What is "spacetime" really?

[jedaisoul]

How is it that you believe that nothingness, emptiness can not be infinite? What do you propose as its finite boundary, and what's on the other side?

 

" And to be infinite, something has to exist." (??)

This defies the meaning of "infinite" as without end or boundary. All "things" are defined by their boundries.

Reification is making something out of nothing in our own minds... like "spacetime" into a medium with various attributes.

It is true that the average dictionary may define "infinte" as "without limits; extremely large or great...", but mathematically (and scientifically), that is not a very accurate definition.

 

To be infinite is not the same as being without end or boundary. A 2D surface bent back on itself in 3D to form the surface of a sphere is without end or boundary. But it is not infinite.

 

Similarly, to be infinite is not the same as being extremely large or great. Something that is extremely large (or great) is not infinite. It's just extremely large (or great). So the sun is extremely large, but it is not infinite. The galaxy we live in is even larger, but it is not infinite. The galaxy cluster that our galaxy is part of is even larger, but it is not infinite. You get the idea?

 

Similarly, the power of a lightning bolt is extremely great, but it is not infinite. The power of a major hurricane is extremely great but it is not infinite. Etc... "Infinite" is a sadly abused word. Saying that the universe is infinite is NOT just saying that it is very large and without boundary.

 

More importantly, you seem to have misunderstood my point about reification. To have "more" of something, that something has to exist (at least conceptually). So I can have more apples, more grain, more planets. I can even have more abstract things, like ideas. But I can't have more nothing. Nothing, by definition, is the absence of existence. Therefore there cannot be more, less, or the same of it! By treating "nothing" as something that there can be more of, you ARE reifying it.

[jedaisoul]

On re-reading my last post, I don't think I expressed the point I was trying to make very well. It comes over as a semantic argument, which is not what I meant. So I'll have another try:

 

Say I have two balls, and I hold them touching each other, there is nothing between them. Ok?

Now I mov them apart, is there something between them? Well, yes, air. But does the air define the distance between them? No. I could, in principle, do the same thing wearing a space suit standing in the bay of the space shuttle in orbit around the Earth. So what defines the distance? Can it be nothing? No. Because it has properties (distance and orientation).

 

Nothing cannot have properties, because, by definition, it does not exist. So when you are talking about space, which does have properties, you are not talking about nothing. Do you see that?

 

Or rather, I'd suggest that to justify the claim that space is nothing, you have to identify something else that those properties belong to. Then you have to explain how things that exists can inhabit something (space) that does not exist.

 

Justifying the claim that space is nothing is not a trivial thing to do.

[Michael Mooney]

Jedaisoul:

Nothing cannot have properties, because, by definition, it does not exist. So when you are talking about space, which does have properties, you are not talking about nothing. Do you see that?

This is going nowhere fast.

The absence of anything is nothing. Between subatomic energy levels/"particles" is the space or emptiness between them. Likewise between atoms, molecules... planets, stars, galaxies. Granted there are 'things" in between, but between any and all "things" is the absence of things... space... emptiness.

If you don't understand this most basic level of the ontology of existence, there is no hope for this conversation.

 

BTW, I mis-spoke on the "bogus" nature of the "metric spacetime." It is only a metric... a coordinate system used very effectively by relativity. What is bogus is its reification into the famous curving, expanding/contracting, dilating, etc medium relativity has made it.

 

Michael

[jedaisoul]

Jedaisoul:

 

This is going nowhere fast.

The absence of anything is nothing. Between subatomic energy levels/"particles" is the space or emptiness between them. Likewise between atoms, molecules... planets, stars, galaxies. Granted there are 'things" in between, but between any and all "things" is the absence of things... space... emptiness.

If you don't understand this most basic level of the ontology of existence, there is no hope for this conversation.

I repeat:

Nothing cannot have properties, because, by definition, it does not exist. So when you are talking about space, which does have properties, you are not talking about nothing. Do you see that?

 

Or rather, I'd suggest that to justify the claim that space is nothing, you have to identify something else that those properties belong to. Then you have to explain how things that exists can inhabit something (space) that does not exist.

 

Justifying the claim that space is nothing is not a trivial thing to do.

You do not justify it by waving your hands.

[watcher]

This is going nowhere fast.

The absence of anything is nothing. Between subatomic energy levels/"particles" is the space or emptiness between them. Likewise between atoms, molecules... planets, stars, galaxies. Granted there are 'things" in between, but between any and all "things" is the absence of things... space... emptiness.

If you don't understand this most basic level of the ontology of existence, there is no hope for this conversation.

 

there might if you care to clarify how you use the word nothing.

if you use it as a noun, you can't give it attributes or properties like infinite.

since it is absurd to say that something that does not exists has a property.

 

now if you use nothing as a pronoun, it is perfectly valid to say that the space between objects is empty. but this time nothing is not a thing but the attribute itself.

you are describing what is between two objects, therefore nothingness is an attribute of two objects.

 

since nothingness is only a description of space between objects, it is perfectly valid to have other description between objects, like curvature. expansion and contraction. it is not necessarily a reification at all to do this specially if we can understand what it corresponds to the real world.

[Boof-head]

If "the number one exists", then we can count "ones". At least, we don't generally assume we "can't count", because counting is something we do when we find 'things we can count'.

If we can count "forwards" we can count "backwards", or if: 1+1+1+..., then 1-1-1...

 

So if +1 and -1, then +1-1 = 0, and +1-1+1-1,... = 0.

 

Zero or "0" is not nothing, it's what you have left after counting "forwards then backwards". You have "really nothing" only when you don't count at all.

[jedaisoul]

...it is perfectly valid to say that the space between objects is empty. but this time nothing is not a thing but the attribute itself.

you are describing what is between two objects, therefore nothingness is an attribute of two objects.

 

since nothingness is only a description of space between objects, it is perfectly valid to have other description between objects, like curvature. expansion and contraction. it is not necessarily a reification at all to do this specially if we can understand what it corresponds to the real world.

Hi Watcher, you are, of course, correct in what you say. However, I had hoped that Michael would pick up on the hints I made, and express that for himself. E.g. I used the term "orientation" hoping that this would prompt the thought "orientation with respect to what"? The "what" is, of course, material objects. So distance and orientation are properties of objects, and "space" is the property of objects that, internally, gives them size, and externally gives them distance and orientation between them.

 

So when we speak of "space" we is using it as shorhand for "the property of objects that, internally, gives them size, and externally gives them distance and orientation". We are not reifying nothing. In fact, the only person reifying nothing is someone who defines space as nothing, but attributes to it the property of distance. As you, and I, pointed out; nothing cannot have properties.

 

Also to deny that space can have the property of curvature, but to allow that it can have the property of distance is simply inconsistent. So, hopefully, we have resolved the question of who is reifying what.

[jedaisoul]

Perhaps a quote from Einstein would be appropriate here:

 

Note to the Fifteenth Edition of "Relativity The Special and General Theoy":

...I have added, as a fifth appendix, a presentation of my views on the problem of space in general and on the gradual modifications of our ideas on space resulting from the influence of the relativistic view-point. I wish to show that space-time is not necessarily something to which one can ascribe a separate existence, independently of the actual objects of physical reality. Physical objects are not in space, but these objects are spatially extended. In this way the concept "empty space" loses its meaning.

A Einstein, June 9th, 1952.

[HydrogenBond]

This idea came to me yesterday. If we look at a mass accelerating into the topology of curved space-time of a large mass source (increasing space-time curvature continuum as we approach the mass source), the units of acceleration are distance/time/time and not space/time. In other words, the mass is dimensionally reacting to something analogous to space-time-time and not space-time.

 

If we look at an orbit of a mass in a simple circle, it will maintain constant velocity which has the dimensionality of distance/time similar to space-time. This acceleration affects the directional vector but not the magnitude of velocity.

 

Energy is different than mass. Energy moving into the same topography of space-time curvature will wavelength and frequency shift with the dimensionality of the effect adding up to the same thing as space-time.

 

The point I was making is mass acceleration due to gravity or GR, does not maintain the dimensional components of space-time, but acts like it is entering space-time-time and not space-time or (space-time)2.

[Pyrotex]

This idea came to me yesterday. If we look at a mass accelerating into the topology of curved space-time of a large mass source... mass acceleration due to gravity or GR, does not maintain the dimensional components of space-time, but acts like it is entering space-time-time and not space-time or (space-time)2.

hello HB.

That is an interesting conjecture.

However, I believe that the phrase "space-time" was not meant to mean "space/time" or "space*time". In other words, there was no intention of referring to the units of space and time.

But I can understand how one might jump to that conclusion.

[Moontanman]

Spacetime is that which is between objects. What is between objects? That which is between objects is called spacetime

[Michael Mooney]

Jedaisoul:

"Also to deny that space can have the property of curvature, but to allow that it can have the property of distance is simply inconsistent.

Me:

"Space is not a thing. "It" is lack of "it-ness." Emptiness. No attributes. No curvature."

 

There are just over 8 light minutes of relative emptiness between earth and sun. We can also apply a variety of other measures of distance like kilometers, miles or earth diameters. Aside from whatever actual stuff is floating around in this space, it is empty. Emptiness does not have curvature, as there is nothing to curve. It is quite obvious that the empty space between objects can be called distance and units of distance, as above, assigned. Ontologically, emptyness does not have the property of curvature, as surfaces of geometric forms and actual roundish objects "have curved surfaces."

 

Erasmus:

"The problem with using meditation/visions as a basis for physics is that two people meditating can experience and report on very different things. Whose vision gets priority?"

 

Its more like simply clear vision of "what is" as seen by a clear mind.

So a "straight line" is still actually straight, not re-defined as "the path of light", therefore curved because light's path is curved, or because "space itself is curved."

 

 

It more like knowing with absolute certainty that there is no such thing as curved nothingness.... space... emptiness between things (and within them, between their parts.)

 

I said that real triangles have a total of 180 degrees.

Erasmus:

"But why? Can you prove it?"

Any elementary school student with a protractor can prove it.

 

Jedaisoul:

"Nothing cannot have properties, because, by definition, it does not exist. So when you are talking about space, which does have properties, you are not talking about nothing. Do you see that?"

Me:

The absence of anything is nothing. Between subatomic energy levels/"particles" is the space or emptiness between them. Likewise between atoms, molecules... planets, stars, galaxies. Granted there are 'things" in between, but between any and all "things" is the absence of things... space... emptiness.

If you don't understand this most basic level of the ontology of existence, there is no hope for this conversation.

 

Einstein(as quoted by Jedaisoul):

"I wish to show that space-time is not necessarily something to which one can ascribe a separate existence, independently of the actual objects of physical reality. Physical objects are not in space, but these objects are spatially extended. In this way the concept "empty space" loses its meaning."

 

Amen to first sentence!

What do you suppose he means by "Physical objects are not in space"?

We know the man was a genius (so am I, according to my IQ scores), but this is a "no brainer!"

"Spatially extended?" Well there is empty space between objects, and "empty" means absence of things, as in nothing in between things. Things or objects occupying space render the space occupied no longer empty! Doh!

No wonder the moderators here are confused, being hypnotized by the inevitability of the TIDE. (Thoroughly Indoctrinated Disciples of Einstein.)

I know... I've already used it, but it/s so cute!;)

 

Going.... goiing....

Michael

[Erasmus00]

So a "straight line" is still actually straight, not re-defined as "the path of light", therefore curved because light's path is curved, or because "space itself is curved."

 

I have not at all talked about redefining straight as "the path of light." You put words into my mouth in order to fit what I'm saying into your misconception. I'm talking about straight lines in space as perceived by some observer in one specific instant.

 

I said that real triangles have a total of 180 degrees... Any elementary school student with a protractor can prove it.

 

Measuring one triangle to have 180 degrees does not prove that all triangles have 180 degrees.

 

Further, GR stipulates (AND DEPENDS ON) the fact that a triangle drawn with straight lines drawn in real space will NOT have 180 degrees.

 

You repeatedly claim that the "math" of GR is right, but the "reification" wrong. At the same time- you contend that a triangle drawn in real space would have 180 degrees. Your assertion about "real triangles" destroys GR, as it contradicts the foundation.

 

Do you see that GR and your ontology are contradictory?

[maddog]

Michael,

I have one simple question which you can answer or not.

Do you feel that a Euclidean Geometry is the only valid geometry that can represent space in any way and that the Euclid's 5th Postulate must always be true ? (Yes/No)

maddog

My experience is that "space" is three dimensional, i.e., distance, area, and volume.... and that ultimately space has no limit or boundary. The "burden of proof" for more spacial dimensions (*in the real world*... not just computer-generated models!) is on the "non-Euclidean space" theorists.... ontologically speaking... not just "my opinion."

Just as I suspected. You view the world as Euclid did. That the 5th Postulate could be viewed as an Axiom and taken as given. This will Always put you in opposition to GR.

As it's viewpoint is antithetical. Now as to your allusion of higher dimension, I sympathize. I, maddog am not completely sold on the Sting Theory per se. I do not like it not being verifiable. I admit to it being elegant. So the Greeks (as a group) sought aesthetic beauty over scientific soundness (as this viewpoint hadn't been created yet). My view of spacetime is not exactly like Pyrotex as I don't [think] I see "spacetime" as being "reified". I see it as similar to a coordinate system. They are concepts created in the minds of men/women. I don't reify Cartesian coordinates, nor Polar coordinates, Spherical coordinates, cylindrical coordinates, etc. Now if I allow the

5th Postulate to be relaxed and willing to local curvature in a coordinate system, then I

can generate a coordinate system that fits the properties of spacetime. I can do things

with this that allow me to predict phenomina about my world. That gives me some utility benefit. This does not mean I am reifying my coordinate system. It's all in my head, at least till I write it down.

 

Your paradigm of using Euclid's work as is (incl 5th Postulate) will likely fall short of making those prediction such as

 

1. Gravitational Lensing of distant galaxies

2. Bending of light experiment by Prof Eddington in 1917 during an eclipse (and every

eclipse since)

3. Processional error of perihelion of Mercury by about 45" arc / century.

There are many others.

 

Throwing out GR will force you to explain all this behavior in the world that GR is in agreement with and your Cartesian Paradigm is not.

I would also like to clarify that "geometric shapes" can take the whole variety of forms as we all know... but that fact does not mean that "space has shape." The "stuff in space" has shape, and ultimate, cosmos, as it expands out *into space* has (whatever) shape. I "see" cosmos as expanding spherically, balloon-wise (with a "thickness of rubber" extending beyond our "cosmic event horizon!")..., outward from the Bang or series of Bangs... tho the non-Euclidean folks thingksuch a cosmology is "outdated." (The jury will remain "out" on that one... maybe "forever!")

If I understand the above comment seems a bit contradictory. If space does not have shape and the "universe" expands spherically then space has shape ?

Parallel lines never intersect. Any representation of parallel lines that has them intersecting misrepresents what the phrase "paralell lines" means.

This is just a restatement of Euclid's 5th Postulate discussed above.

 

I am ok with your viewpoint. You can have it. I don't agree with it. Euclid's methods worked back in classical Greek Period. With all that Mathematics has created has gone

very far past Euclid's concepts. Yet they do not negate all that Euclid has done. Something

I have been reading about that I must admit has me excited is learning of Twistor Theory by Roger Penrose.

In his notion, coordinates are actually Complex [aka: a + ib type variables]. His attempt

along with other Physicists along with Loop Quantum Gravity Theorists to create viable

union of GR with the Standard Model & QM. It would mean that GR would have to tackle

the arena of the Planck domain (x ~ 10-35 m) -- Very small indeed.

 

Let me restate, I make use of Mathematics to solve problems. This may mean I can create concepts like spacetime, etc. To the degree they are useful then I and others use them. If not, they become history (like Ptolemy's view of the solar system)...

 

maddog

[Pyrotex]

Hmmm. So there are no "things" in space?

What counts as a "thing"?

Is it just objects big enough to see or feel?

How about objects we can't see or feel?

Are atoms "things"?

Are neutrinos "things"?

Are electromagnetic waves "things"?

 

Why is a pencil a "thing"? Hmmm? Is it because it is full of atoms? Or would you insist on the terminology: it is made of atoms? What would be the difference besides just a semantic one?

 

There is this cylindrical "volume" about eight inches long and 1/4 inch thick. It is full of atoms, so we get to classify it as a "thing".

 

A synonym for "thing" is "stuff". A beaker of water is a "thing" containing "stuff"--but the words mean much the same thing: the thing is made up of atoms; the stuff is made up of atoms. Generally, a thing's atoms are stationary with respect to the volume of the thing; a stuff's atoms may remain within the volume of the stuff, but can move around.

 

So, let's define a specific cubic meter of space as a "spacter"; where would you like it? How about in orbit around the Moon somewhere? We're talking about a specific spacter here, in a specific location, NOT about the class of spacters, or a spacter in the abstract.

 

So, there's this spacter right ... over ... there. There it is. Is it a "thing"?

 

Well, let's see. Is it full of atoms? Well, there are quite a few--maybe a coupla million. Is that enough to make this spacter a "thing"? No? Well, what is the smallest number of atoms you would accept to have this spacter be a "thing"? Apparently, there is some cutoff, D, defined as the lower density limit of atoms per cubic meter that enables the volume to be classified as a "thing".

 

If the spacter is not a "thing", is it "stuff"? There are a coupla million atoms whizzing around in there. OH! They don't STAY in the volume, they're just passing through. Okay. But air is "stuff" and most of the air atoms are just passing through any given volume. Except if you're assuming the volume of the Earth's entire atmosphere, of course. So, air is "stuff" only if you're talking about the whole planet, but air is NOT "stuff" if you're only talking about one cubic meter of it, because the atoms are just passing through.

 

Back to our spacter. It may only contain millions of atoms, but it contains billions of electromagnetic waves. Surely you're not gonna tell me that an EM wave is not a "thing", are you? That would really give me heartburn. EM waves have GOT to be "things" and that's just that. If you don't agree, I'll just take my spacter and go home. Nyah.

 

Okay, my spacter is just FULL of atoms and EM waves and neutrinos! There must be trillions or even zillions of neutrinos in the spacter. Isn't that enough to make it a "thing"? Or at least a "stuff"? Of course, if it IS a "stuff", then we have already established that that is semantically equivalent to a "thing", so think carefully before answering.

 

Oh? You want "space" to be DEFINED as the "nothing" between the "things"? No matter how many "things"? You're a mean one, mister Grinch.

 

Well, what about all the Quantum "foam" going on at the Plank scale? Particle-antiparticle pairs are forming and self-annihilating continuously, like the foam on the surface of a boiling kettle of water. And ALL those particles and antiparticles are "things", right? So, what is the distance between THEM? I mean, we're talking about trillions of trillions of trillions of "things" now! Continuously! I would say that the distance between them is ... well ... ZERO.

 

So, by your definition, there is no nothing at all! There is no distance between the "things"! Therefore, it makes no sense to call the spacter a "nothing"--it contains no nothing at all!!!!!

 

Then what IS the spacter? It's a cubic meter just chock-a-block FULL of "things" galore--far more "things" then that pencil has atoms. So, it's GOT to be a "thing" (or at least, "stuff"), right?

 

I mean, if that spacter is not a "thing", then WHERE do all those particle-antiparticle pairs COME FROM? Don't they come from the very body, or essence, or substance, or being-ness, or exist-ness, or thing-ness of the spacter? Isn't the spacter the source (and sink) for all those P-AP pairs? I would say, that's an incredible property for a non-"thing" to have!

 

You want to dismiss the spacter as a mere "nothing" JUST because it doesn't contain enough "things" inside it!!! Now, I ask you, is that reasonable? Is that sensible?

 

Is that ontological???????????

[modest]

I just wanted to comment that I've found the issues being discussed recently very gripping.

 

It seems that all the descriptions of space or distance that have been discussed invariably amount to the interaction of matter. JediSoul's quote of Einstein says it well:

 

I wish to show that space-time is not necessarily something to which one can ascribe a separate existence, independently of the actual objects of physical reality. Physical objects are not in space, but these objects are spatially extended. In this way the concept "empty space" loses its meaning.

A Einstein, June 9th, 1952.

 

And, moreover, this one which I think reaches a conclusion likewise reached by many in this thread:

 

That the requirement of general covariance, which takes away from space and time the last remnant of physical objectivity, is a natural one, will be seen from the following reflection. All our space-time verifications invariably amount to a determination of space-time coincidences. If, for example, events consisted merely in the motion of material points, then ultimately nothing would be observable but the meetings of two or more of these points. Moreover, the results of our measurings are nothing but verifications of such meetings of the material points of our measuring instruments with other material points, coincidences between the hands of the a clock and points on the clock dial, and observed point-events happening at the same place at the same time. The introduction of a system of reference serves no other purpose than to facilitate the description of the totality of such coincidences.

 

-Einstein 1916a

 

"What is spacetime" is there answered by Einstein himself. It is a system of reference: "The introduction of a system of reference serves no other purpose than to facilitate the description of the totality of such coincidences". Spacetime is a way of describing the interaction of material points. What exists between those points is the question which drives this thread.

 

Michael's assertion that spacetime should not be reified (or made into something of material and independent existence) is most agreeable. It's the same conclusion Einstein comes to above. This means essentially we should give no ontology to space or time whatsoever. They are properties of matter and energy without an independent ontology.

 

Of course, as a description of the interaction of material points or as properties of the ontology of matter—spacetime can very well be non-Euclidean. It can be bent, curved, expanding, contracting, dragged, foamy, and whatever else. As long as we recognize those things are descriptions of the interaction of matter and energy rather than things in and of themselves then nothing prevents them from taking on those properties.

 

Nothing, after all, demands the ontological elements of the universe interact in a Euclidean way.

 

People before me believed that if all the matter in the universe were removed, only space and time would exist. My theory [general relativity] proves that space and time would disappear along with matter.

 

-Einstein

 

~modest

[Michael Mooney]

Forgive me for I have sinned, having sworn off any reply to Modest.

 

Einstein:

"If, for example, events consisted merely in the motion of material points, then ultimately nothing would be observable but the meetings of two or more of these points"

"The meetings?"

From cosmic perspective all events happen objectively as independent realities regardless of "observability." And the "motion of material points" are real even though they can be separated by immense space/distance... regardless of their "meeting" within Einstein's perspective of observation.

 

Einstein:

"Moreover, the results of our measurings are nothing but verifications of such meetings of the material points of our measuring instruments with other material points, coincidences between the hands of the a clock and points on the clock dial, and observed point-events happening at the same place at the same time. The introduction of a system of reference serves no other purpose than to facilitate the description of the totality of such coincidences."

 

This explains very well Einstein's priority for measurement over the actual independent existence of what is measured. So, "time is what clocks measure" rather than "events happen in their own natural dynamic prior to assigning units of measurement as our clocks tick and tell us the duration of each "clocked" event in terms of our assigned units in human devised terms... seconds, minutes, hours, days... millennia, etc.

 

The last sentence is spot on. The obvious implication then is that spacetime is not an extant entity."it" is emptiness and has no properties "of its own." No "dilation of time" or expand/contract-ability, curvature, etc. of space. Space is the emptiness in which "objects" exist... and space is not empty where objects do exist.

 

Modest:

 

Michael's assertion that spacetime should not be reified (or made into something of material and independent existence) is most agreeable. It's the same conclusion Einstein comes to above. This means essentially we should give no ontology to space or time whatsoever. They are properties of matter and energy without an independent ontology."

 

So, can we now "get over" the "making something out of nothing" reification of "spacetime".... and re-write all the textbooks on relativity which do reify "it?"

 

Modest:

"Of course, as a description of the interaction of material points or as properties of the ontology of matter—spacetime can very well be non-Euclidean. It can be bent, curved, expanding, contracting, dragged, foamy, and whatever else. As long as we recognize those things are descriptions of the interaction of matter and energy rather than things in and of themselves then nothing prevents them from taking on those properties."

 

So now we are "bending" the "description", not empty space "itself" as an entity? Good dodge. And, in this paradigm we are keeping the non-Euclidean nonsense about 'no such thing as straight lines' and the non-entity space still curving, expanding, frame-drag wrinkled, foamy, etc. Yet we still have no ontological (real world referents) basis for this concept.

Modest:

"Nothing, after all, demands the ontological elements of the universe interact in a Euclidean way."

 

"Nothing demands?" Logic demands that anyone who posits a medium with the above properties show evidence of real cosmos referents... which the non-Euclidean fantasy (I mean "thought experiment") does not.

It still doesn't fly in the real cosmos.

 

Einstein:

"People before me believed that if all the matter in the universe were removed, only space and time would exist. My theory [general relativity] proves that space and time would disappear along with matter."

 

In fact space is (has always been and always will be) nothingness... the emptiness between (and within) "things." And time is the "when" of it all. It all"takes time to happen," so then time is reified as some "stuff" that "dilates", etc. (Bogus!)

 

(It is really unbecoming to brag, but i do have 18 IQ points on him.)

 

Michael