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originally posted in:Secular Sevens
Edited by Recon Number 54: 10/27/2013 4:19:06 PM
6

A few questions in regards to Quantum Mechanics

I just picked up a book by Brian Greene and one portion of it mildly stumped me. I figured that a few of you here could lend a helping hand and provide insight on it. I was reading and the book began delving into quantum uncertainty and I completely understood it up to one point and that point was when he began talking about observing the spin of an electron. Maybe he didn't word it properly or I just blew past it without much thought (probably the latter), but he broke down how electrons spin and how if you observe it the electron will "choose" between spinning clockwise or counterclockwise on the axis you picked to observe it from (at least from I gathered, correct me if I am wrong). Now, I'm not very well informed on the tools used in modern day labs and my question is, what happens if you observe the same electron from two different locations at once? Is this possible or with modern day equipment are we only limited to one direction? Would the electron spin clockwise or counter-clockwise from each observation point no matter how many angles we observe it from? Thanks.

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  • I'm stupid and I'm proud

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  • He was simply trying to explain how electrons behave "randomly" thus being uncertain... The quantum uncertainty principle has been used as grounds in a lot of philosophical debates... If electrons move "randomly," then there is not way of defining when and where our particles will be... If you believe this theory, then the notion of predestination from a scientific standpoint is pretty near impossible for you.. I hope this helps

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    • Also something will always appear to spin clockwise or counterclockwise from any angle.. As long as you are looking at it right side up.. So he is saying that electrons can change spin randomly and you can observe this by knowing what the top is I think Make sure you look at my other comment

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    • "Observation" in physics usually basically refers to any interaction with the particle. When the electron isn't being observed, it's in a superposition of its quantum spin states. That means its spin is both up and down, "undefined" for all practical purposes. But when the electron comes into a situation where it has to "choose", where it is observed, it will fall down to either spin up or spin down. If the electron is in a magnetic field, it will more likely "choose" spin down because spin down is a lower energy state. On the other hand, shooting it with a photon and giving it just enough energy can transfer it into the higher energy spin up state. We can never observe it having both spins at the same time. It's a natural limitation of quantum mechanics. Unless the particle has a preferred spin, its spin is impossible to predict before observation. When it's observed, it will only have one spin and one spin only.

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    • Edited by Seggi: 7/29/2013 6:48:12 AM
      I'm really not sure what exactly you're asking, but I [i]think[/i] you're asking if we can measure a particle's spin along different axes at the same time, in which case the answer is no. It's not a limitation of modern technology, though, it's a natural limitation - like the uncertainty principle you're probably familiar with that deals with momentum and position. I can go into more depth if you want, but I'm not even sure if that's what you're asking, so I'll leave it at that for now. Also, small sidenote: electrons don't actually 'spin' in any kind of classical sense, we just call it spin because it's mathematically equivalent to intrinsic angular momentum.

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        Well I think you have to look at the atom itself and look at the electron shell. Because the electron shell could allow you to find the other quantum numbers for the particular atom. You have numbers represented as n, l, ml, and ms. The last quantum number is applied to quantum spin and its dependent on preceding values. To my understand, the spin is clockwise or counterclockwise based on the preceding variables. I don't really think observation point matters, but we never delved that deep into it. I still don't think your point of observation is relevant though.

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