What is "spacetime" really?

[Erasmus00]

Michael, can I suggest the following? sit down with your cosmic observation frame, and starting from this assumption start deriving some physical consequences. What you will find is that you CANNOT, from this frame, create a self consistent physics that also describes reality. Try it.
-Will

[Essay]

Hiya Michael,
Good answers to all those points. The ocean surface was a pretty lame example, but in both cases (ocean + strong gravity field) you did need to invoke your "cosmic perspective." At least with the gravity example, I did specify local perspective....

I think I've kept up with all the posts here, but which post # is the specific "thought experiment" that you're talking about. I'll go look at that again.
===

...but for now I'll just comment on these points here:

"Such cosmic perspective is not the relative perspectives of different observers in different locations. Yes now is simultaneous and omnipresent from cosmic perspective." -MM

I used "simultaneity" to speak to the interactions between things and the measurements that can be made on these things.
Sure (I think anyone would agree) from a cosmic perspective there is the universal now; but in terms of a scientific perspective, the term "now" just isn't very useful.

I guess I don't understand how your observation that the "Cosmic perspective "sees" cosmos as a whole as from the perspective of one omnipresent observer" is useful to any real observations, measurements, or studies of interactions that can be made.

I realize you're familiar with SR and GR, but when you say that,
"In my proposed cosmology, Space, being emptiness, is the endless void and not effected by that which explodes and implodes *in it*...."
aren't you just back to the Newtonian version of reality?

You ask me:

Originally Posted by Michael Mooney

So, Essay, I must turn it back to you. Can you imagine the cosmic perspective again presented here with space being true emptiness and all observable phenomena being cosmos, actual "stuff" *in space? If so, no-thing-ness remains emptiness with *no properties at all* while all "properties" per se belong to the "stuff-in-space."

YES!
Of course I can. Everyone can. It is "the common sense of everyday 'middleworld'."
It is a view that contradicts nothing with which we are familiar (in our limited experience).
Even a 6-year-old has enough experience to understand this common-sense view of reality.
That is what I thought you must picture, and is why I wrote "...rather than just expanding out into and through the void," ...after asking if you could imagine my scenario.
===

So does this mean that semantics is the problem?

You say:

Originally Posted by MM

...while all "properties" per se belong to the "stuff-in-space."

So are you talking about fields (emmanating from the "stuff-in-space") as being the source of these "properties?"
===


...and in which post did somebody already talk about Field Theories?"

Thanks MM!
bbl

~ SA

[Michael Mooney]

Modest,
Your last reply to me was a blatantly pompous appeal to authority totally ignoring my opening statement:

In answering, you may correctly assume that I have thorougly studied the background of the "spacetime" component of relativity theory. Yet the actual nature of the "medium" (or whatever it is *supposed* to be) has never been explained to my satisfaction.

.... and many similar references to my understanding of GR and SR, most recently in reply to Essay:

I have in fact studied both GR and SR in some depth, sans mathematical expertise. They are not "new ideas." By the same token, I am, in this thread, asking for folks to give my "thought esxperiment" in "cosmic perspective" a fair chance as perhaps a "new idea" transcending the thought experiments central to relativity, especially as it pertains to local perspectives as seen by different observers. (Cosmic perspective "sees" cosmos as a whole as from the perspective of one omnipresent observer. (No religious connotations intended.)

Yet you say:

In order to understand the assumptions and statements I've made regarding the analogies of shape and
curvature, it would be necessary to understand the observations of relativity.

... and cite sources which I have gone far beyond in the course of my study.

Then you respond to my reiteration of my familiarity with relativity:

The cosmic perspective which I call objective * is not limited to relativity theory* (see my post #114 with the briefest summary of my understanding of GR and SR) is that It is always now everywhere. This has nothing to do with observations from local perspectives limited by lightspeed.

.... saying:

This has a name. It is called Galilean (or Newtonian) relativity. It's nothing new, and it has been proven wrong....

(Your first pompous-appeal-to-authority.)

I am familiar with Galilean/Newtonian relativity... specifically with the statements in the links you cited above:

Albert Einstein's central insight in formulating special relativity was that, for full consistency with electromagnetism, mechanics must also be revised such that Lorentz invariance replaces Galilean invariance. At the low relative velocities characteristic of everyday life, Lorentz invariance and Galilean invariance are nearly the same, but for relative velocities close to that of light they are very different.

(Sartori's) Understanding Relativity is a textbook....
It begins with Galilean relativity and the Michelson-Morley experiment, then presents the basic postulates of relativity, Lorentz transformations, space time diagrams (including Loedel diagrams, which were new to me), and some of the standard "paradoxes".

You continue to misunderstand my fundamental challenge here. Given that " Lorentz invariance (claims to replace) Galilean invariance. (and that)... "At the low relative velocities characteristic of everyday life, Lorentz invariance and Galilean invariance are nearly the same..."

The Lorentze transformation *assumes* time dilation and space curvature, both of which are clearly cases of erroneous reification, as I have meticulously argued in this thead. I have recognized the improvements in gravitational predictability via relativity with alternative explanations for the medium between gravitation generating masses (i.e., across *empty" space rather than "bending space" and "dilating time." You conveniently ignore all my arguments in this regard and glibly state that Galilean/Newtonian relativity" has been proven wrong"... without specifics to back up the claim.

You cited "one of your favorite philosophers" (who I reviewed in depth) who brought some serious criticisms against the transition from Euclidean to non-Euclidean space *upon which the Lorentz invarience ... and transformations... are based, yet you now sweep those (and my) objections under the rug as having been debunked for a hundred years now.

You say:

Relativity does not demand there be "time between past and future".

This is totally bogus. "Presentism", as you know is the *realization* that "time" is a human artifact, that, indeed "it is always now... everywhere." "Time dilation" is therefore a reification of time and a central principle of relativity.
To my:

Time is indeed the observed duration of a given "event",

...
you replied:

An event in spacetime and an event in philosophy has no duration.

I use "event duration" in its obvious meaning of "elapsed time" between the beginning and ending of observation of a designated "event" and have given many examples of such "events", from the 8 minute journey of sunlight to earth to a day, a year and a complete cosmic "bang/crunch" cycle.
I understand the usage of "event" in the "spacetime" paradigm as locating a phenomenon by its three spacial and one temporal coordinates. Please get over your condescension based on "correct scientific usage" as so superior to my general, common sense usage of such terms as "event duration!"
You say:

Endless" and "empty" do not explain space. An object has height, width, and depth. "Endless" and "empty" don't explain such an object. They don't describe the relationship two objects with height, width, and depth have with one another. "Empty" doesn't explain or describe distance and certainly doesn't explain and describe gravity or motion.

What amazing and arrogant condescension! Everyone with a brain understands 3-D space and the common usage of "time" as a "fourth dimension.
We already went a couple of 'rounds' on your insistence that space can not be simply the void without objects. I have never claimed to know how gravity works across empty space, for instance, but only that positing a mysterious medium to convey forces across space adds nothing to our understanding of the forces in question. The "objects" in space are the proper "objects" of scientific study, not some replacement for the old "aether" theory of transmission.

Light years (seconds, minutes, etc.) describe distance very well without such a mysterious medium as spacetime between "events." So do miles, kilometers, etc. Positing "spacetime" (instead of "aether" doesn't "explain" gravity or motion either.

Time dilation is proportional to relative velocity, not acceleration. So, time dilation cannot be an effect of inertial forces

Prove it. "Time" is not "real." (See above, and my many references to the omnipresent now in relation to event duration (time.)
Of course you are consistently referring to "time dilation" as a given... long ago "proven" and no longer deserving of thoughtful consideration.
The actual difference in forces upon the speeding clock and the control clock, in all cases, is that the former has been "forced" to speed up and slow down, both changes in inertia. I suspect that human metabolism also slows down under exposure to the forces of acceleration /deceleration.

don't mean this as a criticism, but you appear not to understand the most basic concepts of relativity. If you don't understand why there is no absolute distance between the earth and sun then how can you object to the distance being relative?

More condescending arrogance. (Not criticism, of course.)

I understand and disagree. (You give lip service to questioning authority, as per the author of the ontology piece we both like)

I understand that from cosmic perspective, or even a deep space photo of sun and earth that there are are approximately 93 million "miles" (however many kilometers), each standardized earth-commensurate measures of distance. between the two bodies. You can do "thought experiments with a "photon's experience of 'no time or space' in its travel until you talk yourself out of this objectiv measure of the distance, but it remains all in your head, while the actual distance is ontologically real.

Your claim has been considered by everyone. It was the default scientific position until 100 years ago. It has been argued on this forum by scores of people. It is called Galilean invariance or absolute Newtonian space, and it has been proven wrong experimentally. No one is failing to grasp what you're saying, we simply know it is wrong.

Everyone? Really! The epitome of scientific appeal-to-authority arrogance!
Please review my post critiquing of the transition to non-Euclidean geometry, and the attending critique of the limits of math as a descriptive tool of observable cosmos... as the assumed basis fo rthe "proof" you are claiming.
Hope to get to other replies soon.
Michael

[Michael Mooney]

Erasmus:

Michael, can I suggest the following? sit down with your cosmic observation frame, and starting from this assumption start deriving some physical consequences. What you will find is that you CANNOT, from this frame, create a self consistent physics that also describes reality. Try it.

What kind of physical consequences.are you suggesting. That masses pull on each other as per Newton's law and that there are anomalies in Mercury's orbit better explained by the math of general relativity than Newtonian relativity. That they are the same but for phenomena approaching lightspeed.
That absolute cosmic" time" (actually timelessness) transcends observations limited by lightspeed ?

I think that science will soon find the bridge between the quantum effect of interaction between entangled particles *at a distance* and masses' pull on each other *at a distance* without positing the miracle-fabric "spacetime" as a medium required for these forces.

Maybe if you were more specific about what I CANNOT create as a physics which describes reality...
Michael

[Michael Mooney]

Essay,
My original presentation of the "cosmic perspective" (and timelessness in the universal now) was early on but irrelevant if you dismiss my reiteration of it as below:

.... Can you imagine the cosmic perspective again presented here with space being true emptiness and all observable phenomena being cosmos, actual "stuff" *in space? If so, no-thing-ness remains emptiness with *no properties at all* while all "properties" per se belong to the "stuff-in-space."

... with the following brush-off:

YES!
Of course I can. Everyone can. It is "the common sense of everyday 'middleworld'."
It is a view that contradicts nothing with which we are familiar (in our limited experience).
Even a 6-year-old has enough experience to understand this common-sense view of reality.
That is what I thought you must picture, and is why I wrote "...rather than just expanding out into and through the void," ...after asking if you could imagine my scenario.

"Middleworld" indeed! Do you think that a six year old understands that all matter in the cosmos can not be contained in a point of no volume. Maybe. Can you? Do you think that the ontology of truly empty space, "the void" is now obsolete, replaced by the "spacetime continuum" which inflates (faster than light after the "bang") and then magically produces all all cosmic material "later on" and the "nothingness" of space recedes with the expansion of the cosmos? I imagine your scenario as positing a reified version of space with the properties of expandability, curvature, etc... all the "blessings" of non-Euclidean space as tailored to all theories supposedly debunking all Euclidean based cosmology. (Observe-ability or making sense no longer a scientific requirement as long as the math works out to fit the theoriies. See how bazaar M-theory is with between 11 and 26 "dimensions"... but the equations really impress the mathematicians who "understand" the theory. )

So are you talking about fields (emanating from the "stuff-in-space") as being the source of these "properties?"

Yes, without the "medium" between required by scientific materialism.

aren't you just back to the Newtonian version of reality?

Not quite. Newton didn't "like" "action at a distance" either. See my comments above to Modest comparing Newtonian relativity and general relativity.
The advantage of the latter is in dealing with *extremely* large scale gravitational effects and relative observation of events dependent on lightspeed.
I *know* that gravitational force is *steady* among all masses but of course decreasing in force with the square of the distance between them . However *changes in gravitational force" travel (through the void of space) at lightspeed. (See the Homann observations of the periodic Sirius A and B alignment as slowing earth's rotation speed.)

and in which post did somebody already talk about Field Theories?"

I dunno, but what kind of field do you think transmits information *instantaneously* between entangled particles which are quite far apart... no limit yet found? Hmmm... looks like that old bugaboo "action at a distance" rearing its ugly head again!

Gotta go. See ya later.
Michael

[Essay]

Hiya Michael, ...thanks for the nice reply....

Sorry... wasn't meant as anything ...anymore than asking me if I could imagine....
But I really did enjoy your "Middleworld" indeed! paragraph. ...good motivation!

Regardless of what a kid might know about geometric points, I didn't meant to get into a thing about a dimensionless point (and I did soon change to calling it a "spot").

But it got me thinking about the "infinite density" description.

I was thinking that, viewed from "outside," our current universe might still appear to be infinitely dense.
It might even still appear to be pointlike or "a ball of whatever size of matter compacted as much as possible, but short of "infinite density."

It'd be pretty hard to measure ...and all fairly relative....
===

You ask:
"...what kind of field do you think transmits information *instantaneously* between entangled particles which are quite far apart... no limit yet found? Hmmm... looks like that old bugaboo "action at a distance" rearing its ugly head again!" -MM

Yes, well this is why I think everything is still touching, and that spacetime is a derivative effect, an illusion, or an artifact based on the interaction of all those still touching things.

Somewhere... they're still all touching... whether it is through other dimensions, or within Mbranes, or within the mind of God....

We just don't understand space well enough yet, ...or the dimension of intention.

Cheers,
~

[modest]

Originally Posted by Michael Mooney

I am familiar with Galilean/Newtonian relativity...

The Lorentze transformation *assumes* time dilation and space curvature, both of which are clearly cases of erroneous reification, as I have meticulously argued in this thead.

The only thing the Lorentz transformations assume is the invariance of the speed of light.

Derivation of the Lorentz transformations

Originally Posted by Michael Mooney

You conveniently ignore all my arguments in this regard and glibly state that Galilean/Newtonian relativity" has been proven wrong"... without specifics to back up the claim.

If Galilean relativity worked (or correctly described our universe), GPS satellites would not work correctly. Planes would most-likely crash into mountains killing people.

GPS and Relativity

Your problem is claiming that Newton’s law of gravity and Newtonian relativity give the right answers as you do here:

Originally Posted by Michael Mooney

Gravitation is a field which acts as per the universal law thereof, "directly with massiveness and inversely with distance"... Just like Newton said. He didn't like "action at a distance" either, but the equations still work, as all astronomers and "rocket scientists" know.

Until you can get past these basic misconceptions, your conclusions are going to continue to disagree with reality.

Originally Posted by Michael Mooney

Prove it. "Time" is not "real."

That time dilation depends on velocity rather than acceleration is proved by Bailey et al., “Measurements of relativistic time dilation for positive and negative muons in a circular orbit,” Nature 268 (July 28, 1977) pg 301.

The experiment of Bailey et al. referenced above stored muons in a magnetic storage ring and measured their lifetime. While being stored in the ring they were subject to a proper acceleration of approximately 10^18 g (1 g = 9.8 m/s^2). The observed agreement between the lifetime of the stored muons with that of muons with the same energy moving inertially confirms the clock hypothesis for accelerations of that magnitude.

* Sherwin, “Some Recent Experimental Tests of the 'Clock Paradox'”, Phys. Rev. 129 no. 1 (1960), pg 17.

He discusses some Mössbauer experiments that show that the rate of a clock is independent of acceleration (~10^16 g) and depends only upon velocity.

Experimental Basis of Special Relativity

Time dilation is shown not to be an effect of acceleration or inertial forces. It is also shown to be a real effect— regardless of how real or not-real one wishes to consider time.

Originally Posted by Michael Mooney

Of course you are consistently referring to "time dilation" as a given... long ago "proven" and no longer deserving of thoughtful consideration.
The actual difference in forces upon the speeding clock and the control clock, in all cases, is that the former has been "forced" to speed up and slow down, both changes in inertia. I suspect that human metabolism also slows down under exposure to the forces of acceleration /deceleration.

A freefalling observer (such as a clock in orbit) feels no acceleration. Two different such observers (such as two GPS satellites in orbit) have relative time dilation with their relative difference in velocity when neither is subject to inertial forces. Your hypothesis that time dilation is a result of inertial forces interacting with parts of a clock or human metabolism is not supported by observation.

Originally Posted by Michael Mooney

I understand that from cosmic perspective, or even a deep space photo of sun and earth that there are are approximately 93 million "miles" (however many kilometers), each standardized earth-commensurate measures of distance. between the two bodies. You can do "thought experiments with a "photon's experience of 'no time or space' in its travel until you talk yourself out of this objectiv measure of the distance, but it remains all in your head, while the actual distance is ontologically real.

The distance between the earth and sun is a determination of the person who measures it. Newton believed that everyone would measure the distance equally. Einstein demonstrated that different reference frames would measure the distance differently. Observations have consistently disagreed with Newton on this and agreed with Einstein. Any philosophical interpretation should also disagree with absolute Newtonian space and agree with relativity.

You give the example of a "deep space photo" of the earth and sun, claiming that the distance between the two will be "objective" (absolute or fixed) at 93 million miles Your thinking appears to be that a camera far-enough away from the earth / sun distance will assuredly give this objective measure between them. This is not the case. A camera very far from the earth / sun may find the distance to be 1 million miles or 20 million miles or 2 miles or 90 million miles. It all depends on how the camera is moving relative to the earth and sun.

This is how our universe works. Distance, time, and simultaneity are all relative. Your objection to the reification of spacetime is agreeable in that people often take the analogy of spacetime too literally. But, you inappropriately extend this to an objection of relativity itself thinking something along the lines of: if space and time are not like the pictures in the textbook then relativity is needless and wrong.

Such a position is philosophically untenable.

Think of the magnetic field lines a person could draw around a magnet. The field lines are not real physical things. But, that doesn't mean electromagnetism isn't a real physical thing. It doesn't mean that Maxwell's theory of the electromagnetic field is wrong. You are trying to tie these two things (reification and the validity of the theory) together and its not working because the validity of the theory doesn't need reification of the field and the improper reification of the field doesn't necessitate an invalid theory.

~modest

[Michael Mooney]

So many points to consider... will reply later.
Late night focus on one concept::

A freefalling observer (such as a clock in orbit) feels no acceleration. Two different such observers (such as two GPS satellites in orbit) have relative time dilation with their relative difference in velocity when neither is subject to inertial forces. Your hypothesis that time dilation is a result of inertial forces interacting with parts of a clock or human metabolism is not supported by observation.

True, once in orbit there is no change in inertia until the clock slows down and is compared with the control stationary (no change in inertia) clock. I thought that the variable in the experiment was the boost and return (slowing on re-entry) of the orbiting clock. I was unaware of the differences in "time-keeping" of two orbiting clocks in GPS satellites. I will investigate this case if both are subject to equal changes in inertial force. (You must have mis-spoken, as both satellites have been subjected to changes in inertial force as they are are launced into orbital velocity... as compared to identical "stay-at-home" clocks.)

Afterthought:
If two clocks in two GPS satellites have different velocities, they have already been subjected to different acceleration, i.e. different changes in inertial force on one as compared to the other. The only true control of this variable would be if both were launched via identical force into identical orbital speeds.
What say you to this objection?
Michael

[Michael Mooney]

MM:

The Lorentze transformation *assumes* time dilation and space curvature, both of which are clearly cases of erroneous reification, as I have meticulously argued in this thead.

M:The only thing the Lorentz transformations assume is the invariance of the speed of light.

Sheesh! The Lorentz transformation assumes the basic tenants of relativity which include "time dilation" and "space curvature." Good grief! Do want to talk science or nit pick language precision?

M:

If Galilean relativity worked (or correctly described our universe), GPS satellites would not work correctly. Planes would most-likely crash into mountains killing people.

This is simply wrong. I am beginning to believe you are a master of the snow-job.
Maybe you should read the links you are offering me. I will add ("and relativity in general" to the following Wikepedia quote:

At the low relative velocities characteristic of everyday life, Lorentz invariance (and relativity in general) and Galilean invariance (and relativity in general are nearly the same, but for relative velocities close to that of light they are very different.

Your problem is claiming that Newton’s law of gravity and Newtonian relativity give the right answers as you do here:

Quote:
Originally Posted by Michael Mooney
Gravitation is a field which acts as per the universal law thereof, "directly with massiveness and inversely with distance"... Just like Newton said. He didn't like "action at a distance" either, but the equations still work, as all astronomers and "rocket scientists" know.

Until you can get past these basic misconceptions, your conclusions are going to continue to disagree with reality.

To what version of reality are you referring specifically? Be specific and so will I.

That time dilation depends on velocity rather than acceleration is proved by Bailey et al., “Measurements of relativistic time dilation for positive and negative muons in a circular orbit,” Nature 268 (July 28, 1977) pg 301.
Quote:
The experiment of Bailey et al. referenced above stored muons in a magnetic storage ring and measured their lifetime.

There is a lot of controversy over the "life expectancy of muons." For instance, how does the above experiment control for the effect of the intense magnetic field in the storage ring as effecting their "lifespan" as compared with the control muons with the same energy moving inertially? Your "is proved by" above is hyperbole in service to your bias.

Time dilation is shown not to be an effect of acceleration or inertial forces. It is also shown to be a real effect— regardless of how real or not-real one wishes to consider time.

Shall we abandon the common meaning of words to serve the theory of "time dilation? Given the ontological recognition that "time" is simply the "duration of a selected event" (I.e., as per "presentism"... time is not "real") how is it that some-thing not real "dilates?" What is the actual nature of the "real effect" your statement claims?

Also, along these same lines, please answer my "afterthought" objection (last night) to your example of two GPS with two different velocities. How were they *not* exposed to different inertial forces to achieve different velocities?
(Replay): M:

A freefalling observer (such as a clock in orbit) feels no acceleration. Two different such observers (such as two GPS satellites in orbit) have relative time dilation with their relative difference in velocity when neither is subject to inertial forces. Your hypothesis that time dilation is a result of inertial forces interacting with parts of a clock or human metabolism is not supported by observation.

MM:

If two clocks in two GPS satellites have different velocities, they have already been subjected to different acceleration, i.e. different changes in inertial force on one as compared to the other. The only true control of this variable would be if both were launched via identical force into identical orbital speeds.
What say you to this objection?

The distance between the earth and sun is a determination of the person who measures it. Newton believed that everyone would measure the distance equally. Einstein demonstrated that different reference frames would measure the distance differently. Observations have consistently disagreed with Newton on this and agreed with Einstein. Any philosophical interpretation should also disagree with absolute Newtonian space and agree with relativity.

From cosmic (objective, as I call it) perspective the distance between things is not dependent on the perspective of who measures it, i.e., cosmic perspective transcends relative, local perspective .
You are still unable to "wrap your head around" what I mean by cosmic/objective perspective.

An obvious example, quite "local": The distance from earth to moon can be very accurately determined by bouncing a laser light off a mirror on the moon and dividing the light seconds of the round trip in half. This determines the "objective" distance to the moon, regardless of the mind games you want to play with it. Same with distance between earth and sun (sans the laser and mirror... but it is no secret that the sun is 8+ light minutes distance from earth. Again, what a photon "experiences" on its journey is just another mind game disputing the objective, actual distance.

IGotta go.
Michael

[modest]

Originally Posted by Michael Mooney

True, once in orbit there is no change in inertia until the clock slows down and is compared with the control stationary (no change in inertia) clock. I thought that the variable in the experiment was the boost and return (slowing on re-entry) of the orbiting clock. I was unaware of the differences in "time-keeping" of two orbiting clocks in GPS satellites. I will investigate this case if both are subject to equal changes in inertial force. (You must have mis-spoken, as both satellites have been subjected to changes in inertial force as they are are launced into orbital velocity... as compared to identical "stay-at-home" clocks.)

GPS satellites are time dilated every day (and hour and minute). They aren't launched into orbit every day. That only happened once. On any given day, a GPS satellite feels no inertial forces, yet they are time dilated because they have difference in relative velocity. You might be insinuating that the clock on a GPS satellite runs slow today because it felt an inertial force in the 1980's. I hope that is not the case.

Originally Posted by Michael Mooney

If two clocks in two GPS satellites have different velocities, they have already been subjected to different acceleration, i.e. different changes in inertial force on one as compared to the other. The only true control of this variable would be if both were launched via identical force into identical orbital speeds.

The muon experiment I quoted yesterday proves that time dilation is not caused by acceleration and inertial forces—it depends only on velocity. If a person views two clocks with the same velocity that are undergoing wildly different accelerations and inertial forces (perhaps one is moving in a tight circle feeling a large centrifugal force) then the person sees both time dilated equally.

~modest