Quantum mechanics...

Matrix

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I've had an exam about it this morning. Don't know if I made it, but I think I did.

But I'm gonna try here to let normal people (that is: non-alchemists :crazyeyes) understand it as well. Try to understand what I say here.

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The classic laws of physics are known.
Like F=m*a, where F = force; m = mass and a = accelleration.
Or p=m*v, where p = impuls; m = mass and v = velocity.

Now, these formulas work, but only in the macro world. When looking at the smallest objects in the universe, like molecules, atoms, electrons and protons, they don't.

You've probably learned that light is a wave. Red light for example has a wavelength of approx. 400 nanometer. Ultravoilet about 800. That's so-called electromagnetic radiation. Microwaves and radio's use the same, but those waves aren't visible. Only a small part.

Now, there is a problem called the wave-particle dualism. So people said light is a wave; some said light is made of particles. What appeared to be the fact? They were both right. To bring it even further: everything is a particle and a wave! So light isn't made of pure waves, but it comes with very small packets (or quantums). Such a packet has an amount of energy size of h-bar times the wavelength. (h-bar = h (constant of Planck) devided by 2*pi.) So bigger the amount of energy, the smaller the wavelength.

To continue on the wave-particle dualism: they each have their own characteristics. A particle has a shape, mass, colour, etc. A wave has an amplitude, length, form, and it can intervene with other waves, where as particles simply collide. Now, because the amount of energy is disproportionate to the wavelength, a macro-object, like a tennisball, has such a small wavelength that it's characteristics as a wave is neglectible. But when you take an electron, it's wavelength is proportionate to it's environment, like it's distance to the core of an atom.

Edit: forgot to conclude with what I started.
The classic laws of physics is an extreme case of quantum mechanical laws. Either it's a wave or a particle. It works, but only in the macro world.
Quantum mechanics also work, but the scientists have learned not to look at it as the truth, but as a theory that works. No one believes it's the truth, but a theory is true until proven wrong.

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I'm very interested: is this a bit understandable?

And is there another chemist who can correct me or tell me I'm right? :)
 
Originally posted by Matrix
Such a packet has an amount of energy size of h-bar times the wavelength. (h-bar = h (constant of Planck) devided by 2*pi.) So bigger the amount of energy, the smaller the wavelength.

From what I remember this sounds right. I'm not sure about your math though, because I don't remember what Planck's constant is.
 
This sounds correct to me... even though I must admit I have only school knowledge... ( physics was one of my main subjects )
 
This message is late and useless, but Matrix you are absolutely right. I have this on my school as well only a bit more in depth (chemistry student).
You have passed your exam for sure.:goodjob:
 
Originally posted by Matrix


To bring it even further: everything is a particle and a wave!

It works, but only in the macro world.
Quantum mechanics also work, but the scientists have learned not to look at it as the truth, but as a theory that works. No one believes it's the truth, but a theory is true until proven wrong.

:)
Depends what you mean by "truth" and "is" (not to be positively Clintonish about it...) The trouble with discussions like this is that "particles" and "waves" are not real objects at all-- they're basically mathematical/philosophical concepts. Oh, sure, waves in a quite everyday sense are real, but all the properties ascribed to them are ascribed to the mathematical concept, not the real object. Likewise, I can call any small bit of dirt or whatever a particle, but the mathematical, precise definition of particle is quite different, and not necessarily coincident with everyday usage.

To sum up, QM is a theory, and like other physical theories (like Newtonian mechanics) it deals with mathematical concepts, not real things .

So, yes it's a theory that works, that is, is entirely consistent, to date, with the way we reduce real events to mathematical abstractions, i.e. empirical data. The trouble with making reference to "the truth," is that no theory, regardless of its ability to handle empirical data, could be called truth in that sense. Science, to paraphrase Wittgenstein, is a collection of facts, not things.

Or something like that.:confused:
 
RAaahh, at last an exciting thread :)
He he. But if I'm not wrong, concerning the dualism, I've heard now that more and more people do believe finally he photon does have a mass, although it might be incredibly small... Then they wonder whether the wave part may still exist. But I think Planck and Einstein theories will be in students books and dreams (nightmares?) for a while.
Bah with a bit of luck, one day, Scotty will be able to beam me up, who knows, who knows?
or even beam Alicia up to Paris :D
 
It sounds right to me, but you could make up a physical law and it would sound right to me, so.........I'm only 15. Forgive me.
 
Originally posted by Strik
This message is late and useless, but Matrix you are absolutely right. I have this on my school as well only a bit more in depth (chemistry student).
Woh, cool! Another Dutch chemistry student. You probably study in Leiden - too bad. Groningen is the best city to study. ;)
Originally posted by Strik
You have passed your exam for sure.:goodjob:
I didn't. :cry: :cry: :cry:

Knowing the main story is one thing. But there were also a lot mathematics.
undecided.gif
 
He he, I was the opposite of you Matrix. I was really bad in chemistry but i fought well in physics and especially mathematics. Fortunately the competitive examinations gave a higher factor to those matters... :)
And of course i was also bad in biology. Excepted for female anatomy :D :D Naaah, just kidding. Neither good for that :D

Oh and well, sorry for your exams then. :( That suck. But c'mon man, spend less time in GOTM and that would be fine ;)
 
Ahh... quantum mechanics. I really don't know more than the average person about it, but I _am_ definately waiting with bated breath for quantum computers. The prospect of a machine being able to do calculations on information that, in theory, exists in 2 places at the same time is just too much for me.
 
So can I. I'm Omnipotente Deus.... Yeah, really. Being both on MSN and ICQ :D
Actually if that kind of paradox can be applied to human scale, and not microscopic scale, then the small relativity theory might fall. But I really wouldn't mind it became wrong. We could go faster than light... Scotty will be able to beam me up, then :)
 
:lol: I thought you were gonna brag about it (in a positive way)!

Anyway, has anyone ever heard of the string theory? Quantum mechanics says there are four dimensions: x, y, z (location) and t (time). But the string-theory says there are 8 dimensions or so. :eek: Ofcourse I don't know it myself, but I've heard it eliminates the uncertainty relation which quantum mechanics does have, and that kind of appeals to me. :) I'm with Einstein on that part: "God does not play dice." It's just a negative aspect of QM, probably deriven from the fact that QM works statistically and not exact.

Does any brainiac have an answer to that? ;)
 
I've heard of string theory, but aside from science fiction I haven't really heard much discussion.

Many of these theories are in their infant phase of scientific inquiry... give them 100 years and we'll have them more nailed down. Who knows, quantum and string theories could just be our interim ways to explain the universe, before we discover a more exacting theory. If we can hold ourselves back from destroying our planet, we should have a shot at discovering some amazing things.
 
Apparently, the reason no one is certain about string theory is that rather than being discovered by a physicist looking to solve a physics problem, it was stumbled upon by a mathematician who was working on topology at the time and happened to notice that this system of equations might explain some physical behaviour.

due to the backward way it was discovered, we don't really have the maths to be able to truely solve string theory yet. It is one of those "answer waiting for a question" thingies.
 
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