Philosophy Now Forum

Obvious Leo wrote: There's no such thing as a flat space.

No but it is a bloody good approximation to the situation pertaining to us here on the surface of a planet the size of Earth!

Obvious Leo wrote:

nix wrote: We do not know! Is this question even meaningful?

To a philosopher it certainly is. Empty space has no physical properties and yet it can supposedly expand and contract and bend and twist and curve. How does an entity with no physical properties perform such miraculous feats. You accuse me of mystical nonsense and then you try and defend this action at a distance bollocks. No wonder physics makes no fucking sense.

Einstein's position was that space only had meaning in the distances between objects; he rejected the the notion of empty space devoid of matter like an empty container waiting to be filled. So the twisting and curving of space is not some sort of mechanical kneeding of the dough of space, but it is an expression of the measureable geometry between objects.

You keep misusing the term action-at-a-distance: field theories (like GR) have local action between the field and the mass particle. A stationary distribution of mass sets up the field throughout space time "action-at-a-distance" occurs only if the field is established instantaneously everywhere (as in Newtonian gravity) But GR doesn't do this, the field is only established at a finite speed (light speed), so any changes in the distribution of mass causing changes in the field propagate at finite speed as gravity waves.

Usual calculations in GR might look like action at a distance as the field is unchanged by the motion of a small test body as it moves around some much more massive object because of the relative sizes of the objects. In a collision between two black holes you couldn't do this and the calculations become horribly non linear as the field changes propagate and interact with the moving bodies!

[

nix wrote:field theories (like GR) have local action between the field and the mass particle.

This is not a physical statement. A field is a mathematical contrivance devised by an observer to model a certain pattern of organisation he perceives in the behaviour of matter and energy. You make it sound as if the field is a physical entity which is even more absurd than a physical space.

Obvious Leo wrote:[

nix wrote:field theories (like GR) have local action between the field and the mass particle.

This is not a physical statement. A field is a mathematical contrivance devised by an observer to model a certain pattern of organisation he perceives in the behaviour of matter and energy. You make it sound as if the field is a physical entity which is even more absurd than a physical space.

The point im getting at is that GR is not an "action at a distance" theory while Newtonian gravity is; GR accounts for the finite speed of propagation of gravitational interaction between bodies it doesn't have an instantaneous interaction.

I used the notion of field in the usual physics manner (cf Newtonian gravitational field, electromagnetic field, Einstein's field etc because the mathematical apparatus for making predictions of the motion of bodies is most familiar in that language) To be consistent you would have to maintain there is no such physical thing as an electromagnetic field either just photons being absorbed and emitted by bodies. While it is true you can look at electromagnetism like that (Feynman did) you get the same predictions of the theory either way, the field language is easier to visualize and calculate in.

nix wrote:The point im getting at is that GR is not an "action at a distance" theory while Newtonian gravity is; GR accounts for the finite speed of propagation of gravitational interaction between bodies it doesn't have an instantaneous interaction.

I don't deny that GR is an improvement on Newton's idea because the action at a distance is not assumed to be instantaneous. However it IS non-mechanical because to say that matter follows the trajectory of a curved space is not a physical statement, since a curved space is a mathematical construct and not a physical one. GR does not offer an explanation of how this occurs, only how this can be mathematically modelled.

nix wrote:I used the notion of field in the usual physics manner (cf Newtonian gravitational field, electromagnetic field, Einstein's field etc because the mathematical apparatus for making predictions of the motion of bodies is most familiar in that language) To be consistent you would have to maintain there is no such physical thing as an electromagnetic field either just photons being absorbed and emitted by bodies. While it is true you can look at electromagnetism like that (Feynman did) you get the same predictions of the theory either way, the field language is easier to visualize and calculate in.

I'm not questioning any of this. All I'm pointing out is that the "field" is a feature of the map and not a feature of the territory. I am indeed saying that ontologically there is no such thing as a field. Physics speaks of fields as if they were causal agents but fields are nothing more than epistemic descriptions of the behaviour of matter and energy. They are modelling this behaviour, not causing it, and the distinction is not a trivial one. QFT in particular is guilty of this logical fallacy of getting cause and effect arse-about.

Obvious Leo wrote:I don't deny that GR is an improvement on Newton's idea because the action at a distance is not assumed to be instantaneous. However it IS non-mechanical because to say that matter follows the trajectory of a curved space is not a physical statement, since a curved space is a mathematical construct and not a physical one. GR does not offer an explanation of how this occurs, only how this can be mathematically modelled.

You seem to want a mechanism which explains why the planet takes the route it does beyond the ability to predict by calculation the route taken. If our calculation always agreed with observation we would say "nature follows the same rules as we have used to make the prediction" but this will not give a mechanism as to why it follows these rules.

Why of all the possible trajectories over the curved surfaces given by the Einstein equation do all free falling bodies observed in nature take the one particular route corresponding to the 'geodesic curve' ? We do not know the "why it moves this way" only that it does move that way.

Why are Maxwell's equations so good at predicting electromagnetic phenomena? etc etc...Because they correctly represent something about nature. Beyond this we cannot go.

To use your metaphor: when your map is detailed enough and is tested enough against physical measurements and found to give enough correct answers you start to believe, with justification, that it correctly describes the territory.

I had a thought about our disagreement on the expression of time as a distance.

For a given observer The time axis of a space-time diagram is never confused with any of the space axes. There is no legitimate Cartesian rotation of the axes allowed in these diagrams which would mix space and time coordinates for the same event for the same observer. It is always clear what is time and what is space to that observer. It is only when two different observers moving with respect to each other at constant speed observing the same event and compareing their results that the space and time coordinates have to mix and the time coordinate has to be multiplied by c because the velocity of light is the same in both frames; hence transforming the time coordinate into a distance.

On the separate matter of real physical time and real physical space.

If real physical time is measured by real physical clocks then distance has to be considered to be real physical distance: I can make a clock to measure time from a meter rule with two mirrors in which the number of times a light pulse passes back and forward between the mirrors is counted, each pass being one tick of my clock. The time measurement is as real as the distance measurement in this apparatus.

Obvious Leo wrote:

nix wrote:

Obvious Leo wrote:gravity is not seen as a force but as a fundamental property of the universe from which all the other so-called forces derive.

I am sorry if I misread this as asserting that all the other forces derive from gravity but that is what it says!

nix wrote: No that doesn't follow, because everything is not frozen in place, hence time exists as changes in the complexions of this Cartesian space, if it weren't for the objects in the Cartesian space and their variations we could not even define time!

What don't you try and explain why the equations of physics are time invariant and reality is not? Even better. Why don't you try and explain why some but not all of the equations of physics are time invariant? Are you seriously proposing that these equations are modelling a physically real universe. If so you may be interested in an Eiffel tower I have for sale.

I'm still waiting for you to explain the mechanism by which space expands by the way. Does it just thin itself out a bit or do new bits of space appear from somewhere to fill in the gaps?

I'm CAN explain this [the bolded challenge above]. I just responded in the "Models versus Reality..." thread how frustrating it is to get past people's interpretations without having to begin with their perspective. I am confident I can do this but question the effort needed to do it. With you, I'd have to first begin with your premises and thinking regarding time as all that exists to show where your arguments lead to conflict. So I'm faced with having to unravel each person's understanding before I posit my own. See viewtopic.php?f=5&t=16398&p=214774#p214774 for a hint at how this can be done.

nix wrote:
You seem to want a mechanism which explains why the planet takes the route it does beyond the ability to predict by calculation the route taken. If our calculation always agreed with observation we would say "nature follows the same rules as we have used to make the prediction" but this will not give a mechanism as to why it follows these rules.

Why of all the possible trajectories over the curved surfaces given by the Einstein equation do all free falling bodies observed in nature take the one particular route corresponding to the 'geodesic curve' ? We do not know the "why it moves this way" only that it does move that way.

Don't forget that the predictions of orbital motion in GR are only approximations in a precisely defined scenario, albeit very good ones. If a rogue star happens along then all bets are off. The motion of every physical entity in the universe is gravitationally affected by the motion of every other, a simple truth that even Newton was aware of but is often overlooked. If I get up to go for a piss everything in the universe will move as a result. Everything in the universe is causally connected to everything else in the universe and a more precise definition of a non-linear dynamic system is impossible to imagine. Just because a bloke in the Andromeda galaxy will have to wait a couple of million years to feel the effects of the pressing demands of my bladder doesn't make it any the less so.

In philosophy precision of language is important and negligible is NOT synonymous with irrelevant so the spacetime map is only a good approximation to the territory and when it comes to the explanatory authority of any model a miss is as good as a mile. The future is a blank slate and our current models of physics are denying this.

nix wrote: Why are Maxwell's equations so good at predicting electromagnetic phenomena? etc etc...Because they correctly represent something about nature. Beyond this we cannot go.

Wrong. Beyond this we cannot go with the current paradigm. However beyond this we MUST go if we are to achieve a unification model. Thomas Kuhn was easily the most insightful philosopher of physics of the 20th century and this insight is still being ignored. Physics is nothing more than a mathematical method of codifying a procedure of thought and Kuhn quite rightly pointed out that it is the procedure of thought which needs to change before the models can be integrated. I'm claiming that redefining determinism as non-linear rather than linear is the elephant in the room.

nix wrote:To use your metaphor: when your map is detailed enough and is tested enough against physical measurements and found to give enough correct answers you start to believe, with justification, that it correctly describes the territory.

Wrong. No such justification exists according to the philosophy of knowledge. This is a logical fallacy because the map can only describe your own narrative of nature and not nature itself. The cosmology of Ptolemy endured for over a thousand years on the basis of this same logical fallacy. Continuously refining a model with ever greater mathematical intricacy is inherently tautologous and will lead the scientist ever further into a conceptual cul-de-sac if the underlying narrative is flawed. The universe determined according to a suite of laws is a flawed narrative so physics has been chasing a rainbow since Newton.

nix wrote: It is only when two different observers moving with respect to each other at constant speed observing the same event and compareing their results that the space and time coordinates have to mix and the time coordinate has to be multiplied by c because the velocity of light is the same in both frames; hence transforming the time coordinate into a distance.

All I'm saying is that this may be a clever mathematical trick which allows us to make very precise predictions but this doesn't mean we're making a statement about reality. If we design our models specifically to predict what the observer will observe we can claim only a Pyrrhic victory when the observer duly goes ahead and observes what our models have predicted. Surely you can see the tautology here because an observation is an artefact of human consciousness. It has no ontological status whatsoever and its epistemic status is only what the observer assigns to it. There is no reason whatsoever why we couldn't send a mission to Pluto by using Ptolemy's assumptions instead of those of modern physics. I shudder to think what the mathematics would look like because the heliocentric paradigm is far simpler. However to suggest that it is in some sense "truer" is nothing more than an anthropocentric vanity.

Scott. It's rather a pity that this thread is overlapping with the Models V Reality topic but obviously many of the points being raised here are relevant to both. I've never suggested that the model-building methodology of physics is in some way "wrong" but merely point out that we need to exercise great caution when drawing conclusions about what these models can or cannot tell us about the universe. For some reason this inherent shortcoming in the methodology was very well understood by the pioneers of early 20th century physics but nowadays is routinely overlooked.

Obvious Leo wrote: In philosophy precision of language is important and negligible is NOT synonymous with irrelevant so the spacetime map is only a good approximation to the territory and when it comes to the explanatory authority of any model a miss is as good as a mile. The future is a blank slate and our current models of physics are denying this.

while I agree with most of your unquoted comments in the last post, in the quote above you assert that because the "maps" are always by definition approximations they can have no explanatory authority. This is where we differ most. I would say they have provisional explanatory authority. We do not have "the eyes of god" to be able to see the territory, all we have are the maps and a method of testing the question "is the map good at this point" (experimental measurement of phenomena predicted by the map). We get a yes /no answer and continue our investigation.

Pure reason alone will not show us the territory. (cf Kant and endless debate since).

When you say the future is a blank slate what are you asserting? That the Laplacian claim is false? (i.e.given the initial conditions and the Newtonian laws all future time is predictable/determined?). I know of no living physicists who don't believe that Laplace was wrong in this! Current models do not deny this, they ignore it because to formulate say a non linear theories in some areas for example, is beyond our current mathematical methods. The linear theories are tractable and good mathematical first approximations to the non linear theory. It is not that physicists are stiff necked about this, it is a matter of pragmatism!

Thomas Kuhn wrote historical studies about past paradigm shifts in physics, showing in detail how they occurred. But this doesn't give a blueprint as to how to make a paradigm shift happen. It has to occur organically from within the discipline prompted by the continual failure of some specific predictions of accepted theory to match experimental measurements.... Most physicists I know have read Kuhn! Yes the paradigm shifts may involve a change of conceptual perspective in response to some perceived crisis of the investigator ( and that might be aesthetic - i.e. "this theory is more beautiful than that to my eye" cf Dirac's search for his equation when a "perfectly acceptable" amalgam of QM with SR already existed by Kline and Gordon).

Obvious Leo wrote:All I'm saying is that this may be a clever mathematical trick which allows us to make very precise predictions but this doesn't mean we're making a statement about reality. If we design our models specifically to predict what the observer will observe we can claim only a Pyrrhic victory when the observer duly goes ahead and observes what our models have predicted.

But that is not what physics does, it is not just an exercise in curve fitting to existing data in the way you suggest, (model fitting to the data we already have in hand). Theoretical improvement comes when a model is invented which accounts for the data we already have (so in that sense it will just give us back the data it was designed to account for) But it must also predict new possible measurements which we hadn't thought of before and which we can go out and test, so it is not true that because our models just fit the empirical observations they tell us nothing about nature.

Believe it or not we're actually getting somewhere close to meeting on common ground because I agree with most of this.

However I don't agree with this.

nix wrote: I would say they have provisional explanatory authority

I don't think the idea of provisional explanatory authority stands up to logical scrutiny and I stand by my claim that a miss is as good as a mile when it comes to explanations. Just because a model can make very close approximate predictions we can't logically conclude that the narrative we adopt to explain them is "nearly right".

nix wrote: Pure reason alone will not show us the territory. (cf Kant and endless debate since).

I absolutely agree with this and take pains to stress this point throughout my philosophy. I'm not suggesting that we need to throw out the baby with the bathwater and abandon our epistemic models of physics. What we need to be able to do is marry two different approaches to the acquisition of knowledge in such a way that they complement each other rather than contradict each other, as they currently do. The spacetime model contradicts some of the most basic metaphysical first principles without which a comprehensible universe is impossible. The process of logical deduction from first principles must be compatible with the process of inductive inference from observation and empirical experiment. In other words physics must not only conform to empirical data it must also make sense. The bullshit idea of redefining what making sense means has taken physics nowhere in a century and it never will. This is what Kuhn was driving at with his new Copernican revolution.

nix wrote:When you say the future is a blank slate what are you asserting? That the Laplacian claim is false? (i.e.given the initial conditions and the Newtonian laws all future time is predictable/determined?). I know of no living physicists who don't believe that Laplace was wrong in this! Current models do not deny this, they ignore it because to formulate say a non linear theories in some areas for example, is beyond our current mathematical methods. The linear theories are tractable and good mathematical first approximations to the non linear theory. It is not that physicists are stiff necked about this, it is a matter of pragmatism!

This is very nicely expressed. I realise that everybody knows that the Laplacian claim is false but it is nevertheless an implicit conclusion of the model. In other word they know the models are bullshit but they'll keep using them because they work so well. I don't have a problem with this as long as they understand that this means the models can't be used to explain anything.

It's not true that formulating a non-linear theory is beyond our current mathematical methods. This is exactly what Poincare was working on when he died and he never bought into the Minkowksi bullshit for a moment. The answer lies in the 3 body problem which has nowadays been extended to the n-body problem. Fractal geometry is not for the mathematically fainthearted but that's where the future lies for physics, mark my words. Note that I don't claim that such methods are likely to yield more accurate predictions than Newton's calculus but neither are more accurate predictions ever going to be necessary. The simple fact is that the future can only be predicted to a finite order of probability and that's a simple truth we need to learn to live with. The uncertainty in sub-atomic physics has got nothing to do with randomness or uncaused events, nix, it's just a perfectly natural feature of chaotic determinism.

What is always going to be impossible is formulating a non-linear theory within the spacetime paradigm because non-linear dynamic systems cannot be modelled in a Cartesian space with Newton's mathematical tools. This was Einstein's final gift to mankind because he revealed exactly this in one of the last interviews he gave in his life. Sadly he had been written off decades earlier by the logical positivists as a superannuated has-been and nobody took any notice.

You seem to have ignored my attempt to get you to accept that physical time and physical space must have equal ontological status (i.e. if you accept one as real you have to accept the other as real also). I have a final thought on this for you:

The most precise clock we can construct (an atomic clock) measures the passing of physical time. It works by measuring the frequency,F, of light of a spectral line (number of oscillations per second for that light). But for light the velocity, c = F.L where L is the wavelength of light, so the ontological status of the time measure and the length measure stand or fall together if light is given a "real physical" status.