurons. Some people, however, view it as its own thing, something which can thus be divorced from the underlying physical system, i.e. a "soul". (Now certainly, it should be possible to transfer consciousness from one physical substrate to another, but that's not what I'm talking about.) Similarly, some people view "luck" as a supernatural phenomenon, divorced from the more complex total statistical situation. To see why this is, consider this:
When you flip a penny, the chances (we'll pretend it's a perfectly uniform penny, with a randomized flip-force) of it landing on either side are 50%. If you flip it 100 times, chances are the number of times it lands on heads will be about equal to the number of times it comes up tails. However, if you do 1000 sets of 100 flips each, the chances are very good that one of those sets will be all heads, or very close to it. You have to keep in mind that just because something's improbable, in the statistical sense, doesn't mean it'll never happen- in fact, it's highly statistically *likely* that the improbable will happen at least some of the time. A person watching during this particular set might make the claim, halfway through, that the coin flipping mechanism was on a "hot streak", or "lucky", and seem to be proven right when the rest or most of the rest come up heads. Never mind the couple hundred sets before that where the sides came out about even. Because statistically unlikely events are generally more interesting than the likely ones (due to rarity), they tend to gain more attention, and stick in people's minds more. "Local man doesn't win lottery", is not a news story. "Local man buys lottery ticket, wins $23,000,000", is.
When someone mentions Schroedinger's cat, I reach for my gun. -Stephen Hawking