debate over quantum/newtonian physics: NEED HELP.

[victorhadin]

As you said, physics on the macro-scale yields little to subatomic uncertainty, as it is governed by averages and net effects of infuences on many billions of particles. A single particle in a gale might happily zip at a thousand miles an hour against the direction of the local airflow, but on average the net motion follows the direction of the gust.

[victorhadin]

To take a good analogy, take a closed cylinder of air with two separated bodies of air within, separated by a medium which allows no heat/ energy transfer. Heat the air in one side of the cylinder and not the other and the piston will move due to increased pressure in that half until it finds its new point of equilibrium.

Now on the quantum scale, each particle is massively unpredictable. It can go in any direction and at a wide variety of velocities. However on average, taken over all the billions of particles within that half of the cylinder, a fixed pressure is exerted on the walls by the impacts of all the billions of particles ricocheting around inside it. As you raise the temperature in that half, the particles are just as unpredictable, but on average they are moving at greater velocities, thus exerting a higher pressure on the walls of the cylinder.

The piston then moves as a result of the differences between the two pressures, of course, at a predictable rate and to a predictable equilibrium point irrespective of the atomic-scale chaos within.




You know this already, of course, but it is a good analogy to use.

[Xon]

Quantum Physics is a superset of newtonian physcis. That is newtonian physcis is a simplified model which works well for 'normal' conditions (not very small, not very large, not very fast). General relativity evolution of newtonian physics to allow for the modeling of the vrey big & very fast.

[Hobot]

I believe the general discrepancy with Newtonian physics and Quantum physics is that physicists have failed so far to come up with a Quantum explanation of gravity -- the weakest and farthest reaching of the four forces (gravity<electromagnetic<weak nuclear<strong nuclear).

[Kuroneko]

If what you imply is real then the holy grail of physics hence the unifying theroy would be known.laws of time and space we use wont even work in diffrent parts of the universe.Even what we call time is directly governed by gravity hence the effects of time dialation as you approach the speed of light or warp time thru gravity like super heavy bodies like black holes ... All newtonian physics gravity,time enertia simply will not work in diffrent parts of the universe this is a well known and accepted fact

An obsessive-compulsive relativist cross-examines Newton and his physics...
OCR: An object accelerates from rest at 10 m/s² for one hour. What is its final velocity?
Newton: 36000 m/s, obviously.
OCR: Wrong! It's 35999.99982696 m/s!!!
Newton: Well, whoop-dee-doo.


(Edit: fixed quote)

[Kuroneko]

I believe the general discrepancy with Newtonian physics and Quantum physics is that physicists have failed so far to come up with a Quantum explanation of gravity -- the weakest and farthest reaching of the four forces (gravity<electromagnetic<weak nuclear<strong nuclear).

There's an even deeper discrepancy: Newtonian physics is reductionist, while quantum mechanics is holistic. Quantum systems need to be considered as a whole, not as a sum of individual parts.

[Jonathan]

An obsessive-compulsive relativist cross-examines Newton and his physics...
OCR: An object accelerates from rest at 10 m/s² for one hour. What is its final velocity?
Newton: 36000 m/s, obviously.
OCR: Wrong! It's 35999.99982696 m/s!!!
Newton: Well, whoop-dee-doo.


(Edit: fixed quote)

Actually, if you wanted that to be accurate, you'd have to make a force that would, under Newtonian mechanics, cause a 10 m/s2 acceleration for a given mass. The same force would gradually produce reduced acceleration under relativity.

If you're saying constant acceleration without saying that it's because of costant force then the acceleration is equally valid for Newtonian and relativistic mechanics.

I'll stop being a pedantic Physics student now.

[Jonathan]

Quantum Physics is a superset of newtonian physcis. That is newtonian physcis is a simplified model which works well for 'normal' conditions (not very small, not very large, not very fast). General relativity evolution of newtonian physics to allow for the modeling of the vrey big & very fast.

If it was a superset, then Newtonian physics would be part of quantum physics, but they're not. They're an approximation at the macroscopic level of what happens on average, as long as you're not going very fast:

------------Slow------------------------Fast
Small.......Quantum Mechanics.......Quantum Field Theory
Big...........Newtonian Mechanics.....Relativity

Ultimately, QFT is the most accurate theory we have, with the rest being approximations, Newtonian stuff being the worst approximation. Everything in Physics is an approximation. To a scary extent. We use small angle approximations for big angles situation way too much. But that the most disturbing thing is that it seems to work.

[Kuroneko]

Actually, if you wanted that to be accurate, you'd have to make a force that would, under Newtonian mechanics, cause a 10 m/s2 acceleration for a given mass. The same force would gradually produce reduced acceleration under relativity.

If you're saying constant acceleration without saying that it's because of costant force then the acceleration is equally valid for Newtonian and relativistic mechanics.

No, it isn't, because it makes a difference from which reference frame you measure the acceleration. An object can 'think' it accelerates at a constant rate for arbitrarily long periods of time (e.g., by periodically releasing some sort of markers, which would have a small velocity relative to the object, so the acceleration it measures would be Newtonian). An outside observer, of course, would measure a constantly diminishing acceleration, or else superluminal travel would be possible. If Newtonian and relativistic accelerations were equivalent, both measures would be the same, but they are not.

Classical and relativistic physics do have the same notion of force, though. Not F = ma, but F = dp/dt (which is actually the Newton's original definition of force, written in Leibniz notation).

[Jonathan]

Actually, if you wanted that to be accurate, you'd have to make a force that would, under Newtonian mechanics, cause a 10 m/s2 acceleration for a given mass. The same force would gradually produce reduced acceleration under relativity.

If you're saying constant acceleration without saying that it's because of costant force then the acceleration is equally valid for Newtonian and relativistic mechanics.

No, it isn't, because it makes a difference from which reference frame you measure the acceleration. An object can 'think' it accelerates at a constant rate for arbitrarily long periods of time (e.g., by periodically releasing some sort of markers, which would have a small velocity relative to the object, so the acceleration it measures would be Newtonian). An outside observer, of course, would measure a constantly diminishing acceleration, or else superluminal travel would be possible. If Newtonian and relativistic accelerations were equivalent, both measures would be the same, but they are not.

Ah, a frame was never specified. A constant acceleration of 10 m/s2 will always produce a final velocity of 3600 m/s by definition. You only start worrying about frames if the method of acceleration is brought in. Or you go to a situation impossible under relativity such as exceeding the speed of light via constant acceleration. But that is not an issue in the question. And given the bounds of the question, we don't worry about superluminal velocity, so that isn't an issue.

It is perfectly valid under relativity to say that you are constantly accelerating at 10 m/s2 and will reach 3600 m/s after 6 minutes.

Classical and relativistic physics do have the same notion of force, though. Not F = ma, but F = dp/dt (which is actually the Newton's original definition of force, written in Leibniz notation).

But he defined momentum wrongly and if you're working in a Newtonian system, then that wrong definition of momentum will be used, giving you an incorrect definition of force.

[Kuroneko]

Quantum Physics is a superset of newtonian physcis. That is newtonian physcis is a simplified model which works well for 'normal' conditions (not very small, not very large, not very fast)...

If it was a superset, then Newtonian physics would be part of quantum physics, but they're not...

True. He probably meant Newtonian physics as a limiting case rather than subset, in a similar way it is a limiting case for relativity (except the other way around here, for large quantitites instead of small).

Ultimately, QFT is the most accurate theory we have, with the rest being approximations, Newtonian stuff being the worst approximation.

Not as bad as all that, though. It is quite accurate under normal conditions, and gets bonus points for being the most conceptually simple and the most readily applicable theory.

Everything in Physics is an approximation. To a scary extent. We use small angle approximations for big angles situation way too much. But that the most disturbing thing is that it seems to work.

Quite. As my interests are much stronger in mathematics than physics, I am frequently appaled. But at the same time, I recognize that in most cases the accuracy is sufficient.

[Jonathan]

Ultimately, QFT is the most accurate theory we have, with the rest being approximations, Newtonian stuff being the worst approximation.

Not as bad as all that, though. It is quite accurate under normal conditions, and gets bonus points for being the most conceptually simple and the most readily applicable theory.

Actually, it's perfectly true to say that is is the worst approximation, because it assumes everything is big and slow. I didn't say how bad an approximation it is. It was good enough to go unchallenged for a few centuries and still get used for the majority of physics today.

Quite. As my interests are much stronger in mathematics than physics, I am frequently appaled. But at the same time, I recognize that in most cases the accuracy is sufficient.

And I'm appalled at the bizarreness of many mathematical ideas. Like non-integer dimensions. I want to slap by friend with a chilled herring and scream 'YOU CAN'T HAVE HALF A LENGTH!' every time he brings it up. You lot are nuts, quite frankly :^)

[Kuroneko]

Ah, a frame was never specified. A constant acceleration of 10 m/s2 will always produce a final velocity of 3600 m/s by definition.

I admit I should have specified it. Operating under the assumption that it is as measured from the object, and subsequent comparison with the point of origin, the scenario holds.

My apologies. Edit: It was meant to be simply a point that Newtonian physics are more than sufficient under ordinary circumstances, rather than a technical comparison, so it slipped my mind to make more exact specifications...

Classical and relativistic physics do have the same notion of force, though. Not F = ma, but F = dp/dt (which is actually the Newton's original definition of force, written in Leibniz notation).

But he defined momentum wrongly and if you're working in a Newtonian system, then that wrong definition of momentum will be used, giving you an incorrect definition of force.

The definition of momentum was wrong, true, but the definition of force was originally simply change in momentum. Which is true under relativity also. Apply the same force for the same amount of time, and you get the same momentum in either theory. Only the speed is changed (and consequently, the relationship between momentum and speed).

[Darth Wong]

Actually, it's perfectly true to say that is is the worst approximation, because it assumes everything is big and slow. I didn't say how bad an approximation it is. It was good enough to go unchallenged for a few centuries and still get used for the majority of physics today.

Obviously, your definition of "worst" is severely fucked up. In practical application, it is ridiculously difficult to use quantum physics or relativity for 99.9% of applications, so in those applications, Newtonian physics is actually superior.

[Kuroneko]

Not as bad as all that, though. It is quite accurate under normal conditions, and gets bonus points for being the most conceptually simple and the most readily applicable theory.

Actually, it's perfectly true to say that is is the worst approximation, because it assumes everything is big and slow. I didn't say how bad an approximation it is.

Yes, in terms of raw accuracy, it is. However, my only point is that it is more than sufficient in most situations, and the fact that it is very simple makes it a very good theory to use.

Quite. As my interests are much stronger in mathematics than physics, I am frequently appaled. But at the same time, I recognize that in most cases the accuracy is sufficient.

And I'm appalled at the bizarreness of many mathematical ideas. Like non-integer dimensions. I want to slap by friend with a chilled herring and scream 'YOU CAN'T HAVE HALF A LENGTH!' every time he brings it up. You lot are nuts, quite frankly :^)

For a square, if you scale its sides by a factor of two, the content is increased by a factor of four. Hence, its capacity dimension is ln(4)/ln(2) = 2. For a cube, doubling leads to content increase by a factor of eight, so the capacity dimension is ln(8)/ln(2) = 3. Overall, it seems to me like a very intuitive way to define the dimension of objects.

In the case of fractals (a limiting process is actually used since they don't have perimeters), the capacity dimension can be non-integer. I really don't perceive this to be a problem.

[Jonathan]

Actually, it's perfectly true to say that is is the worst approximation, because it assumes everything is big and slow. I didn't say how bad an approximation it is. It was good enough to go unchallenged for a few centuries and still get used for the majority of physics today.

Obviously, your definition of "worst" is severely fucked up. In practical application, it is ridiculously difficult to use quantum physics or relativity for 99.9% of applications, so in those applications, Newtonian physics is actually superior.

My definition of worst was in reference to accuracy, as would be fairly clear from my posts in this thread and it is the least accurate. I thought that was fairly clear from

Ultimately, QFT is the most accurate theory we have, with the rest being approximations,

but apparently not. would you care to point out how I was mstaken in saying that it is the least accurate?

Oh and I never made any claims as to which system was superior for 99.9? of applications, and if your definition of 'accurate' depends on how hard a system is to use.... well, I'm sure you can think of ways to finish that sentence. Maybe we should have a caption competition. That kind of idea seems somewhat lacking from sd.net.

[Darth Wong]

My definition of worst was in reference to accuracy, as would be fairly clear from my posts in this thread and it is the least accurate. I thought that was fairly clear from

Ultimately, QFT is the most accurate theory we have, with the rest being approximations,

but apparently not. would you care to point out how I was mstaken in saying that it is the least accurate?

Actually, rounding error can and will make relativity less accurate when you actually try to use it in most situations, dumb-ass.

Oh and I never made any claims as to which system was superior for 99.9? of applications, and if your definition of 'accurate' depends on how hard a system is to use.... well, I'm sure you can think of ways to finish that sentence. Maybe we should have a caption competition. That kind of idea seems somewhat lacking from sd.net.

Obviously, you are too stupid to recognize the complexities of doing actual work instead of pissing around with numbers. If the accuracy is sufficient to specifications and tolerances (and in many cases, superior because of inherent limitations in calculation methods), then you use it because it is more efficient to do so. In the real world, accuracy is a concept that devolves to tolerances and specifications.

[Jonathan]

I admit I should have specified it. Operating under the assumption that it is as measured from the object, and subsequent comparison with the point of origin, the scenario holds.

My apologies. Edit: It was meant to be simply a point that Newtonian physics are more than sufficient under ordinary circumstances, rather than a technical comparison, so it slipped my mind to make more exact specifications...

I know, I was just getting into the spirit of the OCR and being pedantic to the point where I was expecting to be force fed episdoes of Voyager :^)

The definition of momentum was wrong, true, but the definition of force was originally simply change in momentum. Which is true under relativity also. Apply the same force for the same amount of time, and you get the same momentum in either theory. Only the speed is changed (and consequently, the relationship between momentum and speed).

It depends on how you define 'definition' :^) Is a definition recursive, and therefore dependent ont he defnition of the contents of what is being defined? Under my definition of definition, it is, so the definition of force was wrong, while under your definition, it isn't, so it wasn't, so we were both right, but defining how we define things differently.

Are you confused enough for me to brainwash you now?

[Jonathan]

For a square, if you scale its sides by a factor of two, the content is increased by a factor of four. Hence, its capacity dimension is ln(4)/ln(2) = 2. For a cube, doubling leads to content increase by a factor of eight, so the capacity dimension is ln(8)/ln(2) = 3. Overall, it seems to me like a very intuitive way to define the dimension of objects.

In the case of fractals (a limiting process is actually used since they don't have perimeters), the capacity dimension can be non-integer. I really don't perceive this to be a problem.

My problem was that he insisted that clouds had non-integer dimensions because clouds are approximately fractal. Trouble is, they're not really fractal and you don't physically get things with non-iinteger dimensions. 4 I like. 10 I can live with. I see why some people want 26. There are arguments for others, but if a physicist comes up to me and starts saying there's a fractional number, I'll be finishing my degree from inside a prison cell.

[Kuroneko]

It was meant to be simply a point that Newtonian physics are more than sufficient under ordinary circumstances, rather than a technical comparison, so it slipped my mind to make more exact specifications...

I know, I was just getting into the spirit of the OCR and being pedantic to the point where I was expecting to be force fed episdoes of Voyager :^)

Heh.

The definition of momentum was wrong, true, but the definition of force was originally simply change in momentum. Which is true under relativity also. Apply the same force for the same amount of time, and you get the same momentum in either theory. Only the speed is changed (and consequently, the relationship between momentum and speed).

It depends on how you define 'definition' :^) Is a definition recursive, and therefore dependent ont he defnition of the contents of what is being defined? Under my definition of definition, it is, so the definition of force was wrong, while under your definition, it isn't, so it wasn't, so we were both right, but defining how we define things differently.

This view is prima facie sensible, but I disagree with it, because it removes the levels of abstraction, which I find unacceptable. Even worse, there is no limit how far the definition can be recursively 'expanded', unless it terminates with sense data. Reduction to sense data might be possible, but it reduces morality to, at worst, complete meaninglessness, and, at best, a mere statement of preference (e.g., "killing is wrong" = "I disapprove of killing"). Personally, I'm a moral objectivist, so I find this subjectivism in morality unacceptable.

The only other possibility is that the chain terminates in a primitive (an undefinable term). But this means that language has no semantic content whatsoever. I find this conclusion of complete meaninglessness of language very disturbing.

If the definition of 'definition' is in how the terms relate, without this recursive expansion, then it is not really a problem even if there are primitives--meaning is found in those interrelations.

Are you confused enough for me to brainwash you now?

Don't try to out-nitpick a mathematician!

[Kuroneko]

My problem was that he insisted that clouds had non-integer dimensions because clouds are approximately fractal. Trouble is, they're not really fractal and you don't physically get things with non-iinteger dimensions.

Well, depends on your definition of 'cloud'. In mathematical models, things a frequently assumed to be continuous. In fluid mechanics, for example, one seldom considers the individual particles of the fluid. With a continuous model, something as chaotic as a cloud is inevitably fractal. Of course, the actual physical cloud is made up of discrete particles, and hence cannot be a true fractal, but it is still 'approximately fractal'.

4 I like. 10 I can live with. I see why some people want 26. There are arguments for others, but if a physicist comes up to me and starts saying there's a fractional number, I'll be finishing my degree from inside a prison cell.

One thing to realize is that in mathematics there are several definitions of 'dimension', some of them mutually incompatible. In fact, the definition of fractal is an object whose capacity dimension differs from its topological dimension (which is pretty much the kind of dimension you're insisting on).

How do you feel about infinite-dimensional spaces?

[Jonathan]

This view is prima facie sensible, but I disagree with it, because it removes the levels of abstraction, which I find unacceptable. Even worse, there is no limit how far the definition can be recursively 'expanded', unless it terminates with sense data. Reduction to sense data might be possible, but it reduces morality to, at worst, complete meaninglessness, and, at best, a mere statement of preference (e.g., "killing is wrong" = "I disapprove of killing"). Personally, I'm a moral objectivist, so I find this subjectivism in morality unacceptable.

The only other possibility is that the chain terminates in a primitive (an undefinable term). But this means that language has no semantic content whatsoever. I find this conclusion of complete meaninglessness of language very disturbing.

If the definition of 'definition' is in how the terms relate, without this recursive expansion, then it is not really a problem even if there are primitives--meaning is found in those interrelations.

Yes.

Are you confused enough for me to brainwash you now?

Don't try to out-nitpick a mathematician![/quote]

You're all mad. But you'd have no-one to talk to if not for Physicists. No one else understands you.

[Jonathan]

Well, depends on your definition of 'cloud'.

Lol. It's wet, fluffy and sometimes looks like an MC-90. Or a tree. Depends on how much wind there is.

In mathematical models, things a frequently assumed to be continuous. In fluid mechanics, for example, one seldom considers the individual particles of the fluid. With a continuous model, something as chaotic as a cloud is inevitably fractal. Of course, the actual physical cloud is made up of discrete particles, and hence cannot be a true fractal, but it is still 'approximately fractal'.

And therein lies the problem - it's approximate.

One thing to realize is that in mathematics there are several definitions of 'dimension', some of them mutually incompatible. In fact, the definition of fractal is an object whose capacity dimension differs from its topological dimension (which is pretty much the kind of dimension you're insisting on).

I would ask what a capacity dimension is, but...

Oh, what the heck, you only live twice. Though the second one is for eternity.... But anyway, what is it?

How do you feel about infinite-dimensional spaces?

My first instinct was Mark 8:33.

[Kuroneko]

You're all mad. But you'd have no-one to talk to if not for Physicists. No one else understands you.

Occasionally, an engineer brings cookies. But they never stay long....

[Kuroneko]

And therein lies the problem - it's approximate.

Take it for what it is... if you asked a pure mathematician to model a horse race, it is not unlikely he'll begin with something like "well, if we assume the horses are spherical..." ^_^

I would ask what a capacity dimension is, but...

Oh, what the heck, you only live twice. Though the second one is for eternity.... But anyway, what is it?

Intuitevely, what I illustrated earlier with the square and the cube... the technical definition involves a limit of a cover of open sets, towards infinitesimal size. It's not likely to make any sense at all unless you've taken topology.

How do you feel about infinite-dimensional spaces?

My first instinct was Mark 8:33.

Hah!