owl

Check out my Ontology of Time thread in the Speculations section. How do you deal with the fact that the present means now, and "it is always now"... the past is not still present the future is not yet present. It's just too simple for a complicated mind set about time to comprehend... especially since "time dilation" reified "it" into being an entity in and of itself. Clocks "keep time" differently ("tick" at different rates) in different environments. This does not make time into a variable entity. What say you?

As I said, I simply did not know how to be any more clear than I already had. A vacuum can easily be added to my list of synonyms for space as emptiness, no-thing, nada volume not containing anything,etc. Most relativity theorists say that space curves. It must be something(not nothing) to curve. This doesn't have to be complicated. Those who say that space curves must say what it is that curves. Our previous context was speaking of the distance between objects in spacelike earth to mars or to the sun, to the point that the space between them does not vary with extremes of frames of reference from which those distances are measured. Same with rods of intrinsic, objective length, not shrinking and stretching with different extreme frames from which it is measured like from a near light speed fly by. In the case of earth's diameter, I agree with the measurement of that distance above. I addressed the question of the "true distance" between two points on the surface of a sphere earlier. It could as well have been through the earth. In a later example I called it a ball, which could have been solid or not. The point was that a straight line (or needle) through the ball is the shortest distance between two points on the surface of the ball, not the arc between them on the surface.(Just to again establish the context in which this was previously discusssed.) True, this is a case where the distance (diameter) is not, obviously through empty space but a straight line measure through earth matter. I was speaking of the standard model of cosmology which insists that space is expanding, denying that all stuff is actually move away from all other stuff. I said earlier that the latter model does not 'create more space' between objects, because space is already everywhere not occupied by stuff. This is about the ontology of space. Is it something that expands (curves, etc.) or is it emptiness, or if you prefer, a vacuum? Ontology asks the question, "What is space as 'an expanding metric' in the real world?" You say science can not answer such ontological questions, but a lot of them are seriously trying, as in the ongoing conferences and papers of the ISASS, cited above. You are really not qualified to say what I think science does and does not insist on. Relativity insists that space-time is curved by gravity without saying what it is. I will not repeat what I have said about the two ingredients as still not making a malleable medium, which 'being curved by gravity' certainly makes it, as per relativity. Thanks for the links. I'll check them out. I again ask you to check out the long, tough read on ontology cited early in this thread: Mauro Durato's paper "Is structural Spacetme Realism Relationalism in Disguise, the Supererogatory Nature of the Substantivalism/Relationalism Debate. ( Google Spacetime Realism and find above title, then hit "quick view.") It still leaves us with the ontological question, "What is it?" I have said many times that I accept the predictive power of relativity even as I and many others, as cited above, challenge the actual existence of spacetime. A "metric" can be just a mental model, but relativity texts treat it like an entity. "Gravity curves spacetime." Period. I search for over an hour for Einstein's quote saying that spacetime does not exist independent of matter. Couldn't find it but did find the NASA Q&A scientist's answer (Sten Odenwald) to the same effect, quoted right up front in this thread. If you had read the thread you would not feel the need to reiterate what I have already said, repeatedly. It still leaves the debate about the nature of spacetime as substantive, relational, realist, etc, and a bunch of sub-categories, which I intend to present here in more detail for further discussion. I suggest you read a few of the papers from the several ISASS conferences on space, time, and spacetime. I already addressed this, replying to your engineered triangle as proof of curved space. Beyond significant gravitational influence, laser beams established between three "deep space" stations, without gravity bending the light beams will be straight, and the sum of angles will be 180 degrees. Distance will be easy to measure by reflected light... elapsed time times lightspeed. In a gravitational field, of course light beams as means of measuring will need to take into account the bending or curvature of the beams. The straight line distance between bodies will be found by correcting for the error produced by curved light trajectories (their deviation from straight calculated by amount of gravitational distortion.) The fact that gravity bends trajectories of actual objects and light does not mean that there is no straight line distance between objects. Neither does it mean that "space itself is curved." This is the ontological challenge.

Iggy: What part of my last post did you not understand?(Here it is again to avoid the long scroll-down to bottom of last page): Space "exists" as the emptiness in between (or where there are no) "things." This is the standard doctrine of present day science/cosmology, i.e., that rather than stuff exploding outward into space, that "space itself is expanding." (I thought you were an advocate of standard doctrine.) Space is considered, in relativity theory, to be an entity which began expanding with the "Bang" and continues to expand. It is also said to be curved by gravity, etc. It is considered an entity, a thing, a malleable medium. I really wish you would read the thread before asking me to repeat what i have said already many times in this thread. Space is empty volume. The measurement between two bodies in spaceis linear, i.e., distance. See above about things moving away from each other. Obviously when the space between them increases, the distance (linear aspect of space) between them increases. It's not that complicated. Answered above.

This must be quick. More detail tomorrow. I distinguish between space and things which occupy space. Obviously space is not empty where it is occupied by whatever stuff. Wherever there is no thing is "nothing," empty space wherever it is not occupied.(Maybe repetition helps but I've said this many times in this thread. It may take more than a quick skim to understand it.) Yes things travel through space, rendering it "not empty" where occupied... yet again. I didn't say that space does not exist. Where nothing exists is empty space. I have said many times that space is emptiness. Empty means that volume with nothing in it. Ontology examines what exists. Does nothingness exist? As a lack of entities, it is still the nothing in between entities. Again and again. How else can I make it clearer? As entities move away from each other there is increasing space (emptiness) between them. This does not mean that "space itself is expanding."

I'll get back to specific replies later,but first... absolutely as simple as I can make it regarding the question, What is space? (prior to even complicating it with "time.") What problem do people have with emptiness, absence of "stuff," no-thing-ness (not an entity just because of the "ness," nothing ) void, nada? Without all cosmic 'stuff' there is empty space... or, stated differently, in between stuff which occupies space is empty space, not even an "it." To make a case for 'curved space' is, to posit that "it" is some-thing that has the property of curvature rather than absolute emptiness devoid of 'things' or being a thing itself. But modern science has decided that 'space itself' is expanding rather than that stuff in space is moving ever outward into empty space. Ontology demands that the 'burden of proof' on any claim that something exists in a way that "it" ...has properties (like curvature and ability to expand)... is on the claimant. If space is expanding or curving, what is it? Apparently no one here has read the first paper I introduced. It is a tough read, but it will give a better understanding of the ontology of spacetime to anyone really interested. And there are many more. That was why I entitled this thread, the 'scholarly' debate, so it would transcend personal attacks and condescending attitudes, which has been the norm in other threads.

michel: It is of course a matter of individual interest. But most texts and internet references to relativity start by stating as a matter of fact that gravity curves spacetime, taking for granted that, ever since Minkowski came up with it and Einstein endorsed it, "it" must be an actual malleable medium. My interest is shared by an august body of well credentialed scientists and philosophers of science, The International Society for the Advanced Study of Spacetime (ISASS.) Over several years and conventions on spacetime ontology, they have produced dozens of scholarly papers on the subject. My intent in this thread was originally to introduce excerpts from more of them for discussion here, but it is quite complex and it is easy to get buried in debating details, as we have done here. My back to basics post was an attempt to refocus on the basic issues, but Iggy didn't respond to specific points in that post, and clearly is not interested in the topic. Each to his own interest. Here is a re-statement of some basics from my last post: Me: Care to comment on the actual issues at hand here? Ps: Regarding the triangle measurements you cite; I would like to see such an experiment on very large scale in "deep space" beyond significant gravitational forces (which would bend lasers.) If three 'stations' were set up at rest relative to each other and lasers beams were established between them, and the angles precisely measured... I wonder... If 'curved space' is just a non-Euclidean concept, fine, if it works as a conceptual tool. But if "space curves' in the real world, then it is a very basic question to ask, "What curves, if it is a malleable medium?" Pps: Michel, I totally agree with your post #31 above, but not, of course with your quote at the top of this post. You and Iggy share the opinion here that the ISASS referenced above is much ado about nothing. Well... it is philosophy of science, concerned with what actually exists, not just the pragmatic application of a concept for convenience as a context for the math. Lemur, to you last question above about my, "I'm fine with empty space as absence of things, no thing or nothing. OK?' What is wrong with my laser shot to a mirror on mars and back?... Elapsed time times the speed of light. Of course that introduces light in the space between earth and mars. If you object to that I don't know what your point is.

PS: I wonder what you, michel and lemur and anyone else interested in the topic, think of the basic ontological questions as posed again in my 'back to basics' post yesterday, #18. (We can get lost in the trees and forget the forest without an "overview.")

I said: "I'd like to keep it on that track. What is clearly curved by gravity is the observable trajectories of moving masses and light. Positing "curved space (or spacetime) introduces the mystery entity which is the subject of scrutiny here." You replied; Yes. But mainstream science insists that gravity bends "spacetime," and ontology asks "What is supposedly being bent, other than just object/light trajectories, in which case 'spacetime' can be 'cut out' by Occam's razor. That is the "track" of this thread. I consider space as the emptiness in which all things exist, space being no-thing, the absence of things, not a malleable medium. If two objects move apart, there is more space between them, but that does not create more of some entity, space. Space is already everywhere not occupied by entities. Your examples just obfuscate the above simple ontology of space. Yes, an air bubble in water creates an air space where water was. How does that contradict what I just said about space? Btw, I really think it over-complicates communication to pose hypotheticals like the following: "If the attractive force of the nuclei and electrostatics wasn't what it was, along with the densification-effects of gravity, would their be a gradient of density between one gravity-well and another." Logically, if one compounded set "wasn't what it was," then would another set be what it is? Especially since we have not established a common understanding what you mean by"densification gradients/effects." Huh? The cosmos (masses here) is expanding, and mass attracts mass, directly with amount of mass and inversely with the square of the distance between masses. Whether or not there is enough mass for an eventual gravitational reversal of expansion, initiating an implosion half-cycle is a cosmological question beyond our present focus on spacetime ontology. Whether or not "spacetime" is instrumental as a malleable medium morphed by gravity is the question here at hand. Yes it could, but more mass is being found all the time, in favor of the oscillating model. Your last sentence denies out of hand the "universal law of gravitation" which I recited above. Gravity is simply a weaker force the further away and less massive any/all masses are. Hair splitting? I mean absence of "things," OK? I grant that since gravitational force extends between masses through space, in that sense, space between masses is not empty. The ontological question remains, is space a malleable medium, which would make it a "thing" in a different sense, as an entity, than all omnipresent force fields (however weak or strong.) The similarity between force fields is not my focus here. I get that you are addressing the ontology of what a force field is. Fine. Does gravity as a force field require spacetime as an entity or instrument to guide masses and light in curved trajectories...or not? That is my focus. To the last three questions: ("What...") As in my last post, the bodies (earth, mars, sun)... a clearer example than your "particles", I think,... are well defined as not extending beyond their surfaces, while their gravity fields obviously extend to pull on each other. ("Why...") The particles/bodies are substantive entities while the force fields they generate are relational in nature. The mutual pull between bodies, gravity, has no limit, though diminishing to relative insignificance with distance, while, clearly the bodies themselves are discrete in size. ("Why...") Why are force fields not physical entities? Shall we all agree to a new definition of "physical?" My turn to ask "why?" Shall we have earth and sun merge as physical entities just because their gravitational fields interact? I vote no. I think the above adequately addresses your next paragraph, "What I am saying is..." Why indeed. Why do we distinguish planets and stars as distinct parts of a galaxy, since a galaxy is held together by a common gravitational force field? In that sense, of course, a galaxy is one physical object, albeit it consists of uncountable parts as distinct physical objects themselves with lots of "empty space" between them... empty in the context already established, granting that forces exist between objects. I'm wondering what relevance this question has for the context in which all of that was discussed. I was saying that earth to mars distance is intrinsic to their actual positions in space (objective), not variable with frame of reference from which it is measured. Now its about the gravity between them, sans sun's gravity keeping them in orbit? I'm sure that the G-force between the two planets alone could be calculated from their masses and distance between them. To what point in this conversation? (A rhetorical question, not to make a side issue of it.) First, you continue to consider spacetime as something that would "curve around" me and the ship, curved by my "own gravitation." Do you see how you assume spacetime as a malleable medium/entity, precluding the whole point of this ontological inquiry/challenge? I meant simply that the spaceship's direction (and velocity in my example) would not change if everything else disappeared, NOTHING left. I have never defined "empty space" as "something." Maybe the "ness" in "nothingness" was confusing. Sorry. I'm fine with empty space as absence of things, no thing or nothing. OK? Right. There would be nothing else. And the ship's velocity and direction would not be altered( with no forces left to change them.) Just an example of transcending the "box" of thinking "everything is relative" or that velocity and vector require a "relative to what" to keep on trucking in the same direction at the same speed. Whew! Good exercise.

lemur: This seems to be bogging down in the details of what a relational entity is (according to spacetime relationalists) as compared with what a substative entity is (according to spacetime substantivalists.) Whatever relationship there is between two people is a relational entity as long as there is a relationship. The people in the relationship on the other hand are substantive entities. My example (using marriage as the relationship, just for instance) was introduced as a comparison between spacetime as a relational entity (one "camp") and spacetime as a substantive entity (another "camp.") If the former spacetime it is only relational, dependent on the "stuff" which generates gravity, and does not exist as an independent entity. If the latter spacetime it is a substantive entity which exists whether or not there is any matter present. But in either case ontology asks what is it that is curved by gravity?, the focus of this thread. I'd like to keep it on that track. What is clearly curved by gravity is the observable trajectories of moving masses and light. Positing "curved space (or spacetime) introduces the mystery entity which is the subject of scrutiny here. I said: "...there is space between earth and mars and sun, but they do not "create space between them." Space is already everywhere that is not occupied by 'stuff', as I see it. You replied: If you understand space as the infinite emptiness (what could be an end of space?) in which all things exist, then the rest is debate about specific things in specific locations and gravitational relationships in particular realms of space, like our solar system, which has been our recent focus. In no case do the things create the space. If things move apart, there is more space between them, but the things did not create the extra space, or distance in this case. Science reifies space and gives it properties like curvature and expansion. Ontologists who are specifically interested in the philosophy of science rightfully question such reification, asking what it is beyond a conceptual tool, if anything. "Nothing?" What reference? Second sentence: Why not? Third sentence: Whose need/desire and whose "defined boundaries?" As I understand gravity, it has no limits. It just diminishes with the square of the distance between masses, until it is negligible for most purposes of calculation. If eventually the expanding cosmos stops expanding and reverses to implode (back to a crunch) it will be because gravity has no limit, and whatever force is now making it expand will be exhausted and all things will be "caught in the cosmic gravitational net" no matter how far out cosmos expands, and then pulled back to a crunch and another bang. Last sentence: I did not understand. Like, is it a wave or a particle? Limitations of concepts and language it seems. I said: ..."my rigor is in asking what space is supposed to be besides emptiness, no-thing-ness. As to "its existence", if not an entity what can be said to "exist?" That is a 'rigorous question.' " You replied: I meant, if not an entity what,posited as space can be said to exist as space?... besides emptiness? Not, "What exists?" in general. Yes, the "whole issue" is "whether that's (spacetime is)an epistemological convention or a physical fixture alongside (i.e. transcendent of) matter and energy?" But since epistemology is the study of how we know what we think we know, as a convention, spacetime is a mere conceptual instrument and should not be refied into being a substantive entity without an explicit and detailed explanation of what it is supposed to be composed of. Even as a "relational entity" the question still must be answered, "what is gravity bending?" ?? Earth and sun are massive objects generating gravity, which extends beyond their bodies and mutually pulls on each other over a space/distance which averages about 93 million miles, way beyond the surface "boundary" of each "mass" (object.) So the first sentence above makes no sense to me. The electrons of atoms which compose masses have no or negligible mass, so I still don't get your electrostatic repulsion take as the key to gravity. Space photos of earth show earth as clearly as I see another's body, though technically it is just light reflected from the body. Light carries the image. If you are saying we only see light, not the actual earth, then this is going nowhere, even if you are technically, hair-splittingly correct. Then re: ..." but why couldn't you say that gravitational field-force simply tends toward homogenization/condensation?" Huh?... of what? Masses pull on each other. sometimes they do merge, but that is a special case, and we are speaking of gravity and its pull... with or without "spacetime" as a medium between masses, or mass and light. From "After all..." on down seems to be an amorphous merging of gravity fields, and I have no idea what your "big blobs", as gravity fields are composed of as entities. Ontologically, what are they? Me: "This is the limitation of a theoretical world, like without the sun. It fails if taken too literally. You: "If empirical description is literal description, how can it fail when taken too literally?" If you take away the sun and then mars and earth head off tangent to their previous orbits (as they presumably would) and then you ask what the distance is between them... well... earth could still bounce a laser off mars and calculate its distance... But you didn't like my answer for reasons of your own pertaining to sun's absence, I presume, but sun's absence seemed like an unnecessary complication of the question of determining the distance between the bodies. And my point was simply that an at rest frame of reference (earth) is the best and most accurate frame from which to measure earth-mars distance than a near-light-speed fly-by frame from which to measure... and that those distances are actual, in the real world, not constantly changing with every extreme frame of reference as above. Same for "rods." As above. Space/distance between objects is intrinsic/objective/independent of all the variation we get in measurement from extreme differences in frames of reference. But relativity says that all those distances do actually vary with each measurement, as "there is no preferred frame of reference." Same with rods shrinking and stretching to extremes because measurement of them from extreme frames varies so much. I was speaking of the extreme frame of reference for measurement of a near-light-speed fly by, which would give a way different result for earth-mars distance that as measured from earth, as close as can be to the distance measured and at rest on one of the objects. Yes the laser is visible light. The example is the most direct way to measure that distance. I assume the fly by measurer would also use lasers as measurement instruments, as the constant speed of light would simplify the already complex calculation factoring in the spaceships speed and trajectory. I already answered your last question. Edit: Most recent question: Lemur: (Regarding "cosmic consciousness perspective.") Yes. A thought experiment transcending local frames of reference. The limitations of the latter do not necessarily dictate all of reality on cosmic scale, as per relativity's claim that "everything is relative." A spaceship going a certain velocity/direction would maintain that velocity/direction even if the rest of the cosmos magically disappeared, leaving no "frames of reference" as other objects by which to determine that velocity/direction... as in "relative to what?"

Just checking in on the fly. Back later to address the rest of your reply, but, to the above: A "cosmic overview" is the most highly theoretical of all possible perspectives, totally beyond or transcending all local frames of reference. Religious folks (which I am emphatically not!) would call it a god's eye perspective. I would prefer to describe it as the view of our ship traveling through space from the transcendental perspective of "cosmic consciousness," as a thought experiment rather than a belief in some godlike awareness of the cosmos. That is all I meant, and it definitely transcends all local frames of reference. If one could "see the whole thing" then even one little spaceship would be seen passing through the vastness of cosmos but still in relation to cosmic objects, however distant. (Just an aside, really.)

I'm back to the most basic question concerning the ontology of space, as introduced at the top of this thread. So, to delve more deeply into the above: If that which is not occupied by "stuff" ('things') is empty space, no-thing-ness, what sense does it make to say that space does not exist without the stuff in it? If you take the contents (whatever) out of a box, does it make sense to say that the space inside the box doesn't exist unless the contents are replaced? Obviously not. So how does the above argument by Sten Odenwald (presumable a well respected scientist in the field of relativity) hold up to the scrutiny of logic and common sense? Not well it seems to me. Comments? And yet if space is a non-entity (with which I agree, emptiness being a lack of entities) where does that leave the ontology of spacetime? As in Brown and Pooley's book, (see reference in that first post)... a "non-entity." If one argues that "time" must be mixed in as an ingredient before spacetime becomes an entity, then we must ask what time is as well... a question often beaten to death with no consensual outcome. Obviously cosmos is not a static snapshot, so all movement of all things can be said to "take time" or have the property of event duration, whether an active cesium atom in an atomic clock or the familiar day and year as natural cycles happening "in time." But that does not make "time" an entity either. Anyway, just a move back to basics in case anyone is interested. So what does gravity make curve besides the obvious... the trajectory of objects and light? Same question, still unanswered by the relativity theorists on this forum.

michel: Right. I have no problem with the predictive power of relativity. Even the Lorentz transformation stuff is useful for "transforming" measurements from extreme velocity frames of reference, relative to what is being measured to a basis of making sense of it, but then to say that "there is no preferred frame of reference" (so the rod or earth-sun distance does actually fluctuate with the measurements)... that is my bone of contention with relativity... that and, of course the basic question, "What is spacetime, actually, intrinsically, as an entity of sorts as above?" The invitation remains open of course for our previous antagonists to join in again here. Ontology does belong in the philosophy of science section. And relativity theorists usually do dismiss the "What is it?" question, in favor of the pragmatic attitude that if the concept works as a tool, who cares what "it" is in the "real world." But I do care, and it is an honest question/challenge. This is why I liken the "spacetime fabric" to "the Emporer's New Clothes." Some of us are considered too stupid or unsophisticated to "see" it. (But comparing IQ scores is just too juvenile... yet I am confident.) I agree with 1 and 2. I do understand space as emptiness, wherever there is no "stuff"... nothing to be expanding. And space must be infinite, because no one can come up with a boundary, and there could only be more space beyond such a conceptual boundary anyway. So the doctrine is that 'stuff" is not traveling outward in empty space, but "space itself" is expanding, which makes all 'stuff' look like it is expanding outward... but it is not. I think this is absurd. Thanks. lemur: You are still missing my point. Bodies are substantive entities while marriage is a relational (or "accidental" entity), and the latter ceases to exist (the marriage, regardless of whatever continuing interaction)after a divorce. Likewise, the "official position" (of NASA's Q&A man on relativity... and Einstein's admission) is that space and spacetime do not exist independently of the 'stuff' in it. There is no argument that there is space between earth and mars and sun, but they do not "create space between them." Space is already everywhere that is not occupied by 'stuff', as I see it. I agree that, "they gravitationally attract each other and other matter in a way that results in certain dynamics." The question at hand is "what medium if any is there between them to convey gravitational force?" "Spacetime seems to have been invented as a metaphysical relational entity to 'fill the void' so to speak between masses to explain how gravity works... as an entity that gravity morphs, to explain the gravitational interactions we observe. I asked: "...why can't we call space not so occupied (with stuff) 'empty space?' " You answered: I agree with your last sentence, but my rigor is in asking what space is supposed to be besides emptiness, no-thing-ness. As to "its existence", if not an entity what can be said to "exist?" That is a "rigorous question." I do not think that spacetime is "something" at all. There is no "it" to have any properties, including curvature, in my argument. The trajectories of objects and light are bent/curved by gravity. The question of a medium for that force (if any is required) is posed by this thread. Science abhors "action at a distance" but I have no problem with it. No "gravitons" or curved spacetime is observable anyway, so... they remain metaphysical/theoretical. I don't get how an "electron field" plays in the 'gravity game.' Mass attracts mass (directly with massiveness and indirectly with distance.) That works for me. This is the limitation of a theoretical world, like without the sun. It fails if taken too literally. The question is... Is the distance between planets intrinsic and independent of measurement (granting that it changes as more or less natural proximity) or do extremes of reference frames from which these distances measured (from near-light-speed velocities oblique angle trajectories, for instance) yield just as accurate distance measures as say mars-earth distance measured at a given moment from earth, say by a laser reflected from a mirror on mars? The answer is obvious to me. There is a preferred frame of reference. And the distance is intrinsic/objective. It does not vary just because measurements vary as compared on an extreme continuum, as above. Again, the distance between planets varies with where they are in orbit relative to each other, but at any given instance of measurement, the more accurate distance will be from the laser shot from earth to mars and back, not by a high speed fly by (at whatever angle to the ecliptics) frame. You wouldn't unless your ship placed buoys as it traveled (each with propulsion to make it stop and become stationary relative to the ship.) Then, as above, you create a reference point and will know your velocity and distance traveled... and how much of particle impact is due to particle velocity and how much to your vehicle's velocity. If you insist on no reference point you could not know...unless you had a cosmic overview, a "global perspective."

michel: If you have a specific focus of interest in this ontology debate I would be glad to address it as briefly/succinctly as I can. For instance, if I remember correctly you and I were in agreement, in another thread, about the "true length of a rod" being most accurately measured from the at rest frame relative to the rod... by the guy with the rod in his hand rather than from a 'near speed of light fly by' frame. lemur, Seems I missed a piece when I wrote my 'backtracking' reply. You wrote: If you were " sailing transoceanic" nowadays you would measure distance traveled by your GPS (global positioning satellite) gadget. In outer space one can rely on a steady velocity like "miles per hour times so many hours" to calculate distance traveled. Of course if still in proximity to non-trivial gravitational fields, they must also be factored in as slowing down the velocity (say, if leaving earth) or speeding up the vehicle if approaching another body's gravitational field. In principle (theoretically) the space vehicle could let out a thin wire anchored at a gravity neutral position and just read the "mile markers" on the wire as it trails out, giving true distance traveled from the anchor buoy. (The wire is of course theoretical, so it will not expand and contract with temperature or the pull on it.)

Backtracking... You are getting into very specific examples of the frame of reference debate while already assuming spactime as an entity, the foundation of this debate, not a "given" at all. Example: (My bold.) My whole example was positing an alternative to assuming spacetime as an entity and specifically "dragged frames." My ontology here posits that the natural world does not need our concepts (frames from which we measure in this case) to "unify the disagregate (?) interactions... They are already intrinsically unified. Our concepts and tools (including frames of reference, spacetime, etc) help us to measure, but our measurements do not, of course create the intrinsic properties of what is measured. Topography and variable density can easily explain the observed anomalies in satellite positions without the "invention" of the concept, "frame dragging." My 'marriage as an accidental (relational) entity' example did not claim that our bodies evidence the relationship. The bodies were cited as examples of substantive entities in contrast to the marriage which is a relational entity. The point was that the latter ceases to exist after a divorce, while, of course the bodies remain as substantive entities. Same with spacetime as a relational entity only... if matter were to disappear... which it will not, leaving the question, "what kind of an entity, if any, is spacetime... the focus of the whole title debate. You call empty space "fictional." What do you call all space not occupied by cosmic "stuff?" (May we say "stuff" for matter/energy/plasma?) Quantum physics' "virtual particles" aside for the moment, why can't we call space not so occupied "empty space?" I must be misunderstanding. From the mass and propulsive force and trajectories of all kinds of space vehicles, their velocities and distances traveled are commonly calculated taking into account all significant gravitational forces effecting them. And again you use"spacetime-topographical projections" as if spacetime were already established as an entity in this thread. As to your above comment: " if the sun was suddenly absent, then there wouldn't be any straight-line path from Earth to Mars that wasn't related to their motion vis-a-vis one another and gravitation relative to whatever it was traveling between them, right." I disagree. If nothing else there is a virtual straight line between any two points or objects, like the needle through the sphere between two surface points. The surface arc between them is not a straight line, regardless of the language of intrinsic vs extrinsic curvature relative to different conceptual manifolds (the birth of the non-Euclidean paradigm.) And beyond 'virtual', I think a laser shot from earth to mars, if sun were absent as a gravity source to bend it, would be a straight line. All theoretical of course with no sun in the real cosmos.

Thanks, michel. I am tech impaired "by nature" it seems. Getting old and all that too. I can't remember whether memory is the first or second thing to "go!" (Oh yeah, use logic!) Anyway, such tips are much appreciated. Interesting perspective. I was speaking of "true distance" in the same context as my examples above of the rod (in the hand) as closer to a true perspective of the intrinsic reality of the rod (specifically its length) than the very complex speed and trajectory frame of the theoretical high speed traveler measuring the same rod from the (as I've called it previously) "near-light-speed fly by" frame of reference. (Let's just use FOR as , I think michel introduced.) I have been interrupted by... life. Back asap.

Note: I forgot if i ever knew how to use the quote box tool for one piece at a time quotes. Oh well. You wrote: "Yes, that's the engaging critical way of raising the issue. Maybe the more accurate question, though, should be, "what is it that causes a trajectory to be interpreted as straight?" But you went to a very specific example of the the more general issue I was raising. This brings us to the issue of "intrinsic vs extrinsic" curvature relative to different conceptual manifolds, which is an issue within the historical transition from Euclidean to non-Euclidean geometry and resulting ontology. So, if you draw a line on the surface of a sphere, one could say that it is the shortest distance between two points on the sphere, therefore a "straight line" relative to the spherical geometry. But it is still obviously a curved arc and the straight line is still through the sphere from point to point. I think this addresses your point: "In space, however, a vehicle/projectile can proceed by its own momentum between points without inertial disruption, which implies true straight-line motion (in Newtonian logic), but we can interpret it as curved relative to lines we deem as straight based on what?" Again, I think it is the non-Euclidean concept of "curved space" (in more general terms) which leaves behind an observed cosmos in favor of a merely conceptual one. The "true" shortest distance between two points on my sphere above is still the line through the space within the sphere (a needle through the ball between the two surface points, as it were), not the actual arc on the curved surface between the points. To my example of marriage as an accidental or purely relational "entity," (like spacetime, I argue) you reply: "It's a bad example, because divorce is an institution that relates to another institution, marriage, but the actual material relations that occur outside of the institutions do not exist or disappear because of the institutions. Spacetime, on the other hand, seems to be part of the actual material relations between matter and energy. In fact, I think it could be most simply described as our perception of those relations, the same way you would perceive your marriage as your daily interactions with your spouse even though you could theoretically be interacting in the same way as unmarried people." My point was simply that marriage as an entity ceases to exist when a couple divorces. There is no "actual material" involved in the example except the obvious fact that the participants in the relationship have substantive bodies, which are not in dispute as being actual entities. When you posit that: " Spacetime, on the other hand, seems to be part of the actual material relations between matter and energy." ... you do take the "side" of spacetime as a substantive entity in relational interaction with matter/energy. In the marriage metaphor, this would be equivalent to the assertion that spacetime has a body like each person in the relational entity marriage does. On the rotating vs stationary gravitational field issue you wrote: "So you would treat the frame of planet Earth as gravitational relations between the objects that make up the planet and then treat the objects as having separate frame-relations with satellites, for example? But why would any one frame be any truer than any other? Isn't that subjective and objectively all physical relations between entities in contact with each other are possible reference frames for other interactions measured from them?" Maybe we have too much to eat on the plate at once here. I would leave the "frame" concept out for a moment and just ask what causes the discrepancy in the expected orbital positions of the satellites which are "supposed" to exemplify "frame dragging." If earth had a perfectly smooth surface (no topographical variation) and homogeneous density those satellites would maintain positions easy to calculate, which they do not. I think the actual gravitational variations (as per the above) effect satellites according to their individual proximity to the variations. No need to "drag in" frame dragging, especially if spacetime turns out to be a "non-entity."

Lemur: "To me, some things are being confounded here. I think constructivism has to be disentangled from subjectivism. Spacetime can be "constructed" to exist as antecedent and independent of matter-energy without the belief that its existence is emergent from subjective perception. But spacetime can also be "constructed" with "recourse to spatiotemporal presumptions." In other words, all "constructivism" refers to, imo, is awareness of the relationship between science and its epistemologies, not to whether these epistemologies are ultimately rooted in object or subject." This is a thoughtful analysis, and If I understand you correctly I agree. Your first sentence is an understatement in this arena. Example, Durato's paper title: "Is structural Spacetme Realism Relationalism in Disguise, the Supererogatory Nature of the Substantivalism/Relationalism Debate." It was a long and difficult read for me and there are dozens of similar papers presented at conferences over the years by members of The International Society for the Advanced Study of Spacetime. I have barely scratched the surface. I hope to eventually be able to put the debate into less technical, highly specialized language so the average Joe can better understand the issues. You continue: 'What's confounding is that Norton is assuming that "consensus by the pre-existence of mind-independent real entities" is less a form of consensus than "theoretical negotiation and consensus." While it is very different to agree with other scientists as it is to agree with reality, I don't think it works to obfuscate the reality-claim itself as being an appeal to (or negotiation of) theoretical consensus. In other words, they're not mutually exclusive descriptions." Too bad the debate doesn't just start with posing a question as mundane as, "If spacetime exists in and of itself as an entity, what is it composed of?" (Harkens back to the "lumeniferous aether" doesn't it?) If it is totally a relational or "accidental"* entity, dependent on matter to exist, then it really must be in the nature of a theoretical concept only... which leaves one wondering what exactly is it which is curved and otherwise morphed by matter. To clarify, my body is a substantive entity while my marriage is an "accidental" or relational entity. (My wife would argue with how "accidental" it is! ((Not the present technical definition.) If we divorce, the entity ceases to exist... like spacetime without matter. My intent is to speak plainly about this complicated ontology. I think Norton is saying that consensus through "negotiation" makes it merely an artifact of conceptualization,(less plausible) while starting with the "pre-existence of mind-independent real entities" gives it a more objective, less merely mental foundation. You pose a good question in: "Does the Earth's gravitation rotate along with the observable planet or does it just extend outward without rotating?" This may be relevant or not... I think the claims of "frame dragging" as a new "twist" to spacetime around rotating objects (including black holes) can be well explained without positing distorted spacetime. Earth, for instance has a lot of topographical and density variation which will make the pull on the satellites supposedly exemplifying "frame dragging" vary with proximity to more or less high topography and material density. Finally you write: "I think some physicists would say that these fluctuations are relative to light-energy and the oscillations of electrons, so they are objective. What basis do you have to assume that something being "objectively physical" necessitates that it be dimensionally standardized or fixed?" As I understand it, light as the medium for images, say of rods and distances between objects will convey different lengths and distances at near light speed frames of reference relative to what is being measured... varying with speed and vector of the frame. That introduces the need for Lorentz transformation to make sense of all the extreme variations in measurement. But, as I said, the guy with the rod in his hand (at rest relative to the rod) does not have all those light and speed variables to deal with, so it makes good sense to me that the at rest frame relative to what is being measured will always be the most accurate and give the "true length" or distance of the actual entity, which is as it is independent of measurement... i.e., does not morph just because measurements do.

Hi Lemur,thanks for your reply. "Why does it mean to say that "the construction project only succeed if constructivists antecedently presume the essential commitments of a realist conception of spacetime?" In my understanding of constructivism/realism, antecedent essentialism of realist conceptions are the opposite of constructivism. I.e. how can spacetime emerge from matter-energy if it is viewed from a perspectival commitment to it as an antecedent essence that precedes the matter-energy? Or am I understanding the intended meaning of this language incorrectly? " Well,it is kind of a complex quagmire, and I may not have a full grasp of your meaning above. I was quoting Norton that: "...the constructivist account of theoretical entities (is given) in terms of negotiation and social consensus"... so if there is any reality to "spacetime" besides "negotiation and social consensus" in the scientific community, it must: " result from the properties of matter. Whatever this may mean, it commits constructivists to the claim that these spacetime geometries can be inferred from the properties of matter without recourse to spatiotemporal presumptions or with few of them ." My bold emphasizes that assuming intrinsic qualities of spacetime as an entity is not necessary because matter may still attract matter without a dubious malleable entity spacetime as a medium to explain gravity.. That is how I read it anyway. You ask: "Are you stating it is "less plausible" as a criticism or merely an objective recognition of subjective bias against spacetime as an emergent phenomenon instead of something that precedes and contains matter-energy? Why would a "realist story which explains consensus by the pre-existence of mind-independent real entities" be a matter of physics instead of philosophy? Physics is concerned with mind-independent real entities regardless of whether consensus is explained by them or not, correct?" The "less plausible" are Norton's words... that spacetime as merely the result of theoretical "negotiation and social consensus" (gravity being explained by matter by itself without "spatiotemporal presumption") is less plausible than the realist conception which, "explains consensus by the preexistence of mind-independent real entities.." It does seem that the difference between schools is confused if both believe that spacetime is a mere theoretical convention, and gravity, though still without a defined medium, can ultimately be explained without the "non-entity" (Brown and Pooley) spacetime, by the intrinsic qualities of matter as entities without a merely relational "entity" the existence of which is totally dependent on matter. The classical philosophers distinguished between substantial entities and "accidental" entities, and spacetime would be the latter, disappearing without its relationship to matter... unless you are a substantivalist, claiming that spacetime is not just relational to matter but substantive in and of itelf. (Made of what?, one wonders.) Finally you ask: "Related question: why does it happen so frequently that people want to make a point of linking objective physicalities to perceptual cognition? Are people so afraid they're hallucinating that they need to persistently establish a link between their perceptions and something else external to them? Is sophism this strong an undercurrent in the human psyche that it has to be rigorously challenged at the expense of ontological neutrality?" Good question.Subjective idealism, for instance, denies "objective physicalities,"... There is no "objective cosmos" independent of observation! I'm all about the opposite, that cosmos is quite independent of observation and measurement. That is why I disbelieve the supposed fluctuations in distances (space) between objects and the supposed contraction and stretching of "rods" based on extreme fluctuations in frames of reference from which they are measured. Thanks again for your interest.

My previous approach to this subject got bogged down with a lot of my personal ignorance, so my intent here is, as per title to give examples of the actual debate among spacetime ontology scholars and invite comments. I found the most basic question about the ontology of space at the NASA Astronomy Cafe, Q&A section: ................. "Special & General Relativity Questions and Answers Can space exist by itself without matter or energy around? No. Experiments continue to show that there is no 'space' that stands apart from space-time itself...no arena in which matter, energy and gravity operate which is not affected by matter, energy and gravity. General relativity tells us that what we call space is just another feature of the gravitational field of the universe, so space and space-time can and do not exist apart from the matter and energy that creates the gravitational field. This is not speculation, but sound observation. All answers are provided by Dr. Sten Odenwald (Raytheon STX) for the NASA Astronomy Cafe, part of the NASA Education and Public Outreach program." .............. So if "space and space-time can and do not exist apart from the matter and energy that creates the gravitational field..." and relativity in most general terms "relates" one event to another, what, without matter/energy content is related to what? "To the extent that this (spacetime) is a conception of structure as consisting of relations devoid of relata, it is incoherent." (John Norton. quoted also below.) This context, of course claims that space and spacetime are entities, which I have argued against, so I will now quote Harvey Brown in support of my argument: "The space-time structures (of Newtonian theory and special relativity) are not real entities in their own right at all..." And... "I see the absolute geometrical structures of Minkowski space-time as parasitic on the relativistic properties of the dynamical matter fields.’ " See also the book by Brown and Pooley: Minkowski's space-time: a glorious non-entity. Then John Norton, in "Why Constructive Relativity Fails" criticizes Brown's ontology as follows: "Constructivists, such as Harvey Brown, urge that the geometries of Newtonian and special relativistic spacetimes result from the properties of matter. Whatever this may mean, it commits constructivists to the claim that these spacetime geometries can be inferred from the properties of matter without recourse to spatiotemporal presumptions or with few of them. I argue that the construction project only succeeds if constructivists antecedently presume the essential commitments of a realist conception of spacetime. These commitments can be avoided only by adopting an extreme form of operationalism. " Then Norton compares constructivist spacetime with spacetime realism: "However, the constructivist account of theoretical entities in terms of negotiation and social consensus is less plausible than the alternative realist story which explains consensus by the preexistence of mind-independent real entities.." (My bold) I champion an "objective cosmos" not distorted by high speed frames of reference as measurement perspectives, for instance. It seems to me that an "at rest" frame relative to that which is measured would provide the more accurate measure than, for instance, a near light speed frame relative to the same measured parameter or object, whether a rod or the distance form earth to sun. But that is just my humble opinion, and I know that relativity theory insists that there is no "preferred frame of reference." Another "debatable" point in my opinion, though I am not challenging the predictive accuracy of the instruments and formulae of, for instance the Lorentz transformations. Just that maybe "rod contraction" is an optical error due to extremely high speed, whereas a guy with a rod in one hand and a tape measure in the other would get the actual, accurate measure. (Ontological question: Is space, distance, length malleable as above?) The broader spacetime debate must include both the substantivalism/relationalism debate and "structural spacetime realism." I invite the forum to read Mauro Durato's paper "Is structural Spacetme Realism Relationalism in Disguise, the Supererogatory Nature of the Substantivalism/Relationalism Debate. It's a five line link from my browser, so just Google Spacetime Realism and find above title, then hit "quick view." This will provide one perspective for a scholarly debate for whomever may be interested. Thanks.

Agreed. No point in continuing. I do think the supernova remnant model would be an improvement over the balloon model, though... not like a perfectly spherical shell of a perfectly uniform thickness. And it is an actual explosion of material out into empty space, which is still in the face of the doctrine to the contrary... that that does not happen. (Rather that "space itself expands."... the last word here on what is true and real they say.) Ontologically, what is "space" as such a malleable medium? Who cares? I refer the forum to my post on that on the last page, post 255. Also a summary yesterday in post 260. One last outrageous possibility, I'd like to share before we are cast to the outer darkness: I also "like" a multiple bangs/multiple crunches model... that there is "incoming material" that we can't see yet on the way in to "crunch" even as what we see is "outgoing" ... at an accelerating rate of expansion even! So then we could dump "dark energy" as the anti-gravity factor pushing us ever faster outward... since no one has a clue what "it" might be anyway. The 'stuff further out' from a previous bang would then just be pulling our 'shell' ever faster outward via gravity as we know it. The Cosmic Juggling Act model! Very speculative, of course... and still without an apology!

The 13.7 billion years is the estimated age of the part (sphere of visibility) of the cosmos we can see, not the possible whole shebang "balloon." You are jumping scales here, and the vastly larger scale is way beyond the presently accepted models, based, of course only on what we can see. If you go back to my analogy comparing our solar system to an atom and galaxies to molecules embedded deeply within the balloon's rubber membrane... the isotropic and homogeneous view from any such smaller sphere of visibility would look identical to what we see, anywhere within the balloon membrane except from the viewpoint of those cosmi (?, plural of cosmos) closest to the inner or outer boundary of the 'membrane.' Maybe such locations can already see a thinning of the density of cosmic material. I'm thinking that the balloon analogy is not adequate to convey the probably gradual thinning of cosmic material closer to either the inside or outside of the balloon. Supernova remnants flying out into space without a defined "shell thickness' would probably be a better model on "small scale." But, of course we are just playing with mental silly putty on this scale of cosmology, while I'm sure of all by-the-book cosmologists here are rolling their eyes, sneering and condescending. Oh well. They will get over it and stay snug and comfortable in the 'conventional wisdom' they all learned in school.

You just confirmed that you are not getting the model I am presenting. The "universe" (as you call it) that we can see is limited to the very small sphere deep within the thickness of the "rubber" of a vastly larger expanding sphere in my model, the "whole balloon." Everything we can see to the limit of our small sphere is expanding uniformly. None of us can possibly know anything about what is beyond our cosmic event horizon... the very small sphere of visibility above. But cosmology has a speculative realm which includes what might be beyond what we can see. The whole balloon is that realm, as I see it, being merely an amateur cosmologist, and it is not "falsifiable" even though it is admittedly not very useful either. So what. That does not, as you suppose, make it wrong. The above shows that your first statement above is bogus. And "a model" of the cosmos beyond our vision is still a model, even if it is way beyond your definition of "the universe." My definition of the universe is: all there is, both known and unknown... one "verse" so to speak... not just what we can see and know about. It brings to mind the guy who dropped and lost his car keys but confines his search to the circle of light under the street-light. He doesn't find them but there is no use in looking around in the dark. There is also no use to continue with the above cosmology. It is just speculative and will stay that way until, if ever, the "membrane of rubber" thins enough to see beyond... way beyond the lifetime of our sun, most likely. But other worlds, closer to either "surface" with way better instruments... way in the future... may just verify the Big Balloon model. I will not be holding my breath meanwhile... nor will the current cosmological myopia of the presently accepted model bother me. BTW, the "age" of the cosmos we can see is fairly well estimated, based on... well... what we can see... This should address your objection, airbrush. PS (edit): ,If this turns out to be my last post here I will leave you with a repetition of my primary objection to relativity... which is not its excellent predictive ability but the ontology of how it treats things like distance between objects (sun-earth for instance) and the supposed changing size and temperature of the sun: ............. I don't "reject Relativity" per se. (Cap for being an absolute?) I have not yet reconciled the well proven constant speed of light with the claim of relativity that, for instance, sun-earth distance actually changes with every possible near-light-speed frame of observational reference... or that, as per Lorentz transformation, the size and temperature of the sun actually changes, as extreme frames of reference claim. It is in fact absurd to believe that cosmic bodies move closer and further from each other just because it looks that way from a near-light-speed frame of reference. Whoever believes that observation/measurement makes bodies move around in space... is confused. If sun-earth distance appears to change from one tenth AU to ten AU as different frames of reference at near-light-speed might "see" it, that appearance is not an accurate measure of distance between the two bodies in the real solar system. I rest my case... for now. ...............

Likewise. I couldn't have said it better myself. All your replies are out of the textbook, and you clearly can not even "hear" any challenges to the conventional wisdom. Same meaning for "dogma" as in religion. Airbrush, I am still interested in your reply. You wrote: "What expands is the space between matter." I replied: "Conventional wisdom is that 'space itself is expanding'... that without a second ontological thought about what this "thing, itself' is (besides the obvious... empty volume... no-thing-ness.) Obviously, as actual things move away from each other in space (which is not debated here) we can say that there is 'more space between them.' No problem. But this is way different than claiming that "space itself expanded between them." See the difference?" This distinction is up for grabs by anyone here of course. I challenge anyone who believes that "space itself expands" to tell me exactly what is expanding in that case. An invisible foam? A metaphysical matrix/medium? What? A "metric of coordinates?" (That is the map, not the territory.) Iggy: "From a position inside the skin of a balloon you will see things stretch in tangential directions and things compress in the radial direction. We see galaxies moving away in all directions." Of course that would be true as long as you ignore the model as I presented it: relatively thick skin with our relatively very small sphere of visibility deep within. But, of course nobody here will consider any new possibilities, because we already "know" that the conventional wisdom is the only possible model which is true to what we see. OK, fine.

I think I see the communication problem... at least about the concept of "expanding space." Conventional wisdom is that 'space itself is expanding'... that without a second ontological thought about what this "thing, itself' is (besides the obvious... empty volume... no-thing-ness.) Obviously, as actual things move away from each other in space (which is not debated here) we can say that there is 'more space between them.' No problem. But this is way different than claiming that "space itself expanded between them." See the difference? If space is the infinite emptiness (see above argument for no possible "end of space") in which all "things" exist and move then it is perfectly reasonable to say that things move further apart (more space between them) without claiming that space is some sort of malleable medium. On the "thickness of the balloon skin": With a large enough scale for the whole balloon and a thick enough balloon skin, our sphere of visibility could easily be so deeply buried in the middle of that skin that the difference between lateral expansion of the skin and the thinning of the skin as the balloon expands ( looking in the "in-out" direction) would not be on a scale detectable from our very small sphere of observation. Imagine our solar system as an atom (and galaxies as molecules of "rubber") deep within a relatively very think skin. We would not notice a difference in any direction we look... which is exactly how we see it. Of course we will never know, but that still doesn't make all the self righteous know-it-all declarations criticizing this model correct. There is not just one "correct cosmology" that fits with our observation, but the above is not even being heard for self righteous and cock-sure reason above. And the "space itself is expanding" assertion as absolute truth is in the same category. Edit (PS): BTW, in case y'all missed it, my primary objection to relativity is not how well the equations work. I have no doubt that they have improved scientific predictability "immeasurably" ('scuse the pun.) I'll repeat, as there was no rely the first time other than the usual dogma. "It is in fact absurd to believe that cosmic bodies move closer and further from each other just because it looks that way from a near-light-speed frame of reference." Whoever believes that observation/measurement makes bodies move around in space... is confused. If sun-earth distance appears to change from one tenth AU to ten AU as different frames of reference at near-light-speed might "see" it, that appearance is not an accurate measure of distance between the two bodies in the real solar system. I rest my case... for now.

Spyman: "The Big Bang is not an explosion of matter moving outward to fill an empty universe. Instead, space itself expands with time everywhere and increases the physical distance between two comoving points." This is repetition of the "litany" of the presently accepted doctrine, stated as a fact. I doubt if you have ever considered the ontology of what "space" IS, that "it" expands and all as per the accepted doctrine.I doubt if you have ever thought twice about the possibility that space is simply empty volume, without "end." What IS "it" that expands? This is an ontological question, so it may be over your head as a hard core empirical, well conditioned to accepted doctrine, "scientist." I doubt that you will even consider the extremely vast scale of the "balloon" model I have presented. It will not "compute" with your indoctrination. It will never be "proven" in the lifespan of our sun, but that does not make it wrong or impossible.