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[HolyCheck]

So a few months ago, in one of the science threads that sporadically pop here now and then, the discussion touched a little bit on quantum mechanics (QM). I mentioned that it would be great to have a separate thread just to discuss QM and someone PM'ed me telling me I should create one. At the time, I didn't know much about QM myself, so I didn't really consider it. But after a few lectures in physical chemistry combined with exposure to the official Space thread that gets bumped frequently, and the fairly successful official evolution thread, I've decided to take the plunge. While the chances are likely this will fall on deaf ears, I'd love for anybody interested to participate, because as seen from the quote above, there are no stupid questions.

Wooo, Glad to have half spurred you on!

Having a read now.. at 5am!

 

[The Elite]

So this explains magnets, right?

 

[Yaweee]

Yeah, my professor spoke very highly of Shankar's Principles of Quantum Mechanics.

As for me, I'm not very well versed in the technical side of QM and most of my knowledge comes from McQuarrie's Physical Chemistry, which focuses a lot on thermo and statistical mechanics. It being a p-chem textbook and all. :lol

I hated Shankar's textbook. It can be helpful for some things, but it is too wordy to be useful, IMO. For my PhD qual, I actually spent more time reading Griffith's undergrad text. Yes, it is simpler, and doesn't cover some topics in as much depth, but it does a much better job of presenting the material.

All three of Griffith's undergrad books (EM, Quantum, and Particle) are goddamn amazing.

Doesn't mean a thing, only suckers stop taking courses just because they've graduated.

Most quantum professors I've had have been terrible, and certainly not worth taking unless required.

 

[lethial]

 

[Davidion]

First off, let me say that this thread is great, and I've always been meaning to read up more on Quantum Mechanics.

That having been said:

the fuck does all this shit mean

.



Also, being a geek, quantization just reads like digital vs. analog to me. :lol

 

[HolyCheck]

Also, a joke, goes down well in any situation!

Schrödinger's cat walks into a bar, and he doesn't.

 

[Stinkles]

the fuck does all this shit mean

:lol

Flawless.

 

[ILikeFeet]

No problem! This was definitely going to come up sooner or later so I'll probably put it in the OP. Schrodinger's Cat is a thought experiment proposed by Schrodinger in order to show the ridiculous consequences of the Copenhagen interpretation of quantum mechanics. This interpretation basically states that every particle can be defined by a wavefunction which can only tell you the probability of what state the particle is actually in.

The experiment is as follows:



Basically, the experiment is set up so that the atom has a 50% chance of decaying in the first hour. If it decays, then it will release the hydrocyanic acid and kill the cat. This essentially means that the cat has a 50/50 chance of surviving. Therefore, using the Copenhagen interpretation, the cat must follow the probability produced by this wavefunction, resulting in the cat being in a half-dead/half-alive state. Of course, such a state seemed ridiculous to Schrodinger which is why he could not accept the Copenhagen interpretation. However, some experiments have led people to believe that this is precisely what happens, albeit on a subatomic scale. Further research into the phenomenon has not produced any definitive results and many interpretations still exist today.

So it amounts to the numbers and raw data proving the cat (or whatever) can be alive and dead, but basic observation proves this not possible (a cat can't be alive and dead).

 

[LabouredSubterfuge]

Amazing thread. Thank you SuperBonk.

 

[SRG01]

I should point out that the uncertainty principle is a fundamental mathematical concept that is relevant in more than just quantum mechanics. There used to be a Wikipedia page outlining its uses in other fields, but I guess the Uncertainty Principle page got expanded and the previous versions were removed.

At any rate, one critical area where the Uncertainty Principle is useful is in signal processing, especially with Fourier Transforms. A fundamental limit exists within signal processing called bandlimiting and timelimiting, whereby a sharp transition in either the frequency or time domain would require the entire occupation of the other domain. In other words, a time limited signal would require infinite bandwidth, whereas bandlimited signals require infinite time. Thankfully, we have the Nyquist theorem to help with the reconstruction of signals.

On the same token, we don't necessarily need the entire spectrum to obtain useful information as we are only concerned with specific portions of the spectrum. Like the OP said, we can modify the uncertainty principle to allow us to examine only specific parts of the spectrum. That is how FFTs and digital signal processors work.