Is Classical Primitive

[foodchain]

Will further advances in the understanding of quantum mechanics overtake classical views of the physical world at all levels eventually? Why or why not?

[swansont]

No. QM converges to classical as the scale changes, but generally the classical calcuations are simpler to do, so they won't get replaced. There's no good reason to invoke QM for a block sliding down an inclined plane.

[BenTheMan]

Will further advances in the understanding of quantum mechanics overtake classical views of the physical world at all levels eventually? Why or why not?

 

Absolutely not. Two reasons---one, there is no need to, because we can get accurate results from classical computations (as swansont said). Secondly, the numbers are just too big to deal with. One would have to understand how to calculate a system of something like 10^24 particles, and there are fundamental limitations on how much computing power one can have---for example, your computer can do perhaps 10^10 calculations a second. These are basic calculations, no more than true/false comparissons. To analyze a classical system using quantum mechanics, you would have to solve Schroedinger's equation 10^24 times, which is a second order differential equation.

 

If we could measure things 10^23 decimal places, then it may become important. Otherwise, there are better ways to utilize computer time.

 

There's no good reason to invoke QM for a block sliding down an inclined plane.

 

Unless you have something to prove:)

[swansont]

To go another step "higher" from what Ben said, a lot of thermodynamics exists because it isn't practical/possible to calculate the individual classical behavior of systems of particles. And you keep going up in scale, to chemistry and biology. Sometime you just analyze collective behavior, because it does the job.

[foodchain]

Right, I don’t want to offend anyone as I know close to nothing of course but could that be somewhat the reality of why science cannot fully integrate QM with relativity? Personally as a gut feeling(be warned:D ) I think that QM does lead up to relativity as we understand it somehow. I also think all the little physical realities that make up basically everything share in this, be it playing tennis to the formation of galaxies.

 

So is the reality then as why we keep classical around is simply due to contemporary limitations for calculations? Is this somewhat a product of current models to any extent?

[BenTheMan]

foodchain---

 

Quantum mechanics can be made consistent with relativity---it is a subject most undergraduates study, Relativistic Quantum Mechanics. QM cannot be made consistent with GENERAL relativity, but this has nothing to do with the problems in this thread. The point that swansont and I made is that there is no conceptual barrier, only a computational one---there aren't enough computers in the world to do even simple problems.

[foodchain]

foodchain---

 

Quantum mechanics can be made consistent with relativity---it is a subject most undergraduates study, Relativistic Quantum Mechanics. QM cannot be made consistent with GENERAL relativity, but this has nothing to do with the problems in this thread. The point that swansont and I made is that there is no conceptual barrier, only a computational one---there aren't enough computers in the world to do even simple problems.

 

I respect you opinion fully, I am sure you have forgotten more about physics then I have learnt. I just don’t understand something conceptually when I try to put it together I guess. I mean to me, to think that somehow the reality as a quantum level cannot be fully integrated into the why for larger scale phenomena really bugs me. I also don’t fully understand also how relativity works, which I am does not help. I just don’t think really that relativity is the answer, I see such from my understanding as being something that has to be solved for on a quantum scale. Then again unlike most people I think such has a larger impact on why life exists then just the typical chemistry aspect most take.

 

Well I have to go, and I hope I did not offend.

[BenTheMan]

I mean to me, to think that somehow the reality as a quantum level cannot be fully integrated into the why for larger scale phenomena really bugs me.

 

Well... Try not to lose too much sleep. Think about the numbers involved. Suppose you have, say 10^23 electrons. This is a pretty common number in chemistry---this is like a thimble full of whater. So we have these 10^23 electrons, and we want to do a calculation of something. In order to do the calculation fully, using quantum mechanics, we would have to know instantaneously the state of the 10^23 electrons, spin up or spin down. This means 10^23 bits or 10^14 gigabytes of data all at once. This is roughly five orders of magnitude (10,000 times) more information that the biggest hard drives that I know about. And this is just to know what state the electrons are in---we haven't even done a calculation yet.

 

So it's not that we can't concievably do it, it's that we can't fesably do it.

 

Instead, we use statistical treatment---this is the field of statistical mechanics, which is very useful for people calculating things with lots of electrons.

 

I just don’t think really that relativity is the answer, I see such from my understanding as being something that has to be solved for on a quantum scale.

 

I agree with you. I think string theory is the answer:)

[thedarkshade]

Well... Try not to lose too much sleep. Think about the numbers involved. Suppose you have, say 10^23 electrons. This is a pretty common number in chemistry---this is like a thimble full of whater. So we have these 10^23 electrons, and we want to do a calculation of something. In order to do the calculation fully, using quantum mechanics, we would have to know instantaneously the state of the 10^23 electrons, spin up or spin down. This means 10^23 bits or 10^14 gigabytes of data all at once. This is roughly five orders of magnitude (10,000 times) more information that the biggest hard drives that I know about. And this is just to know what state the electrons are in---we haven't even done a calculation yet.

 

So it's not that we can't concievably do it, it's that we can't fesably do it.

 

Instead, we use statistical treatment---this is the field of statistical mechanics, which is very useful for people calculating things with lots of electrons.

 

 

 

I agree with you. I think string theory is the answer:)

 

I completely agree.

I personally think that the point of each task you get (physics in this case) or any task you set yourself is to get the result, accurate and fast result! Classical methods have no problems getting this, so why replace? on the other hand the "usual numbers" used in QM are astronomical. This would be just like saying "will mankind ever chose the hard way instead of easy way"!

 

And about QM-Relativity!

QM, as you all said, fits with Special Relativity as they both got to deal with high speed and extreme conditions (at least not experienced in out daily life). But the problem (Modern Physic's main problem probably) is that QM does not fit with General Relativity! And I've often heard that one of these Relativities has got to be wrong (thought I don't think so)! Or something inside QM or General Relativity has got to be wrong! They just got to fit, as they're both right on their own "paths". I'm saying this because these paths are part of the same world, same universe! QM and General Relativity both deal with the same universe (differing in scale), so how come two exact theories, about the same thing don't fit? Why do they differ?

[BenTheMan]

And I've often heard that one of these Relativities has got to be wrong (thought I don't think so)!

 

It depends on what you mean by ``wrong''. Personally, I feel that GR is not really a fundamental concept, but emergent. In other words, space-time is only an effective description, that is good classically. I feel that there are good reasons why GR (and all of the things that go along with it) breaks down at short distances, and there is nothing really fundamental about ``geometry''. Martin, I think, will disagree.

[Farsight]

Will further advances in the understanding of quantum mechanics overtake classical views of the physical world at all levels eventually? Why or why not?

 

No. Classical will overtake quantum mechanics. Here's an example of what I mean, an article from last week's New Scientist.

 

Quantum Entanglement: Is spookiness under threat?

 

In a nutshell it says Quantum Physics perhaps isn't so spooky after all, and the answer lies in geometry. I share that view. The link is just a stub I'm afraid, but the full article is worth reading.

[D H]

No. Quantum mechanics will not overtake classical views at all levels. Farsight is just plain goofy again. There is no reason to use quantum mechanics to describe a block sliding down a board and many reasons (over 10²³ reasons) not to. The same applies to relativity. There is no reason to use relativistic velocity addition equations for speeds much, much smaller than the speed of light.

 

Appropriate simplifications are an important part of physics. We even make simplifications within classical physics. For example, for small changes in elevation above the surface of the Earth one can assume a constant gravitational force, making the gravitational potential [math]E=mgh[/math] rather than [math]E=GmM_e/r-GmM_e/(r+h)[/math].

[Farsight]

...Farsight is just plain goofy again...

 

Read the article. Or be an shining example: don't read the article, just insult somebody who offers information that doesn't fit your preconceptions.

[swansont]

No. Classical will overtake quantum mechanics. Here's an example of what I mean, an article from last week's New Scientist.

 

Quantum Entanglement: Is spookiness under threat?

 

In a nutshell it says Quantum Physics perhaps isn't so spooky after all, and the answer lies in geometry. I share that view. The link is just a stub I'm afraid, but the full article is worth reading.

 

No, I don't think that's the nutshell.

 

The only mention of geometry is loop quantum gravity, and this is but one example of many flavors of "physics beyond QM" that are mentioned. One should note that there is nothing mentioned that has any concrete results yet. The paper by the main protagonist is still in review at PRL.

 

Already under discussion at http://www.scienceforums.net/forum/showthread.php?t=29410 followups should go there

[pioneer]

One of the things that happened, when the shift went from classical, to what we have today, is convergence became divergence. The idea of relativity itself ,got philosophically extrapolated, to mean relative, such that anything goes. The only thing it has to do, is correlate. Classical is still important became it provides a common place where all agree. After that, the confusion begins, as to what is real and what is just correlation. Both can be useful, but correlation does not have to be in touch with reality to be functional. As such, functional is assumed to mean reality in the world of relative science, where only correlation is important.

 

What I always thought was odd, was the a-bomb and h-bomb were made with fairly primitive science by modern standards. Yet the new higher standard was never able to make controlled fusion a reality. It may be a case, where too much departure from the classical into relative science, that only has to correlate, has caused a departure from reality. This type of science only works, when it doesn't have to perform in reality.

[swansont]

One of the things that happened, when the shift went from classical, to what we have today, is convergence became divergence. The idea of relativity itself ,got philosophically extrapolated, to mean relative, such that anything goes. The only thing it has to do, is correlate. Classical is still important became it provides a common place where all agree. After that, the confusion begins, as to what is real and what is just correlation. Both can be useful, but correlation does not have to be in touch with reality to be functional. As such, functional is assumed to mean reality in the world of relative science, where only correlation is important.

 

What I always thought was odd, was the a-bomb and h-bomb were made with fairly primitive science by modern standards. Yet the new higher standard was never able to make controlled fusion a reality. It may be a case, where too much departure from the classical into relative science, that only has to correlate, has caused a departure from reality. This type of science only works, when it doesn't have to perform in reality.

 

Ummmmmm. No. This is just so far off base it's hard to comment on it. Relativity does not mean "anything goes" and I don't know what you're talking about with correlation. Controlled fusion being difficult is primarily an engineering issue, not a fault in the science.