Spacetime Ontology, the Scholarly Debate

owl · March 30, 2011

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.

lemur · March 30, 2011

Interesting post. The following part is where I start wondering what the point is:

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. "

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?

"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.."

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?

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?

Edited March 30, 2011 by lemur

owl · March 30, 2011

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.

lemur · March 30, 2011

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 ."

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.

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.

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.

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.)

Usually I think of spacetime as being gravitational field-force, however thin it may be stretched, but lately I've been questioning this because of the idea that it would move along with objects, which would make it like the luminiferous aether idea that was disproven. Maybe that wouldn't be the case, though, if the compound gravitational field of massive bodies behaved as if it was more or less independent of the matter it emerged from. Obviously a magnetic field can move, turn, etc. but can a gravitational field? Does the Earth's gravitation rotate along with the observable planet or does it just extend outward without rotating?

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.

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?

owl · March 31, 2011

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.

lemur · March 31, 2011

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.

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?" Visually, we see object moving undiverted from their inertial path as traveling in straight lines relative to curved lines that trace a longer distance between two points and generally require force-impulses to change their velocity in the course of their journey. The problem arises, it seems, when the planet is observed as being round since that implies that its surface is curved instead of flat. Then, a trajectory due east can seem like a straight line but turn out to be a longer route than a great circle trajectory that changes directions several times. Do any of these paths involve less inertial disruption than the others? I don't think so, because there are so many forces involved other than the momentum of the vehicle. 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? If you were drifting through space in a vehicle without propulsion, in what sense would you perceive your path as curved or straight? You would just see you surroundings changing until something collided with you causing you to experience inertial disruption.

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.

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.

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.

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, 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.

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?

owl · March 31, 2011

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."

michel123456 · March 31, 2011

Highlight the text and use the quote button.

Note, you can do that anytime by editing your old post.

Edited March 31, 2011 by michel123456

lemur · April 1, 2011

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.

I'm not sure how you would even know how much "true" distance was between two points if you had no fixed reference points. The only thing I'm pretty sure about is that if you stopped exerting force in any direction in a vacuum, you would continue along some geodesic path determined by your momentum and the gravity that influences your trajectory. You could plan a "shortcut" based on spacetime-topographical projections you had created from observing patterns of gravity-wells, but I don't know how you could guarantee that your shortcut would work until you actually reached your predicted target.

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.

Actually, relationships between people are not evident in their bodies (unless their are physical traces of contact but that still doesn't tell you what kind of relationship they have). It is evident in their actions, thoughts, feelings, etc. Spacetime is not a body in the material sense. It is patterns of relations among energetic matter. I guess I should qualify this as my opinion since others may disagree. To me, the mass of the sun and the various bodies of matter in the solar system interact gravitationally and these interactions are the basis for smaller objects/particles/light to move in the ways that it is possible for them to move in. I don't think it makes sense to compare the gravitational relations of bodies to some fictional 'empty space' that would supposedly exist in their place if they were absent. E.g. 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?

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."

So mass-topography directly causes spacetime topography via direct gravitational force relations between all matter vis-a-vis all other matter for any affected point? So you want to avoid the whole "frame" concept as unifying the dis-gregate interactions among constituent particles and their forces?

owl · April 1, 2011

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.

I'm not sure how you would even know how much "true" distance was between two points if you had no fixed reference points. The only thing I'm pretty sure about is that if you stopped exerting force in any direction in a vacuum, you would continue along some geodesic path determined by your momentum and the gravity that influences your trajectory. You could plan a "shortcut" based on spacetime-topographical projections you had created from observing patterns of gravity-wells, but I don't know how you could guarantee that your shortcut would work until you actually reached your predicted target.

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.

lemur · April 1, 2011

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.)

What I'm saying, concretely, is that if you are on land, distance travelled is fairly easy to measure in relation to the fixed ground and fixed objects you pass, etc. My bike speedometer measures trip-distance by counting the number of full rotations of the tire and multiplying this by the known circumference of the outer tread. If I was sailing transoceanic, how would I measure distance? I would have no way of knowing when the water is standing still and when it is moving as a current. Unless I have some fixed objects to use to triangulate and compare their observed distances to some empirically-measured distance, how would I know how far I had travelled (or not) at any given moment? Now take motion in outer space: what basis is there for measuring distance-travelled? Sure, you can estimate based on assumptions about the relationship between the scale/brightness of Earth; or maybe you could use relative positions of objects to gage relative changes in position, but beyond interpreting abstract observations, there's no real way to directly observe your motion in your surroundings the way you can with trees, etc. on land or your relationship to a fixed map of the heavens while at sea, is there?

owl · April 1, 2011

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:

So mass-topography directly causes spacetime topography via direct gravitational force relations between all matter vis-a-vis all other matter for any affected point? So you want to avoid the whole "frame" concept as unifying the dis-gregate interactions among constituent particles and their forces?

(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."

Actually, relationships between people are not evident in their bodies (unless their are physical traces of contact but that still doesn't tell you what kind of relationship they have). It is evident in their actions, thoughts, feelings, etc. Spacetime is not a body in the material sense. It is patterns of relations among energetic matter. I guess I should qualify this as my opinion since others may disagree. To me, the mass of the sun and the various bodies of matter in the solar system interact gravitationally and these interactions are the basis for smaller objects/particles/light to move in the ways that it is possible for them to move in. I don't think it makes sense to compare the gravitational relations of bodies to some fictional 'empty space' that would supposedly exist in their place if they were absent. E.g. 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?

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'm not sure how you would even know how much "true" distance was between two points if you had no fixed reference points. The only thing I'm pretty sure about is that if you stopped exerting force in any direction in a vacuum, you would continue along some geodesic path determined by your momentum and the gravity that influences your trajectory. You could plan a "shortcut" based on spacetime-topographical projections you had created from observing patterns of gravity-wells, but I don't know how you could guarantee that your shortcut would work until you actually reached your predicted target.

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.

michel123456 · April 2, 2011

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.

Life, or Wife? (joking)

For Your Information I dislike long posts. I am glad that you found a good companion with Lemur, but I have not the patience to read your (interesting) ideas.

Cheers.

Michel.

owl · April 2, 2011

michel:

For Your Information I dislike long posts. I am glad that you found a good companion with Lemur, but I have not the patience to read your (interesting) ideas.

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:

What I'm saying, concretely, is that if you are on land, distance travelled is fairly easy to measure in relation to the fixed ground and fixed objects you pass, etc. My bike speedometer measures trip-distance by counting the number of full rotations of the tire and multiplying this by the known circumference of the outer tread. If I was sailing transoceanic, how would I measure distance? I would have no way of knowing when the water is standing still and when it is moving as a current. Unless I have some fixed objects to use to triangulate and compare their observed distances to some empirically-measured distance, how would I know how far I had travelled (or not) at any given moment? Now take motion in outer space: what basis is there for measuring distance-travelled? Sure, you can estimate based on assumptions about the relationship between the scale/brightness of Earth; or maybe you could use relative positions of objects to gage relative changes in position, but beyond interpreting abstract observations, there's no real way to directly observe your motion in your surroundings the way you can with trees, etc. on land or your relationship to a fixed map of the heavens while at sea, is there?

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.)

michel123456 · April 2, 2011

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.

Yes. Generally we agree. I follow as a spectator your fight against other distinguished members here. You (we) are lost in conversations that go nowhere IMHO. They (the others) believe that we disagree with Relativity. They don't understand your concern about the ontology of spacetime. I am afraid the word "ontology" is considered part of philosophy, not science. Did you notice a grandiose absence in this philosophy forum?

--------------------------

edit.

To the point:

To me, the "expanding space" is BS, to speak frankly. The "fabric of space" expression makes me vomit. I hope no one hear me.

1.Either space exists, call it "aether" or whatever, and give it properties, expanding shrinking an so on.

2. either space do not exist as an entity, aether do not exist (I thought it had been proved scientifically 100 years ago), and it cannot do anything, of course. If we observe the universe expanding, the explanation is somewhere else.

Edited April 2, 2011 by michel123456

lemur · April 2, 2011

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.

But the marriage isn't even an actual material relation but just a summary institutionalization of the idea that there are various actual material relations that do (or should) be occurring between the two people deemed spouses. So, if you would get divorced, for example, you might stop sleeping in the same bed but would you stop interacting in every possible way? Probably not, which shows that while you would attribute different meanings to your post-divorce interactions than while you were married, they would still exist as substantive interactions, e.g. "discussing whether a child needs new clothes." Spacetime is similar: even if you denied it as a general ontological phenomenon, the Earth would still orbit the sun at a given distance, which would allow other matter, such as Mercury, to get between the Earth and Sun. You can say that various aspects of the Earth and sun "create space" between them, but you could also just say that they gravitationally attract each other and other matter in a way that results in certain dynamics.

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?"

You can, but doesn't that suggest that the space exists independently of the forces that allow things to move "through it?" I think that if you were being really descriptively rigorous, you would just describe everything as being engaged in various levels of force-relations with other things.

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.

I agree that there are epistemological contradictions that emerge when you analyze deeply. Still, I don't see why "spacetime" has to immediately be taken to refer to something that transcends the gravitation that is "its" curvature. A related question is whether gravitational field force is an entity, and whether it should be viewed as emanating from and extending beyond the electron-fields or whether the electron fields should be viewed as embedded near the center of the gravitational field as its own entity.

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.

But Earth and Mars wouldn't even be orbiting near each other, probably, if the sun was absent. So a laser shot between them would be in the context of two lone planets drifting away from each other at some arbitrary distance. It's like with the asteroids. Their relationship with each other (spatially) has everything to do with their orbital motion around the sun. If the sun were absent, they would just be a bunch of rocks drifting in space with, probably, no special relationship with one another. So I think it makes more sense to view space as organizational arrangements among things due to their force-energy interactions. The fact that there appears to be "empty space" between them can be attributed to their relative coalescence relative to the energy that allows them to move away from each other. E.g. if a cloud suddenly condenses into to rain, there is "empty space" between the rain drops; but as long as the cloud was uncondensed water vapor, it was simply a continuous flux of low-density substance, held together (I think) by electrostatic attraction. Once that attraction condenses the drops into mutually separated regions of liquid, their emerges a potential for other things, such as more rain drops, to pass between them.

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.)

Sure, then you would have a set of concrete object relations to use as reference. I.e. you could count the number of atoms in the wire and assume they weren't dilating and contracting relative to each other and whatever gravity they were exposed to. But when there's no wire and just a few random particles here and there, how would you know if you were getting hit by a particle or if you were running into it?

owl · April 4, 2011

michel:

Yes. Generally we agree. I follow as a spectator your fight against other distinguished members here. You (we) are lost in conversations that go nowhere IMHO. They (the others) believe that we disagree with Relativity. They don't understand your concern about the ontology of spacetime. I am afraid the word "ontology" is considered part of philosophy, not science. Did you notice a grandiose absence in this philosophy forum?

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.

To the point:
To me, the "expanding space" is BS, to speak frankly. The "fabric of space" expression makes me vomit. I hope no one hear me.

1.Either space exists, call it "aether" or whatever, and give it properties, expanding shrinking an so on.

2. either space do not exist as an entity, aether do not exist (I thought it had been proved scientifically 100 years ago), and it cannot do anything, of course. If we observe the universe expanding, the explanation is somewhere else.

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:

But the marriage isn't even an actual material relation but just a summary institutionalization of the idea that there are various actual material relations that do (or should) be occurring between the two people deemed spouses. So, if you would get divorced, for example, you might stop sleeping in the same bed but would you stop interacting in every possible way? Probably not, which shows that while you would attribute different meanings to your post-divorce interactions than while you were married, they would still exist as substantive interactions, e.g. "discussing whether a child needs new clothes." Spacetime is similar: even if you denied it as a general ontological phenomenon, the Earth would still orbit the sun at a given distance, which would allow other matter, such as Mercury, to get between the Earth and Sun. You can say that various aspects of the Earth and sun "create space" between them, but you could also just say that they gravitationally attract each other and other matter in a way that results in certain dynamics.

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:

You can, but doesn't that suggest that the space exists independently of the forces that allow things to move "through it?" I think that if you were being really descriptively rigorous, you would just describe everything as being engaged in various levels of force-relations with other things.

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 agree that there are epistemological contradictions that emerge when you analyze deeply. Still, I don't see why "spacetime" has to immediately be taken to refer to something that transcends the gravitation that is "its" curvature. A related question is whether gravitational field force is an entity, and whether it should be viewed as emanating from and extending beyond the electron-fields or whether the electron fields should be viewed as embedded near the center of the gravitational field as its own entity.

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.

But Earth and Mars wouldn't even be orbiting near each other, probably, if the sun was absent. So a laser shot between them would be in the context of two lone planets drifting away from each other at some arbitrary distance. It's like with the asteroids. Their relationship with each other (spatially) has everything to do with their orbital motion around the sun. If the sun were absent, they would just be a bunch of rocks drifting in space with, probably, no special relationship with one another. So I think it makes more sense to view space as organizational arrangements among things due to their force-energy interactions. The fact that there appears to be "empty space" between them can be attributed to their relative coalescence relative to the energy that allows them to move away from each other. E.g. if a cloud suddenly condenses into to rain, there is "empty space" between the rain drops; but as long as the cloud was uncondensed water vapor, it was simply a continuous flux of low-density substance, held together (I think) by electrostatic attraction. Once that attraction condenses the drops into mutually separated regions of liquid, their emerges a potential for other things, such as more rain drops, to pass between them.

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.

Sure, then you would have a set of concrete object relations to use as reference. I.e. you could count the number of atoms in the wire and assume they weren't dilating and contracting relative to each other and whatever gravity they were exposed to. But when there's no wire and just a few random particles here and there, how would you know if you were getting hit by a particle or if you were running into it?

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."

owl · April 5, 2011

I'm back to the most basic question concerning the ontology of space, as introduced at the top of this thread.

"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, 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.

lemur · April 5, 2011

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.

But you're still missing mine, that the marriage as a marriage never existed prior to the divorce either. The only thing that ever existed was the actual material relations between the individuals deemed "spouses" by the marital institution. This is the same for spacetime where the material relations are things like motion and force among entities and "spacetime" is just a summary concept for them, i.e. an institutionalization of a general pattern observed among material relations.

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.

If matter and energy don't cause the relations that take place among them, then what would? Space can't precede or exist externally to something that it isn't independent of, can it? That would contradict the whole fact that it is dependent on them.

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.

Nothing? Could it be that there is absolutely nothing between particles of matter and energy and so they have to interact directly? What I wonder is, epistemologically, why is there such a strong need/desire that things should interact with each other beyond defined boundaries? Are there empirical reasons or is it just a convenience for certain methods of thinking to regard force-fields as bounded? Just because it's painful or even impossible to describe a photon as extending from but not transcending the electron that emitted it, does that make it an impossibility?

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."

What exists? The ability for two electrons to exchange photons between them? The ability for physical events to occur non-simultaneously? The ability for force-strengths to change relative to each other? Of course the awkwardness of all this tempts me to just invoke space(time) but isn't the whole issue whether that's an epistemological convention or a physical fixture alongside (i.e. transcendent of) matter and energy?

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.

Electrostatic repulsion among electrons is the only reason I can think of that mass is distinguished from gravitational field-force. If you are in orbit, isn't the big blue, white, and green ball you see just the electron-portion of the Earth? You are still within its gravitational field, correct, just as it is in yours (albeit to a far weaker extent)? So you could say that mass attract mass, but why couldn't you say that gravitational field-force simply tends toward homogenization/condensation? After all, if any two gravitational fields intersect, then they would have to have some amount of "merging force" that causes them to integrate in a certain way with the corresponding effect on attached electrostatic and nuclear fields, wouldn't they? Isn't it possible to think of gravitational fields as big blobs that endlessly stretch out from each other until they eventually separate, at which point nothing more can go from one to the other, not even light?

This is the limitation of a theoretical world, like without the sun. It fails if taken too literally.

If empirical description is literal description, how can it fail when 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?

Doesn't this just refer to comparing different material interactions between objects in different ways?

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.

Isn't Earth already engaged in a "high-speed fly by" of Mars and wouldn't a laser-shot move the same as visible light between the same two points?

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."

What would the "cosmic overview" be based on except empirical observations and points of reference extrapolated from them and logically applied using taken-for-granted assumptions?

owl · April 5, 2011

What would the "cosmic overview" be based on except empirical observations and points of reference extrapolated from them and logically applied using taken-for-granted assumptions?

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.)

lemur · April 5, 2011

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.)

But aren't you projecting assumptions based on your human-eye perspective onto what you imagine to be a god's eye perspective in terms you are familiar with?

owl · April 6, 2011

lemur:

But you're still missing mine, that the marriage as a marriage never existed prior to the divorce either. The only thing that ever existed was the actual material relations between the individuals deemed "spouses" by the marital institution. This is the same for spacetime where the material relations are things like motion and force among entities and "spacetime" is just a summary concept for them, i.e. an institutionalization of a general pattern observed among material relations.

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 matter and energy don't cause the relations that take place among them, then what would? Space can't precede or exist externally to something that it isn't independent of, can it? That would contradict the whole fact that it is dependent on them.

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? Could it be that there is absolutely nothing between particles of matter and energy and so they have to interact directly? What I wonder is, epistemologically, why is there such a strong need/desire that things should interact with each other beyond defined boundaries? Are there empirical reasons or is it just a convenience for certain methods of thinking to regard force-fields as bounded? Just because it's painful or even impossible to describe a photon as extending from but not transcending the electron that emitted it, does that make it an impossibility?

"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:

What exists? The ability for two electrons to exchange photons between them? The ability for physical events to occur non-simultaneously? The ability for force-strengths to change relative to each other? Of course the awkwardness of all this tempts me to just invoke space(time) but isn't the whole issue whether that's an epistemological convention or a physical fixture alongside (i.e. transcendent of) matter and energy?

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?"

Electrostatic repulsion among electrons is the only reason I can think of that mass is distinguished from gravitational field-force. If you are in orbit, isn't the big blue, white, and green ball you see just the electron-portion of the Earth? You are still within its gravitational field, correct, just as it is in yours (albeit to a far weaker extent)? So you could say that mass attract mass, but why couldn't you say that gravitational field-force simply tends toward homogenization/condensation? After all, if any two gravitational fields intersect, then they would have to have some amount of "merging force" that causes them to integrate in a certain way with the corresponding effect on attached electrostatic and nuclear fields, wouldn't they? Isn't it possible to think of gravitational fields as big blobs that endlessly stretch out from each other until they eventually separate, at which point nothing more can go from one to the other, not even light?

?? 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."

Doesn't this just refer to comparing different material interactions between objects in different ways?

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.

Isn't Earth already engaged in a "high-speed fly by" of Mars and wouldn't a laser-shot move the same as visible light between the same two points?

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:

But aren't you projecting assumptions based on your human-eye perspective onto what you imagine to be a god's eye perspective in terms you are familiar with?

(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?"

Edited April 6, 2011 by owl

lemur · April 6, 2011

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 thought it was a perfect analogy between material interactions and institutionalized relations, but needless to say "curved spacetime" doesn't have to refer to space(time) as an entity. It can just be a patterned skewing of force vectors, no?

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.

I don't understand your thinking. First you question the existence of space as an a priori entity. Then you insist that the space existed between two things before it grew larger. When you tear a piece of paper in half, does the space of the tear exist before the paper is torn? If it does, is it any different than any other two fibers of the paper that are still interwoven? What about with water? When an air bubble is blown underwater, does the air fill a previously empty space? Doesn't the air bubble itself create an empty space within the water by its pressure? Doesn't nuclear force and motion do the same thing within the gravitational field that includes all matter in the solar system? 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?

"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.

Whether or not gravity can continue expanding indefinitely doesn't have anything to do with whether it has a limit or not. It could continue expanding indefinitely without ever developing the strength to retract itself into a re-condensed form. The pertinent issue is whether gravity-wells connect, remain connected, and/or disconnect under certain circumstance and, if so, how can you tell when gravity is completely absent or weakly present?

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.' "

Not "nothing-ness," NOTHING. You could just say that particles reach each other with their field-force because the force-fields are ultimately unbounded. In other words, what you want to regard as empty space could just be filled with various extended fields of force, only far weaker than you might choose to validate as significant enough to consider as a continuation of the particle-fields they extend from.

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.

What I'm saying is that electrostatic force is a force just like gravity. So when you regard an electron as a point-particle with an electrostatic field extending away from it, that is no different from the gravitational field extending away from it. So what basis is there to regard the points as points along a definite boundary? Both the electrostatic and gravitational fields of the particles extend beyond them for various distances. What keeps you from saying that the force-fields themselves are part of the particles? Why are they external to the particles in your epistemology? Why isn't the gravitational field as a whole a physical entity with no essential core, just coinciding electrostatic and nuclear fields?

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.

What I'm saying is that we see what photons bounce off of, i.e. certain electrons. We don't see the gravitational field of Earth, but we do see the electrostatic fields of some of its electrons when they are organized in a way that reflects light. The atmosphere consists of gaseous molecules surrounded by electrons with electrostatic field-force that interacts with light. Why does the gravitation of these particles extend beyond what we typically delineate as the limits of the atmosphere? If the gravitation of Earth extends to the moon and beyond, it extends far beyond the probability area to which we attribute the electrons of the atmosphere, right? Yet, though we can see the atmospheric electrons, we can't see their gravitation, but does that make it less of a boundary-market for the matter than their electrostatics? I.e. gravitation and electrostatics are just two different forces - why should one take precedence in defining the boundaries of matter?

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?

Why do they need to be something more than gravitational field-force itself? Why do electrons need to be more than electromagnetic/gravitational field-force? Why do protons need to be more than electrostatic/nuclear/gravitational field force? Why do neutrons need to be more than nuclear/gravitational field-force? Why does field-force need to exist as something that emerges from something else? What is ontologically essential about calling a point at the center of the force-field a 'particle?'

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."

If the "rest frame" of Earth containing Mars didn't include the sun, what would the strength of gravitational field-force be between Earth and Mars?

(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?"

What does it mean to have a direction without anything in that direction? I think you keep assuming that when no matter/force/energy is present, there's still something else called "empty space" that IS present. What if there was really NOTHING present in front of your rocket ship? What if the strongest force in the universe was your own gravitation? Where would you go? What would you orbit? What would "spacetime" curve around except you yourself? There would be nothing else, right?

owl · April 6, 2011

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;

I thought it was a perfect analogy between material interactions and institutionalized relations, but needless to say "curved spacetime" doesn't have to refer to space(time) as an entity. It can just be a patterned skewing of force vectors, no?

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 don't understand your thinking. First you question the existence of space as an a priori entity. Then you insist that the space existed between two things before it grew larger. When you tear a piece of paper in half, does the space of the tear exist before the paper is torn? If it does, is it any different than any other two fibers of the paper that are still interwoven? What about with water? When an air bubble is blown underwater, does the air fill a previously empty space? Doesn't the air bubble itself create an empty space within the water by its pressure? Doesn't nuclear force and motion do the same thing within the gravitational field that includes all matter in the solar system? 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?

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."

Whether or not gravity can continue expanding indefinitely doesn't have anything to do with whether it has a limit or not.

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.

It could continue expanding indefinitely without ever developing the strength to retract itself into a re-condensed form. The pertinent issue is whether gravity-wells connect, remain connected, and/or disconnect under certain circumstance and, if so, how can you tell when gravity is completely absent or weakly present?

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.

Not "nothing-ness," NOTHING. You could just say that particles reach each other with their field-force because the force-fields are ultimately unbounded. In other words, what you want to regard as empty space could just be filled with various extended fields of force, only far weaker than you might choose to validate as significant enough to consider as a continuation of the particle-fields they extend from.

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.)

What I'm saying is that electrostatic force is a force just like gravity. So when you regard an electron as a point-particle with an electrostatic field extending away from it, that is no different from the gravitational field extending away from it. So what basis is there to regard the points as points along a definite boundary? Both the electrostatic and gravitational fields of the particles extend beyond them for various distances. What keeps you from saying that the force-fields themselves are part of the particles? Why are they external to the particles in your epistemology? Why isn't the gravitational field as a whole a physical entity with no essential core, just coinciding electrostatic and nuclear fields?

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 do they need to be something more than gravitational field-force itself? Why do electrons need to be more than electromagnetic/gravitational field-force? Why do protons need to be more than electrostatic/nuclear/gravitational field force? Why do neutrons need to be more than nuclear/gravitational field-force? Why does field-force need to exist as something that emerges from something else? What is ontologically essential about calling a point at the center of the force-field a 'particle?'

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.

If the "rest frame" of Earth containing Mars didn't include the sun, what would the strength of gravitational field-force be between Earth and Mars?

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.)

What does it mean to have a direction without anything in that direction? I think you keep assuming that when no matter/force/energy is present, there's still something else called "empty space" that IS present. What if there was really NOTHING present in front of your rocket ship? What if the strongest force in the universe was your own gravitation? Where would you go? What would you orbit? What would "spacetime" curve around except you yourself? There would be nothing else, right?

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.

Edited April 6, 2011 by owl

owl · April 7, 2011

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.")

Edited April 7, 2011 by owl

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