lemur Posted April 7, 2011 Posted April 7, 2011 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. How can space precede the entities it is presumed to contain if it doesn't exist independently of them? I say it is an abstraction derived from actual physical interactions that precede and generate it as a result of their motion and relative densities. What's wrong with saying that matter and energy precede and contain space instead of the reverse? 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." Start with a nebula with even consistency, i.e. no density gradation. Then allow it to condense into multiple gravity-wells with density gradations from one well to the next. The low-density areas will be construed as empty space BETWEEN the densified areas of the gravity wells. But why are they now "in-between space" instead of just "low-density areas of the nebula?" Something changed in our perception of the nebula to transform it from a single unit to multiple units with space in between. You could look at the singularity of the big bang the same way, no? Shall we have earth and sun merge as physical entities just because their gravitational fields interact? I vote no. What does anyone's "vote" matter? The issue is whether there's any objective basis for describing gravity fields as separate or multi-centered parts of the same unified field? 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. You seem to have completely lost sight of the issue of whether these formulations are rooted in objectivity or subjective convenience. 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 suppose so, but I guess the deeper point is whether Sorry. I'm fine with empty space as absence of things, no thing or nothing. OK? But then how do you measure the amount of distance between things if there's absolutely nothing between them?
michel123456 Posted April 7, 2011 Posted 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.") Great. That is the point I stopped reading. I'm back to the most basic question concerning the ontology of space, as introduced at the top of this thread. So, to delve more deeply into the above: If that which is not occupied by "stuff" ('things') is empty space, no-thing-ness, what sense does it make to say that space does not exist without the stuff in it? If you take the contents (whatever) out of a box, does it make sense to say that the space inside the box doesn't exist unless the contents are replaced? Obviously not. So how does the above argument by Sten Odenwald (presumable a well respected scientist in the field of relativity) hold up to the scrutiny of logic and common sense? Not well it seems to me. Comments? And yet if space is a non-entity (with which I agree, emptiness being a lack of entities) where does that leave the ontology of spacetime? As in Brown and Pooley's book, (see reference in that first post)... a "non-entity." If one argues that "time" must be mixed in as an ingredient before spacetime becomes an entity, then we must ask what time is as well... a question often beaten to death with no consensual outcome. Obviously cosmos is not a static snapshot, so all movement of all things can be said to "take time" or have the property of event duration, whether an active cesium atom in an atomic clock or the familiar day and year as natural cycles happening "in time." But that does not make "time" an entity either. Anyway, just a move back to basics in case anyone is interested. So what does gravity make curve besides the obvious... the trajectory of objects and light? Same question, still unanswered by the relativity theorists on this forum. As I said before, I basically agree with your points. That means nothing, just another wickle-wackler agreeing... What I believe is that we are missing something. There is something that we have not grasped concerning Space, Time and Gravity. You must be right in the bolded part : "cosmos is not a static snapshot" I have the feeling (how much does that count?) that EVERYTHING is dynamic. What we call matter is dynamic, what we call space is dynamic, what we call time is dynamic. In the word "dynamic", there is not only "motion", which is displacement in space, but something wider. Mainstream physicists talk sometimes about a "scale factor" : something like that. In other words, all discussions about the ontology of Spacetime is useless IMHO, since we don't know what we are talking about.
Iggy Posted April 7, 2011 Posted April 7, 2011 In other words, all discussions about the ontology of Spacetime is useless IMHO, since we don't know what we are talking about. I agree. I skimmed the posts in this thread. There were too few ideas surrounded by too many words to read them in depth, but I get the feeling that the most important point has been missed. That is, the question can't currently be answered. If an engineer makes a big triangle with sides that are locally straight and measures angles different than 180 degrees then space is curved by definition. But, that experiment doesn't logically prove that space is an entity with an independent and malleable existence. If the result of the experiment is 180 degrees then space is, by definition, Euclidean. That also would not prove that space is merely a human concept with no independent existence. In my humble opinion, this thread isn't going to get anywhere. Whatever people's opinions for or against spacetime substantivalism, I don't believe they will stand on any kind of logical foundation. 1
lemur Posted April 7, 2011 Posted April 7, 2011 In my humble opinion, this thread isn't going to get anywhere. Whatever people's opinions for or against spacetime substantivalism, I don't believe they will stand on any kind of logical foundation. And yet people will go on with whatever tacit assumptions they make about the nature of space. Do you think it's possible for humans to suddenly epistemologically cease to conceptualize space because they're not sure about the logic of the foundation of their epistemology?
Iggy Posted April 7, 2011 Posted April 7, 2011 Do you think it's possible for humans to suddenly epistemologically cease to conceptualize space because they're not sure about the logic of the foundation of their epistemology? I think space and time are necessary components of the human psyche. 1
michel123456 Posted April 7, 2011 Posted April 7, 2011 In my humble opinion, this thread isn't going to get anywhere. Whatever people's opinions for or against spacetime substantivalism, I don't believe they will stand on any kind of logical foundation. Sure this thread will not give the solution Mankind is waiting for. But at least it can enhance the need of being coherent. If one decides to accept the meaning of space as "total nothing", it must be obvious that space , under this assumption, cannot curve nor expand nor nothing. On the other hand, if one decides to accept that space can curve and expand, space must be "something", call it aether or wathever, but it cannot be "total nothingness". You must choose. It is important to note that you cannot jump from one definition to the other at will, and say that "space expands" together with "space don't exist", explaining that "distance increases" while "objects don't move". If distance increases, "something" increases, there is no doubt. All those who say the contrary don't have a clear notion of what they are arguing. IMHO.
lemur Posted April 7, 2011 Posted April 7, 2011 (edited) Sure this thread will not give the solution Mankind is waiting for. But at least it can enhance the need of being coherent. If one decides to accept the meaning of space as "total nothing", it must be obvious that space , under this assumption, cannot curve nor expand nor nothing. On the other hand, if one decides to accept that space can curve and expand, space must be "something", call it aether or wathever, but it cannot be "total nothingness". You must choose. It is important to note that you cannot jump from one definition to the other at will, and say that "space expands" together with "space don't exist", explaining that "distance increases" while "objects don't move". If distance increases, "something" increases, there is no doubt. All those who say the contrary don't have a clear notion of what they are arguing. IMHO. I would guess that if you analyzed mixed phase states, such as ice-water or boiling-water, you would find that the reason temperature remains constant throughout the phase change is that any temperature deviation in each component of the mixture transfers its heat to the parts that have not yet reached the higher energy phase. So steam bubbles either heat the water that surrounds them or water that rises above 0C in ice-water immediately gives up its heat to remaining ice. So in that sense, you could say that there is not a phase-change state distinct from the phases themselves. Yet, when you chart temperature variation as a function of temperature, there appears to be flat lines during phase-transitions, right? Why can't making reference to space as a curved 'entity' work the same way? I.e. you could recognize that what is really going on is force(field)-vectors influencing each other, but because there is an observed pattern, this can be referred to as 'space(time) curvature.' Then you could just apply deeper scientific understanding to recognize that just as there is no true "phase transition" state distinct from the other phases, there is no "spacetime (curvature)" distinct from the physical relations between matter and (its) energies. Good point, though, about the conflict between "totally nothing" and "something that curves." Edited April 7, 2011 by lemur
owl Posted April 7, 2011 Author Posted April 7, 2011 (edited) michel: In other words, all discussions about the ontology of Spacetime is useless IMHO, since we don't know what we are talking about. I agree. I skimmed the posts in this thread. There were too few ideas surrounded by too many words to read them in depth, but I get the feeling that the most important point has been missed. That is, the question can't currently be answered. If an engineer makes a big triangle with sides that are locally straight and measures angles different than 180 degrees then space is curved by definition. But, that experiment doesn't logically prove that space is an entity with an independent and malleable existence. If the result of the experiment is 180 degrees then space is, by definition, Euclidean. That also would not prove that space is merely a human concept with no independent existence. In my humble opinion, this thread isn't going to get anywhere. Whatever people's opinions for or against spacetime substantivalism, I don't believe they will stand on any kind of logical foundation. It is of course a matter of individual interest. But most texts and internet references to relativity start by stating as a matter of fact that gravity curves spacetime, taking for granted that, ever since Minkowski came up with it and Einstein endorsed it, "it" must be an actual malleable medium. My interest is shared by an august body of well credentialed scientists and philosophers of science, The International Society for the Advanced Study of Spacetime (ISASS.) Over several years and conventions on spacetime ontology, they have produced dozens of scholarly papers on the subject. My intent in this thread was originally to introduce excerpts from more of them for discussion here, but it is quite complex and it is easy to get buried in debating details, as we have done here. My back to basics post was an attempt to refocus on the basic issues, but Iggy didn't respond to specific points in that post, and clearly is not interested in the topic. Each to his own interest. Here is a re-statement of some basics from my last post: Me: 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." 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. 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. 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.) Whether or not "spacetime" is instrumental as a malleable medium morphed by gravity is the question here at hand. Care to comment on the actual issues at hand here? Ps: Regarding the triangle measurements you cite; I would like to see such an experiment on very large scale in "deep space" beyond significant gravitational forces (which would bend lasers.) If three 'stations' were set up at rest relative to each other and lasers beams were established between them, and the angles precisely measured... I wonder... If 'curved space' is just a non-Euclidean concept, fine, if it works as a conceptual tool. But if "space curves' in the real world, then it is a very basic question to ask, "What curves, if it is a malleable medium?" Pps: Michel, I totally agree with your post #31 above, but not, of course with your quote at the top of this post. You and Iggy share the opinion here that the ISASS referenced above is much ado about nothing. Well... it is philosophy of science, concerned with what actually exists, not just the pragmatic application of a concept for convenience as a context for the math. Lemur, to you last question above about my, "I'm fine with empty space as absence of things, no thing or nothing. OK?' But then how do you measure the amount of distance between things if there's absolutely nothing between them? What is wrong with my laser shot to a mirror on mars and back?... Elapsed time times the speed of light. Of course that introduces light in the space between earth and mars. If you object to that I don't know what your point is. Edited April 7, 2011 by owl
Iggy Posted April 7, 2011 Posted April 7, 2011 (edited) Sure this thread will not give the solution Mankind is waiting for. But at least it can enhance the need of being coherent. If one decides to accept the meaning of space as "total nothing", it must be obvious that space , under this assumption, cannot curve nor expand nor nothing. On the other hand, if one decides to accept that space can curve and expand, space must be "something", call it aether or wathever, but it cannot be "total nothingness". You must choose. It is important to note that you cannot jump from one definition to the other at will, and say that "space expands" together with "space don't exist", explaining that "distance increases" while "objects don't move". If distance increases, "something" increases, there is no doubt. All those who say the contrary don't have a clear notion of what they are arguing. IMHO. I suppose I agree that "space doesn't exist" is not compatible with "space is curved" or "space is straight" (or any other way you could describe it). The question is not "does space exist?". It is either an independent entity that exists in and of itself or it is merely a human concept which expresses relationships between bodies but has no independent and substantial existence. Either way, saying "space is nothing" is kind of meaningless -- like saying "distance is nothing". Entropy would be a good analogy. You wouldn't say "entropy is nothing". You would say "entropy is not something that exists in and of itself -- it is a property of a system". edited to add: lemur gave a similar analogy. It is of course a matter of individual interest... My interest is shared by an august body of well credentialed scientists and philosophers of science... but Iggy didn't respond to specific points in that post, and clearly is not interested in the topic. Each to his own interest... Wow! Owl, your inability to understand what other people are trying to say is really something. Someone says that a question cannot be logically answered based on current evidence and you take that to mean that it is an uninteresting question. That is really something. But most texts and internet references to relativity start by stating as a matter of fact that gravity curves spacetime, taking for granted that, ever since Minkowski came up with it and Einstein endorsed it, "it" must be an actual malleable medium. Because space-time is non-linear (or "curved") it must be an actual malleable medium? Where did you get this? Kinetic energy is also non-linear. Does this make it "an actual malleable medium"? Is entropy a malleable medium? Space-time expresses the relationship between events. That relationship may represent something substantial that exists in and of itself or it may just be a human concept representing something more fundamental that we don't currently know or understand. Either way, just because the relationship is non-linear doesn't mean it must be the subject of reification. Just to be clear... Plot the kinetic energy between two bodies and it will be curved. That doesn't mean that kinetic energy is a malleable medium. Plot the space-time between two events and it will be curved. That doesn't mean that space-time is a malleable medium. Edited April 7, 2011 by Iggy 1
lemur Posted April 7, 2011 Posted April 7, 2011 (edited) What is wrong with my laser shot to a mirror on mars and back?... Elapsed time times the speed of light. Of course that introduces light in the space between earth and mars. If you object to that I don't know what your point is. I guess it depends on how you regard the motion of photons. If you regard the photons as moving "between" Earth and Mars, then there is some "empty space" that they are traveling "through." If, on the other hand, you regard photons as inter-electron information WITHIN convergent gravitational fields, then you don't really have "space" between Earth and Mars since their gravitational fields merge into one another. Then you would have to decide if you view gravitation as "space" between the electrostatic fields of electrons or if you can treat photons as extending the electron fields they emanate from as they propagate along to their receiving electrons (i.e. are photons moments of extension and merging between different electrons?). If you treated gravity, electromagnetism, and other force fields this way, i.e. as interwoven instead of bounded and separated within a spatial container, then you could theoretically escape relying on space as a container concept for interactions between multiplicities of field-forces. Edited April 7, 2011 by lemur
owl Posted April 7, 2011 Author Posted April 7, 2011 I'll get back to specific replies later,but first... absolutely as simple as I can make it regarding the question, What is space? (prior to even complicating it with "time.") What problem do people have with emptiness, absence of "stuff," no-thing-ness (not an entity just because of the "ness," nothing ) void, nada? Without all cosmic 'stuff' there is empty space... or, stated differently, in between stuff which occupies space is empty space, not even an "it." To make a case for 'curved space' is, to posit that "it" is some-thing that has the property of curvature rather than absolute emptiness devoid of 'things' or being a thing itself. But modern science has decided that 'space itself' is expanding rather than that stuff in space is moving ever outward into empty space. Ontology demands that the 'burden of proof' on any claim that something exists in a way that "it" ...has properties (like curvature and ability to expand)... is on the claimant. If space is expanding or curving, what is it? Apparently no one here has read the first paper I introduced. It is a tough read, but it will give a better understanding of the ontology of spacetime to anyone really interested. And there are many more. That was why I entitled this thread, the 'scholarly' debate, so it would transcend personal attacks and condescending attitudes, which has been the norm in other threads.
Iggy Posted April 7, 2011 Posted April 7, 2011 (edited) What is space? What problem do people have with emptiness, absence of "stuff," no-thing-ness (not an entity just because of the "ness," nothing ) void, nada? You say that objects occupy space. You say that stuff moves through space. Those statements are completely inconsistent with the definition of "space is nothing". If space is nothing then objects cannot occupy it. If there is no such thing as space then objects can't move through it. If space is nothing then there can't be more of it between the earth and sun than there is between the earth and moon. The word "space" obviously means something other than "nothing". To make a case for 'curved space' is, to posit that "it" is some-thing that has the property of curvature rather than absolute emptiness devoid of 'things' or being a thing itself. You are right -- saying "curved space" does posit that space is something, even if that something is just a human concept reflecting relationships between material bodies void of any independent and substantial existence. But, saying "flat space" also posits that it is something. Ontology demands that the 'burden of proof' on any claim that something exists in a way that "it" ...has properties (like curvature and ability to expand)... is on the claimant. But, your claims require no less proof. You think that saying "things move into and through space" doesn't give space properties? That doesn't make sense at all. You can't say that space doesn't exist and say that things move through it at the same time. I think you need to clarify your own idea of space. Edited April 7, 2011 by Iggy 1
owl Posted April 8, 2011 Author Posted April 8, 2011 (edited) This must be quick. More detail tomorrow. I distinguish between space and things which occupy space. Obviously space is not empty where it is occupied by whatever stuff. Wherever there is no thing is "nothing," empty space wherever it is not occupied.(Maybe repetition helps but I've said this many times in this thread. It may take more than a quick skim to understand it.) Yes things travel through space, rendering it "not empty" where occupied... yet again. I didn't say that space does not exist. Where nothing exists is empty space. I have said many times that space is emptiness. Empty means that volume with nothing in it. Ontology examines what exists. Does nothingness exist? As a lack of entities, it is still the nothing in between entities. Again and again. How else can I make it clearer? As entities move away from each other there is increasing space (emptiness) between them. This does not mean that "space itself is expanding." Edited April 8, 2011 by owl
michel123456 Posted April 8, 2011 Posted April 8, 2011 I suppose I agree that "space doesn't exist" is not compatible with "space is curved" or "space is straight" (or any other way you could describe it). The question is not "does space exist?". It is either an independent entity that exists in and of itself or it is merely a human concept which expresses relationships between bodies but has no independent and substantial existence. Either way, saying "space is nothing" is kind of meaningless -- like saying "distance is nothing". Entropy would be a good analogy. You wouldn't say "entropy is nothing". You would say "entropy is not something that exists in and of itself -- it is a property of a system". edited to add: lemur gave a similar analogy. Wow! Owl, your inability to understand what other people are trying to say is really something. Someone says that a question cannot be logically answered based on current evidence and you take that to mean that it is an uninteresting question. That is really something. Because space-time is non-linear (or "curved") it must be an actual malleable medium? Where did you get this? Kinetic energy is also non-linear. Does this make it "an actual malleable medium"? Is entropy a malleable medium? Space-time expresses the relationship between events. That relationship may represent something substantial that exists in and of itself or it may just be a human concept representing something more fundamental that we don't currently know or understand. Either way, just because the relationship is non-linear doesn't mean it must be the subject of reification. Just to be clear... Plot the kinetic energy between two bodies and it will be curved. That doesn't mean that kinetic energy is a malleable medium. Plot the space-time between two events and it will be curved. That doesn't mean that space-time is a malleable medium. It is not a good idea IMO to replace a subject we have difficulties to understand with another even more difficult. What is energy? What is kinetic energy? You say that objects occupy space. You say that stuff moves through space. Those statements are completely inconsistent with the definition of "space is nothing". Quite the contrary. Do you remember those little pocket games with squares you had to slide from one place to other in a step by step procedure (forgot the name): those games work only because there was a square empty. Emptiness was necessary to allow movement. If space is nothing then objects cannot occupy it. If there is no such thing as space then objects can't move through it. If space is nothing then there can't be more of it between the earth and sun than there is between the earth and moon. You are thinking of emptiness as an obstacle. I my view emptiness is the absence of obstacle. The word "space" obviously means something other than "nothing". Nothing is obvious. I think you need to clarify your own idea of space. We all do.
Iggy Posted April 8, 2011 Posted April 8, 2011 I didn't say that space does not exist. Where nothing exists is empty space. Just so we're clear -- space does exist? As entities move away from each other there is increasing space (emptiness) between them. This does not mean that "space itself is expanding." Let's focus on this. Without repeating yourself ad nauseum, what does "space itself is expanding" mean? Most people think of space as distance. Earlier in the thread you used the words space and distance interchangeably. Most people think of expanding as getting larger or growing. To most people "space is not expanding" would just mean "distance is not getting larger or growing". Are you trying to say that the distance is increasing, but that the distance isn't getting bigger. That doesn't make sense to me. In case you don't follow what I mean. Change the word "space" in your quote to "distance" and change the word "expanding" to "getting larger". As entities move away from each other there is increasing distance (emptiness) between them. This does not mean that "distance itself is getting larger." Is that what you mean? If not then how are the words I used different from the words you used? Please be brief in your response. Plot the kinetic energy between two bodies and it will be curved. That doesn't mean that kinetic energy is a malleable medium. Plot the space-time between two events and it will be curved. That doesn't mean that space-time is a malleable medium. It is not a good idea IMO to replace a subject we have difficulties to understand with another even more difficult. What is energy? What is kinetic energy? Seriously? I was talking to Owl. I was using an analogy and I don't need the forum analogy police interrupting and telling me to stop. Owl used the same analogy himself earlier and said that the whole issue was whether space-time was like energy. 1
lemur Posted April 8, 2011 Posted April 8, 2011 Most people think of space as distance. Earlier in the thread you used the words space and distance interchangeably. Most people think of expanding as getting larger or growing. To most people "space is not expanding" would just mean "distance is not getting larger or growing". Are you trying to say that the distance is increasing, but that the distance isn't getting bigger. That doesn't make sense to me. I'm curious if anyone sees a distinction between distance-between-points and distance-within-a-field. It seems to me that much physics relies on the idea that fields have center-points and measures the distance-between those points. If fields were regarded as independently self-constituted, I wonder whether distance would continue to be a viable measurability. With EM waves, for example, are the electric and magnetic fields that constitute it measurable? Yes, there is wavelength/frequency, but these are not fields that emerge from a central point, the way the electrostatic fields of electrons and the nuclear fields of nucleons supposedly do. So if the point-epistemology would be replaced with a diffuse-field approach, would distance become fundamentally uncertain at every level because there would never be definite points to identify as the exact location of a 'particle'-field?
owl Posted April 8, 2011 Author Posted April 8, 2011 Iggy: Just so we're clear -- space does exist? What part of my last post did you not understand?(Here it is again to avoid the long scroll-down to bottom of last page): Post 38;I distinguish between space and things which occupy space. Obviously space is not empty where it is occupied by whatever stuff. Wherever there is no thing is "nothing," empty space wherever it is not occupied.(Maybe repetition helps but I've said this many times in this thread. It may take more than a quick skim to understand it.) Yes things travel through space, rendering it "not empty" where occupied... yet again. I didn't say that space does not exist. Where nothing exists is empty space. I have said many times that space is emptiness. Empty means that volume with nothing in it. Ontology examines what exists. Does nothingness exist? As a lack of entities, it is still the nothing in between entities. Again and again. How else can I make it clearer? As entities move away from each other there is increasing space (emptiness) between them. This does not mean that "space itself is expanding." Space "exists" as the emptiness in between (or where there are no) "things." Let's focus on this. Without repeating yourself ad nauseum, what does "space itself is expanding" mean? This is the standard doctrine of present day science/cosmology, i.e., that rather than stuff exploding outward into space, that "space itself is expanding." (I thought you were an advocate of standard doctrine.) Space is considered, in relativity theory, to be an entity which began expanding with the "Bang" and continues to expand. It is also said to be curved by gravity, etc. It is considered an entity, a thing, a malleable medium. I really wish you would read the thread before asking me to repeat what i have said already many times in this thread. Most people think of space as distance. Earlier in the thread you used the words space and distance interchangeably. Most people think of expanding as getting larger or growing. To most people "space is not expanding" would just mean "distance is not getting larger or growing". Are you trying to say that the distance is increasing, but that the distance isn't getting bigger. That doesn't make sense to me. Space is empty volume. The measurement between two bodies in spaceis linear, i.e., distance. See above about things moving away from each other. Obviously when the space between them increases, the distance (linear aspect of space) between them increases. It's not that complicated. In case you don't follow what I mean. Change the word "space" in your quote to "distance" and change the word "expanding" to "getting larger". Answered above.
Iggy Posted April 9, 2011 Posted April 9, 2011 (edited) What part of my last post did you not understand? Your definition of space. Repeating it doesn't help. Space "exists" as the emptiness in between (or where there are no) "things." Space is empty volume. This is very different from the normal definition so I would have to prod some more to understand. What you are describing I believe most people would call "vacuum". Most people think of an "empty volume... between things" as a vacuum. Most people think of space as something a little different. I would have a problem with your definition for this reason... Earth's equatorial diameter is 12,756 km. That is the distance of a line drawn through the earth. You say that space is "the emptiness between things". How much space is there between one side of the earth and the other? Is it 12756 km or is it something less because earth's volume is filled up with matter? In other words, if space is defined as "empty volume" then what about filled volume? Is there no space there? This is the standard doctrine of present day science/cosmology, i.e., that rather than stuff exploding outward into space, that "space itself is expanding."... Space is considered, in relativity theory, to be an entity which began expanding with the "Bang" and continues to expand. Not exactly. People who try to describe the big bang to people who don't understand it end up explaining the difference between an expanding metric like the robertson-walker metric and a static metric like the de-sitter metric. The big bang is usually modeled with the robertson-walker metric so they say "space expands rather than things moving into static space". That is true as far as the robertson-walker metric goes, but it is not necessarily true of general relativity and GR is the more fundamental science. In other words, "expanding space" is true of the most popular model of the big bang, but it is not true of "the big bang" in general. In general relativity you are free to choose an expanding metric like the robertson-walker metric or a metric where stuff moves out into "preexisting" static space like the de-sitter metric. The first is favored for its elegance and how easy it is to solve, but the second is just as admissible. So, science really doesn't insist on what you think it does. There are many articles that stress this -- some philosophical and some scientific. This one stresses how "expanding space" is often misunderstood as a result of simple analogies being carried too far: When the mathematical picture of cosmology is first introduced to students in senior undergraduate or junior postgraduate courses, a key concept to be grasped is the relation between the observation of the redshift of galaxies and the general relativistic picture of the expansion of the Universe. When presenting these new ideas, lecturers and textbooks often resort to analogies of stretching rubber sheets or cooking raisin bread to allow students to visualise how galaxies are moved apart, and waves of light are stretched by the “expansion of space”. These kinds of analogies are apparently thought to be useful in giving students a mental picture of cosmology, before they have the ability to directly comprehend the implications of the formal general relativistic description... However, the very meaning of the phrase expanding space is not rigorously defined, despite its widespread use in teaching and textbooks. Hence, it is prudent to be wary of predictions based on such a poorly defined intuitive frameworks. http://arxiv.org/PS_cache/arxiv/pdf/0707/0707.0380v1.pdf This explains how "stuff moving through space" is a valid interpretation of general relativity's big bang solution... A common belief about big-bang cosmology is that the cosmological redshift cannot be properly viewed as a Doppler shift (that is, as evidence for a recession velocity), but must be viewed in terms of the stretching of space. We argue that, contrary to this view, the most natural interpretation of the redshift is as a Doppler shift, or rather as the accumulation of many infinitesimal Doppler shifts. The stretching-of-space interpretation obscures a central idea of relativity, namely that it is always valid to choose a coordinate system that is locally Minkowskian. We show that an observed frequency shift in any spacetime can be interpreted either as a kinematic (Doppler) shift or a gravitational shift by imagining a suitable family of observers along the photon's path. In the context of the expanding universe the kinematic interpretation corresponds to a family of comoving observers and hence is more natural. http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.1081v2.pdf This link also explains what is happening in this thread... Arguably an enlightened cosmologist never asks this question. In the curved spacetime of general relativity, there is no unique way to compare vectors at widely separated spacetime points, and hence the notion of the relative velocity of a distant galaxy is almost meaningless. Indeed, the inability to compare vectors at different points is the definition of a curved spacetime. In practice, however, the enlightened view is far from universal. The view presented by many cosmologists and astrophysicists, particularly when talking to nonspecialists, is that distant galaxies are “really” at rest, and that the observed redshift is a consequence of some sort of “stretching of space,” which is distinct from the usual kinematic Doppler shift. In these descriptions, statements that are artifacts of a particular coordinate system are presented as if they were statements about the universe, resulting in misunderstandings about the nature of spacetime in relativity. http://arxiv.org/PS_cache/arxiv/pdf/0808/0808.1081v2.pdf A couple more in case you are interested: http://arxiv.org/PS_cache/arxiv/pdf/0809/0809.4573v1.pdf http://blogs.discovermagazine.com/cosmicvariance/2008/10/06/does-space-expand/ It is also said to be curved by gravity, etc. It is considered an entity, a thing, a malleable medium. You probably heard an analogy about how space-time is like a curved rubber sheet and thought "general relativity must insist that space-time is a malleable medium like a rubber sheet". But, the analogy is not the theory so let me ask -- what if it was the analogy that was wrong and not the theory? What if general relativity did not insist that space-time is an independent malleable medium that exists in and of itself? I hope you would you accept the new information in that case. Einstein, the person who invented general relativity, and probably understood it the best, said that the theory proves that space-time coordinates are not physical entities that exist in and of themselves. He said "According to the general theory of relativity the four coordinates of the space-time continuum are entirely arbitrary choosable parameters, devoid of any independent physical meaning". The truth is that science has very little to say on the physical and ontological nature of the thing we call space. You can't take the analogies that are out there too seriously. The measurement between two bodies in spaceis linear Using what method of measurement is distance linear in a gravitational field? In other words, what measurement procedure would give you linear measurements of distance? Edited April 9, 2011 by Iggy 2
owl Posted April 11, 2011 Author Posted April 11, 2011 (edited) Your definition of space. Repeating it doesn't help. As I said, I simply did not know how to be any more clear than I already had. This is very different from the normal definition so I would have to prod some more to understand. What you are describing I believe most people would call "vacuum". Most people think of an "empty volume... between things" as a vacuum. Most people think of space as something a little different. A vacuum can easily be added to my list of synonyms for space as emptiness, no-thing, nada volume not containing anything,etc. Most relativity theorists say that space curves. It must be something(not nothing) to curve. This doesn't have to be complicated. Those who say that space curves must say what it is that curves. I would have a problem with your definition for this reason... Earth's equatorial diameter is 12,756 km. That is the distance of a line drawn through the earth. You say that space is "the emptiness between things". How much space is there between one side of the earth and the other? Is it 12756 km or is it something less because earth's volume is filled up with matter? In other words, if space is defined as "empty volume" then what about filled volume? Is there no space there? Our previous context was speaking of the distance between objects in spacelike earth to mars or to the sun, to the point that the space between them does not vary with extremes of frames of reference from which those distances are measured. Same with rods of intrinsic, objective length, not shrinking and stretching with different extreme frames from which it is measured like from a near light speed fly by. In the case of earth's diameter, I agree with the measurement of that distance above. I addressed the question of the "true distance" between two points on the surface of a sphere earlier. It could as well have been through the earth. In a later example I called it a ball, which could have been solid or not. The point was that a straight line (or needle) through the ball is the shortest distance between two points on the surface of the ball, not the arc between them on the surface.(Just to again establish the context in which this was previously discusssed.) True, this is a case where the distance (diameter) is not, obviously through empty space but a straight line measure through earth matter. Not exactly. People who try to describe the big bang to people who don't understand it end up explaining the difference between an expanding metric like the robertson-walker metric and a static metric like the de-sitter metric. The big bang is usually modeled with the robertson-walker metric so they say "space expands rather than things moving into static space". That is true as far as the robertson-walker metric goes, but it is not necessarily true of general relativity and GR is the more fundamental science. In other words, "expanding space" is true of the most popular model of the big bang, but it is not true of "the big bang" in general. I was speaking of the standard model of cosmology which insists that space is expanding, denying that all stuff is actually move away from all other stuff. I said earlier that the latter model does not 'create more space' between objects, because space is already everywhere not occupied by stuff. This is about the ontology of space. Is it something that expands (curves, etc.) or is it emptiness, or if you prefer, a vacuum? In general relativity you are free to choose an expanding metric like the robertson-walker metric or a metric where stuff moves out into "preexisting" static space like the de-sitter metric. The first is favored for its elegance and how easy it is to solve, but the second is just as admissible. Ontology asks the question, "What is space as 'an expanding metric' in the real world?" You say science can not answer such ontological questions, but a lot of them are seriously trying, as in the ongoing conferences and papers of the ISASS, cited above. So, science really doesn't insist on what you think it does. There are many articles that stress this -- some philosophical and some scientific. This one stresses how "expanding space" is often misunderstood as a result of simple analogies being carried too far: You are really not qualified to say what I think science does and does not insist on. Relativity insists that space-time is curved by gravity without saying what it is. I will not repeat what I have said about the two ingredients as still not making a malleable medium, which 'being curved by gravity' certainly makes it, as per relativity. Thanks for the links. I'll check them out. I again ask you to check out the long, tough read on ontology cited early in this thread: Mauro Durato's paper "Is structural Spacetme Realism Relationalism in Disguise, the Supererogatory Nature of the Substantivalism/Relationalism Debate. ( Google Spacetime Realism and find above title, then hit "quick view.") You probably heard an analogy about how space-time is like a curved rubber sheet and thought "general relativity must insist that space-time is a malleable medium like a rubber sheet". But, the analogy is not the theory so let me ask -- what if it was the analogy that was wrong and not the theory? It still leaves us with the ontological question, "What is it?" I have said many times that I accept the predictive power of relativity even as I and many others, as cited above, challenge the actual existence of spacetime. A "metric" can be just a mental model, but relativity texts treat it like an entity. "Gravity curves spacetime." Period. What if general relativity did not insist that space-time is an independent malleable medium that exists in and of itself? I hope you would you accept the new information in that case. Einstein, the person who invented general relativity, and probably understood it the best, said that the theory proves that space-time coordinates are not physical entities that exist in and of themselves. He said "According to the general theory of relativity the four coordinates of the space-time continuum are entirely arbitrary choosable parameters, devoid of any independent physical meaning". I search for over an hour for Einstein's quote saying that spacetime does not exist independent of matter. Couldn't find it but did find the NASA Q&A scientist's answer (Sten Odenwald) to the same effect, quoted right up front in this thread. If you had read the thread you would not feel the need to reiterate what I have already said, repeatedly. It still leaves the debate about the nature of spacetime as substantive, relational, realist, etc, and a bunch of sub-categories, which I intend to present here in more detail for further discussion. The truth is that science has very little to say on the physical and ontological nature of the thing we call space. You can't take the analogies that are out there too seriously. I suggest you read a few of the papers from the several ISASS conferences on space, time, and spacetime. Using what method of measurement is distance linear in a gravitational field? In other words, what measurement procedure would give you linear measurements of distance? I already addressed this, replying to your engineered triangle as proof of curved space. Beyond significant gravitational influence, laser beams established between three "deep space" stations, without gravity bending the light beams will be straight, and the sum of angles will be 180 degrees. Distance will be easy to measure by reflected light... elapsed time times lightspeed. In a gravitational field, of course light beams as means of measuring will need to take into account the bending or curvature of the beams. The straight line distance between bodies will be found by correcting for the error produced by curved light trajectories (their deviation from straight calculated by amount of gravitational distortion.) The fact that gravity bends trajectories of actual objects and light does not mean that there is no straight line distance between objects. Neither does it mean that "space itself is curved." This is the ontological challenge. Edited April 11, 2011 by owl
lemur Posted April 12, 2011 Posted April 12, 2011 (edited) This is about the ontology of space. Is it something that expands (curves, etc.) or is it emptiness, or if you prefer, a vacuum? If it is a vacuum, where does a given particle end and 'the vacuum' begin? When it is said that the majority of an atom is empty space, what does that mean, that the 3D volume staked out by the various particles is greater than the sum of its 0D (point) parts? How is it sensible to claim a 3D volume is mostly empty space because it is a constellation of 0D points? If space is an entity that curves separately from the gravity that is attributed causation for the curving, why is gravitation separate from the space it curves? What is matter and what are its boundaries? That question is the underlying one that reveals the ontology of space, imo, that is to say if there is such an ontology that is not just an extension of the epistemology of boundary-attribution and separation of distinct entity-ness thereby. Edited April 12, 2011 by lemur
Iggy Posted April 12, 2011 Posted April 12, 2011 A vacuum can easily be added to my list of synonyms for space as emptiness, no-thing, nada volume not containing anything,etc. You don't suppose that was my point? Your definition of space is synonymous with "vacuum" and for most people it is not. Your definition introduces problems. You really didn't get that I was saying that? Most relativity theorists say that space curves. And most classical theorists say that space is Euclidean, or straight. It must be something(not nothing) to curve. You view insists that it is "something (not nothing)" which is straight and through which things move and that which things occupy, so... so what? What is your beef with relativity when you make the same ontological assumptions -- and more for that matter? You don't see this, do you? This doesn't have to be complicated. Those who say that space curves must say what it is that curves. And those who say space is Euclidean and is something through which things travel (you) must say what it is that is Euclidean and what it is through which things travel. You haven't done that. The truth is that either curved space or Euclidean space may serve to be nothing more than a useful approximation of some as-of-yet understood phenomenon -- just like entropy was before the kinetic theory of atoms was developed. The paper you linked in the OP -- Minkowski space-time: a glorious non-entity -- talks about this exactly. Did you read the paper that you mentioned? Maybe you read it but didn't understand it, but liked the title anyway. In the case of earth's diameter, I agree with the measurement of that distance above. I'm sure you agree with the distance. My point was your definition of space. If space is "emptiness", then how can the measurement of space not depend on how empty it is? Is the distance through the earth the same as a line that doesn't pass through the earth? In other words, if your measurement of the amount of space has nothing to do with your definition of space then why are you defining it that way? Do you know, and do you understand what I'm saying? You didn't give a meaningful answer to that part of my post, and your tendency to keep repeating things isn't helping. I was speaking of the standard model of cosmology which insists that space is expanding No, you weren't. You were speaking of general relativity. I'll quote the part of your post that I was responding to: This is the standard doctrine of present day science/cosmology, i.e., that rather than stuff exploding outward into space, that "space itself is expanding." (I thought you were an advocate of standard doctrine.) Space is considered, in relativity theory, to be an entity which began expanding with the "Bang" and continues to expand. I'm telling you: General relativity does not insist on that. Standard cosmology metric that says "space expands" is an arbitrary solution of GR -- other solutions exist where things are moving through space rather than space expanding. You should examine the implications of these facts You are really not qualified to say what I think science does and does not insist on. That's it. I won't be reading the rest of your post. I did not say what you are qualified, or not qualified, to insist science says or does not say. This is my quote -- the part you're talking about: So, science really doesn't insist on what you think it does. There are many articles that stress this -- some philosophical and some scientific. This one stresses how "expanding space" is often misunderstood as a result of simple analogies being carried too far: You are really not qualified to say what I think science does and does not insist on. I said that science doesn't insist on what you think it does and that is true. How you get "really not qualified" is beyond me. 2
owl Posted April 12, 2011 Author Posted April 12, 2011 Iggy: You don't suppose that was my point? Your definition of space is synonymous with "vacuum" and for most people it is not. Your definition introduces problems. You really didn't get that I was saying that? Our "conversation" is a near perfect example of miscommunication. And since you said, " I won't be reading the rest of your post," I assume you will not continue to read this thread, so this clarification is about what I meant that you did not understand, for the benefit of anyone interested. I am here challenging what "most people" in science define as space, specifically those who reify it. You sounded like I left out your favorite synonym, a vacuum, so I included it, obvious as it was. The main "problem" of defining space as emptiness/vacuum is that if it is nothing then it can not expand (as in "space itself expands" cosmology), or curve, (as in non-Euclidean curved space.) This ontology challenges both of those standard assumptions, the point of this thread. And most classical theorists say that space is Euclidean, or straight. The language of "straight" or even "flat" space does not apply to space as emptiness. It can have volume if so defined within designated boundaries, but "straight" is linear, not applicable to volume. Neither is "flat space" applicable to empty volume, whether bounded, as above or in the sense of infinite, unbounded empty space. "Flat" applies to a plane, not volume, and "straight" applies to a line, not a plane or a volume. (Just a review of elementary geometry.)... And, yes, I know that "flat space" is in common usage in science, which does not deter me from criticizing the usage. You view insists that it is "something (not nothing)" which is straight and through which things move and that which things occupy, so... so what? What is your beef with relativity when you make the same ontological assumptions -- and more for that matter? You don't see this, do you? A prime example of total lack of communication. I have always argued that space is nothing(ness)... emptiness or lack of things. I have never referred to space as "straight." (See above.) "Things" do in fact move through and occupy space. Obviously, wherever so occupied, space is no longer empty, but emptiness remains between things which render it 'not empty.' "So what," indeed. I emphatically do not make the same assumptions about space as does relativity theory. My "beef" with curved space has been a constant theme here. Ontologically, to have the property of curvature, space must be some kind of extant entity. I and many others argue that it is not. That is my "beef" with the reification of space in relativity. And those who say space is Euclidean and is something through which things travel (you) must say what it is that is Euclidean and what it is through which things travel. You haven't done that. It seems to be beyond your ability to comprehend that things can travel through empty space without reifying "it", making "it" into "something" (some "thing.") Ontology is about what exists. As I posed before, "Does nothingness exist?" If space is the absence of things, no-thing, there is no need to argue for its existence. If it is supposed to be something (that curves, expands, etc.), then the burden of proof, in ontology, is on those who claim that "it" is something... i.e., "what is it?" The truth is that either curved space or Euclidean space may serve to be nothing more than a useful approximation of some as-of-yet understood phenomenon -- just like entropy was before the kinetic theory of atoms was developed. The paper you linked in the OP -- Minkowski space-time: a glorious non-entity -- talks about this exactly. Did you read the paper that you mentioned? Maybe you read it but didn't understand it, but liked the title anyway. I liked the title and read the abstract but did not buy the book. (The book is not available as a whole online, to my knowledge, and I have searched. If I missed it, someone please clue me and I will read it.) But I have read and quoted in this thread comments by Brown to the effect that spacetime does not exist and further, that Minkowski's concept of it was "parasitic" upon the intrinsic dynamics of the physical entities and their relationships. This would make it not only a non-entity but unnecessary to the the dynamics of gravitational force... subject to being cut out as per Occam's razor, as I have always maintained. I'm sure you agree with the distance. My point was your definition of space. If space is "emptiness", then how can the measurement of space not depend on how empty it is? Is the distance through the earth the same as a line that doesn't pass through the earth? In other words, if your measurement of the amount of space has nothing to do with your definition of space then why are you defining it that way? Do you know, and do you understand what I'm saying? You missed that the conversation here was about the distance between objects with "empty space" between them. I went into great detail in answering lemur's questions/challenges about such measurements of distance. Whether or not there is space debris, dust, or gasses in space, say between earth and sun, is beside the point. Also beside the point is whether the sphere we were talking about before your arrival is empty inside or solid, or earth itself. The distance through it, point to point (or earth's diameter in your example) is measured on a straight line between the points or through the earth. Distance does not depend on space between points or objects being empty, as you have erroneously assumed as my argument. As to your last three questions... 1: Obviously, earth's diameter is a given length or distance. Two objects could be launched into space and made to rest that distance apart... same distance whether through earth's matter or through empty space. 2: The above does not conflict with my definition of space as the emptiness between things... or infinite emptiness, for that matter. 3: I understand that you misunderstand me, as reflected in those questions and most of your replies to me. You didn't give a meaningful answer to that part of my post, and your tendency to keep repeating things isn't helping. To which part I am not sure. To the solid earth or empty space question of distance measurement, I have answered as clearly as I can. To the next exchange... Me: "I was speaking of the standard model of cosmology which insists that space is expanding" You: "No, you weren't. You were speaking of general relativity. I'll quote the part of your post that I was responding to: View Postowl, on 8 April 2011 - 09:58 AM, said: "This is the standard doctrine of present day science/cosmology, i.e., that rather than stuff exploding outward into space, that "space itself is expanding." (I thought you were an advocate of standard doctrine.) Space is considered, in relativity theory, to be an entity which began expanding with the "Bang" and continues to expand." You continue: I'm telling you:[*]General relativity does not insist on that. [*]Standard cosmology metric that says "space expands" is an arbitrary solution of GR -- other solutions exist where things are moving through space rather than space expanding. [*]You should examine the implications of these facts. My focus in recent context has been the ontology of space, whether it is something which expands (as per one standard version of cosmology, ever since the "big bang")... and whether or not it is something which curves (as per relativity theory.) I admit that I misspoke in my last sentence. I should have said, "in a popular cosmology" rather than "in relativity theory," the latter pertaining to curved space instead. My hope is that a misspoken phrase will not derail my whole ontological argument about the nature of space (and time and spacetime.) Finally re: I said that science doesn't insist on what you think it does and that is true. How you get "really not qualified" is beyond me. Very simply, you are not qualified as an expert on what I think, no matter the content or subject. I am the only expert on what I think. A lot of what I think and say is "beyond" you. I will not be disappointed if you quit this thread. There is no hope of actual communication with you. -1
Iggy Posted April 13, 2011 Posted April 13, 2011 (edited) I liked the title and read the abstract but did not buy the book. (The book is not available as a whole online, to my knowledge, and I have searched. If I missed it, someone please clue me and I will read it.) I called that It's a published scientific paper. It is readable, and I ded read it, online: http://philsci-archive.pitt.edu/1661/1/Minkowski.pdf Owl, you didn't reply to any of my concerns. I'm almost certain you didn't consider (or were unable to consider) my post at all. All you did was repeat yourself, so you are right -- I won't be reading this thread anymore. You misunderstand scientific implications and argue against your own misunderstandings, and you're apparently not able to understand that you do that. You are basically arguing against analogies -- a pointless gesture. I apologize for my part in encouraging your repetition. Edited April 13, 2011 by Iggy 2
Spyman Posted April 13, 2011 Posted April 13, 2011 I apologize for my part in encouraging your repetition. For what it's worth, at least I enjoyed your arguments. (Even though I suspected them to be futile.)
owl Posted April 13, 2011 Author Posted April 13, 2011 (edited) Iggy, I guess you are gone, but, if you happen to glance back... regarding your statement: Owl, you didn't reply to any of my concerns. I'm almost certain you didn't consider (or were unable to consider) my post at all....I replied literally point by point to your previous post. In a real conversation you would have pointed out specifically how you thought I fell short of answering you. You, on the other hand did not address any of my last post to you. Anyway, thanks for the link. Off to read it as soon as i finish this post. But, right up front, how do you deal with the Harvey Brown quotes on the non-existence and "parasitic" nature of Minkowski's space-time? Here it is again: "But I have read and quoted in this thread comments by Brown to the effect that spacetime does not exist and further, that Minkowski's concept of it was "parasitic" upon the intrinsic dynamics of the physical entities and their relationships. This would make it not only a non-entity but unnecessary to the the dynamics of gravitational force... subject to being cut out as per Occam's razor, as I have always maintained." Your lack of comment on the above is another example of no communication here. For the benefit of anyone still interested in the ontology which is the focus of this thread, here is a recap (aka, a dreaded repetition) of that focus, which went unanswered above: The main "problem" of defining space as emptiness/vacuum is that if it is nothing then it can not expand (as in "space itself expands" cosmology), or curve, (as in non-Euclidean curved space.) This ontology challenges both of those standard assumptions, the point of this thread. Ontologically, to have the property of curvature, space must be some kind of extant entity. I and many others argue that it is not. That is my "beef" with the reification of space in relativity. If it is supposed to be something (that curves, expands, etc.), then the burden of proof, in ontology, is on those who claim that "it" is something... i.e., "what is it?" Edit: Finished the Brown-Pooley paper. Whew! Another tough read. I took a lot of notes, but here is just for openers: Abstract------------- It is argued that Minkowski space-time cannot serve as the deep struc- ture within a “constructive” version of the special theory of relativity, contrary to widespread opinion in the philosophical community. -------------- ... in contrast to constructive-theory expla- nations, such a principle-theory explanation will “have nothing to say about the reality behind the phenomenon” (2003, 331). It seems to me . . . that a physical theory can be satisfactory only when it builds up its structures from elementary foundations. (Ein- stein, 1993)12 . . . when we say we have succeeded in understanding a group of natural processes, we invariably mean that a constructive theory has been found which covers the processes in question. (Einstein, 1982, 228) A theory which has "nothing to say about the reality behind the phenomenon” does not, of course, address the ontology of spacetime. I agree with Einstein's statements above and have been pursuing those "elementary foundations" in the context of spacetime ontology. Deeper into the text is the following Einsteinian perspective: We have seen that for Einstein the inertial property of matter requires explanation in terms of the action of a real entity on the particles. It is the space-time connection that plays this role: the (ed: glitch) geodesics form ruts or grooves in spacetime that guide the free particles along their way. Ruts or grooves in some substantive "thing?" The perennial ontological question still stands, "What thing?" Edited April 13, 2011 by owl
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