[JP]

It's an integral part of the theory because it comes out of the mathematics needed for quantum mechanics automatically.  Its hard to draw a parallel to classical mechanics, but perhaps its similar to elliptic orbits for planets and Newton's theory of gravity.  You wouldn't usually say you were starting from elliptic orbits as a basis for the theory, but it's something that comes naturally out of the math and that is clear evidence the math is right.

In other words, quantum mechanics implies uncertainty principles, but uncertainty principles do not imply quantum mechanics.  In fact, there are uncertainty relations in signal analysis, optics, acoustics, and many other areas.  I do agree completely that it's a good point to bring up in explaining quantum mechanics.  Most people want to know what quantum mechanics predicts that plain old classical mechanics lacks, and the uncertainty principle is a classic example. 

[DoctorBeaver]

OK, I get that. Thanks.

[rhade]

Yeah, guys, but with all due respect, I think you are missing the semantics of the question, which was, "basically, what is it?" So I was trying to give a BASIC answer. I know the uncertainty principle and all those other wider issues are tied in, and I wasn't suggesting that they are not, but the guy asked for the basics. I think if you plunge into all the complexities without explaining what I did above, you're trying to walk before you can run, so to speak. Do you see where I'm coming from?

[JP]

Good point, rhade.  This forum tends to dive into complexities quickly.  Your statements about Planck are on the right track, but you got a few details wrong.  Planck postulated a theory that correctly explained the light emitted by a black body (a perfect absorber/emitter of electromagnetic radiation).  In order to do so, he had to model the energy as being emitted by little radiation-generators (harmonic oscillators), which each only emitted one particular energy (which was the frequency of the light multiplied by Planck's constant).  However, Planck thought of this as a mathematical trick that gave the right answer, and didn't know about quantum mechanical particles. 

[DoctorBeaver]

Wasn't it Einstein who proved that light can be treated as particles? Was it something to do with pollen? Or was that something else? []

[JP]

Planck (1901) came up just short of treating light as particles.  He assumed that the wave sources in the cavity could be well-modeled by harmonic oscillators.  The result was that the energy (E) from each harmonic oscillator was E=hf (where f was the oscillation frequency and h is Planck's constant).  By summing up the energies from all oscillators, Planck accurately modeled black body radiation.  However, Planck never thought of the light itself as coming in packets of energy E=hf.  He just thought his model of oscillating sources was a good one to get the black body spectrum right. 

Einstein (1905) came up with the idea that light energy itself came in discrete packets of E=hf.  This was independent of the source it came from.  In hindsight, it seems obvious, but at the time, people were far more ready to accept Planck's model of oscillating (but still classical) sources, whereas Einstein's idea that the light itself was divided into energy packets was shocking.

[DoctorBeaver]

And, if I remember correctly, Einstein got the Nobel for that.

[McQueen]

QM is the most wonderful , fantastic development in physics!!! It opens up and expands minds like never before!!  Unfortunately it comes with some pre-concieved litter carried over from classical physics. Take for instance the phenomena of electricity which was formulated before ever photons were discovered, which has resulted in one hell of a humongous bollocks up!

[DoctorBeaver]

QM is the most wonderful , fantastic development in physics!!! It opens up and expands minds like never before!!  Unfortunately it comes with some pre-concieved litter carried over from classical physics. Take for instance the phenomena of electricity which was formulated before ever photons were discovered, which has resulted in one hell of a humongous bollocks up!

How can you say that? QM turned conventional physics upside-down, inside-out, and every which way. The "pre-conceived litter" was put through the mincer.

[rhade]

I just read my last post and realised I said "walk before you can run," and not "run before you can walk." Whoops! I was up against the clock when I was typing that.
Thanks, jpetrucelli, for the above responce. I certainly don't claim any great expertise on the subject, and was pretty much quoting the brief explanation given in Brockhampton's Dictionary of Science (which is a useful little book) in my "back to basics" comment.
Of course, contemporary thinking tends to see energy as either particles or waves, depending on your point of view, just as where (or indeed, when) the energy is depends on your point of view.
Hopefully, if we all throw in what we think we know about the subject, this question will eventually get answered. Say, where's stana, the guy who posted the question in the first place. Is any of this helping, stana?

[rhade]

Oh, and thanks, mcqueen for the phrase "humungous bollocks up." That's one of the technical terms scientists use, right?

[DoctorBeaver]

Oh, and thanks, mcqueen for the phrase "humungous bollocks up." That's one of the technical terms scientists use, right?

I can well imagine that it actually is!