What is "spacetime" really?

[Pyrotex]

I was wanting to say that myself. I was about to call Michael "right", leave it that without explaining myself.

 

You have to go all to the Mountain King to Pertify this thread. No wonder it takes so long....

Well, to give him credit, Michael ONLY made one mistake. He came here totally attached to persuading us of his point of view. Being "right" was everything, even his motive for being here. Now, I sure do like being "right" (on those rare occassions when it works out that way) but I also know that "being right" and learning something new are mutually exclusive states.

 

There is a distinct possibility (however small) that Michael was also CORRECT. :confused: But when faced with the (ontological) choice between defending his correctness and demanding his rightness -- he chose to be right. Fine. He got to be right. He got the last word. He got to prove to himself that we were boobs unworthy of his brilliant insight. But he will never know for sure and neither will we. That's the sad part.

 

I would really, REALLY like to have a friendly discussion with him on "ontology". No frikkin kidding. But he's ticked off and will prolly not be back.

 

I just threw that stuff in about the Hall of the Mountain King so you would be appropriately impressed. :)

[JMJones0424]

Please forgive me, for I have been away from this conversation for a while. I assure you that I am not being disingenuous, I just have other things going on in my life. I tried to read the posts that I missed, but I became frustrated, and I have jumped to this conclusion.

 

"What is "spacetime" really?"

 

I don't know, neither does anyone else. In fact, we can't know, because it is absolutely impossible to obtain an unbiased "view" of spacetime. There are no unbiased frames of reference. There is no static ether. There is nothing that is unchanging by which we can compare everything else. There is no "universal constant". This whole argument has become meaningless.

 

What do we measure spacetime to be? This question must recognize the fact that we experience the world in three dimensions plus time, and time may be mathematically figured to be a fourth dimension. There are many irrefutable experiments that provide evidence that our current understanding of spacetime is at least more accurate than the Newtonian, Euclidian understanding. Evidence has been given numerous times in this thread.

 

If photons have no mass, why then are their paths bent by massive objects? This is fundamental in GR, and either my understanding is severely flawed (in which case I would appreciate correction) or MM is failing to recognize the consequences of what he claims to recognize as verifiable evidence of the "actual" representation of the universe.

 

I realize that the "ontological" universe may differ from the "epistemological" universe, but that difference would manifest itself primarily because we can not inhabit an omniscient perspective. If one's "ontological" view disagrees with "actual" experimental data, one should be able to provide more than just that their "ontological" view is obvious. I have found absolutely no evidence to suggest that MM's "ontological" view of the universe is in any way supported by "epistemological" evidence. Excepting, of course, his claims of a unique frame of reference.

 

So, what is spacetime, really? Spacetime is the correlation between one's position in three dimensional space, and one's position in time. There is reason to believe that the fourth dimension of spacetime (time itself) is only positive in larger objects, though I have no idea why. (Imaginary time comes into play, and I immediately scream for help, yet my failure to understand does not mean that the concept is incorrect). There is also reason to believe that "space" is not limited to just three dimensions, but this argument is far beyond my understanding. Finally, there is reason to believe that "spacetime", or the combination of an event's three dimensional location in space plus it's time of occurance, is affected directly by the mass of nearby objects, which is the basis of GR, and the very concept that makes the whole idea of the "reification" of spacetime so difficult to understand. I am not in the position to coherently explain this understanding, and I am waiting eagerly for someone else to do so.

 

What is spacetime? This question is fundamental to all of cosmological physics. I thank you, MM, for questioning the common definition as your questioning, and the answers of others, has helped me understand concepts that I previously didn't understand, but I am afraid that you are not willing to accept the indirect consequences of experiments and observations that have been made by others. If you wish to propose an answer to this question that differs dramatically from theirs, then you must understand that we would demand outstanding evidence.

 

What evidence do you have that the universe is "ontologically" Euclidean?

[Michael Mooney]

Hi JMJones,

I had given up last night, but your sincere inquiry, sans "know it all" attitude (like me and the moderators here) has inspired me to give at least one more try. And I will do my best to just say it like I see it without claim to omniscience.

 

What is "spacetime" really?"

 

I don't know, neither does anyone else. In fact, we can't know, because it is absolutely impossible to obtain an unbiased "view" of spacetime. There are no unbiased frames of reference. There is no static ether. There is nothing that is unchanging by which we can compare everything else. There is no "universal constant". This whole argument has become meaningless.

 

My understanding of ontology is the attempt to know what is real, as distinct from what we have always been told, or whatever.

If you look up "spacetime" anywhere, you will get the GR doctrine invented by Einstein, Minkowski, et al *assuming* and stated as an established "given" that "It" has certain properties. "It" curves expands, contracts, dilates, etc.

Now, obviously objects, including light traveling *through space* (whatever that is or is not) have curved trajectories as masses pull on each other and on light gravitationally. This does not require a curved, etc. medium "spacetime."

 

What do we measure spacetime to be? This question must recognize the fact that we experience the world in three dimensions plus time, and time may be mathematically figured to be a fourth dimension. There are many irrefutable experiments that provide evidence that our current understanding of spacetime is at least more accurate than the Newtonian, Euclidian understanding. Evidence has been given numerous times in this thread.

 

I agree up to the point that Euclidean understanding has been proven wrong. Yes, even "empty space" has three dimensions... distance, area, and volume.... all the way out to infinite volume if one can see that arbitrary finite boundaries can not limit "space" in the universal sense. And "time" of course is simply the "when" in all cases as applied to all observations of all "things."

 

If photons have no mass, why then are they bent by massive objects? This is fundamental in GR, and either my understanding is severely flawed (in which case I would appreciate correction) or MM is failing to recognize the consequences of what he claims to recognize as verifiable evidence of the "actual" representation of the universe.

 

Light has momentum which gives it the property of mass so it can be deflected by gravity without requiring "curved space" as an explanation. (Light trapped in a box of mirrors gives the box added inertia exactly as if the trapped light had mass.)

 

I realize that the "ontological" universe may differ from the "epistemological" universe, but that difference would manifest itself primarily because we can not inhabit an omniscient perspective. If one's "ontological" view disagrees with "actual" experimental data, one should be able to provide more than just that their "ontological" view is obvious. I have found absolutely no evidence to suggest that MM's "ontological" view of the universe is in any way supported by "epistemological" evidence. Excepting, of course, his claims of a unique frame of reference.

 

It has always seemed to me that the "burden of proof" is ontologically on those who would "make something of it" (spacetime) rather than letting it be the emptiness within matter and between objects. Einstein his-esteemed-self said that without all the objects relativity deals with that there would be no "spacetime" as an independent medium. So this begs the ontological question this thread poses, "what is 'it' then?"

 

So, what is spacetime, really? Spacetime is the correlation between one's position in three dimensional space, and one's position in time.

 

Exactly! But that leaves the ontological question unanswered, "What curves, dilates, etc."... besides of course the trajectories of objects as they move through (perhaps empty) space with an "elapsed time" for any measurement thereof?

 

There is also reason to believe that "space" is not limited to just three dimensions, but this argument is far beyond my understanding.

 

I would have to ask, "what reason?" Looks to me like three spacial dimensions have all three axes covered and time covers the "when." What else is required to explain what we can observe about "space" and "time?"

 

Finally, there is reason to believe that "spacetime", or the combination of an event's three dimensional location in space plus it's time of occurance, is affected directly by the mass of nearby objects, which is the basis of GR, and the very concept that makes the whole idea of the "reification" of spacetime so difficult to understand. I am not in the position to coherently explain this understanding, and I am waiting eagerly for someone else to do so.

 

Occam's Razor can cut away "spacetime" as a medium with properties "of its own" and gravity is still the mutual attraction between masses and that mysterious phenomenon "light" traveling at the ultimate speed and bending as it is effected by masses. No one knows how gravity is propagated, so curved "spacetime" was invented to explain it. Yet how gravity is propagated remains a mystery. Naming a malleable medium (curving expanding, contracting, dilating) out of "thin air" really adds nothing to our understanding of the mystery.

 

What evidence do you have that the universe is "ontologically" Euclidean?

 

Makes sense to me. What evidence is there that it isn't.... that "space has curvature, shape" etc. or that there are four spacial dimensions, as discussed above?

 

Thanks for your post. Could be this thread "ain't dead yet."

 

Michael

[maddog]

Well, to give him credit, Michael ONLY made one mistake. He came here totally attached to persuading us of his point of view. Being "right" was everything, even his motive for being here. Now, I sure do like being "right" (on those rare occassions when it works out that way) but I also know that "being right" and learning something new are mutually exclusive states.

Totally concur. You know my dad once told me he made mistake once... He thought once

that he had made a mistake. He later found he hadn't made a mistake after all... :hyper:

There is a distinct possibility (however small) that Michael was also CORRECT. :) But when faced with the (ontological) choice between defending his correctness and demanding his rightness -- he chose to be right. Fine. He got to be right. He got the last word. He got to prove to himself that we were boobs unworthy of his brilliant insight. But he will never know for sure and neither will we. That's the sad part.

About the ultimate ontological nature of spacetime. Yes, correct he may have been.

About that Euclid was "right" all along that Euclidean Geometry is "all" that is "correct" and every "other" geometry that does not uphold the 5th Postulate; I have a lot of examples where that would be in "Error" {Mathematical Error(s) not Physics ones}.

I would really, REALLY like to have a friendly discussion with him on "ontology". No frikkin kidding. But he's ticked off and will prolly not be back.

I could have easily have had this chat over a beer/whatever. In person, I think it might have gone better. Of course if the pompous attitude of "I'm better" had came out, I

might have found another table to carouse with.

I just threw that stuff in about the Hall of the Mountain King so you would be appropriately impressed. :)

I liked it.

 

maddog

 

ps: He's back (previous post).

[Rade]

Would it be correct to say that "space-time", since it is that which is intermediate between moments of "things", is what "field theory" tells us it is, and then "thing theory" (such as QCD, QED, etc.) tells us what "things" are. If so, then "field theory" + "thing theory" = epistemology as informed by ontology = Existence ?

[modest]

Light has momentum which gives it the property of mass so it can be deflected by gravity without requiring "curved space" as an explanation.

There is an exact relationship between energy, mass, and momentum. The relationship is derived on sound principles and it has been tested with every conceivable particle at every conceivable energy—so, we don’t need to guess about something like this. We know pretty well for sure. The relationship is:

[math]e^2 = m^2c^4 + p^2c^2[/math]

Here e is energy, c is the speed of light, m is mass, and p is momentum. Momentum is a property something has when it is moving relative to you. A bowling ball, for example, has zero momentum while you’re holding it waiting for the pins to set. But, after you throw the ball down the lane it might have 30 kg-m/s. Usually when somebody is talking about energy they mean something that is right in front of them, or at least not something with *a lot* of velocity. In this case we can set p=0 in the equation above which simplifies it to:

[math]e = mc^2[/math]

Which most people would find familiar. But, we can’t make this simplification in the case of light because it is not sitting in front of us at slow relative speed. We have to use the full energy / mass / momentum equation. We will do that now to find the mass of a photon. Both the momentum and the energy of a photon can be found experimentally such as with the photoelectric effect. The momentum is Planck's Constant divided by wavelength. Energy is Planck's Constant times frequency. We solve these for a 700 nanometer photon (red light).

[math]e = h \nu = 6.626 \times 10^{-34} \times 4.285 \times 10^{14} = 2.84 \times 10^{-19}[/math]

[math]p = \frac{h}{\gamma} = \frac{6.626 \times 10^{-34}}{7 \times 10^{-7}} = 9.47 \times 10^{-28}[/math]

We solve the energy / mass / momentum equation for mass since that’s what we’re trying to figure out:

[math]m = \sqrt{\frac{e^2-p^2c^2}{c^4}}[/math]

Plugging in our well-tested and experimentally confirmed values,

[math]m = \sqrt{\frac{(2.84 \times 10^{-19})^2-(9.47 \times 10^{-28})^2(3 \times 10^8)^2}{(3 \times 10^8)^4}}[/math]

trusting the calculator,

[math]m = \sqrt{0}[/math]

[math]m = 0[/math]

The mass of a photon of red light is zero :eek: Certainly this must be some kind of mathematical voodoo. Something with energy and momentum must have mass. It just has too. Never mind that anything with mass cannot travel the speed of light. We demand (for the sake of argument) that light have mass.

 

Well, I’m actually ok with that. Newtonian mechanics is a first order approximation of relativistic mechanics, so we’re going to have to make approximations to make things work—we might as well let light have mass for the sake of gravity. So, the question is immediately “what mass do we give it”. Believe it or not, this is not important. A 10 kilogram ball will drop with the same acceleration as a 5 kilogram ball or a 1 kilogram ball. Where the Newtonian “force” equation of gravity is:

[math]m_2a =G \frac{m_1 m_2}{r^2}[/math]

The value of [math]m_2[/math] does not affect acceleration. It then becomes a very straightforward exercise to calculate the expected deflection of light where gravity is a “force” acting on the “mass” of light in Euclidean *flat* space. While this is straightforward, it is computationally intense so I will not do it in this post. It is, however, fully derived on this webpage:

Bending Light

along with the expected deflection in general relativity. The conclusion is that gravity as a force predicts light to deflect half as much as gravity as spacetime curvature. This is a testable difference between the theories. Despite Michael’s assertions that it doesn’t matter which way we look at things—yes, it absolutely does matter. Light deflection has been tested to ridiculous precision and it incidentally disagrees with all the “force” theories of gravity and agrees precisely with the spacetime theory of general relativity.

 

In general relativity the path of light is rather special. Imagining the path taken from one spot to another. If you travel this path you will experience a certain amount of proper time between spots. The faster something travels the path, the less proper time it takes. Special relativity tells us that if we could travel light speed there would be zero proper time between spots. This is the path of a photon. It travels instantly *from its perspective* from one spot to another.

 

Now consider gravity in general relativity. We are drawn to the planet’s surface because time is curved into our spatial dimensions. Each second we spend hanging out on the surface is a second in which our path is diverted from being inertial and space is accelerated downward around us toward the center of the planet and we feel acceleration on the surface as if we were accelerating in a rocket. So what about the photon? If it has no proper time then its path cannot be diverted by the curvature of time into space—there’s none of it to curve. The path of light then shows us humans the curvature of space *only*... no curvature of time. This is how the deflection of light is derived in general relativity. It says: the photon is moving in a straight line, but space is curved by exactly this much giving us exactly this much deflection. It predicted this and it later turned out to be precisely correct.

 

The path of light is curved because the thing us humans measure and conceptualize as “space” is curved. That is what our observations and theories are telling us. The ontological question is: what is being curved? Michael wants to say that the spatial dimension do indeed exist ontologically. He says it explicitly in his most recent post:

Yes, even "empty space" has three dimensions... distance, area, and volume.... all the way out to infinite volume if one can see that arbitrary finite boundaries can not limit "space" in the universal sense. And "time" of course is simply the "when" in all cases as applied to all observations of all "things."

Yet he does not let this ontological entity curve. He argues that it has the property of straight and cannot have the property of curved because *it* is nothing (keep in mind this nothing apparently does exist) and "nothing" is apparently straight. That makes no sense to me. Straight is just as much a property as curved. Euclidean is no more basic a geometry as non-Euclidean. Once you describe something as straight you have to allow for the possibility that it is not straight.

 

My conclusion: at no level does Michael's argument make sense to me. Not ontologically, or epistemologically, or physically. As intuitive as it seems, it just doesn't work. :shrug:

 

~modest (sorry, again, for the long post)

[watcher]

There is also reason to believe that "space" is not limited to just three dimensions, but this argument is far beyond my understanding.

I would have to ask, "what reason?" Looks to me like three spacial dimensions have all three axes covered and time covers the "when." What else is required to explain what we can observe about "space" and "time?"

 

reason? what about things like electrons are not in your beloved 3d space prior to measurement? this is one reason to assume that space is not limited to 3d. or do you even understand what this means?

 

first: what is your proof that objects are actually in 3d space? except to say that we feel it is.

 

second: does wave propagates in space or wave propagate in nothingness? while the former is an accepted assumption, the latter is nonsense. how do you justify that nothingness has an existence of its own?

[modest]

To keep things in perspective, General relativity's spacetime has 3 spatial dimensions and one temporal dimension. No more are required.

 

~modest

[watcher]

To keep things in perspective, General relativity's spacetime has 3 spatial dimensions and one temporal dimension. No more are required.

 

in response to this,

] It has always seemed to me that the "burden of proof" is ontologically on those who would "make something of it" (spacetime)

you have provided a clear proof of GR vis a vis MM's gravity force that bends objects trajectory path, i am afraid that this will again ignored. while the OP also believes in the invariance of lightspeed, he doesn't seemed to follow its logical consequence.

 

but this is what bothers me ...

 

rather than letting it be the emptiness within matter and between objects

 

there seemed to be an attitude coupled with firm conviction by the OP that the above statement is already the case without the benefit of proper investigation therby excluding the possibility that 3d space could also be an electronic construct.

 

the allusion to the question "where is the electron before you measure it" is only to hopefully shake his present belief about space as limited to 3 dimension and emptiness as an intrinsic property of existence.

[watcher]

I was for this reason, I posed "what is the Ontology of Thought ?" I wanted a real world

example where you can describe the underlying Metaphysics "is-ness" of something

where the existence has no "Physical-World" evidence.

 

maddog

 

for the real world examples to have validity, it must be based on empirical evidence. and the non availability of physical evidence would mean that we have come to realize the limit that we can perceived the underlying metaphysics of this is-ness.

 

which left us nothing but to infer using logic and reason to map it out.. so when we said that the ontology of things cannot be known, what we meant is that it is beyond our ability to measure and therefore unquantifiable. iow word, science wouldn't have anything of it we are just physicists.

 

i asked loosely the ontology of things to make him realize that perhaps things like electrons don't simply float in space as he seemed to naively believe.

[Michael Mooney]

JMJones:

"There is also reason to believe that "space" is not limited to just three dimensions, but this argument is far beyond my understanding."

Me:

"I would have to ask, "what reason?" Looks to me like three spacial dimensions have all three axes covered and time covers the "when." What else is required to explain what we can observe about "space" and "time?"

Watcher:

"reason? what about things like electrons are not in your beloved 3d space prior to measurement? this is one reason to assume that space is not limited to 3d. or do you even understand what this means?"

 

If I understand you correctly you seem to believe that these little swarms of energy we call electrons are simply not located in conventional 3-D space until we take our observational snapshot. Then they magically appear from "another dimension."

 

Assuming the above, if I read you correctly is simply an ontological "quantum leap" of imagination positing a mystery dimension which lies beyond human comprehension. I will not take that leap. And there is no need for it.

 

Watcher:

"first: what is your proof that objects are actually in 3d space? except to say that we feel it is. "

 

No proof... but very good evidence, as follows:"Energy waves" (in 3-d space) manifest like "particles" when we make them run through the detector medium at the accelerator, leaving their signature "trails."

 

But, ontologically "back atcha"... what is your proof that electrons (as above) don't exist in 3-D space before we make them show their little faces? And what is your proof that a "4th spacial dimension exists?"

 

The burden of such proof is on 4th dimensional theorists here, strictly, ontologically speaking. (I just saw Modest's comment on this and agree. (Very rare indeed!)

 

Watcher:

"second: does wave propagates in space or wave propagate in nothingness? while the former is an accepted assumption, the latter is nonsense. how do you justify that nothingness has an existence of its own?"

 

Please try very hard to "hear" this, as I've said it many times before.

"Things" can be very broadly defined as various phenomena we can observe or detect... even "electrons." But the universe is clearly not "solid", made of solid "thingness." There is actually empty space between things (on all levels, micro to macro) as the English language assigns meaning to words, like "empty." So assuming that "emptiness" is just another "thing" is an ontological error. Emptiness is where no "things" exist, in between what does exist, rendering each such locus of "thingness" not "empty" at each locus.

 

So the vast majority of the universe is the empty space between things.

 

This empty space, for instance, accounts for the difference between the size of Earth as she is and the size she would be if all the empty space in her matter were gravitationally compressed out, making here a small black hole. The Swarzchild radius formula specifies this resulting extremely dense matter as about pea sized.

 

The difference is "empty space." Same applies on macro-scale as (no doubt) a different ratio but same principle between stars, planets, galaxies. Lots and lots of "empty space" compared to space occupied by things.

 

I do 'thing' I am done with the ontology of "empty space" at this point. :phones: If the above doesn't clarify it, being my best effort in the present, then... well... to heck with it. I've done my best on "the ontology of empty space" as a subset of the ontology of "spacetime.

 

Michael

[Michael Mooney]

Well Modest,

You've out-gunned me again with those big mathematical guns (and me with my little ontological "switchblade" (I'd rather call it an adept use of Occam's Razor)

 

I will not, obviously critique your equation formulae, except to openly doubt the claim that GR proves that space must be curved on the grounds that the deflection of light by conventional understanding of gravity alone accounts for only half of its deflection. Maybe all that math lacks just a little understanding of the full "impact" of the meaning of momentum as applied to light.

My favorite little "box of mirrors" example certainly gives the box more static inertia just as if those little photons had mass. I'm not saying they do, as they couldn't travel at "lightspeed" if they did...( or so the math and expewrimental results (so far) say.. Maybe that ultimate speed confers more "momentum" than your examples are taking into account. But the equations are over my head... as you well know. But I think, your mathmatical expertise notwithstanding, you still don't understand the otological inquiry this thread is about.

 

We both know that Einstein said that spacetime has no independent existence of "its own"... that "it" would not exist without the "objects" which are the primary focus of relativity .

Have you actually thought about what it is that is no longer without the objects which actually generate the gravity, etc.?

 

This, then is the ontological question. What is "spacetime" all by itself. Nothing. It doesn't exist "all by itself." What then "confers existence" (reality, ontologically speaking) on "it."

 

The actual phenomena wich generate the actual forces. So what are these forces acting on? The bodies which mutually attract each other and light. The fact that gravity bends light is the more fundamental truth than the "how much" question you so belabor in service to the "curved space" theory.

 

Shucks.... I have a lot more in specific reply to your post, but it will have to wait.

 

Michael

[Michael Mooney]

(The interruption turned out to be a quickie.)

On to the reply.

Modest:

In general relativity the path of light is rather special. Imagining the path taken from one spot to another. If you travel this path you will experience a certain amount of proper time between spots. The faster something travels the path, the less proper time it takes. Special relativity tells us that if we could travel light speed there would be zero proper time between spots. This is the path of a photon. It travels instantly *from its perspective* from one spot to another.

 

A photons perspective is a fiction. And "proper time" is a fiction. See my "what is time" post. (I'll find it if requested.)

Granted that "units of time" are simply earth-commensurate ticks of the clock as fractions of an earth rotation... we conventionally say that a measured event has an elapsed time.

 

For a photon traveling from sun to earth... an actual "distance through space"... the elapsed time in minutes is 8.3 (or so) minutes. the statement that "for a photon there is no elapsed time" is blatently nonsense.

 

This is the path of a photon. It travels instantly *from its perspective* from one spot to another.

This is nonsense.

 

Modest:

Now consider gravity in general relativity. We are drawn to the planet’s surface because time is curved into our spatial dimensions.

 

" elapsed time" is the duration of a measured event. The act of measuring tells us how many of our "seconds" etc elapsed asr a selected event (object of the observer's focus) happened.

This is the ontology of time, btw, not your assumption about time based on what you have been told time is "all by itself." (Ontology, Modest. The contemplation of what, if anything, is real about "time itself."

So you agiain blindly repeat what you have been told about "time" and believe it, making it "Real" in your own mind. This is the error of reification, which you have never understood in this thread.

And on to 'curved space" .... more reification.

 

The path of light then shows us humans the curvature of space *only*... no curvature of time. This is how the deflection of light is derived in general relativity. It says: the photon is moving in a straight line, but space is curved by exactly this much giving us exactly this much deflection. It predicted this and it later turned out to be precisely correct.

 

See my objections to the "twice the expected degree of deflection" argument as requiring "empty space" (this presented ontology) to be filled with a mysterious stuff "spacetime"... which doesn't really exist by itself but only as a metric to facilitate the predictions of relativity.

I truly doubt that you have an "opening" in your obvious degree of certainty to actually "hear" what I just said.

And frankly, I am tired of saying it to ontologically deaf ears.

 

The path of light is curved because the thing us humans measure and conceptualize as “space” is curved.

If there were no object trajectories curving, there would be no "space"curving. "It" is just a visual aid... nothing "there"... really.

That is what our observations and theories are telling us. The ontological question is: what is being curved? Michael wants to say that the spatial dimension do indeed exist ontologically. He says it explicitly in his most recent post:

Quote:

Originally Posted by Michael Mooney View Post

Yes, even "empty space" has three dimensions... distance, area, and volume.... all the way out to infinite volume if one can see that arbitrary finite boundaries can not limit "space" in the universal sense. And "time" of course is simply the "when" in all cases as applied to all observations of all "things."

Yet he does not let this ontological entity curve. He argues that it has the property of straight and cannot have the property of curved because *it* is nothing (keep in mind this nothing apparently does exist) and "nothing" is apparently straight. That makes no sense to me. Straight is just as much a property as curved. Euclidean is no more basic a geometry as non-Euclidean. Once you describe something as straight you have to allow for the possibility that it is not straight.

"Straight" is not a property like curvature is. Straight is the concept of "not curved, crooked or roundabout." (my quote.) It is the shortest distance between any two points or objects.... not... btw the path of light between them. Curvature can describe the latter path, but it is not a "property of space" which, in this ontology, is the void between all things with properties. I am sorry that you simply can not comprehend this very basic ontological difference. You are hard-wired (programed) to believe that space, time, and spactime are extant entities of some kind. They are not.

 

My conclusion: at no level does Michael's argument make sense to me. Not ontologically, or epistemologically, or physically. As intuitive as it seems, it just doesn't work.

 

The last statement is obviously true. It works just fine if you set aside your dogma long enough to hear my argument.... which you have never done in this exhaustive debate.

 

Michael

[modest]

"proper time" is a fiction.

No. Proper time is what your watch keeps. My clock doesn't keep your proper time and your clock doesn't keep my proper time. Each of our own clocks keeps our own proper time... get it?

 

Granted that "units of time" are simply earth-commensurate ticks of the clock as fractions of an earth rotation... we conventionally say that a measured event has an elapsed time.

Yeah, what you call "elapsed time" is what physicists call "proper time". So we should be on the same page. Your whole objection seems based on the problem that you didn't look up "proper time" to see what it actually is before you decided it is complete fiction. Here, I'll help:

Proper time - Wikipedia, the free encyclopedia

For a photon traveling from sun to earth... an actual "distance through space"... the elapsed time in minutes is 8.3 (or so) minutes.

8.3 minutes is *your* proper time between those events. But, we're not talking about your proper time, are we? At this point in this thread (after all the discussion along these lines) it should be obvious that your clock doesn't keep the time experienced by something moving relative to you.

the statement that "for a photon there is no elapsed time" is blatently nonsense.

It's nonsense to you because you don't understand it.

This is the path of a photon. It travels instantly *from its perspective* from one spot to another.

This is nonsense.

Which is why you can't describe the physics of a photon any more than Newton could. It's just not going to work. You can't describe reality with a Newtonian view of mechanics. Things will just look like nonsense :phones:

 

I can't make your Newtonian view work, and neither can you. Yet you will accept no other view (either through a complete lack of understanding or an unwillingness to change your thinking). So this thread is at an impasse. The rest of your post hits the same brick wall.

 

~modest

[Erasmus00]

Michael, I'm going to post what is most likely my last post to this thread- it has become clear to me that you aren't listening to what people are saying, you are instead waiting to talk.

 

This will probably fall on deaf ears but- to seriously engage in discussion about the ontology of spacetime you absolutely NEED to have some ability to read and talk in the language of mathematics.

 

When a mathematician or physicist says space is curved, they don't really mean like a beach ball- they mean that space has certain mathematical features akin to a beach ball-i.e. if you draw a triangle in space with absolutely straight lines it will not have 180 degrees. A sphere in space will not have a volume exactly equal to 4/3 pi * the radial distance^3. The mathematical concept has meanings and implications far more accurate than the english words "curved space." I have tried to make this clear, but fear I have failed.

 

Finally, you clearly have some interest in pursuing and developing your ontology. To do this, you will need mathematics. In large part, mathematics (in particular calculus) was designed to describe nature in accurate detail. Instead of saying to modest "I can't follow these equations" you should begin to start asking questions and trying to learn what the equations are saying.

[JMJones0424]

Occam's Razor can cut away "spacetime" as a medium with properties "of its own" and gravity is still the mutual attraction between masses and that mysterious phenomenon "light" traveling at the ultimate speed and bending as it is effected by masses. No one knows how gravity is propagated, so curved "spacetime" was invented to explain it. Yet how gravity is propagated remains a mystery. Naming a malleable medium (curving expanding, contracting, dilating) out of "thin air" really adds nothing to our understanding of the mystery.

 

I could not disagree more with this statement. Occam's razor states that when multiple competing arguments are equally valid, the most simple should be accepted. It does not say that all valid arguments are simple.

 

I could (not easily) make the argument that the earth is the center of the universe, and heavenly bodies revolve around the earth. I could even come up with mathematical formulas that accurately describe the motion of the sun, moon, planets, and stars, and if the formulas were exceedingly complex, they would accurately predict measurements made on Earth. But other, equally valid arguments could be made, using vastly simpler equations to explain the apparent motion of heavenly bodies. Occam's razor states that those simpler theories are more likely to be correct.

 

In a similar way, GR is an attempt to explain the observed motion of both massive (like planets) and massless (like light) motion. Newtonian mechanics is likewise an attempt that relied on Euclidean geometry. It isn't Newton's fault that he thought space was Euclidean, as it certainly appears to be on scales that we experience in every day life. The fact of the matter is though, that space does not appear to be Euclidean on larger scales, and without huge fudge factors, Newtonian mechanics does not even accurately describe the orbit of Mercury, much less objects with vastly larger distances from the observer, or vastly different velocities, or significantly closer location to massive objects.

 

I do not worship at the altar of Einstein. I actually think Newton was more revolutionary than Einstein (but I'm not German, so I tend to forget about Leibniz). What upsets me is your apparent disregard for a theory that quite accurately describes the universe that we experience.

 

No one knows how gravity is propogated, but the theory that "gravity" itself is just a result of the "curvature of spacetime" by massive objects is, by Occam's razor, a more acceptable theory than that gravity is a force propogated through 3D space.

 

Your denial of the possibility of "spacetime" as actually being a maleable medium, without providing an acceptable, verifiable alternative, provides nothing to our understanding.

[Pyrotex]

Hi Michael,

I thought you said you had nothing more to say on this thread? :)

Seems you had quite a lot.

 

So, do you want to start a thread on Ontology and actually teach me something, or do you want to keep beating that dead space-horse?