Re: [Vo]:Three Words That Could Overthrow Physics
On 9/6/2008 3:51 PM, Stephen A. Lawrence wrote: Harry Veeder wrote: On 4/6/2008 10:53 PM, Stephen A. Lawrence wrote: Harry Veeder wrote: I am calling your bluff. ;-) Not a bluff, though it involves some fuzzy reasoning. The difference between a proof and an explanation has bugged me since junior high, when I found out that most mathematical facts are proven without ever being explained. As I said before, a model may predict what's going to happen but will never tell you why. Using a model is a tacit admission that we don't know what the reasons behind things are, or even if there are any such reasons. I would think the _construction_ of a model depends on some a-priori explanations (or stories?) of the world. Not necessarily, though some certainly seem to be. Aether theory is predicated on the notion that there is some kind of aether which carries some kind of vibrations; as such that's a sort of fuzzy explanation (though the details are pretty wild if you stop and think about what sort of material aether must be, keeping in mind the obvious fact that planets and stars plow through the aether with no impediment to their motion, along with the fact that vibrations traveling in any known medium go faster as the medium becomes stiffer and slower as the medium becomes floppier -- and vibrations in the aether travel really wicked fast, so it must be really wicked stiff, which makes those planets cruising through the middle of it all the harder to understand). An aether is untenable if one begins with the assumption that the aether is some sort of medium which obeys Newton's three of laws motions. One could argue that the medium offers no resistance (i.e. has no inertia), but instead is limited by how fast it can part or give way to the motion of a body through it. This parting occurs at the speed of light. An an illustration consider this non-mechanical analogy: A queen is walking through a crowd of loyal subjects. The crowd offers no drag, but the speed of the queen is limited by the ability of the crowd to part. But to take a contrary example, special relativity postulates no mechanism at all for anything; it's just a proposal that the geometry of space is just like what you get if you assume the distance between any two events is fixed for all observers *if* you measure distance as x^2 - t^2. The justification for it is that it works, with no reference to whether or not it makes sense or explains anything. Another contrary example is Ptolemaic cosmology, which as far as I can see explains nothing, and is really just a mathematical construct. You have to situate it within the cosmology from which it emerged to find the explanation. In that cosmology a distinction exists between the celestial relm and the earthly relm. Heavenly bodies had to move in circles because circular motion expressed the perfection of the heavens. What is the difference between an explanation and a model? You have said something substantive about models, but nothing substantive about explanations, except to say that explanation is not a model. Or is it just an issue of semantics? Maybe it's just semantics, but I actually think it's more a matter of gut feel, and satisfaction level. If you look at the link Terry gave, the author's objection is that physics doesn't say why magnets attract. Well, what would it mean to say why they attract? This is the heart of the issue -- just exactly what is an explanation? In physics it's hard to say, for me, at least, because I don't know of any explanations. As far as I know modern physics has none. It does and it is called mechanics, I can't really agree. We tend to think mechanics explains something because it so neatly matches our experience with stuff, but really it is nothing more than a *description* of what Newton thought things did. A centerpiece of Newtonian mechanics is the law of gravity, which is simply a bald statement that two bodies attract with a force equal to G m_1 m_2 / r^2 Although it was formally consistent with his laws of motion Newton's notion of gravity as universal attraction was very unmechanical, as it violated another aspect of the mechanical paradigm which only permits one body to influence another body by collision or through the action of an intervening material (inertial) medium. with no hint of an explanation -- and what's more, that's a description of action at a distance, with information as to where each body is located being transmitted to the other body in *zero* time, with, again, no proposed mechanism for this information transfer. Newton, as I recall, had misgivings about that (and he was right, of course). He was not the first to suggest gravity was a kind of attraction. At the time this would have been called an occult theory. I believe he distanced himself from his own occult theory because the mechanical paradigm had become the dominant
Re: [Vo]:Three Words That Could Overthrow Physics
On 4/6/2008 10:53 PM, Stephen A. Lawrence wrote: Harry Veeder wrote: I am calling your bluff. ;-) Not a bluff, though it involves some fuzzy reasoning. The difference between a proof and an explanation has bugged me since junior high, when I found out that most mathematical facts are proven without ever being explained. As I said before, a model may predict what's going to happen but will never tell you why. Using a model is a tacit admission that we don't know what the reasons behind things are, or even if there are any such reasons. I would think the _construction_ of a model depends on some a-priori explanations (or stories?) of the world. What is the difference between an explanation and a model? You have said something substantive about models, but nothing substantive about explanations, except to say that explanation is not a model. Or is it just an issue of semantics? Maybe it's just semantics, but I actually think it's more a matter of gut feel, and satisfaction level. If you look at the link Terry gave, the author's objection is that physics doesn't say why magnets attract. Well, what would it mean to say why they attract? This is the heart of the issue -- just exactly what is an explanation? In physics it's hard to say, for me, at least, because I don't know of any explanations. As far as I know modern physics has none. It does and it is called mechanics, and to ensure mechanical explanations remain dominant and universally applicable they have been revamped by the quantum hypothesis. In math it's easier to see the difference. For example, we can find pi by integrating the arctan function, or by integrating sqrt(1-x^2), both of which are stunningly opaque approaches. We can prove that the area of a circle is pi*r^2 using calculus, which is, again, an amazingly opaque approach. Alternatively, we can find the circumference and area of a circle using Pythagoras's theorem and some simple drawings, and we can extract a value for pi that way. I would call the latter approach an explanation, because, to me, it explains why the circumference and area of the circle are what they are. But something this is pointing up is that the word explanation is rather slippery. I could struggle with it a bit more, and perhaps say that an explanation works from simple things which we know to be true to show that other more complex things follow inevitably from those simple things -- but the phrase know to be true is already flirting with vagueness. So I'll just let it go at saying that an explanation leaves one feeling satisfied; a model may not... I guess the question becomes how do we learn a particular sense of satisfaction, and are there other senses of satisfaction that should be allowed in physics other than those rooted in mechanics and probability theory. By the way, the derivation of pi from Pythagoras's theorem to which I referred, and the derivation of the area of a circle and volume of a sphere using geometric arguments, are here: http://physicsinsights.org/pi_from_pythagoras-1.html http://physicsinsights.org/sphere-volume-1.html You may not feel these pages actually explain anything, of course! :-) That was, however, part of the reason for putting them together, and perhaps these pages will give you an idea of what I think an explanation is. Or maybe not... Aristotle's explanation of why some things fall (gravity) and why other things rise is that each element seeks its natural place of rest. Bodies made of the element earth tend to fall, while bodies made of the element air tend to rise. This may not be satisfying from a modern sensibility, but it was satisfying to many people in the past. Likewise, the sensibilities of future generations might regard today's physics as unsatisfying. In fact many people do right now. ;-) Harry
Re: [Vo]:Three Words That Could Overthrow Physics
Harry Veeder wrote: On 4/6/2008 10:53 PM, Stephen A. Lawrence wrote: Harry Veeder wrote: I am calling your bluff. ;-) Not a bluff, though it involves some fuzzy reasoning. The difference between a proof and an explanation has bugged me since junior high, when I found out that most mathematical facts are proven without ever being explained. As I said before, a model may predict what's going to happen but will never tell you why. Using a model is a tacit admission that we don't know what the reasons behind things are, or even if there are any such reasons. I would think the _construction_ of a model depends on some a-priori explanations (or stories?) of the world. Not necessarily, though some certainly seem to be. Aether theory is predicated on the notion that there is some kind of aether which carries some kind of vibrations; as such that's a sort of fuzzy explanation (though the details are pretty wild if you stop and think about what sort of material aether must be, keeping in mind the obvious fact that planets and stars plow through the aether with no impediment to their motion, along with the fact that vibrations traveling in any known medium go faster as the medium becomes stiffer and slower as the medium becomes floppier -- and vibrations in the aether travel really wicked fast, so it must be really wicked stiff, which makes those planets cruising through the middle of it all the harder to understand). But to take a contrary example, special relativity postulates no mechanism at all for anything; it's just a proposal that the geometry of space is just like what you get if you assume the distance between any two events is fixed for all observers *if* you measure distance as x^2 - t^2. The justification for it is that it works, with no reference to whether or not it makes sense or explains anything. Another contrary example is Ptolemaic cosmology, which as far as I can see explains nothing, and is really just a mathematical construct. What is the difference between an explanation and a model? You have said something substantive about models, but nothing substantive about explanations, except to say that explanation is not a model. Or is it just an issue of semantics? Maybe it's just semantics, but I actually think it's more a matter of gut feel, and satisfaction level. If you look at the link Terry gave, the author's objection is that physics doesn't say why magnets attract. Well, what would it mean to say why they attract? This is the heart of the issue -- just exactly what is an explanation? In physics it's hard to say, for me, at least, because I don't know of any explanations. As far as I know modern physics has none. It does and it is called mechanics, I can't really agree. We tend to think mechanics explains something because it so neatly matches our experience with stuff, but really it is nothing more than a *description* of what Newton thought things did. A centerpiece of Newtonian mechanics is the law of gravity, which is simply a bald statement that two bodies attract with a force equal to G m_1 m_2 / r^2 with no hint of an explanation -- and what's more, that's a description of action at a distance, with information as to where each body is located being transmitted to the other body in *zero* time, with, again, no proposed mechanism for this information transfer. Newton, as I recall, had misgivings about that (and he was right, of course). More basically, Newton's second law (I think it's the second law -- it's hot has heck here today and my head's full of fuzz as a result) says that sum (dx_i/dt * m_i) must be constant. No reason is given; no mechanism is provided; it is merely a mathematical statement, chosen to match Newton's observation. Of course it turns out that there can be no simple (and correct) mechanism given for either Newtonian gravitation nor the conservation of Newtonian momentum, because both laws turn out to be untrue at the edges -- over very large distances, at very high velocities, they don't work perfectly. So their mechanism, if it were stated, would necessarily be something which doesn't quite apply in all situations. That would tend to make it less than satisfactory as an explanation, I would think. and to ensure mechanical explanations remain dominant and universally applicable they have been revamped by the quantum hypothesis. But again, they're not explanations, at least not as I understand the term. Tell me *why* momentum is conserved -- that would be an explanation. But Newton didn't tell us *why*, he merely told us that it *is* conserved. It's like the following little convsersation: Go to bed NOW! Why? Because I told you to! In math it's easier to see the difference. For example, we can find pi by integrating the arctan function, or by integrating sqrt(1-x^2), both of which are stunningly opaque approaches. We can prove that the area of a circle
Re: [Vo]:Three Words That Could Overthrow Physics
Robin van Spaandonk wrote: In reply to Stephen A. Lawrence's message of Mon, 09 Jun 2008 16:51:17 -0400: Hi, [snip] Aether theory is predicated on the notion that there is some kind of aether which carries some kind of vibrations; as such that's a sort of fuzzy explanation (though the details are pretty wild if you stop and think about what sort of material aether must be, keeping in mind the obvious fact that planets and stars plow through the aether with no impediment to their motion, along with the fact that vibrations traveling in any known medium go faster as the medium becomes stiffer and slower as the medium becomes floppier -- and vibrations in the aether travel really wicked fast, so it must be really wicked stiff, which makes those planets cruising through the middle of it all the harder to understand). Perhaps it becomes easier to accept, if it is not a matter of ploughing *through* the medium. Consider how a wave passes through water. The energy of the wave is passed from molecule to molecule, but the molecules themselves don't actually go very far. Maybe the aether works the same way. Particles (e.g. electrons) are then *patterns* in the aether. The pattern can move, simply through the transfer of energy, without the aether itself moving. But then it seems like this would lead to an issue with aether dragging, doesn't it? Classical aether theories can't be reconciled with the results of the Fizeau, Michelson-Morley, and Sagnac experiments unless there is partial or complete dragging of the aether along with the Earth. If the Earth itself is just a pattern traveling through the aether that doesn't seem like a very obvious thing to have happen. Alternatively one could assume the Earth is a traveling pattern in a Lorentz aether, which avoids the need for dragging, but the Lorentz ether theory loses a lot of the pleasingly sensible feel of classical aether. It leads to the same mathematical model as special relativity, which implies, in particular, that, while there is a distinguished aether rest frame in Lorentz ether theory, it cannot be detected in any way. There is no way at all to tell how fast you're moving relative to the aether, because all experiments produce the same results regardless of your absolute velocity; consequently you can't tell if you're stationary with respect to the aether or not. In fact, in so-called LET, the aether cannot be detected in any way; the theory is, in a word, indistinguishable from special relativity. This leaves one in a somewhat uncomfortable position, which is that of taking the existence of the central object in the theory entirely on faith. *If* the aether itself is incompressible, then compression waves travel at infinite velocity, however transverse waves are probably limited to the velocity of light. Regards, Robin van Spaandonk The shrub is a plant.
Re: [Vo]:Three Words That Could Overthrow Physics
In reply to Stephen A. Lawrence's message of Mon, 09 Jun 2008 21:36:23 -0400: Hi Stephen, [snip] Perhaps it becomes easier to accept, if it is not a matter of ploughing *through* the medium. Consider how a wave passes through water. The energy of the wave is passed from molecule to molecule, but the molecules themselves don't actually go very far. Maybe the aether works the same way. Particles (e.g. electrons) are then *patterns* in the aether. The pattern can move, simply through the transfer of energy, without the aether itself moving. But then it seems like this would lead to an issue with aether dragging, doesn't it? Classical aether theories can't be reconciled with the results of the Fizeau, Michelson-Morley, and Sagnac experiments unless there is partial or complete dragging of the aether along with the Earth. If the Earth itself is just a pattern traveling through the aether that doesn't seem like a very obvious thing to have happen. [snip] I don't see why there can't be some aether dragging, after all, waves do move molecules to some extent, just not much. Perhaps this depends on the extent to which the aether is frictionless? Regards, Robin van Spaandonk The shrub is a plant.
Re: [Vo]:Three Words That Could Overthrow Physics
Terry Blanton wrote: What is Magnetism http://discovermagazine.com/2008/may/02-three-words-that-could-overthrow-physics The author of the piece wants something that will explain why magnets do what they do. Physics doesn't explain. It models. There's a huge difference. The model of reality which is modern physics includes magnetism and the magnetism in the model behaves pretty much like the magnets we see in the real world. The model has proven to have valuable predictive power, which is why it's currently in use and considered more or less correct. But the fact that the model seems to behave like the real thing doesn't in any way explain why the real thing behaves the way it does. No physical theory ever will. If the author ever gets to converse with God perhaps God will explain /why/ things are the way they are, but until then, all we've got are models, and the best that can be said about any model is that it acts like the real world within its domain of applicability. Consider this: Nearly all of reality goes unobserved. Of the parts which are observed, nearly everything which is observed is unmeasured. Our judgment as to the accuracy of physical theories is based on the tiny fraction of observed events for which someone takes some measurements. Those few measurements, which represent a tiny fraction of the observed events, which in turn represent a vanishingly small fraction of all that takes place in the Universe, are the only points of contact between reality and theory. If a mathematical model agrees reasonably well with that relative handful of measurements, we accept it as apparently correct... Terry
Re: [Vo]:Three Words That Could Overthrow Physics
I am calling your bluff. ;-) What is the difference between an explanation and a model? You have said something substantive about models, but nothing substantive about explanations, except to say that explanation is not a model. Or is it just an issue of semantics? harry - Original Message - From: Stephen A. Lawrence [EMAIL PROTECTED] Date: Wednesday, June 4, 2008 4:31 pm Subject: Re: [Vo]:Three Words That Could Overthrow Physics Terry Blanton wrote: What is Magnetism http://discovermagazine.com/2008/may/02-three-words-that-could- overthrow-physics The author of the piece wants something that will explain why magnets do what they do. Physics doesn't explain. It models. There's a huge difference. The model of reality which is modern physics includes magnetism and the magnetism in the model behaves pretty much like the magnets we see in the real world. The model has proven to have valuable predictive power, which is why it's currently in use and considered more or less correct. But the fact that the model seems to behave like the real thing doesn't in any way explain why the real thing behaves the way it does. No physical theory ever will. If the author ever gets to converse with God perhaps God will explain /why/ things are the way they are, but until then, all we've got are models, and the best that can be said about any model is that it acts like the real world within its domain of applicability. Consider this: Nearly all of reality goes unobserved. Of the parts which are observed, nearly everything which is observed is unmeasured. Our judgment as to the accuracy of physical theories is based on the tiny fraction of observed events for which someone takes some measurements. Those few measurements, which represent a tiny fraction of the observed events, which in turn represent a vanishingly small fraction of all that takes place in the Universe, are the only points of contact between reality and theory. If a mathematical model agrees reasonably well with that relative handful of measurements, we accept it as apparently correct...
Re: [Vo]:Three Words That Could Overthrow Physics
Harry Veeder wrote: I am calling your bluff. ;-) Not a bluff, though it involves some fuzzy reasoning. The difference between a proof and an explanation has bugged me since junior high, when I found out that most mathematical facts are proven without ever being explained. As I said before, a model may predict what's going to happen but will never tell you why. Using a model is a tacit admission that we don't know what the reasons behind things are, or even if there are any such reasons. What is the difference between an explanation and a model? You have said something substantive about models, but nothing substantive about explanations, except to say that explanation is not a model. Or is it just an issue of semantics? Maybe it's just semantics, but I actually think it's more a matter of gut feel, and satisfaction level. If you look at the link Terry gave, the author's objection is that physics doesn't say why magnets attract. Well, what would it mean to say why they attract? This is the heart of the issue -- just exactly what is an explanation? In physics it's hard to say, for me, at least, because I don't know of any explanations. As far as I know modern physics has none. In math it's easier to see the difference. For example, we can find pi by integrating the arctan function, or by integrating sqrt(1-x^2), both of which are stunningly opaque approaches. We can prove that the area of a circle is pi*r^2 using calculus, which is, again, an amazingly opaque approach. Alternatively, we can find the circumference and area of a circle using Pythagoras's theorem and some simple drawings, and we can extract a value for pi that way. I would call the latter approach an explanation, because, to me, it explains why the circumference and area of the circle are what they are. But something this is pointing up is that the word explanation is rather slippery. I could struggle with it a bit more, and perhaps say that an explanation works from simple things which we know to be true to show that other more complex things follow inevitably from those simple things -- but the phrase know to be true is already flirting with vagueness. So I'll just let it go at saying that an explanation leaves one feeling satisfied; a model may not... By the way, the derivation of pi from Pythagoras's theorem to which I referred, and the derivation of the area of a circle and volume of a sphere using geometric arguments, are here: http://physicsinsights.org/pi_from_pythagoras-1.html http://physicsinsights.org/sphere-volume-1.html You may not feel these pages actually explain anything, of course! :-) That was, however, part of the reason for putting them together, and perhaps these pages will give you an idea of what I think an explanation is. Or maybe not...
Re: [Vo]:Three Words That Could Overthrow Physics
In reply to Stephen A. Lawrence's message of Wed, 04 Jun 2008 23:53:35 -0400: Hi, [snip] This is the heart of the issue -- just exactly what is an explanation? In physics it's hard to say, for me, at least, because I don't know of any explanations. As far as I know modern physics has none. [snip] I think the bottom line is that there is no such thing as certainty. By definition, an explanation is something that someone has provided, i.e. it comprises a transfer of assumed knowledge. However since there is no such thing as certainty, there is therefore also no such thing as knowledge, and all explanations should be taken with a grain of salt, including this one. ;) BTW proofs are logical derivations based upon assumption, and as such are just as uncertain as explanations. I.e. if the assumptions are wrong or incomplete then so is the proof. BTW none of this means that they are useless, it just means that we really do base our entire existence on faith, even though we are frequently unaware of doing so. Regards, Robin van Spaandonk The shrub is a plant.
