What is "spacetime" really?

[modest]

This is philosophy, not physics.

 

I should probably explain since there are a number of new people joining the thread. Four hundred and fifty some posts ago Michael asked a very sensible question: “what is spacetime really?” I moved his thread from Q&A to philosophy of science to which Michael adamantly objected. I explained that his question was philosophical and, in particular, ontological. He thought this was meant to be an insult saying:

My question was labeled a philosophical one, specifically ontological, and the thread was moved to the "Humanities" section, "Philosophy of science."

Being a newbie, will someone please explain how the direct question, "What is spacetime" belongs in ontological debate.

I explained (along with Will, Essay, Watcher, and others) that philosophy was a necessary part of science and naming his argument as such was not derogatory but simply appropriate. We encouraged and helped him develop his ideas through to some logical consequences.

 

Michael’s philosophy is indistinguishable from Galilean relativity. He treats time exactly how a Galilean transformation treats time (t’ = t) as he does space and velocity. He explains that clocks slow when they change velocity because the physical forces of acceleration affect the mechanics of the clock making it slow. He compares this to holding a clock under water where friction with the water would make it slow.

 

This is an understandable conclusion. If Newtonian mechanics is our chosen world view then some mechanical explanation is needed to explain relativistic effects. This is no different in principle from the aether theories of SR proposed by Poincare and Lorentz and the philosophical reasons they held to those theories are no different from the philosophical reasons Michael holds to his ideas.

 

So... a change in velocity is accompanied by a pseudo force which Michael argues affects any system capable of measuring “event duration” in a way that is described by the physics of special relativity. The problem, as it has been explained, is that muons and other particles have been subjected to large centrifugal forces and they are shown to be time dilated equally with particles that move in a straight line where the velocities are equal. This supports the clock hypothesis and refutes the idea that clocks and other timing systems are slowed as a result of pseudo forces. Michael doubts the credibility of these experiments.

 

Where I think Michael needs help is developing his ontology of space and time into something other than a world view of Galilean relativity. He says “space is nothingness” and “there’s no such thing as time” and he would do well to develop those ideas into something consistent with SR and hopefully in a way where pseudo forces don't affect a clock's timing :evil:

 

~modest

[watcher]

Now, I'm still not sure that Michael's secondary conclusions are correct,

 

yes it all started here. obviously it was viewed here as a direct challenge to relativity and so the rush to explain/defend/justify it. so why don't you throw your take on it so we too can find fault to your understanding. :evil: {joke}

 

but I'm willing to grant him that the Ontological Universe does in fact exist, it's out there. We will never be able to "see" it, but it's out there. :doh:

 

the problem with this statement is that it assumes that the ontological universe is a different and other than the universe that we perceived. and the universe that we see is not a part of it. but you are right this is in the realm of philosophy and we don't wanna drag ourselves into that.

 

since this seemed to be a one long confused thread already and your gallant attempt to moderate and steer it to the right direction seemed futile and you yourself have fallen to one of its rabbit holes. LOL. because michael really wasn't after the ontology of the universe, the question what is spacetime was rather after to some "axioms" we can establish about spacetime based on our current knowledge in physics. so i may not have totally confused philosophy and physics although i admit to have dabbled my philosophical take to what you have brought out.

[Michael Mooney]

First, Modest is correct about one thing: I was wrong about where this thread belonged. It is an ontological question and it does belong in the "Philosophy of science" forum. I assumed my inquiry was being devalued as a "mere ontological inquiry"... "spacetime" being already a "given"... and I wasn't far off on that point!

 

Modest continues to be wrong about how I see SR and GR in the context of this thread's inquiry. He insists that I am stuck in an interpretation (based entirely on Newtonian relativity and Euclidean geometry... true in the latter case) which has been proven wrong long ago by relativity. Yet everyone keeps saying "spacetime" and "the fourth spacial dimension" as if they were established facts, yet no one will show what either is "supposed" to be in "the real world."

For instance, as I said in post #1, I am familiar with the basics of GR. Her3e again as introduced by Wiki as follows:

 

"General relativity or the general theory of relativity is the geometric theory of gravitation published by Albert Einstein in 1916. It is the current description of gravity in modern physics. It unifies special relativity and Newton's law of universal gravitation, and describes gravity as a property of the geometry of space and time, or spacetime.

(MM: Notice the assertion based on "spacetime" as a "given" prior to and precluding argument In particular, the curvature of spacetime is directly related to the four-momentum (mass-energy and linear momentum) of whatever matter and radiation are present. The relation is specified by the Einstein field equations, a system of partial differential equations."

 

I am also familiar with the basics of SR, as Wiki introduces:

 

"The laws of physics are the same for all observers in uniform motion relative to one another (Galileo's principle of relativity),

The speed of light in a vacuum is the same for all observers, regardless of their relative motion or of the motion of the source of the light....

The resultant theory has many surprising consequences. Some of these are:

 

Relativity of simultaneity: Two events, simultaneous for some observer, may not be simultaneous for another observer if the observers are in relative motion.

Time dilation: Moving clocks are measured to tick more slowly than an observer's "stationary" clock.

Length contraction: Objects are measured to be shortened in the direction that they are moving with respect to the observer.

Mass-energy equivalence: E = mc2, energy and mass are equivalent and transmutable."

 

MM: I have argued with the ontology of the first three statements in the "surprising consequence" section here at length in this thread. The fourth is well founded as the formula for conversion of mass to energy.

 

I am also familiar with (still quoting Wiki) "Some of the (ed: *supposed*) consequences of general relativity:

 

"Time goes more slowly in higher gravitational fields. This is called gravitational time dilation."

 

MM: This assumes that "time" is some "thing" in and of itself... more than just "what clocks measure." I *know* that clocks slow down under the influence of various changes in forces acting on them! Modest and I beat this difference to death early in the thread... to no avail. (He still contradicts himself, insisting that "time is what clocks measure" in the "same breath" as "time (itself) dilates"

 

"Orbits precess in a way unexpected in Newton's theory of gravity. (This has been observed in the orbit of Mercury and in binary pulsars).

 

MM: No argument, But this vindication of GR's predictive math does not establish the ontological reality of "curvature of space" or "dilation of time."

 

"Rays of light bend in the presence of a gravitational field."

 

MM: Undoubtedly.But light's "momentum" interacts with mass/gravity just as if it had mass. For instance, light trapped in a "box of mirrors" gives the box more inertia exactly as if it added mass to the box... still no need for "curved space."

 

"Frame-dragging, in which a rotating mass "drags along" the space time around it."

 

MM: As I said in post # 1:

"I know also about the new satellite telemetry which is said to confirm "frame dragging" as solid evidence of distorted "spacetime" around Earth. Yet the irregular topography of Earth's gravitational field explains the anomalies of the tracked satellites' orbits without insisting on "spacetime distortion."

 

Same with the whirlpool effect around black holes. Material is clearly "going down the drain" into the black holes in a spin just like water, but why cite it as another confirmation of this mysterious *theoretical fabric*, "spacetime?"

 

Continuing in the spirit of historical review of this thread, I will go back to my first unanswered request for ontological clarification.

 

 

Tormod (p.1, post#2):

"Spacetime isn't an attempt to "create something where there is nothing". Rather it is an attempt at explaining what there *is* that comprises the space between "things" in the cosmos.

 

That objects bend the paths of light traveling through space was proven back in 1919. The only apparent explanation for this (since light is a massless particle) is that light travels "through" something. Since the aether had been disproved there was no need to add a cosmic "fluid".

 

There was however a need to unite space and time since it was apparent that light traveled through space, and that the speed of light was finite (another of Einstein's insights). Thus the way light shifts when it passes around an object can be used to measure the gravitational pull of that object. In relativity theory, gravitational pull is actually a distortion of spacetime. Spacetime is, however, four dimensional, and therefore the "sheet with holes" is used to simplify and make it possible to understand the concept."

 

MM (post #3)

"Thank you Tormod for you prompt reply.

But your answer does not seem to address the title question. Not only does

"Nobody really knows what 'spacetime' is"... I am questioning *whether or not 'it' actually exists other than a handy metaphore or concept... like "time"... the measured "duration" of any "event", though the ongong present is not naturally segmented into "units of time" in nature.

Rather you replied that "We do however know a few things about how *it* behaves." You posit "it" as already existing as an actual entity which exibits behavior. This assumes its existence, bypassing my question altogether.....

 

If space is actually the emptiness in which all observable phenomena take place, being nothing in and of itself, then the mystery of gravity (how it works) remains a mystery without the assertion that this "fabric" is indeed *something real* as in my reference to "The Emporerer's New Clothes."

 

You conclude by, again assuming the actual existence of "spacetime"... which, as I said begs the original question.

 

"In relativity theory, gravitational pull is actually a distortion of spacetime. Spacetime is, however, four dimensional, and therefore the "sheet with holes" is used to simplify and make it possible to understand the concept."

 

We all know that the vector of light is bent by gravity, as amply reviewed in the Wikipedia article. Yet you assert again that gravity distorts "spacetime" and, further, that "it" is "four dimensional." Yes, the graphics of the sagging sheet are fine as aids to understanding the vectors which gravity creates in light and massive objects. Yet the agent of gravity remains a mystery, and creating a theoretical "distorted fabric" adds no understanding to the mystery... especially if, in fact, space remains the emptiness in between "things" and "time" merely the measure of selected "event duration" in an "always-now-everywhere" universe.

Please answer without assuming a-priori the existential validity of spacetime as an actual medium... i.e., the point of the title question.

Thanks.

 

Now... back to the present...

 

There was no reply from Tormod, and no one here yet has answered the fundamental question this thread poses.

 

Michael

[modest]

There was no reply from Tormod, and no one here yet has answered the fundamental question this thread poses.

 

Re: What is "spacetime" really?

 

Spacetime is an element of the theory of general relativity (and many other theories) which model the universe.

 

If earth were the universe then spacetime would be the lines of longitude and latitude on the map of earth. Any and all human understanding of the earth is a map. We try to make the map as close to the "ontological earth" as possible. We try to make the map useful.

 

Be careful not to assume your ideas are building an earth... your ideas, Michael, are building a map like Einstein built and like Newton built before him. Your idea of "space" and your idea of "time" are parts of a map. Is there any way you can show us that your map fits the ontological earth?

 

~modest

[Michael Mooney]

Pyrotex:

 

The ontological reality can ONLY present itself to us as a philosophical insight.

It CANNOT be "observed". We CANNOT "perceive" the ontological universe as Michael has described it.

 

Epistemologically speaking, what we can *know* is not limited to what we can *percieve.* My life as a mystic is a testament (which you deny) to such knowing as is called gnosis. This is admittedly not presently "scientifically acceptable," but it represents a possibility which you flatly deny. (Empirical science is not the ontological "know it all" you believe it to be!)

 

In Wiki's intro to epistemology one finds the following (quite controversial!) section:

 

Main article: A priori and a posteriori (philosophy)

The nature of this distinction has been disputed by various philosophers; however, the terms may be roughly defined as follows:

 

A priori knowledge is knowledge that is known independently of experience (that is, it is non-empirical, or arrived at beforehand).

A posteriori knowledge is knowledge that is known by experience (that is, it is empirical, or arrived at afterward).

 

I have previously given the example of the holographic metaphor to attempt description of "a-prior knowledge." As the minutia "resonate" with the whole hologram, a miniature of the whole, mystic gnosis "resonates" in identity with cosmos as a whole, and enters "cosmic consciousness," not as a state of omniscience (which is impossible) but as awareness without the usually imposed and assumed boundaries, such as "my identity/consciousness" in contrast with "your identity/consciousness." Like the omnipresence of NOW, this omnipresence of consciousness becomes "self evident" in the state of transcendence which I have experienced for an hour a day for 40 yrs... which you again, as a scientific materialist *must* flatly deny. And I do not claim it as "scientific." Yet it is a way of *knowing* just as I *know* cosmos exists independent of all "percpetion" of it.

 

How can I *know* this if all knowing is dependent on perception? How, indeed. Yet you don't deny it either. You just say, 'yes, it's out there, but we can't know it as it actually is."

 

Well then, how do you even know there is an "objective cosmos" (as I call it) if all we can know is through our fallible subjective perceptions? Are you sure you are not, at heart a subjective idealist... even a solopsist?

 

The ontological reality can ONLY present itself to us as a philosophical insight.

It CANNOT be "observed". We CANNOT "perceive" the ontological universe as Michael has described it.

 

Yet we *know* it exists independent of our perception of it. How is that possible?

 

It's just that you are talking about the subjective universe that we can see, touch, smell, etc. Michael is talking about a Platonic Ideal -- the Ontological Universe -- the pure Beingness of the Existence of Reality Itself. This is philosophy, not physics.

 

What I know as in gnosis is not necessarily limited to Platonic Idealism. But the difference is beyond the scope of "the philosophy of science." Maybe a subject for a thread on transpersonal psychology... or "beyond theology... enlightenment."

 

You CANNOT observe the Ontological Universe. That would require that the speed of light be infinite, and consequently, that the energy density of the universe be infinite, which is obviously false.

 

Another subject for a thread on "enlightenment." It ain't science.... yet, as presently defined, but...

Just a priview of what might lie beyond, your materialistic worldview, Pyrotex:

 

A wise man once said, "Let your eye be single and the whole body will be filled with light."

The "single eye" here can be interpreted metaphorically as a single "I", one in cosmic identity. And "the whole body" can be interpreted as the whole cosmos, as "I Am One" with it... in gnostic resonant identity. Still not "science" but,... "there is more to (the universe) than your philosophy can dream of... Horatio. (Sorry, rough paraphrase, and I've forgotten the author.)

 

Now, I'm still not sure that Michael's secondary conclusions are correct, but I'm willing to grant him that the Ontological Universe does in fact exist, it's out there. We will never be able to "see" it, but it's out there. :D

 

So, again, how do you know its not all in your mind, all based on subjective perception... of nothing objectively existing at all. Just a guess? Prove it without reference to your (our) all too fallible perceptions.

 

Our "organs of perception", being as they are bound by the laws of physics, the constant speed of C, Special Relativity, etc, can ONLY perceive the "subjective universe". Mind you, everything YOU have said in response to Michael is absolutely True! :hihi: Nothing you have said is false.

You CANNOT observe the Ontological Universe. That would require that the speed of light be infinite, and consequently, that the energy density of the universe be infinite, which is obviously false.

 

Now, I'm still not sure that Michael's secondary conclusions are correct, but I'm willing to grant him that the Ontological Universe does in fact exist, it's out there. We will never be able to "see" it, but it's out there. ;)

 

How, now, again without reference what you have merely perceive. Yes it does get repetitive. But ain't it fun to consider the possibilities... Actualities in my experience.

 

Michael

[Pyrotex]

...the problem with this statement is that it assumes that the ontological universe is a different and other than the universe that we perceived. and the universe that we see is not a part of it. ....

:hihi:

 

I hate to be picky about this, but now that I understand Michael's point of view on this "Ontological Universe Thingie" (OUT), I find that I am "compelled" to help others understand it. :D

 

The OUT is exactly one and the same with the Perceived Universe Thingie (PUT).

 

The difference is, we can only observe the PUT. The PUT is what we observe.

 

It's like this: [Analogy] You are totally blind and find yourself in a strange house of unknown size. You are chained to an anchorbolt in the floor, and have only about ten feet of slack. Being a scientist, you immediately set out to "map" this house and its contents. You touch things, feel for walls and doors and furniture, all the while building up a mental "picture" of your surroundings. When you are at the end of your chain, you are reduced to "experiments" where you throw pingpong balls (you have these in infinite supply) in a certain direction and listen for their bounces, to determine if there are walls, or other objects "out there". In this fashion, you "observe" as much of your "universe" as you can. [/Analogy]

 

Now. ;) What if somebody suddenly turned on ALL the lights--and you could SEE!!!

 

In an instant, you would know where EVERYTHING was!!! We can even assume that the walls and floors are transparent, so you can even see into neighboring rooms, and the rooms upstairs!!! And since light is so fast, you see everything as it is NOW.

 

In the first scenario, you are observing the PUT. You are limited to what you can touch and bounce pingpong balls off of. And since PPballs travel so slowly, if one went through a closing door, by the time the PPball hit the floor beyond the door, and you heard the sound and said "aha, the door is open", the door might already be closed. You cannot know that everything stays where you think it must be.

 

In the second scenario, you are observing the OUT. Now you can see the doors opening and closing in real time, the cat going back and forth, the windows going up and down, and all in real time. In the Everywhere Eternal Now.

 

Now, let's go back to the real universe we live in. We can ONLY observe the PUT, due to the huge distances and the high speeds. Nothing is faster than light. We can never, never, never "observe" the OUT in "instant time". We can never, never, never see where everything is in the Everywhere Eternal Now. It is forbidden to us.

 

But we can think about it. We can posit its reality.

 

MM asked, "But how can we *know* it's real if we can't perceive it?"

 

I answer, "Hell, it just makes common sense, Michael. What's your problem?"

;) ;) ;)

[Michael Mooney]

Modest:

Is there any way you can show us that your map fits the ontological earth?

 

My last review above covered a lot of territory. Maybe you can address a few of my points above before you bat the ball back at me.**

 

I've just reviewed the axioms of Euclidean geometry, for instance (several times recently) as being clearly descriptive of all three well known spacial dimensions in the "real world." Then I've repeatedly asked proponents of a "4th spacial dimension" to "show me what that is in the real world." I get metaphors of expanding cubes and basically "b.s." about the fourth being 90 degrees from the obvious three dimensional volume or infinite space. Right, sure!

 

Then, in every argument for "spactime" it is assumed as an ontological medium on the grounds that gravity needs a medium besides empty space to carry its force, especially so to make light bend. And all acounts talk about "curved space" and "dilated time" as if the argument were over and settled.

I am here to inform y'all that it ain't!

Again, see my coments to Tormod in last post/review.

 

Again, see ** above. You habitually ignore and brush aside whole posts as you did here and put the challenge back on me.

Remember, space is empty until the theorist makes the argument for what "it" actually is, in the real cosmos.

Likewise "time." A very convenient convention for velocities and movement of all things. It does "take time." So then the mind automatically reifies "time" and then "it" dilates and such. Way more of an ontological assertion than, "Of course clocks slow down when... (detail specific conditions.)

 

It's your turn to answer a few of these points, dodger. :hihi:

 

Michael

[modest]

:umno:

 

I hate to be picky about this, but now that I understand Michael's point of view on this "Ontological Universe Thingie" (OUT), I find that I am "compelled" to help others understand it. :)

 

The OUT is exactly one and the same with the Perceived Universe Thingie (PUT).

 

The difference is, we can only observe the PUT. The PUT is what we observe.

 

If OUT is exactly one and the same as PUT and we observe PUT then we by extension observe OUT. This might be what Watcher is saying here:

 

...the problem with this statement is that it assumes that the ontological universe is a different and other than the universe that we perceived. and the universe that we see is not a part of it. ....

 

I like your analogy:

 

It's like this: [Analogy] You are totally blind and find yourself in a strange house of unknown size. You are chained to an anchorbolt in the floor, and have only about ten feet of slack. Being a scientist, you immediately set out to "map" this house and its contents. You touch things, feel for walls and doors and furniture, all the while building up a mental "picture" of your surroundings. When you are at the end of your chain, you are reduced to "experiments" where you throw pingpong balls (you have these in infinite supply) in a certain direction and listen for their bounces, to determine if there are walls, or other objects "out there". In this fashion, you "observe" as much of your "universe" as you can. [/Analogy]

 

Now. :) What if somebody suddenly turned on ALL the lights--and you could SEE!!!

 

In an instant, you would know where EVERYTHING was!!! We can even assume that the walls and floors are transparent, so you can even see into neighboring rooms, and the rooms upstairs!!! And since light is so fast, you see everything as it is NOW.

 

The physicist is mapping the house. He makes 2 floor plans—one with ping pong balls and the other with the light on. The question is essentially whether or not the 2 floor plans will differ from one another.

 

Unlike Watcher, I think they would differ. I'll first explain why I think they would differ and second explain which is the better choice as a floor plan.

 

If we abandon locality and say instant action at a distance or communication at a distance is possible then the constant c in the Lorentz transformations approaches infinity:

[math]\lim_{c \to \infty } \left[\mathbf{ x=\frac{x' + vt'}{ \sqrt[]{1 -\frac{v^2}{c^2}} }} \ ... \ t=\mathbf{\frac{t' + \frac{vx'}{c^2}}{ \sqrt[]{1 -\frac{v^2}{c^2}}}}\right] [/math]

and we get the Galilean transformations:

[math]x = x' + vt' \ ... \ t = t' [/math]

So when the physicist turns the lights on and he sees everything in the house communicated to him instantly then it's at least a fair assumption to think he will come up with a different floor plan. The mechanics of the house will be Newtonian rather than Relativistic (assuming mechanics are part of the floor plan).

 

So, the assumption that lights off represents the PUT while lights on represents OUT is probably a bad assumption. The physicist makes 2 maps and the question is which better represents the OUT ("Ontological Universe Thingie"). I contend that lights off will make the better map. The reason being: the lights are out in our universe. Imagining instant communication at a distance does not give us a 'realer' map—it just gives us a map that does not reflect what we know about the universe.

 

I hope I've communicated what I'm thinking well-enough that it not be misunderstood.

 

~modest

[watcher]

if, in fact, space remains the emptiness in between "things" and "time" merely the measure of selected "event duration" in an "always-now-everywhere" universe.

 

the always now everywhere universe is a problematic proposition.

are you familiar with einstein hidden variables,? he searched for it because he cannot accept that if there is no hidden variables, we have to stop thinking that the world is objective. and he doesn't like the idea. this is of course assuming that he understood the implication of QM during his time.

 

and if you aren't shock by it, this means that in every instant of time you called "always right now, our observable universe is incomplete.

 

so thought experiment of an eternal now that reveals the entirety of the universe is a fallacious proposition at least in physics since this eternal now can't be the same as a moment of time or an instant of time and therefore cannot be the same as time. it is more like timelessness. it is non existent and cant be a taken as a valid point of view in physics.

[modest]

I've just reviewed the axioms of Euclidean geometry,

Good. Euclid built his geometry with 23 definitions, five common notions, and five postulates (or axioms). The only difference between his geometry and that of Lobachevsky (or some other non-Euclidean geometry) is a difference in the 5th postulate. It is not (this is important) *not* possible to derive the 5th postulate (the parallel postulate) from the other axioms of Euclidean geometry. It is independent. This was proven by Eugenio Beltrami in 1868.

 

This means there is absolutely no way to say "here is what geometry is" and then come to the conclusion that Euclid's geometry is the consistent or correct geometry over Lobachevsky's or Riemann's geometry. They are all just as fundamental and internally consistent. As far as I know, the universe didn't hold a popularity contest between these fellas and decide Euclid won.

 

for instance (several times recently) as being clearly descriptive of all three well known spacial dimensions in the "real world."

This depends. I know it sounds like BS, but the geometry that represents the three spatial dimensions does not have to be Euclidean. If we include gravity in the geometry then it can be non-Euclidean.

 

The real world is not a geometry. As you correctly say, geometry is "descriptive" of the real world. Whichever geometry is best descriptive can be used and I do not like your a priori assumption that it must be Euclid's. If you've come to the conclusion that the real world must be modeled with Euclidean geometry then let us know what reasoning brought you to that conclusion.

 

Then I've repeatedly asked proponents of a "4th spacial dimension" to "show me what that is in the real world." I get metaphors of expanding cubes and basically "b.s." about the fourth being 90 degrees from the obvious three dimensional volume or infinite space. Right, sure!

 

I agree. A metric that has 4 spatial dimensions would not seem to describe our universe very well.

 

Then, in every argument for "spactime" it is assumed as an ontological medium on the grounds that gravity needs a medium besides empty space to carry its force, especially so to make light bend.

I don't know if "gravity needs a medium", but I think it is safe to assume there is some connection between bodies that affect one another gravitationally. Can this connection be empty space? If general relativity is interpreted rather literally then empty spacetime is indeed the connection that ties things together.

 

And all acounts talk about "curved space" and "dilated time" as if the argument were over and settled. I am here to inform y'all that it ain't!

 

A distinction needs to be made. "Curved space" and "dilated time" refer to physical observations which have indeed been confirmed and settled. They are shorthand which I will define more explicitly now since you are apparently not taking them as such:

 

Confirmation of curved space:

Given what we know about physics of photons and mass and whatnot, if straight lines at the sun are considered straight to the earth and to infinity then light passing the sun on the way to earth is expected to be deflected by a certain amount. If those spatial lines are allowed to curve as general relativity describes then light should be deflected twice as much as was expected with straight lines. Detailed measurements have been done and they have confirmed the not-straight-spatial-line prediction.

 

Confirmation of dilated time:

If there is a variable "time" which represents the reading on a clock or the evolution of decaying particles (or however else you want to describe duration) then that variable (t) is predicted to change according to the relationship [math] dt' = \gamma dt[/math] where t is that variable time and gamma depends on velocity and the universal constant c. Wherever and however this has ever been measured, it has been found true.

 

That's what "confirmed prediction" means. "Curved space" and "dilated time" being confirmed experimentally and observationally is shorthand for what I just wrote. Now then... what does that prove about the ontology of elements "time" and "space"? I don't think it necessarily *has* to *prove* anything about their ontology. What these confirmed predictions mean is that given a certain definition of time and space—time will dilate with velocity and space will curve with mass.

 

I personally like the definitions of time and space which lead to those conclusions. They are intuitive and useful. But, if you want to propose some different ontological elements besides time and space or if you want to give them different definitions then by all means...

 

But, simply denying that time and space exist or defining them as "no-thing-ness" doesn't get you anywhere. You can continue to repeat that ad nauseum and it won't advance this discussion. You need to start with your nothingness ontology and make them into a working description of the universe. In other words: "use it to make some physics".

 

Remember, space is empty until the theorist makes the argument for what "it" actually is, in the real cosmos.

This is just not logical. You assume the property "empty" belongs to "space" before space is defined. You make the argument and theorize that there is "space" which is explained to be "empty" without or before the theorist makes the argument. Well... you are a theorist and you just made an argument.

 

Your inclination to believe you are describing the state of the real world apart from any human description is very odd.

 

Likewise "time." A very convenient convention for velocities and movement of all things. It does "take time." So then the mind automatically reifies "time" and then "it" dilates and such. Way more of an ontological assertion than, "Of course clocks slow down when... (detail specific conditions.)

 

Saying "Of course clocks slow down when... (detail specific conditions.)" is not an ontology at all. It would be what is called a physical law. Under X conditions Y will happen. Newtonian gravity is a physical law. There is no explanation and no ontology to a law.

 

It's your turn to answer a few of these points, dodger. ;)

 

A good amount of very capable people have joined this thread recently so I intend to step out of the way. I will say as a recommendation, you might take care to appear more appreciative of the feedback they give you. For nearly 500 posts you've had multiple professional physicists and experts in philosophy give you honest and thorough feedback. I won't say how it appears you've taken that, but it's something you might want to think about.

 

~modest

[Michael Mooney]

Watcher:

..."as to curved space. please understand that the geometry of curved space is done in 4d."

 

No comprehension of ontology here apparent. "Curved space" is the subject debated. Asserting curved space as a proven or given avoids the debate, saying 'science proves you wrong... period... prior to even understanding the nature of the inquiry.' (fictional quote.)

 

Same with assuming "4-D."

I destroyed your argument depending on the expanding cube computer graphic. And the ''90 degree out" rule for a fourth dimension is totally without "logical necessity." I'll explain that.

 

(Ifall three Euclidean dimensions of space "grow" at right angles to the last...and they do!... then that justifies a fourth dimension at a 90 degree "angle" to volume ... or infinite empty space. So then their could be a fifth spacial dimension 90 degrees to the fourth... etc... until you reach the total absurdity of 11 to 26 "dimensions" in the fantasy physics of "string/M-theory. It just doesn't cut the ontological mustard!

 

We all "get" the three axes of 3-D space. But there are no more "axis" for "space." Three covers all directions... line, area, volume... and I've added infinite volume, just because I can... and there can be no "end of space."

There is no further "dimension to space." All three axes are obvious, and positing a forth (90 degrees in relation to what fantasy?) is itself a fantasy. Cool computer graphics have fooled you into discarding your own process of rational thinking... I would guess! You are not alone. Most of "science by the Book" is with you. I am not intimidated.)

PS:

Thanks for stepping aside, Modest. Your last post is an excellent example of your refusal to answer even a single point I made in the "historical post" just rendered... which you totally dodged, yet again.

Then you go into superior attitude mode, as Teacher (a Moderator, after all!) and lecture me some more as to what science has confirmed that I don't yet understand.

 

You do not reference to the SR and GR quotes I shared and my commentaries on them. I honestly do not believe you are capable of discerning the distinctions I have made in my critique of relativity within the "visionary" paradigm I have presented here. (Your bigotry against mysticism is all too apparent. )

 

Michael

[watcher]

michael,

 

i have finally find a way to grok with your thought experiment of seeing the universe in its entirety in the present moment you call now. pyrotex provided the nice analogy here

 

It's like this: [Analogy] You are totally blind and find yourself in a strange house of unknown size. You are chained to an anchorbolt in the floor, and have only about ten feet of slack. Being a scientist, you immediately set out to "map" this house and its contents. You touch things, feel for walls and doors and furniture, all the while building up a mental "picture" of your surroundings. When you are at the end of your chain, you are reduced to "experiments" where you throw pingpong balls (you have these in infinite supply) in a certain direction and listen for their bounces, to determine if there are walls, or other objects "out there". In this fashion, you "observe" as much of your "universe" as you can.

 

Now. What if somebody suddenly turned on ALL the lights--and you could SEE!!!

 

In an instant, you would know where EVERYTHING was!!! We can even assume that the walls and floors are transparent, so you can even see into neighboring rooms, and the rooms upstairs!!! And since light is so fast, you see everything as it is NOW.

 

and this

 

You CANNOT observe the Ontological Universe. That would require that the speed of light be infinite, and consequently, that the energy density of the universe be infinite, which is obviously false.

 

it is implied in his posts that it is possible (as a thought experiment) to see the whole universe at once simultaneously only if the speed limit "c" would near infinite speed. this is a logical necessity of seeing the universe all at once, other wise your thought experiment without setting the speed limit to infinite is only arbitrary and has no validity..

 

now if we set the speed limit at infinite velocity , we need to ask what would happen to our equations. for example, at infinite velocity, our spacetime interval would change, the potential energy per unit mass will change at even planck's constant will change, iow, setting a different speed limit for our universe changes its constant.

 

changing these constants will change the very structure of the atom and with it the whole universe as we know it. so when we often the light of this dark room, we may find a totally different room from the one we are familiar with before. the conclusion is that velocity changes the universe, space, time and all.

 

now suppose that there exists two speed limits in the universe, one is c and the other is 2c. if a physicist make measurement in universe one, again space is empty between points , shortest distance straight line. he might have to treat time as imaginary and still get the right answers. same with physicist in universe of 2c. euclidean space will suffice. but what if the 2 physicists want to measure one point in spacetime 1 and another point 2 in space time 2. using euclidean space in their calculations, they can't find a solution but when then use non - euclidean, they got the right answer ...hehe i know it is a self serving thought provocation

[Moontanman]

 

now if we have to set the speed limit at infinite velocity , we need to ask what would happen to our equations. for example, at infinite velocity, our spacetime interval would change, the potential energy per unit mass will change at even planck's constant will change, iow, setting a different speed limit for our universe changes its constant.

 

Can you tell us what this constant would be if c was infinite?

 

to change these constant will change the very structure of the atom and with it the whole universe as we know it. so when we often the light of this dark room, we may find a totally different room from the one we are familiar with before.

 

How would the Atom "look" if the speed opf light was changed to infinite? What else would be different and in what way?

[modest]

michael,

 

i have finally find a way to grok with your thought experiment of seeing the universe in its entirety in the present moment you call now. pyrotex provided the nice analogy here

 

and this

 

it is implied in his posts that it is possible (as a thought experiment) to see the whole universe at once simultaneously only if the speed limit "c" would near infinite speed. this is a logical necessity of seeing the universe all at once, other wise your thought experiment without setting the speed limit to infinite is only arbitrary and has no validity..

 

now if we set the speed limit at infinite velocity , we need to ask what would happen to our equations....

 

Yes, indeed... That's very much what I was thinking in post #467.

 

Apparently, a person can derive a set of transformations by postulating homogeneous space and time as well as isotropic space along with the principle of relativity. When the transformations are derived this way it is not necessary to postulate the invariance of the speed of light. This should be very insightful as far as Pyrotex's thought experiment.

 

The method of derivation is examined exhaustively in:

• Reciprocity principle and the Lorentz transformations (1968) and a less extensively in,
  
• Faster-than-c signals, special relativity, and causality (section 2.1)
  

 

With isotropy, homogenity, and the principle of relativity they derive:

[math]x = \frac{x' + vt'}{\sqrt{1+ K v^2}}[/math]

[math]t = \frac{t' + Kvx'}{\sqrt{1+ K v^2}}[/math]

K is a velocity-independent constant with dimensionality [math]1/v^2[/math] that arose naturally from the derivation. We can constrain it to be negative or zero by the following reasoning:

It now remains to show that K can only take zero or negative real values. For if K is positive, the expression leads to the physically absurd result that two velocities in the same direction may add to a velocity in the reverse direction.

 

http://www.hep.princeton.edu/~mcdonald/examples/mechanics/lee_ajp_43_434_75.pdf

 

If K is zero then our transformations become Galilean,

[math]x = x' + vt' [/math]

[math]t = t'[/math]

With instant communication at a distance possible and simultaneity universal.

 

If K is negative then we get a Lorentz transformation where some speed (to be determined which exact speed) is invariant. We normally call that speed c, and setting c = (-K)^(-1/2) the transformations become:

[math]\mathbf{ x=\frac{x' + vt'}{ \sqrt[]{1 -\frac{v^2}{c^2}} }} [/math]

[math]t=\mathbf{\frac{t' + \frac{vx'}{c^2}}{ \sqrt[]{1 -\frac{v^2}{c^2}}}}[/math]

There is now an invariant speed C which all observers will measure. No frame can exceed this speed relative to any other frame.

 

So, the thought experiment about seeing the universal "right now" essentially demands Newtonian/Galilean mechanics/relativity. Essentially, if the ontology of the universe includes a universal present moment, space and time are homogeneous, space is isotropic, and the principle of relativity is valid then we should expect the invariant speed to be infinite—or basically, there wouldn't be one.

 

We know from experiment that the invariant speed is not infinite, but just under 300 million meters per second. So, the thought experiment and concepts proposed don't seem to build our universe.

 

~modest

[AnssiH]

I have to say I am quite puzzled by your reply. Decided to give it one go anyway :)

 

Sorry if I'm restating something that's already been beaten to death, I admit I have not read through the whole thread.

 

I think we all understand 3D space and the concept of time as the motion or "duration of event" factor in the cosmos... i.e., dynamic, not static.

 

A point is a locus. (no dimension) A line is a distance, one dimensional. A plane is an area, two dimensional. A volume is three dimensional space. It can either have a shape or be infinite space with no boundary in any direction (no "end of space.)

 

This clearly describes the real world/cosmos.

 

Yes we all understand 3 dimensional euclidean spaces easily. And yes, that form clearly describes reality in very useful way as we all succesfully use that interpretation every day.

 

But here's my first point of confusion; I don't know if you are jumping to conclude that us being so fluent in understanding reality in this form also means reality is ontologically a 3D euclidean space?

 

I mean, surely you can also say that relativistic spacetime describes reality (and I mean that without implying any ontology to "spacetime" itself). But the point you seem to focus on is "what is the form we are intuitively fluent with"? That by itself leads to some interesting epistemological questions, but I'd advice you to not jump into any ontological conclusions.

 

While we intuitively and fluently see reality as 3 dimensional euclidean space, there must exist a great number of definitions (one way or another) in order for us to interpret patterns in form of objects that move in such a way that we can say they operate inside an euclidean space.

 

We also intuitively and fluently interpret some patterns as sounds and language, but that doesn't mean that ontologically there exists sounds and language. It's just, whatever it is that we interpret as sounds... ...or whatever we interpret as objects in space.

 

This all reminds me of:

Definitions on space

 

I think you've said "space is what is empty" a few times here, and I would advice you to weight your thoughts really carefully right there as well, as you need fairly carefully define what you mean by empty. (And that will lead to all the questions of how space, and "straight lines" through space are measured and what is the associated naive realistic idea in our head)

 

How then is the leap made to four spacial dimensions?

How is it that in non-Euclidean "space" a straight line is no longer the shortest distance between two points? Drawing it on a spherical surface is cool, but then the shortest distance (in the "real world") is through the sphere... like the needle I put through the arched paper in that argument awhile back. (Not refuted... no reply.)

 

Then on to parallel lines... which converge/diverge in non-Euclidean "space." How is that "really?"

 

Then there is the "hypercube" which, in the link (by Watcher) above was illustrated as merely an enlargement of the original cube. This does not establish a "real fourth spacial dimension."

 

Same with all the different "shapes of space"... spherical, parabolic saddle or inverted saddle... torus, etc. What is it exactly in the "real cosmos" that has shape?" It is the "stuff" *in space* in all of its various forms, or taken as a whole as "the cosmos" expanding out *into space.*

 

I'm assuming you know the "straight line no longer being the shortest distance" etc, these are simply the logical consequences springing from whatever exact definitions have been given for whatever space is under discussion.

 

I'm guessing the point you are trying to make here is simply that no one is able to visualize or intuitively understand 4 spatial dimensions and/or non-euclidean spaces in their head. That is of course true. What is there to conclude from that fact?

 

These are the ontological challenges I present in this thread.

And, "Oh, it's just a theoretical matrix" does not answer the ontological challenge.

 

I'm not sure what else you would want to hear. I think "it's just a theoretical matrix" means; "it's not an ontological construct, it's an epistemological construct, inside our head."

 

We can imagine all kinds of constructs in our head, and the only ontological challenge involved there would be when a "theoretical matrix" yields valid predictions of reality. Whatever the essential relationships of that theoretical matrix are, they can be expressed in many different sorts of spaces and forms. In the case of relativistic spacetime, the logical (epistemological) reasons of it being valid can certainly be investigated, without knowing anything about the real ontological form of what we are investigating.

 

I guess you should be interested of the epistemological question; why is 3 dimensional euclidean space so intuitive for us? I think there was some interesting commentary about that issue at:

http://hypography.com/forums/philosophy-of-science/18619-why-should-universe-appear-three-dimensional.html

 

I have to say it was really hard to try and figure out what you meant to say really, so my apologies if I'm reading you completely wrong.

 

-Anssi

[Michael Mooney]

Modest,

I must, after all clarify a few of your misconceptions as stated in your last post to me.

 

You wrote:

"Good. Euclid built his geometry with 23 definitions, five common notions, and five postulates (or axioms). The only difference between his geometry and that of Lobachevsky (or some other non-Euclidean geometry) is a difference in the 5th postulate. It is not (this is important) *not* possible to derive the 5th postulate (the parallel postulate) from the other axioms of Euclidean geometry. It is independent. This was proven by Eugenio Beltrami in 1868.

 

'This means there is absolutely no way to say "here is what geometry is" and then come to the conclusion that Euclid's geometry is the consistent or correct geometry over Lobachevsky's or Riemann's geometry. They are all just as fundamental and internally consistent. As far as I know, the universe didn't hold a popularity contest between these fellas and decide Euclid won."

 

Most of us are probably familiar with Euclid's "definitions, notions, and postulates." I know I am. But you insist on lecturing me anyway, as usual, on what I already know.

I've made no claim that the parallel line postulate is based on previous postulates.

But it is impossible to make an ontological case for parallel lines converging or diverging (as in non-Euclidean "geometry") in the "real world"... or for the shortest distance between two points being other than a straight line. Think "real world" as in "ontology" rather than "according to a metric based on curved space..." etc.

 

Lobachevsky's or Riemann's geometry is based on the the latter "metric" the ontology of which is the subject of this thread's challenge!

 

Ontology is not a "popularity contest" between belief systems. If you apply epistemology to non-Euclidean geometry, you come up with "Here is the theoretical metric... no referent in the real world required." Well ontology requires such referents to establish the reality of "things" like curved space and dilating time as existentially extant, i.e., as actually existing in "the real world."

 

You continue:

"I don't know if "gravity needs a medium", but I think it is safe to

assume there is some connection between bodies that affect one another

gravitationally."

 

(Notepad format... sorry)

 

Gravity is an undeniable force. It *is* the "connection" without

 

"making something out of nothing" (space.)

 

Modest:

"Can this connection be empty space? If general relativity is

 

interpreted rather literally then empty spacetime is indeed the

 

connection that ties things together."

Me:

"Empty spacetime??"...Space being empty and time not an extant entity

 

either? What then does the word "spacetime" add to the emptiness

 

through which the force of gravity travels, connecting masses and

 

pulling on light?

 

Modest:

 

"That's what "confirmed prediction" means. "Curved space" and "dilated

 

time" being confirmed experimentally and observationally is shorthand

 

for what I just wrote. Now then... what does that prove about the

 

ontology of elements "time" and "space"? I don't think it necessarily

 

*has* to *prove* anything about their ontology. What these confirmed

 

predictions mean is that given a certain definition of time and

 

space—time will dilate with velocity and space will curve with mass."

 

So this is your "take" on the ontology of space and time... that given

 

a certain definition of time and space, time will dilate with velocity

 

and space will curve with mass.

 

You don't have a clue to what "ontology" is... the study of what

 

actually exists, not what are the consequences of our "given

 

definitions" of time as something besides a defined concept... something

 

that can actually slow down... as distinct from the rate of atomic

 

decay slowing down... and space as "something that curves as influenced

 

by gravity." You have never in this thread indicated that you understand the difference which I have again contrasted above.

 

Modest:

"I personally like the definitions of time and space which lead to those conclusions. They are intuitive and useful. But, if you want to propose some different ontological elements besides time and space or if you want to give them different definitions then by all means..."

 

This is ontology, Modest. Definitions do not create extant entities in

 

the real world. Atoms decay at different rates under the famous clock

 

experiment conditions. No doubt about it... no "time" required as

 

"dilating" in this observation of differences in atomic decay.

 

Likewise "space." Gravity is mass attracting mass, and deflecting

 

light's path of momentum too. No "curved space" ontologically required.

 

See?

No, you obviously don't see, as in evidence in your next paragraph:

 

"But, simply denying that time and space exist or defining them as

 

"no-thing-ness" doesn't get you anywhere. You can continue to repeat

 

that ad nauseum and it won't advance this discussion. You need to start

 

with your nothingness ontology and make them into a working description

 

of the universe. In other words: "use it to make some physics".

 

MM:"Remember, space is empty until the theorist makes the argument for

 

what "it" actually is, in the real cosmos."

 

Your "make some physics" is a very telling phrase. Physics is our attempt to describe the real world with in a way that helps us understand and predict it. I have granted the predictive power of relativity... lets just say "a lot"... in this thread, even as I challenge the ontology of curved space and dilated time as part of relativity.

 

Modest:

"This is just not logical. You assume the property "empty" belongs to "space" before space is defined. You make the argument and theorize that there is "space" which is explained to be "empty" without or before the theorist makes the argument. Well... you are a theorist and you just made an argument."

 

 

Your inclination to believe you are describing the state of the real

 

world apart from any human description is very odd."

 

You really don't get what a logical argument is. If a "spacetime"

 

theorist is arguing that space is something besides the emptiness which

 

is defined as no-thing-present or the no-thing-ness between "things",

 

then the "burden of proof" is logically on the relativity theorist to

 

give ontological evidence for its "existence" as something rather than

 

nothing. Get it yet? You seem to believe that ontology is making things

 

real "by definition." It isn't.

 

Modest:

" Saying "Of course clocks slow down when... (detail specific

 

conditions.)" is not an ontology at all. It would be what is called a

 

physical law. Under X conditions Y will happen. Newtonian gravity is a

 

physical law. There is no explanation and no ontology to a law."

 

Ontology is the philosophy of what is real. Epistemology is the tool

 

kit for knowing what is real and examining how we know what we know. Do you "know" the difference?

I think not. We *know* that "clocks slow down...".etc. Relativity theorizes that "time slows down." That makes

 

an entity out of time based on no evidence but the slowing clocks.

The latter is an ontological error... my point throughout this thread.

 

Modest:

"I will say as a recommendation, you might take care to appear more

 

appreciative of the feedback they give you. For nearly 500 posts you've

 

had multiple professional physicists and experts in philosophy give you

 

honest and thorough feedback. I won't say how it appears you've taken

 

that, but it's something you might want to think about."

 

I find it amusing that you think I should "take care to appear more

 

appreciative..."

This thread is a direct challenge to the ontology of "spacetime" and

 

the mainstream epistemological toolkit which relativity applies to make

 

its theoretical *metric* take on the "reality quotient" of the material

 

*metric* of "the real world", i.e., that "time, space, and spacetime"

 

are "real" in the same sense that the cosmos and all its actual

 

contents are "real."

I am not intimidated by the "authority figures" to which you appeal,

 

even if there is a consensus among them as establishing "mainstream

 

science." Rather I challenge the assumed validity of that consensus.

 

Michael

[modest]

Michael, you're just arguing for the purpose of arguing now. I won't engage you because there's no utility in it. You're also being quite rude. Why would you consider telling me I don't know what ontology is when I'm the person who told you 6 months ago that your question and your argument was one of ontology? You got mad at me then for telling you the OP was a matter of ontology and now you're saying I don't understand that the OP is a matter of ontology. Think about that... you're just waving your hands and yelling for the purpose of waving your hands and yelling. I'm not interested.

 

As you continue your discussion with others in the thread please keep these site rules in mind:

 

5. Statements like "I just know that this is the way it is"... are considered ignorant and might be deleted. Likewise, users who have an obvious agenda behind the majority of their posts may be banned.

 

7. If you ask for opinions, respect the replies you get.

 

9. Do not endlessly show us that *your* theory is the *only* truth. And don't follow this up by making people look stupid for pointing out that there are other answers, especially if they provide links and resources. It will get you banned!

 

10. Rude and offensive behaviour is not tolerated and might lead to instant banning (at the discretion of the forum staff). This includes forum posts, e-mails to users, messages in the chatroom, and private messages.

 

~modest