What is "spacetime" really?

[Michael Mooney]

Modest:

Distance between spacetime points will exist if they are measured or not, if we assign a number to them or not. But, if we want to define either the concept of distance or a specific example of distance then we do need to rely on "numbers and measurement".

 

No doubt. Quite obvious. Seems like what Ive been saying all along. But you *were saying* that for observer A[/i a distance is one value while [i]for observer B in a different frame of reference the distance ( earth to moon or to sun in your examples) is different, implying, again that "It's all relative," and there is no "actual distance." I really don't see how that is *not* what you were saying... which *was* the position with which I was arguing. Seems like you changed your mind.

 

For example, two spacetime points may be a certain distance while two others are twice that distance. We can explain that difference by saying the measurement of one will be twice the measurement of the other. Since our interaction with the universe is via measurement (or observation) and since we use numbers to express relationships then this is only natural.

It would be very helpful if you would not designate "spacetime points" as if we both understand the "spacetime" designation in the same way. For instance, at any given moment, a "snapshot"of the distance between two points (or objects) does not require a "time" designation but just "the line... distance" between them. It only confuses the issue to be comparing one point/object last Thursday with another point/object right now... er... then... when I said "mark."

As for the rest above, I agree, but I *do insist*that measurement is an artifact after the fact of the independent existence of the objects in question.

 

Defining something with a measurement does not mean such a thing cannot exist without the measurement—it simply means that such a thing exists to be measured.

This implies a *teleolgy* with which I disagree, i.e., that things exist *for the purpose of being measured. Surely this is not what you mean. I *must* be misunderstanding you. Maybe just that since things already exist, they can be measured.

Nobody (as far as I know) is saying that the measurement is the cause of the ontology. It is, rather, a necessary result of the ontology. I still think you're slightly misunderstanding us on that.

Why is it "necessary" that these distances (the space between objects) be measured? The latter act in no way establishes the ontological existence of the objects or the extent of empty space between them.

 

No, I agreed that "the cosmos exists whether or not any *perceivers* ever evolved" before and after I said "but". The miscommunication is this: I'm saying "independent of relative perspectives" and you're reading "independent of human relative observation". What I'm saying requires no intelligent life or observation.

 

How can you have a "relative perspective" without a point of *view*... the 'spect' part of "perspective?" A view implies a viewer, does it not? If it is just a theoretical perspective, you would not have denied "actual distance" in the first place or made distance relative to "for (as seen by) observer A as being a different distance than "for (as seen by) observer B. Again, if you have changed your mind, excuse me for "hammering on" what you said earlier.

 

The relative perspective is a physical fact that will persist regardless of observation.

 

Again, how is relative perspective a physical fact? It is a point of view... no?

 

Consider the decay rate of some atoms. If they make different paths through spacetime (the entity in question in this thread, not an ontological reality already established, as you insist!...) then their decay rates will differ.

If you are referring to the rate of decay of atoms in an atomic clock... you must not here assume "victory" in the long debate we had on "time dilation" vs forces which make clocks slow down.The "relative perspective" *is* that difference regardless whether someone is there to observe that difference or not. In this case the decay rate is considered an "observable" because it can be determined physically with observation or measurement which should indicate that it is something that is physically real. But, the measurement isn't what makes it real.

Yet you insist that the "time" component of the "spacetime" you believe is real is "that which clocks measure. You are contradicting your own... or was it Einstein's definition and meaning here. Relativity certainly doesn't claim anything like that. The measurement is a property of physical reality—not the other way around. I absolutely disagree that measurement is a property of physical reality. Measurement is an artifact after the fact of physical reality, as I've argued above. Of course measuring devices..." rods and clocks" are physical, and the act of measuring is a physical act. Maybe this is what you mean.

 

Relativity does not imply subjective idealism! I really think your arguments against subjective idealism are missing the target. "The target" in this case was your insistence that there is no "actual distance" but rather that it is "all relative" to the different perspectives of "observer A and observer B, as above.

 

Einstein developed the hole argument and interpreted it in a way that you would find very agreeable. Where you think general relativity reifies spacetime, it in fact demonstrates with the hole argument that the spacetime manifold is most-likely not a physical reality which exists in and of itself. So, once again, it seems like you're missing the target and arguing against a bit of a strawman.

 

I will come back to this in my commentaries on the links you provided. The example I cited above (to Pyrotex) from the quoted history of the "hole argument" in fact shows how artificial his concept of the hole vs matter outside the hole was. Same as the artificiality of his (and Minkowski") concept of "spacetime" as an actual medium, even though it depended for its existence on the matter (and its curved trajectories, etc.,) passing throut "it." He denied that gravity can be transmitted through empty space without such a "curved medium" as spacetime.

 

The images you see in textbooks of rubber sheets signifying spactime is only an analogy. The fabric of spacetime represents the path of material objects and the distances and durations that such objects experience. The reality or ontology of what those paths and distances and times mean is entirely up to you (so long as it is consistent with observation). It need not be made into something mechanical like a rubber sheet. It represents *whatever* it is that we measure with rulers and clocks whether that something is something physical and malleable or nothing more than a description regarding how matter interacts.

See my earliest references in this thread to the image of the 'sagging sheet" as not establishing the ontology of "the fabric, spacetime!

I have been saying all along that spacetime is only a visual aid for understanding the effects of gravity... as per the curved trajectories of masses and light as pulled by gravity through no known medium but empty space. It is quite ironic that you now lecture me on what I have been arguing throughout this thread!

 

Michael

[Michael Mooney]

Hi watcher,

My comments interjected in bold:

 

spacetime interval is the map. what is out there is the territory. Like I said...

the saying is a caveat not to confuse the two. My point exactly.

but in the end, the map stills represents the territory.

the map has physical meaning and representation.

The map is the analytical overlay superimposed on the territory. The key word is that it re-presents the real world/cosmos... ontologically a mental/analytical construct, not to be confused with the former

 

the territory is real. ontology necessitates to have unprovable assumption, Huh??

but there is a difference between "mapping" your territory from proven theory "proven theory? and a highly arbitrary subjective higher perspective. Not "arbitrary." Merely the philosophical "what is" as independent of the analytical and mapping process, no matter how accurate a re-presentation it is of said "what is"... reality.

 

now if you have not entirely trashed the equation of spacetime interval,(a non-arbitrary and sensible way to do it is to disprove the constancy of light in an actual experiment . not necessarily the rate itself but its novel characteristic that it refuses to add and subtract with other velocities). so if you can't let me ask you a simple question.

 

I give up on convincing you that I understand and am not arguing with SR. And "spacetime" is reified as more than a time "interval" for events "in space." It is constantly referred to a malleable (bendable, curving, expanding... dilating, etc "fabric." The latter reification is the target of my challenge which is the essence of this thread.

 

does the math of spacetime interval makes distinction between space and time? yes or no?

 

I reject the assumptions upon which the question is based.

("Have you stopped beating your wife yet? Yes or no!")

 

Spacetime is a visual aid/metaphor, not an actual medium/fabric. "It" is supposed to be the coalescense of space and time. I will not repeat my "take" on the latter two yet again.

 

if no and math makes no distinction, ergo space and time are the same (what is it?) thing and the model that space is absolute and time is imaginary is simply out of touch with the map (equation)

 

]Beyond the map, and the mental tool "spacetime" is the actual "stuff" we call cosmos which exists in an infinite volume of emptiness we call space. As the 'stuff" moves around, we invoke "time" to say how "long" a given event took to "happen,", and so we create "time." Space is, has always been, and will always be the emptiness in which all actual events exist and dynamically "happen."

 

further more, you can see the effect of time as a fourth dimension perpendicular to the 3d space. (oh yes, that is the rule in math, the next higher dimension must be 90 deg out of phase with the lower d. that explains why higher dimensions are partly perceptible if not entirely unobservable in lower dimensions, it always appear pointlike).

 

I reject the premise that there is a "fourth spacial dimension perpendicular to the well known three. (Time is usually referred to as the fourth.)

 

I have studied and "participated" in the exercise in the link you gave. Ain't computer graphics amazin'!!

Most of us "got" the first three spacial dimensions in elementary geometry class. The "fourth" illustrated in the link is nothing more than expanding the 3-d cube by extending its corners outward diagonally from its center. If you had a cubical balloon (can you imagine?) and blew it up bigger... same effect... a bigger cube!

 

Ultimately, beyond all geometric shapes, space (volume) is without walls/boundaries... in fact infinite. I challenge you to formulate/describe an "end of space."

 

Some folks are easily impressed by such easily manipulated computer graphics. I am not among them, as describing the ontology of the 'real world'... the supposed existence of a fourth spacial dimension in this case re-presented by making a cube enclose a larger volume... i.e., growing the cube bigger.... even if you can "rotate it!"

Thanks anyway.

Michael

[Michael Mooney]

An afterthought addressed to you, Watcher,

You wrote to Pyrotex:

still the the distance between two events are not actual spatial distance.

the two points in space that does not change for all observers is the distance in the spacetime diagram and not in actual spatial distance.

 

MM: You are back to the fallacy of believing there is no actual, objective distance (linear space) between objects (or "events") as happening with time-lapse or "duration" but rather that different observers, from different frames of reference are the ultimate criterion of distance... i.e., subjectively percieved distance. Do you not know that relativity corrects for such relativiistic effects to establish actual, objective distance? Do you think the earth-sun distance varies with observer perspective? If so I am wasting my time talking with a subjective idealist... the most absurd conceivable philosophy of the ontology of what is real in the world. There is, of course a time-delay perception differences.

 

so when we say there is an actual distance in space, it is only if you treated space as absolute. in relativity, we are not even allowed to think that way, because the "actual distance between two points" is a spacetime event.

 

You keep attributing "absolute space" to me as my misconception. I have said dozens of times that space is the no-thing-ness, the emptiness between actual things/"events." It doesn't expand, contract, curve, or do cute tricks like stand up and beg when teased by a passing massive object. ;) ... "It" can not be an "absolute", because "it" is not really an "it" but the absence of being anything... nothing at all, really.

 

Your last sentence above gives away your indoctrination about "spacetime." No blame, really. No one can "pass" a class in modern physics without giving "spacetime" the required ontological nod as an established reality. You are no exception.

 

I am just asking you to consider thinking outside this "frame of reference" box which you have been told is "not even allowed!!"

 

Michael

[modest]

Distance between spacetime points will exist if they are measured or not, if we assign a number to them or not. But, if we want to define either the concept of distance or a specific example of distance then we do need to rely on "numbers and measurement".

No doubt. Quite obvious. Seems like what Ive been saying all along. But you *were saying* that for observer A[/i a distance is one value while for observer B in a different frame of reference the distance ( earth to moon or to sun in your examples) is different, implying, again that "It's all relative," and there is no "actual distance." I really don't see how that is *not* what you were saying... which *was* the position with which I was arguing. Seems like you changed your mind.

Very interesting. You see these two concepts as incompatible:

1. Spatial distance is relative to velocity
   
2. Spatial distance exists whether or not it’s measured by intelligent life
   

When someone says b you assume they’re denying a. You might think that through again. Try substituting some other frame-dependent value for spatial distance and see if it still makes sense—like this:

1. Momentum is relative to velocity
   
2. Momentum exists whether or not it’s measured by intelligent life
   

Do you still think b implies a is wrong?

 

For example, two spacetime points may be a certain distance while two others are twice that distance. We can explain that difference by saying the measurement of one will be twice the measurement of the other. Since our interaction with the universe is via measurement (or observation) and since we use numbers to express relationships then this is only natural.

It would be very helpful if you would not designate "spacetime points" as if we both understand the "spacetime" designation in the same way.

A “spacetime distance” is invariant. It does not depend on velocity, but is rather absolute and universal. A “spatial distance” is not invariant. It does depend on velocity and is not absolute or universal. The concepts are therefore not interchangeable in conversation. Since you object so strongly to ‘actual’ spatial distance being relative you might consider the utility of using spacetime distance which is not relative.

 

You really need to accept (or at least understand) the very *reason* space and time are relative to velocity is explained by 4D spacetime. Notice:

 

If the universe is four-dimensional, then the space-time interval will be invariant, rather than spatial length. Whoever measures a particular space-time interval will get the same value, no matter how fast they are traveling. The invariance of the space-time interval has some dramatic consequences.

 

The first consequence is the prediction that if a thing is traveling at a velocity of c meters per second, then all observers, no matter how fast they are traveling, will measure the same velocity for the thing. The velocity c will be a universal constant...

 

The second consequence of the invariance of the space-time interval is that clocks will appear to go slower on objects that are moving relative to you.

 

The modern approach to special relativity

 

So, "relative perspectives" is not a problem for the philosophy of spacetime. If our universe is 4D we expect distance (as measured by rulers) and duration (as measured with clocks) to be relative to velocity. This is not a problem for my philosophy. Neither is the invariance of the speed of light.

 

But, you have rejected spacetime and speak in terms of Newtonian relativity. The results of this are quite predictable. Your philosophy does not predict or explain the relative nature of space and time nor the invariance of the speed of light. So, those things are going to be problematic in your world-view. So, I'm not sure I can completely avoid talking in terms of spacetime. I have very earnestly tried to accommodate that in deference to the "ontology" you're putting forward. But, that honestly has gone nowhere. If you really attempted to gain an understanding of modern relativity then I think this conversation would move forward by leaps and bounds.

 

For instance, at any given moment, a "snapshot"of the distance between two points (or objects) does not require a "time" designation but just "the line... distance" between them. It only confuses the issue to be comparing one point/object last Thursday with another point/object right now

But, you don't see the problem with this. A "snapshot" view of the universe would mean every event in the universe (at the time of that snapshot) is simultaneous. Simultaneous means "happening at the same time". That is defined as the "present instant". We know for fact as we have experimentally confirmed: simultaneity is relative to velocity.

 

I'm not sure you know what that means. People have explained relativity in terms of observers like so,

If two events are simultaneous to observer A then they may not be simultaneous to observer B.

But you take from that some kind of theory of perception or phenominalism. People have explained in terms of physics and frames of reference,

If there exists an inertial frame of reference where spatially separated events are simultaneous then there must exist another equally valid inertial frame of reference where the events are not simultaneous

But you then object saying surely the events are either simultaneous in objective reality or they are not. You see it as an either/or situation: The events either happen at the same time or they don't.

 

So, I'm at a loss for how else to explain it. I'll simply say: if you give up the demand of looking at things in the "snapshot" way and allow time to be part of distance speaking in terms of *events* rather than just objects then the universe will make more sense. When you picture the universe in this way it will comply with the things we know about the universe. The philosophy will explain the physics and the observations rather than disagreeing with them.

 

This implies a *teleolgy* with which I disagree, i.e., that things exist *for the purpose of being measured. Surely this is not what you mean. I *must* be misunderstanding you. Maybe just that since things already exist, they can be measured.

Yes. If something exists (already) then we should be able to measure it.

Nobody (as far as I know) is saying that the measurement is the cause of the ontology. It is, rather, a necessary result of the ontology. I still think you're slightly misunderstanding us on that.

Why is it "necessary" that these distances (the space between objects) be measured? The latter act in no way establishes the ontological existence of the objects or the extent of empty space between them.

Cause and effect (causality) as well as locality are consequences of Minkowski spacetime. The methods we humans have to use to find distance (i.e. measurement) are consequences of locality and causality.

 

]The miscommunication is this: I'm saying "independent of relative perspectives" and you're reading "independent of human relative observation". What I'm saying requires no intelligent life or observation.

How can you have a "relative perspective" without a point of *view*... the 'spect' part of "perspective?" A view implies a viewer, does it not? If it is just a theoretical perspective, you would not have denied "actual distance" in the first place or made distance relative to "for (as seen by) observer A as being a different distance than "for (as seen by) observer B. Again, if you have changed your mind, excuse me for "hammering on" what you said earlier.

;)

A GPS clock in orbit ticks faster than an identical clock on the ground. Relativity makes no claims regarding the observation of such clocks. The clock up there ticks faster if intelligent life recognizes it or not.

 

It is common in physics to refer to inertial frames of reference in terms of observers. That's just the language used... "observer A moving .5c relative to observer B will notice clock B...". I suppose it's understandable that someone who isn't familiar with that sort of language could take that to mean the act of observation is somehow causing the results of the experiment. But, I'm explicitly telling you now that in relativity that is not the case. The only purpose of the observer is to recognize something that's already there and/or already happening. Space, time, and mass are relative to velocity if an intelligent person is in that 'velocity' frame of reference or not.

 

The relative perspective is a physical fact that will persist regardless of observation.

Again, how is relative perspective a physical fact? It is a point of view... no?

No. It is not *just* a "point of view". If distance is relative to velocity then muons created in the upper atmosphere should hit the ground before they decay. If distance is not relative to velocity then muons should decay before they hit the ground.

 

"Relative perspectives" is not very precise language. But, the relative nature of distance and duration are physical fact. Muons do indeed reach the ground—physically. Length contraction and time dilation physically happen. Relativistic effects don't just make things appear different to an observer.

 

The 5d electron in a gold atom moves fast-enough to relativistically contract it's orbit. Without relativistic effects gold is predicted to be a silvery color. But, with length contraction the element gold is predicted to be a goldish color. (1) So, length contraction is as physically real as the color of gold.

 

Saying "distances don't really get shorter because of relativity, they just appear shorter" is the same as saying "the metal gold only 'appears' to be a gold hue, but it's really silver in color". So, I reject that position.

In this case the decay rate is considered an "observable" because it can be determined physically with observation or measurement which should indicate that it is something that is physically real. But, the measurement isn't what makes it real.

Yet you insist that the "time" component of the "spacetime" you believe is real is "that which clocks measure. You are contradicting your own... or was it Einstein's definition and meaning here.

... I have to wonder if you actually mean these objections or if you just want to debate on any and all things.

 

If I have a rock and a piece of balsa wood and a bucket of water and I want to find out which is more dense (the rock or the piece of balsa) then I could put them in the water and notice the wood floats while the rock sinks. From this I've inaccurately measured their density—the rock is greater than 1 kg/L while the wood is less than 1 kg/L. The rock is more dense than the balsa.

 

Is the act of putting them in the water and determining what floats the thing that gives these objects density? In other words: if we don't measure their density does that mean they don't have a density?

 

Of course not! You can define something (quantitatively) by referring to a measurement even if the thing you're measuring exists perfectly well without being measured. I could define mass with force times acceleration. Would this mean some given object would have no mass until I exert a force on it and measure the acceleration? Of course not. If I define spatial distance as "that which gets measured by a ruler" that doesn't mean any distance not measured by a ruler doesn't exist. That's just silly.

 

The images you see in textbooks of rubber sheets signifying spactime is only an analogy. The fabric of spacetime represents the path of material objects and the distances and durations that such objects experience. The reality or ontology of what those paths and distances and times mean is entirely up to you (so long as it is consistent with observation). It need not be made into something mechanical like a rubber sheet. It represents *whatever* it is that we measure with rulers and clocks whether that something is something physical and malleable or nothing more than a description regarding how matter interacts.

See my earliest references in this thread to the image of the 'sagging sheet" as not establishing the ontology of "the fabric, spacetime!

I have been saying all along that spacetime is only a visual aid for understanding the effects of gravity... as per the curved trajectories of masses and light as pulled by gravity through no known medium but empty space. It is quite ironic that you now lecture me on what I have been arguing throughout this thread!

 

No, it's not ironic. It's the same thing I told you in post #7 and notice again from post #37:

This question has been answered in unanimous agreement. Spacetime is not a malleable medium. It is not made of matter and it is not tied to a preferred reference frame. It is non-mechanical in nature. The analogies that you bring up are just analogies. They mean to relay characteristics of the theory in an easily envisioned way. They do not mean to imply anything ontological about any aspect of the theory.

 

In a general sense, the variables of space and time in GR are the same as the variables of space and time in special relativity. They are distance and duration. They are 'whatever' clocks and rods measure.

 

You are arguing against a strawman. You envision spacetime as something mechanical like matter in order to object to its reification. There's no need for that. Relativity describes a metric that works for motion and gravity. What that metric represents (i.e. space and time) is the question. If you want to answer that question then by all means...

 

But, objecting to relativity because your ontology of space and time don't work in the theory while you have absolutely no evidence for your ontology isn't going to get you anywhere. You can say "space is nothingness" all day long, but that doesn't invalidate general relativity. If you had an argument or an observation which demanded space and time be Euclidean then that would be a valid argument against relativity. But you don't and it isn't.

 

~modest

[AnssiH]

Stumbled upon this thread last night when browsing around, and probably would not have conjured up the energy to comment otherwise, but I thought I'd bump up this post from DD because it pretty much sums up everything you need to understand, to stop the unnecessary bickering.

 

This thread is essentially concerned with an issue discussed in many places throughout the literature. There is a dichotomy in the philosophic world which is quite familiar to anyone with any reasonable knowledge of philosophy of science: the study of logical structures commonly referred to as “explanations” is called “epistemology” and the study of “what exists” is called “ontology”. Science is very much concerned with explaining the world we find ourselves in and thus falls almost entirely into the field of epistemology. Exactly what it is that is being explained (what exists) falls into the field of ontology. The reader should recognize that epistemology is the respected central issue of science whereas the subject of ontology has been essentially ignored by the hard scientists as being “metaphysics” (beyond physics).

 

It is at this point that we run into another very important insight which is buried in the frequently debated issue, “Is Metaphysics Possible?”. Thus it is quite widely held that establishing the validity of one's ontology is not possible and this is most probably the reason that the study of metaphysics has fallen into such disrepute. :)

 

Of course, science needs their ontology (what exists) as much as any field and they need to justify to themselves that the ontology they are working with is valid. With regard to this issue, “Science” (and here I refer to what is called the “scientific method”) generally makes the presumption that the validity of its ontology is a strong function of the success of the specific epistemology (that scientific explanation) based upon that ontology. By this means, the scientific community avoids the metaphysical question entirely. :)

 

The central issue of this thread is exactly such a metaphysical question: “What is spacetime-really?” It is very much an excellent example of the thoughtless phenomena which always seem to embroil such a discussion. If you read the thread, you will discover that the educated posters (all those who have a decent understanding of Einstein's relativity) invariably use the logical consequences of the epistemology as a defense of the validity of their ontology: i.e., they concentrate on the fact that the logical consequences of Einstein's “space-time” agree with the scientific experiments (their expectations) without ever confronting the actual ontological nature of the question.

 

The rest of the posters would certainly do exactly the same except for the simple fact that they cannot follow the required logic. The answer to the question is actually quite obvious to anyone who understands the underlying issue posed by the question. Einstein's “space-time” is no more than an ontological concept required by his “theory of relativity”.

 

I think that's fair and succint commentary of the situation.

 

"epistemology is the respected central issue of science whereas the subject of ontology has been essentially ignored by the hard scientists..."

 

Yes... I wouldn't really mind, if the physics community was explicitly trying to avoid making ontological arguments, and I've been told that most physicists intentionally try to stay away from ontological arguments. If so, some of them are doing rather poor job. In a larger scale, it seems to me that this whole issue between epistemology and ontology is quite poorly understood, and especially the mainstream publications use very bad language in their communication on a regular basis.

 

Also, I do not think it displays very good understanding of the situation, when the same people who assure me that "physicists understand ontological arguments are a function of chosen epistemology (and vice versa) and thus don't concern themselves with such questions", then turn around and say physics is about explaining what "really exists".

 

Likewise I do not think it displays very good understanding of the situation, when there are polls telling which QM interpretation physicists most believe to be true. It is somewhat mind-boggling to me that any self-respecting physicist could look at the handful of so-far created ontological interpretations, completely ignore the vast possibility space of "all valid interpretations", and actually choose to believe in one arbitrarily chosen interpretation.

 

...“Science” generally makes the presumption that the validity of its ontology is a strong function of the success of the specific epistemology based upon that ontology."

 

Yes. The theory of relativity is almost invariably discussed in terms of relativistic spacetime, and it looks like many people consequently assume that the theory is about the ontological validity of spacetime. I.e. that its prediction-wise validity also proves spacetime ontologically exists.

 

Worth mentioning again, that relativity became to be understood in terms of relativistic spacetime due to Minkowski making that interpretation. Einstein had not made that interpretation when putting out the first paper about SR, and initially was not too thrilled about Minkowski's idea. What led Minkowski to the spacetime interpretation was of course the idea of relativity of simultaneity in Einstein's paper. Relativistic simultaneity was required for allowing "isotropic C" and "principle of relativity" to co-exist in the same model self-coherently, but apparently Einstein initially avoided the arguments regarding the ontological meaning of such concepts being valid (as the originators of new models often do).

 

I should mention the book "Schrödinger's Kittens" here again, as for a mainstream publication it makes rather decent commentary about this whole ontology/epistemology conundrum. E.g. about how, in order to probe the structure of atoms, we first had to have a good model (based on guessing) about the structure of atoms.

 

the educated posters invariably use the logical consequences of the epistemology as a defense of the validity of their ontology... ...without ever confronting the actual ontological nature of the question... ...The answer to the question is actually quite obvious to anyone who understands the underlying issue posed by the question. Einstein's “space-time” is no more than an ontological concept required by his “theory of relativity”.

 

Exactly right, are you guys sure you understood exactly what that last sentence means? I'm guessing not because you are still continuing the thread ;)

 

I'm thinking of further commenting this in the context of map-territory relationship. I made a post about that issue some time back, and I would like to thank Pyrotex and Modest for letting me know that they thought it was an easy-to-follow exposition of the subject (I seem to be somewhat clueless as to what people find easy to understand).

 

I think many posters in this thread would benefit from understanding the issue, so first try;

 

http://hypography.com/forums/philosophy-of-science/17472-what-exists-no-really-3.html#post249520

(Post #27)

 

Then notice that the concepts or the definitions behind "relativistic spacetime" are a map, offering a terminology to have a meaningful discussion about reality, or rather, a discussion about our expectations of reality.

 

"Relativistic spacetime" is a set of defined entites; it gives a specific definition for "space", "time" and "matter", and defines specific interaction between them. For example, what it means that the "space" can have a "shape" is embedded in those definitions and how the expected interaction supposedly reveals that shape. What that means ontologically, that space is "bubbly" or "curved" (in what space?) or "deliciously creamy", is up to everyones very own naive realistic interpretation of the issue. And insisting on the ontological existence of some entity we have just defined, is a religious issue just like the ontological existence of "soul".

 

In terms of map/territory relationship, relativistic spacetime is a valid map in the sense that, when you choose to see the raw data from reality in its terminology, it will offer correct predictions.

 

But that its terminology offers you a way to draw correct predictions, does not mean it is the only valid map that can be built. Certainly it is possible to see the same exact raw data in completely different terminology, i.e. in terms of completely different ontological entities and their definied behaviour, still offering equally valid predictions.

 

I.e. (if you are discussing the relationship between epistemology and ontology), "Einstein's “space-time” is no more than an ontological concept required by his “theory of relativity”."

 

This is getting little bit longer than I intented, but I still should mention that I just saw this little article on a science magazine about how "two physicists have calculated how a spaceship could move faster than light". It was actually an iteration on Alcubierre drive. I am not familiar with the details of the issue, but the basic idea is to create a spacetime bubble ("soapy", I'm sure ) and move that. You know, because it's things inside space that can't move at superluminous speeds, but space itself can move at any speed.

 

Of course the reader should recognize, that this raises some rather interesting questions regarding, where exactly does space move? Once again, what is meant by the "motion of space", is embedded in the exact definitions and in how we consequently suppose that motion manifestates itself as observable effects (just like in the inflation theory). The whole idea, how it's represented, is a consequence of the chosen terminology (= relativistic spacetime)

 

I think in the context of SR, it should also raise some rather trivial questions regarding self-coherent view on causality, as it is supposed that the spaceship inside the spacetime bubble would be seen to move at superluminous speeds by an external observer.

 

Notice that the meaning of the relativistic speed barrier is also something whose validity hinges on the careful definitions of the meaning of "motion". We can say the distant stars are allowed to recede from us faster than C, as long as we attribute that motion to the motion of space. Likewise, we are allowed to travel thousands of light years in seconds, as long as we say the covered distance was shrunk into less than light-seconds. Of course from your perspective you did pass all the mile markers, so, the meaning of "covered distance" is, you guessed it, embedded in the original definitions.

 

-Anssi

[Michael Mooney]

AnssiH,

Most Excellent!

Back asap for further conversation. You have very eloquently and clearly said, in fine detail what I have been trying to say for over 40 pages here.

I would have engaged with Doctordick as also an excellent philosophical perspective but I was put off in the extreme by his condescending attitude toward me and my apparently "limited intellectual capacity" for understanding the logical consequences of relativity theory.

 

Thanks a big bunch.

Michael

[Doctordick]

I would have engaged with Doctordick as also an excellent philosophical perspective but I was put off in the extreme by his condescending attitude toward me and my apparently "limited intellectual capacity" for understanding the logical consequences of relativity theory.

Perhaps I misunderstood you; if that is the case, I apologize. You weren't very clear and I just grouped you with the rest of the crowd. :hihi:

 

Have fun -- Dick

[freeztar]

But that its terminology offers you a way to draw correct predictions, does not mean it is the only valid map that can be built. Certainly it is possible to see the same exact raw data in completely different terminology, i.e. in terms of completely different ontological entities and their definied behaviour, still offering equally valid predictions.

 

First of all, great post AnssiH.

 

The paragraph above invokes my curiosity. Can you offer an example?

[Michael Mooney]

Post party post... scattergun style.

(More organized and focused reply tomorrow.)

Dr.dick:

"epistemology is the respected central issue of science whereas the subject of ontology has been essentially ignored by the hard scientists..."

AnssiH:

Yes... I wouldn't really mind, if the physics community was explicitly trying to avoid making ontological arguments, and I've been told that most physicists intentionally try to stay away from ontological arguments. If so, some of them are doing rather poor job. In a larger scale, it seems to me that this whole issue between epistemology and ontology is quite poorly understood, and especially the mainstream publications use very bad language in their communication on a regular basis.

 

Also, I do not think it displays very good understanding of the situation, when the same people who assure me that "physicists understand ontological arguments are a function of chosen epistemology (and vice versa) and thus don't concern themselves with such questions", then turn around and say physics is about explaining what "really exists".

 

Dr.dick:

...“Science” generally makes the presumption that the validity of its ontology is a strong function of the success of the specific epistemology based upon that ontology."

AnnsiH

"Yes. The theory of relativity is almost invariably discussed in terms of relativistic spacetime, and it looks like many people consequently assume that the theory is about the ontological validity of spacetime. I.e. that its prediction-wise validity also proves spacetime ontologically exist."

 

Relativistic simultaneity was required for allowing "isotropic C" and "principle of relativity" to co-exist in the same model self-coherently, but apparently Einstein initially avoided the arguments regarding the ontological meaning of such concepts being valid (as the originators of new models often do).

 

MM: I've attempted to share a realization of the cosmic reality that "it" is always "now" everywhere, always... ongoing. Yet Modest in his last post still clings to the belief that "now" is not simultaneous for all "observers" (read amended "relative perspectives") but rather that "time" not only separates such "perspectives" but actually (my word!) changes the distance (read linear dimension of space) between objects (not sure where he stands on geometric points in this regard.)

 

 

"I should mention the book "Schrödinger's Kittens" here again, as for a mainstream publication it makes rather decent commentary about this whole ontology/epistemology conundrum. E.g. about how, in order to probe the structure of atoms, we first had to have a good model (based on guessing) about the structure of atoms.

 

MM: So the "matrix field" (model) assumes the same 'reality quotient' as the "material field" and even very intelligent people, like Einsten and Minkowski, begin to confuse the two realms... the map with the territory, as I have said recently.

 

Spacetime was "born" this way. So was the "hole argument" before it was refined by feedback from others not so willing to attribute the same ontological reality to such *maps* as to the territory (the real world/cosmos, if I may call it that... I will without permission... :phones:

 

So, spacetime is a "matrix map" which has become reified (by "science" and "true believers" in Einstein and Minkowski) into the self existing entity it has (erroneously) become in science today. They *do* get so caught up in these matrix-models... and the math to verify them, that they lose fundamental perspective on the ontology. This could be the purpose statement of this thread... to expose this fallacy.

 

 

DR.dick:"

he educated posters invariably use the logical consequences of the epistemology as a defense of the validity of their ontology... ...without ever confronting the actual ontological nature of the question."

 

MM:

Seems (clarify if I'm misunderstanding, doctor) that this is exactly what you accused me of in the condescending post to which I gave you the "notorious finger" and got my "bad boy" 'citation.' Now, Modest fits the profile of the above "educated poster" very well. But I think you got me wrong on this particular criticism. And then you refused to engage my "point by point" challenge as to how you thought I lacked the capacity to understand the finer points of relativity which I was both agreeing with, in part (how it predicts certain gravitational effects better than classic Newtonian physics, and disagreeing with it in other parts (the ontology of spacetime as a "expanding, contracting, curving, possessing-shape... distorting "time"... entity, or whatever less tangible self existing "thing" (in the broadest sense.)

(Sorry about the run-on sentence. I have little respect for periods.)

 

Oh... just saw your last post. Maybe we can approach a sense of mutual respect after all.

But this post is a patchwork with no priority organization... notes and comments thrown together after a mighty fine party. Not well focused. Better tomorrow.

Thanks. Seems like there are, after all, at least two people here who understand what "ontology" is. And yet another who thinks he does and I don't. Guess who. NaH... we "made up" already after I laid down my credentials.

 

Later... sorry for the off-the-wall flavor of this post. (I'll be "sharper" tomorrow.)

Michael

[Michael Mooney]

I am not ignoring you, Modest. I just found a new playmate and maybe a new friendship with an old adversary.

This will be brief, as Sat. nite has altered my focus... if you know what I mean.

From the top down... 'til I go bleary-eyed:

 

Very interesting. You see these two concepts as incompatible:

Spatial distance is relative to velocity

I am calling "spacial distance" the linear, straight line distance between either actual objects in space or points, as on paper. It stays the same without considering velocity until the objects or points actually move relative to each other.

Spatial distance exists whether or not it’s measured by intelligent life Yes.

When someone says b you assume they’re denying a. [bI deny that distance, per se changes with velocity of perspective/ viewpoint.[/b] You might think that through again. You might try getting off your condescending high horse and actually trying to comprehend what I am saying. Try substituting some other frame-dependent value for spatial distance and see if it still makes sense—like this:

Momentum is relative to velocity Obviously... more velocity, more momentum.

Momentum exists whether or not it’s measured by intelligent life Of course.

Do you still think b implies a is wrong? No "still think" about it... never did think that b was correct in the way you mean it... "relativistically" and all!.

Edit: Just to clarify, I don't agree that "spacial distance is relative to velocity"... of the perspective "viewing" the objects or points, the space between being the distance.

The velocity of the objects or points relative to each other obviously changes the distance between them ... unless of course it is the same velocity in the same direction!

 

A “spacetime distance” is invariant. It does not depend on velocity, but is rather absolute and universal. A “spatial distance” is not invariant. It does depend on velocity and is not absolute or universal. The concepts are therefore not interchangeable in conversation. Since you object so strongly to ‘actual’ spatial distance being relative you might consider the utility of using spacetime distance which is not relative.

 

A "spacetime distance" is a conceptual contrivance. See my many statements on the ontology of space, time, and spacetime. You ignore everything I've said in this thread on the "reality factor" (or lack therof) for these three words and then continue to use them as established realities. Real distance exists, as youv'e said, independent of measurement. It varies, as above as the objects/points in question move. So, "spacetime distance" is "Absolute and universal" you say. Do you see how this is not an intelligent conversation? Spacial distance, again, stays as is, in the real world, until one or the other (or both) objects or points on paper (or in space) move. I am not using "spacetime distance" in conversation as if the phrase had meaning. Spacetime, again is an artificial construct. You have understood nothing I have said in this thread in this regard.

 

You really need to accept (or at least understand) the very *reason* space and time are relative to velocity is explained by 4D spacetime. Notice:

 

You have no clue that space is emptiness and time is an artifact of measurement... *not* to deny that everything in the universe is in constant dynamic motion... just that "the beginning" and "ending" of each "event" is created by the measurement... the guy with the stopwatch.

 

That's all I've got in me tonight... for this thread;).

 

Maybe I'll "take apart" the rest of your post tomorrow.

 

Michael

[modest]

What a pleasant surprise to come online this morning and see Anssi’s post :phones:

 

...to stop the unnecessary bickering.

 

You might consider that the present bickering is not so much in regards to anything your post so eloquently addresses ;)

 

Science generally makes the presumption that the validity of its ontology is a strong function of the success of the specific epistemology based upon that ontology.

Yes. The theory of relativity is almost invariably discussed in terms of relativistic spacetime, and it looks like many people consequently assume that the theory is about the ontological validity of spacetime. I.e. that its prediction-wise validity also proves spacetime ontologically exists.

 

While this is mostly true, it’s actually completely unnecessary from the standpoint of recent discussion. All the recent discussion in this thread has centered around how the universe behaves given certain definitions of space and time. A logically consistent answer can follow from those definitions without bringing ontology into focus at all. Just as easily, a logically inconsistent answer can follow which is what has happened to Michael.

 

Put simply: Newtonian relativity is incompatible with an invariant speed of light regardless of the ontology of spacetime. So, your point (and Doctordick’s point) is valid and would be a joy to discuss... but I assure you, it is not the problem at hand.

 

Einstein's “space-time” is no more than an ontological concept required by his “theory of relativity”.

Exactly right, are you guys sure you understood exactly what that last sentence means? I'm guessing not because you are still continuing the thread

As far as Minkowski spacetime and GR—I don’t think they assume some specific ontology as strongly as you indicate. There is more than one valid way to interpret GR. There is more than one underlying ontology on which that theory makes sense. I recall Einstein making reference to rods lying on a flat disc which is heated unevenly. The rods would expand in some places more than others and they would together define a non-Euclidean geometry. Were all measurements on that plate confined to those rods then there would be no way to tell if the surface were *truly* curved or not. Both interpretations are valid. The choice of including the curvature in the geometry is logical but, I don’t think that choice has to come from any necessary assumption of ontology as you both explicitly say above.

 

It also strikes me that you are focusing on multiple valid interpretations of current theories. But, just as often, some logically consistent theory and ontology is ruled out by epistemology. How else, in fact, are we to rule out some seemingly valid ontology but through epistemology? I tend to believe there are truths about our universe which persist regardless of our method of finding those truths. There are three macroscopic spatial dimensions. Four would be consistent, and four would be logical... but four would be wrong as would 5 and 6 and an infinite number of other possibilities which I think *can* be ruled out through our knowledge of the universe.

 

~modest

[Pyrotex]

AnssiH,

That was a fabulous essay, an incredibly lucid epistogram of space-time.

Thanks immensely.

Pyro

[watcher]

You keep attributing "absolute space" to me as my misconception. I have said dozens of times that space is the no-thing-ness, the emptiness between actual things/"events." It doesn't expand, contract, curve, or do cute tricks like stand up and beg when teased by a passing massive object. ... "It" can not be an "absolute", because "it" is not really an "it" but the absence of being anything... nothing at all, really.

 

emptiness is a concept. nothingness means it never interacts. something that does not interact is considered absolute. these are how classical space was used to be treated .

something unobservable and invisible is not the same as empty. so when you say there is nothing but emptiness between two objects is just an idea. then you have to ask yourself if this idea is correct or not.

so to avoid misunderstanding, does space relate to other physical entities or not?

does space has structure or none?

 

Your last sentence above gives away your indoctrination about "spacetime." No blame, really. No one can "pass" a class in modern physics without giving "spacetime" the required ontological nod as an established reality. You are no exception.

 

everything occupies space. so space has reality. the challenge of ontology is to get thru our false beliefs about the nature of things brought about by the limitation of our perception and our interpretation of it. flat still earth ya know.

 

I am just asking you to consider thinking outside this "frame of reference" box

sorry, when i think outside a frame of reference i still get a different conclusion about space and time that you do.

 

which you have been told is "not even allowed!!"

 

because to place a imaginary point in space is an abstraction. to define a location in space is an approximation. this is customary in everyday life because we usually neglect time. these practice is an arbitrary treatment of "real" space as if it is a coordinate system. if you want to model real space, place a particle instead. a complete description of particle in space must have 4 coordinates, x,y,z,t. because the particle in a snapshot is something that occupies the same amount of space in an instant. otherwise, the information about the particle is not complete and do not correspond to the real world. these points are called events. series of events is a happening. a happening is a history like the declaration of Independence. wars, big bang, procreation are nothing but a CHANGE of matter from one state to another. all changes happens in its most fundamental level when a particle move to the next position in the next instant of time.

 

can you explain to me in your outside of the box thinking how time is just an artifact of human thinking? is this tick of the clock just an imagination? what is this thing called "instant" that has the power to effect great change?

[Michael Mooney]

Modest,

To continue... You wrote:

So, "relative perspectives" is not a problem for the philosophy of spacetime. If our universe is 4D we expect distance (as measured by rulers) and duration (as measured with clocks) to be relative to velocity. This is not a problem for my philosophy. Neither is the invariance of the speed of light.

 

Of course, as usual, yourfirst statement above assumes the ontological reality spacetime as a given. You simply ignore the argument that space remains emptiness until the nature of space as a malleable medium is supported by evidence. You deny the designation as malleable, but I simply mean the claim that "it" bends, curves, expands, contracts, and assumes whatever shape.

By 4D I assume you mean line (distance), plane (area) and volume (either) enclosing a geometric space or infinite space without boundary designation) and "time" as the dynamic, "how long whatever event takes to happen" as defined by measuring "duration" in whatever arbitrary "units of time."

OK so far?... on the 4D part?

 

But, you have rejected spacetime and speak in terms of Newtonian relativity.

I speak in terms of Euclidean space.... emptiness as described yet again above, rejecting the ontology of whatever it is that non-Euclidean space claims is curved, etc.

I speak of "time" as above. I accept relativity insofar as it improves on understanding and predicting gravitational effects, but I reject its ontological assumptions which make something out of nothing re: both time and space.

 

The results of this are quite predictable. Your philosophy does not predict or explain the relative nature of space and time nor the invariance of the speed of light.

 

The math instrument of relativity works without its reifying assumptions about space and time, as above. I think that the invariance of lightspeed is evidence that a different principle of physics applies to massless phenomena (as "waves" or "particles") than to objects with mass. I don't claim to *know* why, but I do not deny the confirming experimental results. (Hope you got the latter... at last.)

I can "visualize" the interface between the mass of a bullet and the energy of the powder exploding (as shot ahead of the speeding spaceship at a cumulative velocity of both ship and bullet. Then I can "see" how a laser "shot ahead" in the same manner will not "push" the massless light in the same way to achieve cumulative velocity... which it does not. Here the "interface" of the speeding laser gun has no mass to "push against" as does the explosive gas against the bullet. So there is no cumulative effect. Lets just call it a layman's guess and leave it at that.

 

So, those things are going to be problematic in your world-view. So, I'm not sure I can completely avoid talking in terms of spacetime. I have very earnestly tried to accommodate that in deference to the "ontology" you're putting forward. But, that honestly has gone nowhere. If you really attempted to gain an understanding of modern relativity then I think this conversation would move forward by leaps and bounds.

 

So the above is my answer to a non-existent "problem." And again you arrogantly assume that I just don't understand "modern relativity." For you, disagreement equals my misunderstanding. I think, like Doctordick that you fail to distinguish your firm belief in the epistemological basis of your absolute: ..."Its all relative... from the ontology of what it is when speaking of space, time, and spacetime.

 

But, you don't see the problem with this. A "snapshot" view of the universe would mean every event in the universe (at the time of that snapshot) is simultaneous. Simultaneous means "happening at the same time". That is defined as the "present instant". We know for fact as we have experimentally confirmed: simultaneity is relative to velocity.

Your "fact" above is not a fact at all. This instant (mark!) is the same instant everywhere. One hypnotized by "time" can not even "grok" what this means. Your "relative to velocity" mantra, based on the absolute conviction that "Everything is relative" makes it impossible for you to even imagine the universe as a whole "experienceing" (theoretically, let's say... it is a science forum) the present instant as one omnipresent reality. If you could you would "see" that the limit of lightspeed and the delay in seeing things at a distance does not mean that faraway objects are "in another timeframe." Now is still now "for" all stars, even though we can not see "what's happening now" *there!* It will take a few years (or a billion) for the image of their "now" to reach us. But it is still now everywhere, always.

 

I think this will conclude my discussion with you. If you simply can not make sense of what I just said, then there is an insurmountable communication gap between us... and the rest are trivial details.

In sum: You say

If two events are simultaneous to observer A then they may not be simultaneous to observer B.

I say If two events are happening at the same time anywhere in the universe, they are simultaneous. But if you are obsessed with when observers A and B "see" an event, of course time delay comes into play, and they will not see the event at the same time.

See the difference? I think not. And, again I give up.

 

When you said, absolutely, "Everything is relative," and I said "Everything is relative as seen from local perspective, but Now is everywhere omnipresently, absolutely" or something like that, I knew this was going nowhere. It still hasn't. It is as if that conversation so many pages ago never happened. So here it is again... still... never to be resolved.

If there exists an inertial frame of reference where spatially separated events are simultaneous then there must exist another equally valid inertial frame of reference where the events are not simultaneous

 

But you then object saying surely the events are either simultaneous in objective reality or they are not. You see it as an either/or situation: The events either happen at the same time or they don't.

Sounds like logic, but what is the logical necessity? There is none. It is nonsense. All events are happening right now simultaneously, regardless of how far apart they are. An event that happened last year is not happening now. :) Uh, yeah, ok...

 

Events are either simultaneous or they are not. Those happening now are simultaneous and those happening at different times are not simultaneous. Brilliant!

 

Done.

Michael

[watcher]

Sounds like logic, but what is the logical necessity? There is none. It is nonsense. All events are happening right now simultaneously, regardless of how far apart they are. An event that happened last year is not happening now. Uh, yeah, ok...

 

Events are either simultaneous or they are not. Those happening now are simultaneous and those happening at different times are not simultaneous. Brilliant!

 

think it this way michael.

if you take a snapshot of two point particles in space, there is a probability that you would capture 1. both in a picture 2. only either one in the picture 3. none. if you take lot of series of snapshots, then and only then you can know what is happening. what do you make of it.

[Erasmus00]

Sounds like logic, but what is the logical necessity? There is none. It is nonsense. All events are happening right now simultaneously, regardless of how far apart they are. An event that happened last year is not happening now. :doh: Uh, yeah, ok...

 

If the speed of light is constant for all observers, then this is deductively not possible. In special relativity its not just that events are observed in a different order, its that the events must have happened in a different order.

 

Please, Michael, try to use your ontology to make predictions. It certainly can be done. You seem reluctant to develop an actual physics based on your ontology.

[Doctordick]

Modest, I am afraid I find many faults with your assertions.

But, just as often, some logically consistent theory and ontology is ruled out by epistemology.

This statement is simply illogical. A theory can only be ruled out if a logical inconsistency can be found!

How else, in fact, are we to rule out some seemingly valid ontology but through epistemology?

Aren't you being a bit caviler with the phrase “seemingly valid”. There are a lot of things which people think are valid which are actually just presumed to be true.

I tend to believe there are truths about our universe which persist regardless of our method of finding those truths.

Belief is not a scientific position. Belief is a squirrel conclusion (you need to read, and comprehend, what I am talking about in Defining the nature of rational discussion!).

There are three macroscopic spatial dimensions. Four would be consistent, and four would be logical... but four would be wrong as would 5 and 6 and an infinite number of other possibilities which I think *can* be ruled out through our knowledge of the universe.

That you “think” such things can be ruled out is not sufficient! If you are going to state it as a fact, you need to prove it. As per Anssi, “are you guys sure you understood exactly what that last sentence means? I'm guessing not because you are still continuing the thread”. I am afraid Anssi is dead on with that comment. Counter to your assertion, it is exactly the problem at hand. :naughty:

 

And, Michael,

Perhaps I misunderstood you; if that is the case, I apologize. You weren't very clear and I just grouped you with the rest of the crowd. :doh:

you are continuing to be as unclear as you were and I have no idea as to what you are thinking other than that “you are right”. Erasmus00 is quite correct; you are not working out the logical consequences of your position. That is, in fact, the major flaw in most all “belief systems”. Squirrel thought is a very powerful mechanism for making life and death decisions but you are just plain fooling yourself to think it is without flaw. :naughty:

 

Have fun -- Dick