Want a quick lesson in how to break your mind trying to visualize Quantum Physics? Let me help!
(Will edit for format in a few hours)
The conundrum: [/u/HousHalter]
How can the universe "reshape" itself when you observe it? The universe isn't intelligent, it can't be aware of your observations. How do you know that the universe hasn't already "decided" what the result is, and you just don't know until after you look at it? As far as I know everything can be broken down into simple deterministic rules that don't change.
The explanation: [/u/MereInterest]
This is a common misconception based on the double slit experiment.
"observe" is actually "measure", and that's only because the measurement tools used to measure the spin state of an electron work by changing the spin state of an electron.
Thank you. I'd had a difficult time with the terminology myself, even knowing what it *should* mean. I just had trouble putting the concept into concrete terms, which is where you helped nicely. Let me see if I can talk it out for my own sake, to make some metaphors as teaching tools for my casual peers.
* (The following two paragraphs are less precise because after typing them I realized we're working with discrete states, rather than continuous scales. I'm leaving them up to show my train of thought.)
I -know- that particle spin state isn't really physically spinning, but assuming that we can keep the two straight in our head I'm fuddling out a visualization. I'd liken this to a dynamometer - it needs to apply friction (or torque, but let's simplify) against the thing it's measuring, then it records the change in its own rotation. But that necessarily means that the measuring device has affected the measured item, so it's no longer going exactly the same speed at which it had been spinning before the reactive force of the dynamometer was applied.
Translation into smaller words, mostly for my own practice:
Say you've got a wheel and a tachometer. In order to measure the RPMs, the tach has to exert some resisting force opposite the wheel's rotation, thus slightly lowering the resulting RPMs.
Now this is on a macroscopic scale, and the measuring instruments' change in force is often negligible. But you get down to the subatomic level, and the quality to be measured (spin state) is discrete, not continuous.
So it's actually more like throwing a beanbag-camera through a [Toss Across](http://en.wikipedia.org/wiki/Toss_Across) tic-tac-toe board, where you're only allowed to look at the camera's evidence. You don't know what the tile's going to be, so you toss the camera, it changes the X to an O and takes a picture of it, and you can figure out that it had been an X before.
... Except that this metaphor is perfect for the Hidden Variable argument, and /u/MereInterest links [Bell's Theorem](http://en.wikipedia.org/wiki/Bell%27s_theorem) just above, which negates the precision of the metaphor. Goddammit.
I think I'm still going to use the beanbag camera metaphor, I'm just going to add a caveat that quantum physics is weird, we have indeed proven experimentally that there is no hidden variable. So that means either the tile itself does not have an X/O state until we toss the camera (Copenhagen), or it's already both (Many Worlds).
The conundrum: [/u/HousHalter]
How can the universe "reshape" itself when you observe it? The universe isn't intelligent, it can't be aware of your observations. How do you know that the universe hasn't already "decided" what the result is, and you just don't know until after you look at it? As far as I know everything can be broken down into simple deterministic rules that don't change.
The explanation: [/u/MereInterest]
This is a common misconception based on the double slit experiment.
"observe" is actually "measure", and that's only because the measurement tools used to measure the spin state of an electron work by changing the spin state of an electron.
Thank you. I'd had a difficult time with the terminology myself, even knowing what it *should* mean. I just had trouble putting the concept into concrete terms, which is where you helped nicely. Let me see if I can talk it out for my own sake, to make some metaphors as teaching tools for my casual peers.
* (The following two paragraphs are less precise because after typing them I realized we're working with discrete states, rather than continuous scales. I'm leaving them up to show my train of thought.)
I -know- that particle spin state isn't really physically spinning, but assuming that we can keep the two straight in our head I'm fuddling out a visualization. I'd liken this to a dynamometer - it needs to apply friction (or torque, but let's simplify) against the thing it's measuring, then it records the change in its own rotation. But that necessarily means that the measuring device has affected the measured item, so it's no longer going exactly the same speed at which it had been spinning before the reactive force of the dynamometer was applied.
Translation into smaller words, mostly for my own practice:
Say you've got a wheel and a tachometer. In order to measure the RPMs, the tach has to exert some resisting force opposite the wheel's rotation, thus slightly lowering the resulting RPMs.
Now this is on a macroscopic scale, and the measuring instruments' change in force is often negligible. But you get down to the subatomic level, and the quality to be measured (spin state) is discrete, not continuous.
So it's actually more like throwing a beanbag-camera through a [Toss Across](http://en.wikipedia.org/wiki/Toss_Across) tic-tac-toe board, where you're only allowed to look at the camera's evidence. You don't know what the tile's going to be, so you toss the camera, it changes the X to an O and takes a picture of it, and you can figure out that it had been an X before.
... Except that this metaphor is perfect for the Hidden Variable argument, and /u/MereInterest links [Bell's Theorem](http://en.wikipedia.org/wiki/Bell%27s_theorem) just above, which negates the precision of the metaphor. Goddammit.
I think I'm still going to use the beanbag camera metaphor, I'm just going to add a caveat that quantum physics is weird, we have indeed proven experimentally that there is no hidden variable. So that means either the tile itself does not have an X/O state until we toss the camera (Copenhagen), or it's already both (Many Worlds).