Reductionist Doubts by Julian Barbour

You deleted all my comments because I did not read Shape Dynamics? The punishment is unproportional to the crime, Julian Barbour.

Pentcho Valev

You are "in the job of actually salvaging absolute simultaneity away from the clutches of Einstein", Julian Barbour. So Harvey Brown says. You confirm:

Aspects of Time, Julian Barbour, Warwick, August 24th 2011: "Was Spacetime Glorious Historical Accident? (...) ABSOLUTE SIMULTANEITY RESTORED!"

The problem is that, in textbooks, the relativity of simulteneity is derived from the principle of constancy of the speed of light (Einstein's 1905 light postulate). So if asked:

Can absolute simultaneity and the light postulate coexist in Einstein's relativity?

any textbook author would give a negative answer. Now my question:

Can absolute simultaneity and the light postulate coexist in Shape Dynamics?

Please don't delete the question, Julian Barbour. If your answer is "yes", then Shape Dynamics is a miraculous science, even more miraculous than relativity, and I promise to study it very carefully.

Pentcho Valev

Dear Mr Julian Barbour

Our intuition gives that Machian principle is foundation of physics, although it is not yet proved. Similar unproved intuition appears at fundamentality of consciousness and that gravitational force is different that other forces.

You wrote that time arrow is a holistic phenomenon. I wrote similarly in one old article: "Important time's arrow is also the cosmological time's arrow. It is very likely that all in our cosmos is connected, so it has the same direction of time's arrow. It is not possible to communicate with someone who travels in opposite time direction. Therefore, time's arrow at the collapse of a wave function can choose arbitrary plus or minus direction, but it is motivated by direction of time's arrow in the cosmos. (By the way, it is very likely that explanations of big-bang need improvement. For instance, why is entropy at big bang very low?! Low entropy does not happen spontaneously.) Hitoshi Kitada [15] wrote that absolute time of universe does not exist and that only time for local observers exists. This is true in principle, but time also exists as connection between local observers, local observers are connected and this gives one direction of time's arrow of cosmos."

I claim also that space-time is an emergent phenomenon caused by matter. Otherwise, interpretation of general relativity also claims, whether all matter is removed from universe, nothing remains - neither empty space. This is a holistic consequence of general relativity similarly as Machian principle is.

This is written in my essay: "SR gives also that space-time is emergent so time exists only in matter [8], although, formally, every point in space in SR has attributed time. This is rarely mentioned, but it is very important. Namely, if all matter had been removed from our universe, there would not remain anything, not even space-time. Otherwise, this is given also by GR by its "diffeomorphism invariance" and by the "background free space-time" [9, p. 138]. Similar conclusions are given also by Markopoulou, namely that space-time arises as a consequence of relations between the elementary particles (or other elements of matter) [10]."

Maybe you should mentioned in introduction that quantum field theory is also holistic principle where field is more important than single particles.

My speculation: Maybe all universe has also properties of a particle. Otherwise, I am sure that black holes are elementary particles, maybe also universe is one particle, that means that it shows some properties of elementary particles.

Because of clarity it should be mentioned that Machian principle is also generalization of relativization: relations between objects are more important than location in one inertial system or in one coordinate system - similarly is at relativity principle.

Maybe You should explicitly mentioned that because angular momentum of universe is zero and because universe is finite, the Newton's bucket is so explained as not contradictory with Machian principle.

You replace time with time of universe. This is a cunning and something grounded idea, maybe it will show as good.

You mentioned that only six components of metric tensor is physically important, this means one volume and five angles. I do not understand what means which component? Can you explain this on three and two dimensional metric tensor and on a four dimensional example of Schwarzschild Black hole. Here non-diagonal components are zero, thus angles are only 90°? Do You think also about angles between coordinate axes?

You write also about dimensionless quantities. Do you see any advantage of using Planck's distance.

I suspect in my essay, that interior of black holes does not exist, similarly as tahions do not exist. Is this in any accordance with Your theory? Do You propose and novelty about Big Bang?

Otherwise You write very clearly.

Dear Julian

Original, thoughtful and well explained. But is reductionism a 'mutually exclusive' methodology? Should the real solution to the workings of the universe not be valid on a macro as well as micro scale, deriving observed reality from a consistent mechanism applicable to both ends of the 'known' scales, quanta to universe? (both ends of course yet unconstrained).

I now better understand your shape dynamics, but wonder where evolution from relative motion lies within it, as it seems not at the centre. Am I wrong? I found myself desperately hoping for a 'success' to hang this new set of beliefs on, but despite incisive analysis nothing materialised. May I offer an ADM based option.

You'd need to read my essay, but what this does is derive the effects we term SR from a quantum mechanism, and the mechanism from the morphology and evolution of universes. It may be seen as defining and creating the boundaries of closed three-geometries, each a mutually exclusive but nested inertial frame, defined by relative kinetic states. These have real evolving shapes, but size is immaterial. From the foundational structure of truth function logic an ontologial construct is described in the essay entirely from epistemological elements. A pre big-bang (not really a 'bang') state emerges as logically as local CSL.

I quite understand how improbable this seems, it is none the less the case. As Feynman said it does at first look wrong, so fails the test of 'beliefs' most use, but it has passed all falsification. I hope you may give it a stern test, and look forward to your critique. http://fqxi.org/community/forum/topic/1330

Interestingly, the physical reality of the boundary mechanism is shown and correctly interpreted in the experimental findings in Rich Kingsley Nixey's essay Fig.2.; http://fqxi.org/community/forum/topic/1448

Yours is a more clearly written essay than my own, with perhaps too dense an Architecture of the components, though I do add a little superficial theatre for fun.

Best wishes and good luck in the competition.

Peter

Dear Dr. Barbour,

I just read your essay. The idea of shape dynamics appears to be a form of Regge calculus. I watched a video presentation of yours on the FQXi blog. The time evaluated from the Jacobi variational principle

δt = sqrt{m_iδx_iδx_i/(E-V)}

is related to a proper time, or an interval. This got me thinking about how you could describe this in a completely non-time manner.

It dawn on me how one could think about this according to light rays. In this way there is no matter of time involved with the "motion" of a shape, for null rays have no proper time. I illustrate this with two diagrams I attach to this post. The first is a flat spacetime description. This is also pictured in 2-space plus 1-time spacetime in 3 dimensions. Two points on a spatial surface emit light pulses. These converge on three points on a subsequent spatial surface. These then define a triangle on that spatial surface. The two points then emit subsequent light pulses and map the triangle onto a third spatial surface. In Minkowsk spacetime this continues indefinitely.

In the curved spacetime situation null rays are curved. Since the metric

ds^2 = g_{00}c^2dt^2 - g_{ij}dx^idx^j

is such that for ds = 0 we can have

U^iU^j = (g_{00}/g_{ij})c^2dt^2

And the optical path change due to curvature has a c^2 term. Hence we can assume the triangles on the spatial surface are flat. The deformation of null rays will then map the first triangle on the second diagram I attach into the second. The picture here is then completely described by null rays which have no proper time.

The time computed by the Jacobi variation is then an "emergent" or computed quantity. This is a parameter which emerges from the "motion" of the triangle, or the map from the first to the second.

On another vein I am not convinced that time is a complete illusion. Maybe I will go into this later, but I think that in quantum spacetime it may be that if you only have space then time is not defined. Conversely, if time is defined you have no space. I suspect the two are complements.

Cheers LCAttachment #1: light_rays_and_triangles.JPGAttachment #2: null_rays_and_triangles_in_curved_spacetime.JPG

This post above is mine; I forgot to include my name. My essay is on a different path.

Cheers LC

Lawrence Crowell wrote: "On another vein I am not convinced that time is a complete illusion. Maybe I will go into this later, but I think that in quantum spacetime it may be that if you only have space then time is not defined. Conversely, if time is defined you have no space. I suspect the two are complements."

How can one qualify this without facing deletion? "Not even wrong" seems to be a suitable euphemism. Brendan Foster? Is "not even wrong" too rude? Are you going to delete this comment?

Pentcho Valev

here is what I wrote and got deleted without the link. do you think it is prime for deletion.

"The standard physics has failed to really tell us what reality is, your theory as non-standard is the most interesting one in my opinion. My theory QSA confirms your hypothesis as to the nature of time and is close to other aspects of your theory. It is also the most direct description of reality and it is a natural outcome of the mathematical universe hypothesis. My theory just like yours says that each point carries the information about the rest of the points in the universe; as a matter of fact that is how interaction is described (or brought about). My theory ties space (time indirectly), energy, matter, forces in one concept based on the line. The theory spits out the mass of the electron from purely random numbers, the first theory to naturally predict the mass of the electron. Moreover, the non-local behavior also naturally appears as an automatic consequence of invariance. Many other results are obtained including the amazing formulas."

Hi Julian,

I am always impressed with your commitment to relativity in its purest form.

I fail to understand, however, that you admit this barrier:

"I have given what I believe is the correct definition of Mach's principle [5] and argued that if the universe is closed up in three dimensions like the earth's surface in two then GR does implement Mach's principle [5]. If the universe is spatially infinite, the answer is equivocal. It is Machian however far you can imagine, but infinity is unreachable, and one can never establish a complete sense in which the whole determines the part."

Surely there are solutions to GR in an open universe that do not contradict Mach's principle. The conventional "finite and unbounded" interpretation of GR as finite in time (bounded at the singularity of creation) and unbounded in space, closed up like a 3-ball as you say -- suffers no loss of generality when transposed to a model finite in space and unbounded in time. This latter interpretation requires topology to implement global boundary conditions, and it agrees with your angle-preserving evolution of shapes without regard to the length-preservation inherent in ordinary geometry.

As always, thanks for a masterful presentation, and best wishes in the contest. (I hope you get a chance to visit my own essay site, "The Perfect First Question.")

Best,

Tom

don't try with the probelm of language and the name sphere and the name ball, for me a sphere is a ball ok dude ! You cannot arrive at your aim without bad strategies poor thinker.

Insert my spheres balls in yopur parallelizations of frustrated in team.I eat your sciences at my breakfast band of comics.And you know it all furthermore and you insit like poor obliged strategist of nothing for nothing.

put the ball in your sphere dude and buy people to kill me band of comics and don't say that it is FQXi, no it is you and your team,.FQXi it is a wonderful platform, unfortunally poor corrupted act with the soa .It is not a probelm you know.all is said in fact between us. your hate eats you in fact.You are not able to make other things in your life, because your hormons are probably weak.so you make a revenge. the ball and the sphere now, put it where I think and you brendan , delete boy of the team paid in the future .I have pity band of comics.

I will go at New York so kill me , it is better band of comics , your name are already in a letter copied for the attorneys and my friends all around this planet and even if you have utilized false name like a false friend, don't forget my quick analyze and the conclusion easy to see. and You Mr Barbour, you accept this comportment also, no not you?

You think what Tom that you can steal a thing impossible to steal.try like you make, you shall see on the entropical arrow of times, we shall discuss when we shall be in the aether poor thinker limited furthermore. I see only a publicity and always a kind of comportment of generalist, but no tam, you are not a generalist.patrick Murphy said to shane steiçnman that bruce watkins improve, let me laugh band of comics.and kill me, and still you shall loose in the aether ahahahh sleep well .I will be there all the nights in your dreams, just to show you what are the contemplations of the universe.pray so or buy a bibble and the talmud and the texts of siddartha Gottam, because be sure dude.You shall understand.

Regards and put the balls in your sphere comics vanitious full of hate, your hate increases still, logic in front of the truth for the pseudos.

and also dude decreasing the veloccity of your country,you know what, you can even try with the faith, and even with all the discriminations, that will not change the spherization of all high spheres. you can trying with all what you want, but you know the better I am repeating is really to kill me. It is more easy if you begin to have doubts you know dude. Am I a danger for USA no !!! I love USA.Am I a danger for the bad systems, yes because I dislike the bad.

Regards

Dear Julian

Freeman Dyson described reductionism in physics as the effort "to reduce the world of physical phenomena to a finite set of fundamental equations".

Please read my 2 essays

http://www.fqxi.org/community/forum/topic/946

http://fqxi.org/community/forum/topic/1413

It is a real triumph of reductionism.

No doubt about reductionism...

All the best

Yuri

Dear Dr. Barbour,

You kindly deleted the following comment of mine but I find it important so let me repost it.

You are looking for a no-expansion explanation of the Hubble redshift:

JUlian Barbour: "The greatest need is for an EXPLANATION OF THE HUBBLE RED SHIFT THAT DOES NOT RELY ON EXPANSION OF THE UNIVERSE. (...) The estimates of section 7 show how readily the scale-invariant potential energy can increase if the universe becomes more clumpy. Scale-invariant gravity must, in the first place, yield a cause of the Hubble red shift. The only plausible candidate that I can see is this change in the 'potential' of the universe induced by such clumping. It is suitably great and, according to the standard model, has been happening since the end of inflation. Therefore, the conjecture has to be that somehow the change in potential causes the Hubble red shift. This is not inherently impossible. We know that differences in the gravitational potential give rise to a gravitational red shift."

But the speed of light VARIES with the gravitational potential, according to both general relativity and Newton's emission theory of light. So perhaps the redshifted light coming from distant celestial objects has a speed lower than c? What does Shape Dynamics say?

Sincerely yours, Pentcho Valev

Hi Julian,

Take a look at: http://digitalwavetheory.com/DWT/22_Classical_Gravity.html

and: http://digitalwavetheory.com/DWT/21_Self-Gravity.html

It may give you some ideas on how to get a red shift without expansion. It is possible that the red shift may come from increased gravity and not increased speed.

OH, and if you get a chance check out my entry: http://www.fqxi.org/community/forum/topic/1403

Greetings from a fellow Machian.

Don L.

The computer and the universe

John Archibald Wheeler

Abstract

The reasons are briefly recalled why (1) time cannot be a primordial category in the description of nature, but secondary, approximate and derived, and (2) the laws of physics could not have been engraved for all time upon a tablet of granite, but had to come into being by a higgledy-piggledy mechanism. It is difficult to defend the view that existence is built at bottom upon particles, fields of force or space and time. Attention is called to the "elementary quantum phenomenon" as potential building element for all that is. The task of construction of physics from such elements is compared and contrasted with the problem of constructing a computer out of "yes, no" devices.

Preparation for publication assisted by the University of Texas Center for Theoretical Physics and by National Science Foundation Grant No. PHY78-26592.

http://www.springerlink.com/content/ck753337h0515573/

Julian Barbour wrote:

"First, I deleted nothing..."

Then I apologize. But my comments - 7 or 8 perhaps - all disappeared so... Brendan Foster, what are you doing?!?

"...second, they [absolute simultaneity and Einstein's 1905 light postulate] are compatible according to Shape Dynamics."

But, Dr. Barbour, in textbooks the relativity of simultaneity is directly deduced from the light postulate - see pp. 9-10 in David Morin's text. In other words, according to special relativity, absolute simultaneity and Einstein's 1905 light postulate are incompatible.

I think you should explain this contradiction between Shape Dynamics and special relativity.

Pentcho Valev

Dear Pentcho, Dear Julian,

thank you for clarifying your positions, so i can see more clearly.

Stefan

Pentcho

Has it ever struck you to ask what the speed at which any given photons happen to travel has got to do with anything? Except that is, the timing relationship between the incidence of observation and the occurrence of the reality which affected the state of those photons.

The whole issue of the supposed relationship between the speed of light and simultaneity is based on simple mistakes (section 1 1905). Unless they occurred in immediate proximity(!), the point in time when two events occurred simultaneously was deemed to have a relationship with the distance between them. This is nonsense. Either events occurred at the same time, or they did not, distance is irrelevant.

Distance was then expressed in terms of duration of light travel, which is irrelevant as such, in that the distance AB is one distance, however expressed. The next mistake was confusion over timing and duration. So the point in time at which both events occurred was defined as being when the time (ie duration) for light to travel in one direction equalled the time (ie duration) to travel back. Although nonsense anyway, this was then incorrectly expressed. Hence: when t(b) - t(a) = t'(a) - t(b), a duration of time has been confused with a point in time, ie this involves the concept of 'and then' back. Following on from this, the constant velocity of light is derived as: 2AB/ t'(a) - t(b).

Paul

Dear Julian,

An intriguing enjoyable and intriguing essay from an author I really respect. However I am not completely convinced that a holistic approach is always indispensable. Could one not argue, that if the result of the reductionist approach is a concept, idea or formula that is physically *very close* to nature then the whole would emerge from it on its own without further ado? As a minimalist example cellular automata interact according to a local rule and from it the whole emerges in due time.

Even so, perhaps I have implemented a species of Mach's principle in my Beautiful Universe Theory (BU) on which I based my fqxi essay Fix Physics! . My reductionist idea is that the Universe is made up of a lattice of just one type of building block. These blocks or nodes are discrete bundles of angular momentum rotating around their axes in units of (h) and the axes have various angular orientations in each timeless universal State. . Thus L =/= 0 in this scheme. Attached is figure 11 from my BU theory showing how a twist in the angular orientation of two nodes to lock into matter is caused by (or causes) the entire linkage of nodes throughout the universe to mimic the twist, and explaining why E=mc^2

I did not know about Mach's idea that time is emergent from motion. Interesting. I feel that the reductionist source idea in GR (space-time warping = gravity) is physically misleading. GR's Achilles heel is that it includes SR. Why should an observer-related physics enter in realms out there where it is only nature interacting with itself in the same inertial frame - for example light curving around the sun? Without SR, GR becomes very simple - gravity can be reduced to an optical density field, as Eddington proposed, and I have explained in BU.

Shape Dynamics (SD) sounds like a new concept that, at first sight, I wish I do not need to think about! - if there is a simple, local,causal explanation for gravity=acceleration=curvature I would be satisfied with that. In BU it is the curvature of the classical gravitational potential streamlines (or the orthogonal wavefronts) that defines this equivalence. You wrap SD in a probabilistic interpretation.

Quantum probability as a physically realistic phenomena is another of my bête noires . In BU I have shown how probability emerges naturally in the lattice interactions, and how the false point-photon idea made it seem that probability is an abstract interpretation of a dualistic particle-wave nature resistant to physical realism. Have you read the amazing experimental work of Eric Reiter reported in his current fqxi essay in which he proves that gamma rays are not point photons? In such a Nature where probability is the result of systematic, linear local interactions, entanglement can be understood simply and directly without resorting to further ingenious but perhaps complicating holistic ideas as SD.

Hope I have made some sense! I welcome your learned response to my rather qualitative and incomplete ideas.

With best wishes,

VladimirAttachment #1: 2_BUFIG11.jpg