Leibniz v. Newton: Handbags at dawn.

[uwot]

...I disagree with the 'whatever; the maths works.'

If someone's story is consistent with the empirical facts, corroborated by the mathematical model, on what grounds would you dismiss it?

I disagree in the sense that the only reason for philosophy (setting aside ethics, perhaps) lies in the notion that it is important to have an answer as to why the math works.

I'm not sure what sort of reason you think there should be. I think it is incredibly unlikely that a universe could exist that didn't behave in ways that are predictable and that it is this predictability that maths 'counts'. I suppose that's just some weak anthropic principle, which I know doesn't really answer the question.

Philosophy is concerned with the relationship between rules, models and reality in a way that physics is not.

I agree. I think I have said that a philosophy is a context in which everything 'makes sense', but even physicists have philosophies.

The intersection of rule, model and reality (knowledge) that seems to happen again and again in mathematics and physics is still an unsolved mystery after several thousand years of science and philosophy.

I think we are getting into Wigner territory, I shall have to read this again: http://www.dartmouth.edu/~matc/MathDram ... igner.html .

It (knowledge, that same busy intersection) also seems to involve the intersection of ontology and epistemology, as well as psychology and physics. Isn't such an important intersection a worthwhile subject of study in it's own right?

Absolutely. You lead, I'll follow. Thank you, Wyman, I really enjoyed your post.

[uwot]

(though I am still not with you on conservatism)

I think it is demonstrably the case that some conservatives are weak minded, there are several in this forum, but it would be over stating it if I were to insist that is true of all conservatives. There are actual reasons that conservatives can offer, I just don't think they are very persuasive.

[Wyman]

...I disagree with the 'whatever; the maths works.'

If someone's story is consistent with the empirical facts, corroborated by the mathematical model, on what grounds would you dismiss it?

I certainly wouldn't dismiss it or think that it is invalidated. I am just expressing a curiosity in why the math works.

The Feynman lectures I referenced drew a comparison between the 'Babylonian' and 'Greek' approaches to maths (I am starting to get used to the British term 'maths' for 'mathematics'). The Greeks of course created the deductive system, with all theorems tracing back to a set of independent axioms with undefined terms. What Feynman called the 'Babylonian' approach ignores, or places little emphasis on, a formal axiomatic system, favoring a pragmatic, rule of thumb approach.

The difference Feynman emphasizes between the two, I think, is that the Babylonian approach allows you to jump around large areas of math as it suits you - kind of a math by associative method. While studying a phenomenon, your mind wanders around until perhaps you are struck by something that reminds you of... e.g. something you remember from working with hyperbolic geometry. However, the Greek approach forces you to explore and dissect all unstated assumptions of the unanalyzed rules of thumb, which often, in the analysis, also takes you to new and unforeseen areas of thought.

I extrapolate his point about mathematical 'approaches' to differing models of the same system - like spacetime gravity versus quantum models. Feynman also talks about these models (as well as Newton's action at a distance model) in the lecture on gravity. I think he makes the point I am interested in there as well although I am not sure; if so, it is not the emphasis of that lecture. But he points out that the two models of gravity (Newton's falls short for reasons you are aware of) are exactly the same (mathematically), and yet completely different. Each model, if worked through, will give the physicist different insights (for lack of a better term) into the subject matter.

Here's a question for those more versed in the physics than I am: can the two models be translated one to the other?

Another question:

If I divide a whole (reality) into parts a,b,c,d (spacetime model) and explain the history of interactions of those parts and then explain the same whole by dividing it into different parts w,x,y,z (quantum model) and explain their history, have I described the same whole if I cannot translate a,b,c,d into w,x,y,z?

[uwot]

As a rule, I wouldn't disagree with Feynman, and if I did, my first instinct would be to change my mind, but generally people use the tools available to them. Some mathematicians will hammer away with the one that has worked up to that point, others will try something else in the toolbox, but then yet others will invent something new. It is never clear which approach will work, until a viable solution is found. All three, potentially will provide an answer, they may all be equally accurate and there's no reason to suppose that any one is 'better' than the others. The usual criteria for choosing in such instances is ease of use, elegance, simplicity or beauty; which are, as you say, psychological factors.

Another question:

If I divide a whole (reality) into parts a,b,c,d (spacetime model) and explain the history of interactions of those parts and then explain the same whole by dividing it into different parts w,x,y,z (quantum model) and explain their history, have I described the same whole if I cannot translate a,b,c,d into w,x,y,z?

The point that Newton and Bohr were making is that you can never know for certain what the underlying reality is. You don't know that the equipment available to you in the future will not reveal something you don't know now. In that sense, there will always be something 'metaphysical'.

[Wyman]

Is it impossible to know or just unlikely? The possibility or impossibility (in a theoretical sense) of describing the world is an epistemological question. I think Einstein believed in the possibility of describing the world. A full description of the world would be: given a baseline state, could the future and past be predicted fully? I think the theoretical possibility of this is accepted by many physicists, for instance Hawking. The practical possibility of course is not.

If we (theoretically) describe the world in this way - completely predict its past and future states in entirety - then haven't we fully described reality? And hence, hasn't the metaphysical question gone away? For what would be left to say about it?

[uwot]

Is it impossible to know or just unlikely? The possibility or impossibility (in a theoretical sense) of describing the world is an epistemological question. I think Einstein believed in the possibility of describing the world. A full description of the world would be: given a baseline state, could the future and past be predicted fully?

You can predict all you like, but the thing with the future is that you don't actually know until it happens. I may be wrong, but I predict that will always be the case.

I think the theoretical possibility of this is accepted by many physicists, for instance Hawking. The practical possibility of course is not.

Even if a model could account for everything we see, I don't see that that would rule out the possibility of another, equally powerful model, predicting things with the same accuracy, but based on different premises.

If we (theoretically) describe the world in this way - completely predict its past and future states in entirety - then haven't we fully described reality? And hence, hasn't the metaphysical question gone away? For what would be left to say about it?

Well, that's why, generally, physicists don't get bogged down with metaphysics. Could any conceivable observation prove there is no god, for instance? I don't think so.

[Wyman]

Even if a model could account for everything we see, I don't see that that would rule out the possibility of another, equally powerful model, predicting things with the same accuracy, but based on different premises.

That's what I was getting at earlier, asking whether two such models could be translated into one another and if not, would that preclude us from saying that we 'know' that which is described by both models. Could we say that they describe the same reality? I don't have an answer, I'll have to think about it. But if anyone else has any thoughts...

Maybe it like asking whether the spacetime and quantum gravity models describe 'gravity' or describe 'observed phenomena.' I suppose you are saying that they both predict observed phenomena, but do not purport to describe one thing called 'gravity.'

[uwot]

Well, gravity is the force, the thing that is responsible for the phenomena. The force causes apples to fall on scientists heads and planets to orbit stars; there is no (reasonable) doubt that the force exists. Newton described the action of the force of 'gravity' without providing a model for how it worked. Einstein postulated a substance called space-time, which I wrote about on Sat Aug 30, 2014 12:06 pm. It is entirely possible to measure and understand the force in great detail, without knowing what causes it, which in fact is the situation we now have. Somewhere or other, I made the point that the same is true of all the fundamental forces of nature; none of which has the slightest effect on our ability to measure the strength of the fields. You can make up any reason that pleases you to account for forces, provided the measurable effects don't contradict it.

[Ginkgo]

Even if a model could account for everything we see, I don't see that that would rule out the possibility of another, equally powerful model, predicting things with the same accuracy, but based on different premises.

That's what I was getting at earlier, asking whether two such models could be translated into one another and if not, would that preclude us from saying that we 'know' that which is described by both models. Could we say that they describe the same reality? I don't have an answer, I'll have to think about it. But if anyone else has any thoughts...

Maybe it like asking whether the spacetime and quantum gravity models describe 'gravity' or describe 'observed phenomena.' I suppose you are saying that they both predict observed phenomena, but do not purport to describe one thing called 'gravity.'

Einstein did attempt to to reconcile his relativity with Newton's universal gravitation with his field equations. I guess this type of things is always the 'Holy Grail' of physics- reconciling one theory with another. Einstein did it with Newton and now it is the turn of someone to reconcile all of the fundamental forces (including gravity) into a single theory. Quantum loop gravity and string theory appear to be the the main candidates at this stage.

There is no observed phenomenon at the moment that we can invoked in order to prove string theory or quantum loop gravity. The scales are too tiny. I guess 'direct' observations would be useless anyway because of the incredible complexity and dynamics happening at those small scales. It would be incomprehensible to us, anyway. We can only ever base our understandings on experiences in the large scale world. The way physicists get around this is to use mathematics and simple models. Simple in relative terms. That is to say, simple compared to the actual complexity and dynamical nature of reality at this level.

Gravity like all of the other fundamental forces must play a part; ranging from the very large, which is well understood, down to the incredibly small. Gravity is the fly in the ointment because it is so incredibly weak compared to the other forces, yet at the smallest scales it must play a important part of any theory. I guess the thing that drives physicists on is the fact at the very beginning of the universe all the fundamental forces must have been united into a single force. Unfortunately even the LHC cannot produce anywhere near the energies required to simulate the very beginnings of time.

Anyway, that is my understanding. Other may disagree,

[Ginkgo]

Hi uwot,

I didn't see your post above mine. looks as though you were going to say pretty much the same thing as myself.

[Wyman]

Well, gravity is the force, the thing that is responsible for the phenomena. The force causes apples to fall on scientists heads and planets to orbit stars; there is no (reasonable) doubt that the force exists. Newton described the action of the force of 'gravity' without providing a model for how it worked. Einstein postulated a substance called space-time, which I wrote about on Sat Aug 30, 2014 12:06 pm. It is entirely possible to measure and understand the force in great detail, without knowing what causes it, which in fact is the situation we now have. Somewhere or other, I made the point that the same is true of all the fundamental forces of nature; none of which has the slightest effect on our ability to measure the strength of the fields. You can make up any reason that pleases you to account for forces, provided the measurable effects don't contradict it.

I guess I am not following how you see a level of causation beneath gravity - that we can know gravity but not what 'causes' it. You seem to posit a metaphysical 'cause' or 'reality' that is unknowable which causes things like gravity. Or else, you attribute such a view to Newton and Bohr. But then you say things like:

'Well, that's why, generally, physicists don't get bogged down with metaphysics.' If there is some unknowable something underlying the observed world, that sounds like a metaphysical statement to me.

Also, did Einstein postulate a new substance? Space and time have always been postulated. Arguably, he took the equivalence of inertial mass and gravitational mass (and other postulates) and gave it an interpretation which in turn necessitated a change in how we regard space and time. That is, the four coordinates, x,y,z, and t were always there, he just gave them a new interpretation (t is not constant and they follow non-Euclidean rules).

[uwot]

I guess I am not following how you see a level of causation beneath gravity - that we can know gravity but not what 'causes' it. You seem to posit a metaphysical 'cause' or 'reality' that is unknowable which causes things like gravity. Or else, you attribute such a view to Newton and Bohr. But then you say things like:

'Well, that's why, generally, physicists don't get bogged down with metaphysics.' If there is some unknowable something underlying the observed world, that sounds like a metaphysical statement to me.

Also, did Einstein postulate a new substance?

Yes he did. He gave a lecture at the university of Leiden, in Holland, 6 months after the results of Eddington's expedition to photograph stars 'behind' the sun during a total eclipse had confirmed that light bent around the sun as General Relativity said it would. An English translation is available here: http://www-history.mcs.st-and.ac.uk/Ext ... ether.html . Sample quote: "according to the general theory of relativity space is endowed with physical qualities; in this sense, therefore, there exists an ether."
The particular physical quality that Einstein endowed space with was the ability to be warped. This is often described by analogy with a 2 dimensional rubber sheet that is warped by placing a weight on it. This introduces a third spatial dimension into the analogy, so if the analogy holds, we are compelled to introduce a forth spatial dimension into spacetime; not a lot compared to string theory.
I think there is a simpler explanation. The bending of light that Eddington observed is indistinguishable from the effect due to refraction; light 'slows down' in a dense medium. In the same lecture Einstein makes the point that:
"according to our present conceptions the elementary particles of matter are also, in their essence, nothing else than condensations of the electromagnetic field"
Later quantum fields theories, QED and QCD in particular and more recently Higgs, postulate different fields, but the idea that fundamental particles are 'condensations' is the same. Given that massive objects are made of things that are condensations of fields it seems entirely plausible that the density of the combined field dissipates with distance very much as the strength of the gravitational field does. As I said, the starlight that Eddington captured looks as though it has been refracted; if that is what is happening, then you can expect the same effect on any particle that moves in the same plane. As the constituent particles in atoms that make massive objects are effectively tumbling over each other, there is a component of their motion that is parallel to the starlight. There is also an equal component in the opposite direction; electrons and quarks are hence refracted twice; the net result is a 'force' towards the denser medium.

Space and time have always been postulated. Arguably, he took the equivalence of inertial mass and gravitational mass (and other postulates) and gave it an interpretation which in turn necessitated a change in how we regard space and time. That is, the four coordinates, x,y,z, and t were always there, he just gave them a new interpretation (t is not constant and they follow non-Euclidean rules).

If you take a rubber sheet that is warped by mass and turn it upside down, you have a graph, the x and z coordinates of which give distance from the source, the y axis gives field strength; it works just as well if y represents field density.
As to 'Well, that's why, generally, physicists don't get bogged down with metaphysics.' the same graph works just as well if you say: "That is how hard the fairies push things together."

[Ginkgo]

I guess I am not following how you see a level of causation beneath gravity - that we can know gravity but not what 'causes' it. You seem to posit a metaphysical 'cause' or 'reality' that is unknowable which causes things like gravity. Or else, you attribute such a view to Newton and Bohr. But then you say things like:

'Well, that's why, generally, physicists don't get bogged down with metaphysics.' If there is some unknowable something underlying the observed world, that sounds like a metaphysical statement to me.

This is where uwot and I part company. My position is basically that gravity is a fundamental force in the same way as the other other forces are fundamental. In other words, said forces cannot be explained in terms of anything else.

I am sure uwot will have a fair bit to day about my statement, and fair enough I might add. This sort of thing is subject to volumes of philosophical debate.

Also, did Einstein postulate a new substance? Space and time have always been postulated. Arguably, he took the equivalence of inertial mass and gravitational mass (and other postulates) and gave it an interpretation which in turn necessitated a change in how we regard space and time. That is, the four coordinates, x,y,z, and t were always there, he just gave them a new interpretation (t is not constant and they follow non-Euclidean rules).

I don't think so. Einstein is not postulating any new substance. From my point of view he outlining a more dynamic role for space and time when we add gravity into the mix. In other words, space and time are no longer the background or backdrop where physical events are played out. As as per Newton. I guess we can say that under Einstein, universality switches from space/time to the idea of gravity being universal. As one would expect this idea is not without problems as well.

[Wyman]

I guess I am not following how you see a level of causation beneath gravity - that we can know gravity but not what 'causes' it. You seem to posit a metaphysical 'cause' or 'reality' that is unknowable which causes things like gravity. Or else, you attribute such a view to Newton and Bohr. But then you say things like:

'Well, that's why, generally, physicists don't get bogged down with metaphysics.' If there is some unknowable something underlying the observed world, that sounds like a metaphysical statement to me.

This is where uwot and I part company. My position is basically that gravity is a fundamental force in the same way as the other other forces are fundamental. In other words, said forces cannot be explained in terms of anything else.

I am sure uwot will have a fair bit to day about my statement, and fair enough I might add. This sort of thing is subject to volumes of philosophical debate.

Also, did Einstein postulate a new substance? Space and time have always been postulated. Arguably, he took the equivalence of inertial mass and gravitational mass (and other postulates) and gave it an interpretation which in turn necessitated a change in how we regard space and time. That is, the four coordinates, x,y,z, and t were always there, he just gave them a new interpretation (t is not constant and they follow non-Euclidean rules).

I don't think so. Einstein is not postulating any new substance. From my point of view he outlining a more dynamic role for space and time when we add gravity into the mix. In other words, space and time are no longer the background or backdrop where physical events are played out. As as per Newton. I guess we can say that under Einstein, universality switches from space/time to the idea of gravity being universal. As one would expect this idea is not without problems as well.

So I am reading things the same as gingko. That's not to say we're right, but just that that is how I interpret what I have read about physics, which is a 'layperson's' understanding at best (speaking for myself, not gingko). I'll have to think about uwot's position some more and maybe re-read some Einstein and/or Hawking in light of it.

[Ginkgo]

I guess I am not following how you see a level of causation beneath gravity - that we can know gravity but not what 'causes' it. You seem to posit a metaphysical 'cause' or 'reality' that is unknowable which causes things like gravity. Or else, you attribute such a view to Newton and Bohr. But then you say things like:

'Well, that's why, generally, physicists don't get bogged down with metaphysics.' If there is some unknowable something underlying the observed world, that sounds like a metaphysical statement to me.

This is where uwot and I part company. My position is basically that gravity is a fundamental force in the same way as the other other forces are fundamental. In other words, said forces cannot be explained in terms of anything else.

I am sure uwot will have a fair bit to day about my statement, and fair enough I might add. This sort of thing is subject to volumes of philosophical debate.

Also, did Einstein postulate a new substance? Space and time have always been postulated. Arguably, he took the equivalence of inertial mass and gravitational mass (and other postulates) and gave it an interpretation which in turn necessitated a change in how we regard space and time. That is, the four coordinates, x,y,z, and t were always there, he just gave them a new interpretation (t is not constant and they follow non-Euclidean rules).

I don't think so. Einstein is not postulating any new substance. From my point of view he outlining a more dynamic role for space and time when we add gravity into the mix. In other words, space and time are no longer the background or backdrop where physical events are played out. As as per Newton. I guess we can say that under Einstein, universality switches from space/time to the idea of gravity being universal. As one would expect this idea is not without problems as well.

So I am reading things the same as gingko. That's not to say we're right, but just that that is how I interpret what I have read about physics, which is a 'layperson's' understanding at best (speaking for myself, not gingko). I'll have to think about uwot's position some more and maybe re-read some Einstein and/or Hawking in light of it.

Hi Wyman,


Fair enough, none of this stuff is set in concrete. It is quiet possible we are all wrong- laypeople or otherwise.