What is "spacetime" really?

[Michael Mooney]

Me too... a quickie:

Pyrotex:

How do you define a straight line?

There is only one way I've ever heard of -- use the flight-path of a photon.

 

I've acknowledged a few dozen times that gravity bends the path of light. No intelligent person will deny this.

You can call it just a Platonic Ideal if it makes you feel superior... and it obviously does, but... using light's path as the *definition* of a straight line when it doesn't travel in a straight line is... well... logically absurd!

Invoking the "curvature of space" as proof that space is not simply emptiness is... well... dogmatic.... especially in a thread challenging the ontology of "curved space" and re-asserting the validity of Euclidean space...

This without throwing out the baby with the bathwater, vis-a-vis the improved math of relativity for predicting gravitational effects.

 

Michael

[maddog]

From your post #417 ...

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

I will have to read that. A book by Roger Penrose is very good "Road to Reality" though

does involve somewhat of college mathematics. He does cover the physics pretty well.

 

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

I believe you need to preface your discussion by defining term. I am not clear of the

following in this context:

"matrix field"

'reality quotient'

 

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

Again more terms without explanation.

"matrix map"

I got the mathematical notion of a map, however would a "matrix map" be a 2-d array

of maps ?? I think not. You might be thinking a "lattice" -- (kind of synonym for map -

though not quite -- though this is a bit of a nitpick).

Matices come into GR as Tensors defining the coordinate systems.

 

maddog

[maddog]

If GR's *assumption* about the "curvature of space" is wrong, then the shortest distance between any two points or objects anywhere, on whatever scale, is still a straight line... or three of them in the case of "connecting the dots" or the galaxies... not cuved lines. Please understand that non-Euclidean "four dimensional space" (as a part of GR) is not, as you assume, already established as indisputable fact!

Well, not to you. Even so indisputable or not, the shortest distance between any two

points is a straight line -- Euclidian or not. Euclidian you know well. In non-Euclidian

the "straight line" in a non-Euclidian space would be curved when seen from a point of

out of that space. Within it, the light would be as straight as possible.

Your beef is with allowing the 5th postulate of Euclid to possibly be false.

Everything else is derived from that.

Yes, regardless of scale, a straight line is still not a curved line, and a curved line is the longer line or linesr between the galaxies. This is based on an ontology that "space itself" is simply empty volume, not actually an "itself" with any properties, including curvature.

Already discussed above.

The metric field upon which GR is based assumes not only that space is a "thing" which curves but that time is a thing that dilates. You assume both are true... that the "spacetime metric" is valid without even entering the ontological debate.

(See references above to Doctordick's observations in this regard and AnssiH's concurrence.)

"spacetime metric" is NOT a Thing, has No Thingness present. It is a coordinate system just as much a polar coordinates.

 

Distance exists whether it is measured or not. If we want to measure the distance between two objects, we must first agree on a unit of measure. Take your pick. There is an objective, well known and precisely measured distance between, say, earth and sun. It of course varies with earth's orbital path at any given moment. It can be stated in earth diameters, miles, kilometers, light minutes... or whatever.

The standard metric is fine

Space

[math]ds^2 = (x^2 + y^2 + z^2)^(1/2)[/math]

Spacetime

[math]ds^2 = (x^2 + y^2 + z^2 + (ict^2))^(1/2)[/math]

You are not engaging in the ontological debate on spacetime here by simply asserting that my challenge is "at odds" with the "accepted" doctrine, metric, whatever of "curved space" as an element of "spacetime." Of course it is!

You know Monty Python's Flying Circus had a skit for that line of reasoning:

"Well, I came here for an argument!"

"No you didn't!"

...

Well... I "used it" already, and I clarified what I mean by "metric"... "the map, not the territory" pages ago and again recently in reply to you.

I have observed you often don't define your terms well.

 

maddog

[maddog]

General comment:

So... this forum will not sustain a *respectful dialogue* or debate on what spacetime actually is without indulging in the usual "know it all" attitude of emprical science and its materialistic worldview condescending with smug smirks on some faces and malicious mystic bashing by others, like "maddog", fighting his way to the top of a bloody battle/dogfight... to the top of the heap, his own mind.

I can be respectful. I don't take well to having the "gauntlet" thrown at me on this

thread regarding my explanation not being sufficiently "ontological".

You must be willing to take what you dish out.

Also, you might be confusing me with Pyrotex, as "I" am not a mystic basher.

My religious leanings are of the Gnostic variety. Though I was raised a Roman Catholic,

I often fought with my catechism instructor.

The important distinction I make is Physics and Metaphysics are Not equivalent.

As AnssiH said in his last post (well said) and I must agree ya' aren't quite using the notions

behind the word Ontology all that accurate.

The underlying existence of something being an Ontology would be independent of its

being observed. Yet observability is what makes something "in the world".

This discussion has made me want to dig up my book "On Being and Time" by Martin

Heidigger. I haven't found it yet, now I desire to tackle it again.

If you were to just accept that you view Geometry as being only what Euclid originally

said (5th Postulate is true), then you wouldn't view me as the "maddog" as my moniker.

 

It is just a nickname.

 

I remind you all that I have never claimed that my visions, and resulting cosmology are founded in empirical evidence or even that they are "scientific." But, as philosophy of science, the question remains, "Is there an objective universe independent of relative perspectives or perception by intelligent life forms?" If you say "yes", as I do, then others can demand how you know this to be true without invoking your perceptions. It is not allowed to say that the objective existence of the universe is "self evident", as is my gnosis of the universal NOW and omnipresent consciousess is self evident.

Nor can I claim any of my visions to have "proof" attached. I do know that my Metaphysical

beliefs have colored my outlook and what I studied in college. For me to answer you

in the question of yours I bolded above, I would ammend it as I think (my opinion)

you might have it backwards.

I do view a independent "subjective - inner" Reality which is independent of perception

and related to Gnosis or "cosmic knowing". This is Not Objective. The Objective/Outer

Reality is THE world you or I perceive.

 

So, tho Pyrotex dodged the question with a wink and a grin, it still remains. Are there any mature "philosophers" of science in this forum?

That is a question I think which CANNOT be answered, Only questioned.

I do it all the time.

 

maddog

[Erasmus00]

Irrelevant huh? Seemed to be replying spot on to your exercise as having been addressed in previous "triangle" exercises... If GR's *assumption* about the "curvature of space" is wrong, then the shortest distance between any two points or objects anywhere, on whatever scale, is still a straight line...

 

Right, thats fine. The question that you keep refusing to answer is: we take those three straight lines, measure the angle between them, and find the triangle has more than 180 degrees!! What does that mean? This is the most important question in my post, so please address it. What does it mean if our galactic triangle has other than 180 degrees?

 

The metric field is the map, the system of coordinates, not the territory, and the "matter field" is the actual territory, the "real cosmic stuff" being mapped by the metric.

 

Metrics are a map from what to what? I think you are confused, metrics are not the coordinates, you can have coordinates in a space with no metric, for instance. I'll discuss what metric means below.

 

You assume both are true... that the "spacetime metric" is valid without even entering the ontological debate.

 

Before you can enter the ontological debate, you have to be clear by what you mean by spacetime metric!

 

Distance exists whether it is measured or not. If we want to measure the distance between two objects, we must first agree on a unit of measure. Take your pick.

 

We need more than a unit of measure, we need a method. A good method allows everyone get the same answer.

 

But, when a mathematician, or physicist says "distance" what they mean is the number the measurement produces. You might say that the two masses, or two points, or whatever exist independently of the measurement, but when you say "distance" what other people THINK you are trying to say is the actual numerical measurement.

 

A set of coordinates is, in some sense, a map. It takes each point in space, or each mass, or whatever, and gives a it a number.

 

A metric is a recipe for turning those coordinates on the map into an actual distance (where I mean an actual measurement/number). You might think of the metric as akin to the scale on the roadmaps.

 

You are not engaging in the ontological debate on spacetime here by simply asserting that my challenge is "at odds" with the "accepted" doctrine..

 

I'm trying to ease our communication by making sure your words and my words mean the same thing. We can have a discussion when we are on the same page about our definitions. I'm not talking accepted doctrine, rather standard definitions.

[watcher]

"Is there an objective universe independent of relative perspectives or perception by intelligent life forms?" If you say "yes", as I do, then others can demand how you know this to be true without invoking your perceptions.

so how do you know this without invoking your perception?

 

It is not allowed to say that the objective existence of the universe is "self evident",

 

yes when we say the universe is objective, we are speaking in behalf of the universe. ultimately the word objective is a human defined concept. the universe may neither be objective nor subjective.

 

as is my gnosis of the universal NOW and omnipresent consciousess is self evident.

 

NOW, is only a perception of being at rest or stationary in time.

the same way we perceived to be at rest or stationary in space. our brains develop a motion cancelers so we can always perceived ourselves to be a rest relative to everything, a good evolutionary adaptation for making sense of moving in space. the same with now, our brain have time cancelers, to make sense of ordered of events.

[Pyrotex]

Well, Michael,

here we are. :D

 

If there is another philosopher of physics in this thread, it would prolly be me.

Though my degree is in physics, I have done massive amounts of reading in the history of how physics came about, and its early background in metaphysics and philosophy.

Flexibility of viewpoint is one of my middle names. :)

 

I really would have liked it had you been able to bring more to the table.

The Ontological viewpoint was good, really good, and I was willing and able to keep up with you on that one. But you didn't have any follow-through. :(

 

Specifically, you weren't able to take your Ontological viewpoint and use it to establish a basis for making useful, verifiable conclusions.

 

Like the cartoon with the two physicists standing in front of a blackboard.

The left side and right side of the blackboard are full of equations.

In the middle are the words, "then a miracle happens..."

The physicist on the right scratches his chin and says something like, "I think your logic in the middle there may need some more work."

 

Michael, you made a valiant try. You didn't "lose" because your opponents were narrow minded, or negative, or any of the other insults you threw out. You "lost" because you did not have enough facts, logic and creative reasoning on your side. You were outgunned, pure and simple.

 

I suggest you take a break, take a deep breath, and think your proposition through again. See if you can replace your mystic vision with something more substantial. Then come back and give it another try. :) Ask for me.

 

Good luck! :) I may not agree with you on all points, but I'm rooting for you. :) :) :) :)

 

I am The Pyrotex :) :)

[freeztar]

Specifically, you weren't able to take your Ontological viewpoint and use it to establish a basis for making useful, verifiable conclusions.

 

 

How does one make "useful, verifiable conclusions" based on an ontology that specifically disregards the concept of spacetime? :lightning

[Pyrotex]

:hihi:

 

How does one make "useful, verifiable conclusions" based on an ontology that specifically disregards the concept of spacetime? :lightning

Well...

 

There you go! That's one of the problems with his viewpoint.

 

It seems to me that the worth of an Ontological description of the universe would be to "imagine" one that would have the same properties that we can observe and eventually confirm or refute (if we can't do it now).

 

It appears that Michael wants us to buy an Ontology that has properties that are incompatible with what we can already observe. :hihi: :hihi:

[Michael Mooney]

EVERYONE... please!.. review my first statement in this thread and then my post #462 on p.47.

http://hypography.com/forums/philosophy-of-science/17037-what-is-spacetime-really-47.html

 

Maybe... finally what I am saying in this thread about the reification of "spacetime" (as per "curvature of space" and "dilation of time" ) will gain perspective in contrast to what I accept about relativity and it's excellence (over Newtonian physics) in describing and predicting gravitational effects.

And I do accept that lightspeed is constant as per SR. I have offered my possible explanation of this counter intuitive mystery also. Will find it and footnote as an edit.

 

In reply to Modest's:

"Your philosophy does not predict or explain the relative nature of space and time nor the invariance of the speed of light."...

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

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

 

Thanks.

Michael

[Michael Mooney]

Michael,

 

It seems that the only response that will make you happy is a denunciation of the concept of spacetime.

 

I fully understand your ontological arguments against spacetime. The gnostic sense of the eternal now is not lost upon me.

Thank you. Please explain to Watcher that "Now" is perpetually ongoing (everywhere), not a static snapshot of a cosmos without movement.

 

But...what then?

 

If everyone suddenly agreed with you, what would be the point of continuing this dialogue?

In this respect, I wholeheartedly agree with DoctorDick and AnssiH.

 

What then? Then "curved space" would be replaced, in all textbooks on relativity with "curved trajectories of objects traveling through space" without reifying "space itself" as a "thing" with curvature and shape.

Likewise "time dilation" would be replaced with precise descriptions of the conditions under which clocks slow down, and science could then focus on investigating why forces which change a clock's velocity make the rate of atomic decay slow down... rather than reifying "time" as some "thing" which "in itself" slows down.

Then I would be a very happy camper. :lightning

 

Oh... also... relativity would "get over" the bogus claim that distances vary with relative perspective rather than being physical facts all by themselves. And "length contraction*" will go out the window along with "time dilation."

(* Not referring to a "rod" being compacted by accelleration.)

 

Michael

[Michael Mooney]

Again, if they are curved lines, they are not straight lines. :doh:

Your non-Euclidean concept of "four dimensional curved space" has created a three dimensional pseudo-triangular slice of a sphere, the "sides" of which are arcs of the sphere's great circle rather than the straight lines of a true triangle as defined on a plane.

 

First, we aren't talking about four dimensional space, merely three dimensional space. At no point has a fourth dimension crept in.

 

No, I'm saying the straightest lines you can draw between each point. If you draw the straightest possible lines (straight lines) of a triangle between three galaxies, the angles will not add up to 180 degrees (the difference will be very slight). The lines ARE NOT curved, and yet the triangle doesn't have 180 degrees.

 

Saying the sides are arcs and not straight is rewriting the question!

[Michael Mooney]

Another loose end:

Pyrotex:

To make a long story short, the Sun doesn't "pull" on the photon with a force, but it distorts the normally "flat, Euclidian" space that the photon normally travels through. The path skirting the edge of the Sun, "curved" to our way of thinking, is STILL the minimum energy path between two points. That's also the minimum time path. It's also the path of zero effort, meaning that no additional force or energy is required by the photon.

 

To emphasize the obvious, you take "space distorted by gravity" as a given... still ignoring the ontological question (what is "it" that is being distorted?) You assert as an established fact that "the Sun doesn't "pull" on the photon with a force, but" (distorts space)...

 

Then you speak of "the minimum time path" as if "the fastest speed there is" (granted) must describe the shortest possible path. It doesn't when it curves.

 

I will remind you that the "momentum" of light acts exactly as if it had mass. I've (at least twice here) shared a summary of the "box of mirrors" experiment, capturing light and giving the box more static inertia just as if the captured light bouncing off the walls had mass. Likewise the sun does "pull" on light, bending *its trajectory* (not" bending space," as all thoroughly indoctrinated disciples of Einstein believe. :doh:

Michael

[Erasmus00]

Again, if they are curved lines, they are not straight lines.

Your non-Euclidean concept of "four dimensional curved space" has created a three dimensional pseudo-triangular slice of a sphere, the "sides" of which are arcs of the sphere's great circle rather than the straight lines of a true triangle as defined on a plane.

 

First, we aren't talking about four dimensional space, merely three dimensional space. At no point has a fourth dimension crept in.

 

Now, I'm saying the straightest lines you can draw between each point. If you draw the straightest possible lines (straight lines) of a triangle between three galaxies, the angles will not add up to 180 degrees (the difference will be very slight). The lines ARE NOT curved, and yet the triangle doesn't have 180 degrees.

 

Saying the sides are arcs and not straight is rewriting the question!

 

Lets pose another, lets say you measure the radius of a sphere, and find that the volume of the sphere is not equal to [imath]4/3 \pi r^3 [/imath]. What does that mean?

[Pyrotex]

EVERYONE... please!...... finally what I am saying in this thread about the reification of "spacetime" ...in contrast to what I accept about relativity... and predicting gravitational effects. ... I do accept that lightspeed is constant as per SR. ...

Hi Michael,

okay, I went back and read several of your posts, including the one you specified.

 

How in the world did this thread get so gnarled up? :lol: :hihi: :lol:

 

oh, well. :lol: so, is the whole "issue" just the reification of "space-time"?

Is that what this is all about?

 

:huh: :doh:: :D :lol: :(

 

I can address that to some extent if that is the issue here.

and I apologize for the confusion. :hihi:

[modest]

In reply to Modest's:

"Your philosophy does not predict or explain the relative nature of space and time nor the invariance of the speed of light."...

The math instrument of relativity works without its reifying assumptions about space and time, as above.

Yes, the "math" (physics) of special relativity does work—but, that is not the issue. The issue is one of philosophy. The philosophy of spacetime explains why the math of special relativity works. Your philosophy does not explain why it works. That was my comment, notice: "Your philosophy does not predict or explain the relative nature of space and time nor the invariance of the speed of light."

 

So, what are you doing Michael? Why are you here waving your hands about? You say that scientists should reject the ontology of time so that they can "focus on investigating why forces which change a clock's velocity make the rate of atomic decay slow down"... as if it is up to scientists to fix your broken philosophy.

 

If you reject the ontology of time calling it "no-thing-ness" and therefore conclude that time cannot be dilated then it's up to YOU to explain observations and experiments of time dilation. It is not enough to say: "I don't know how gravity and time work, but It doesn't work how them darn science folks say it works. Them scientists need to figure out some other theory that doesn't disagree with my philosophy."

 

And, guess what... the very thing you say scientists should be focusing on: "investigating why forces which change a clock's velocity make the rate of atomic decay slow down" has already been investigated multiple times:

 

Scientists have already ruled out inertial forces as the cause of timing differences in clocks!!

 

Bailey et al., “Measurements of relativistic time dilation for positive and negative muons in a circular orbit,” Nature 268 (July 28, 1977) pg 301. Bailey et al., Nuclear Physics B 150 pg 1–79 (1979).

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/s2). 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 - The Clock Hypothesis

 

You propose an alternative philosophy which requires "forces" to do things which we know they do not do. If you want to object to the way modern philosophy treats space and time then you need to bring something else to the table. Something like... oh I don't know... a philosophy that works. One with definitions which can be used. One that has been thought through and avoids internal inconsistencies.

 

Consider, you just said these two statements within an hour of each other:

 

Then I can "see" how a laser "shot ahead" in the same manner will not "push" the massless light in the same way to achieve cumulative velocity... which it does not. Here the "interface" of the speeding laser gun has no mass to "push against"

 

I will remind you that the "momentum" of light acts exactly as if it had mass.

 

The truth is laser guns do recoil and mass bends light more than it would according to Newtonian gravity. These things have been considered. There are physicists participating in this thread like Pyrotex and Erasmus who have made it their life's work to understand and use these concepts. If you are unwilling to take anything from that except derision then this thread's continuation has truly become pointless. It has become a pointless argument, and I've concluded the argument is the thread's only purpose.

 

At the beginning of the thread the argument was: "why are you treating my question philosophically?", and the argument has now become "why won't anyone address my philosophical question?" The only constant through all that is the argument, and that has no purpose.

 

~modest

[maddog]

A quick note on straight lines in the universe.

There is the Platonic Ideal of a straight line, and I believe this is (I think) what Michael believes the universe can be "drawn" with.

It this idealized notion of lines that definitely what Michael is using as his "yardstick". Just

as idealized as Plato himself used. Michael is looking at the Universe is some Platonic,

Metaphysical way as being "real". This is where we differ.

But photons are affected by the Sun's gravity! :doh:

Michael is dismissing the whole differentiable mainfold notion used in GR as not being in

Union with Eclid's 5th Postulate.

 

maddog