Seasons

I like this one http://www.ncsu.edu/felder-public/kenny/papers/quantum.html
<-2>We'll start with the single-slit experiment. Instead of a light source, we have an M&M-throwing-machine. Each M&M is covered with white ink so that it leaves a stain on the black wall behind (since, as we all know, the milk chocolate only melts in your mouth). You set your M&M-throwing-machine going, it throws out a ton of M&Ms one at a time, and then you look at the ink pattern on the wall—this will tell you where the M&Ms hit. What do you see? Well, the machine is just mechanically spitting out M&Ms in the same way every time, so of course there is just one spot on the wall, where they all hit. M&Ms, unlike light, don't radiate outward in all directions: they just follow a single course to a single destination.

So that wasn't much fun. Let's mix it up a bit: say, stand behind the M&M machine and rattle it around a lot, so the M&Ms get thrown off in all directions. Now, a lot of them bounce off the cardboard. The ones that get through tend to hit the wall near the slit, but not all right behind the slit. So, after enough M&Ms hit, you get a result very much like the single-slit experiment with light: a big white bar that gets dimmer as you move out.

Now, let's add a second slit and do it again, still throwing M&Ms at random angles. What do you see this time? Are there alternating bands of white and black? No, certainly not. Since we are throwing the M&Ms one at a time, what you will see is all the ink from M&Ms that went through the left slit, and all the ink from M&Ms that went through the right slit, added together. So there aren't any bands that suddenly go dark. There's a big white bar behind each slit, and it gets darker as you go away from the slits.



(Note from our lawyers: the authors of this paper accept no responsibility for the consequences if you attempt to repeat this experiment at home.)

PS yeah, I need help. At least I'm not hitting on a toaster.

Prob123, did you use really fine print or did my expression of intellectual self gratification make me go a little blind?

Oooh! Now, This site has really cool graphics! (Did I use "cool" correctly?)

http://www.colorado.edu/physics/2000/schroedinger/index.html

Bev, message 3947:

[blush] Well, er, {blush!] er, ah, well, maybe {BLUSH] once or twice, with a book I REALLY LIKED!!!!!

Bev 3947:

spurts??? What gender do you think I am?

I like the multiple solutions idea, though!

Prob123 3948:

I like the idea of bringing chocolate into it!!!

Chocolate covered quantum physics? I'd bite tthe ears off that bunny.

Schroedinger's bunny. Half of it melts in your mouth!

The interesting question is where was the chocolate before it melted? Not in your hands.

Psimagus:

Are we embarrassing you with all this girl talk? We may be talking about waves, but at least we're not discussing periods!

You wrote:

But how do you view the eigenvalues? Are they anything more than a mathematical device to explain what we observe, or do you see them as describing something that is causally "real"?

Well, technically, an eigenvalue is just a number. But an eigenvalue associated with an operator associated with a physical quantity in QM - that eigenvalue also has physical significance. For example, for a pointlike particle, the eigenvalues of the position operator are all the positions that the particle can have (actually, since space is three-dimensional, it takes three eigenvalues, one for each co-ordinate). A simpler example is spin, which in certain situations can have only one of only two values, "up" and "down." So Psi gives a probability that the spin is "up" and the probability that the spin is "down". Such claims can be empirically tested by repeating the experiment many times, measuring the spin each time. If the probability of spin "up" is 2/5, then in the long run the measurement should yield "up" about 2/5 of the time (and hence "down" about 3/5 of the time).