What do we mean by space ?

[TaoRich]

If we want to talk about the "origin of space" or the "emergence of space" as a first principle - before we introduce anything inside it ... what is it that we are actually referring to ?

 

Sometimes the simplest questions are the hardest:

 

"What do we mean by 'space' ?"

 

Outer space ... sure that's easier to define:

 

http://en.wikipedia.org/wiki/Space

Space is the boundless, three-dimensional extent in which objects and events occur and have relative position and direction

But what is "space" as we commonly refer to it, the "framework":

• in which we exist
• in which "things" exist
• in which we define and conduct experiments, observe the results and interrelationships, and deduce conclusions

How do we define this "framework" from first principles:

 

"Something" with:

1. dimension
2. volume or capacity (to store or house something)

Is that complete ?

• Are both conditions necessary ?
• Are they sufficient ?

And what is the "something" ?

 

{ Too tired to engage my brain to find a better word for now. }

 

 

[michel123456]

Good question.

There is a procedure when coming to very basic question.

It is to make it even simpler, to reduce to minimum, then to ask again.

Following standard theories, space is not alone, there is a spacetime continuum of 4 dimensions.

 

The procedure consists to eliminate as many dimensions possible.

 

From the x,y,z,t dimensions, you can easily get rid of some. Consider a point object moving along a straight path, you need only x & t, y & z are redundant.

The remainings x & t, these are distance & time.

 

So the question of "what is space" can be reduced (??) in a more complicated double question: what is distance and what is time?

 

Well, because "what is time" was not part of the opening question, and it is too difficult to get any straight answer, you may avoid to go into this part.

 

The question is then "what is distance"?

 

Keeping in mind that the answer must involve time somehow, because time & space are intricated, and not answering simultaneously the question "what is time" was basically an error.

[Schrödinger's hat]

It's a way of sorting events.

Without spacetime there'd just be events, no order to them. No system or way of interacting to anything.

event a1 is tied to event b1 which interacts with c1 and so on

but a1 also interacts with a2 etc

so we pick an order call one of these sets of links up/down

then left/right, there are still lnks we haven't accounted for, so forward/back, time

until we run out of degrees of freedom

lots of these events are boring (empty space), but one event is linked to those around it forward in time, and backward in time, we look at these links, and what types of links there are, these are the laws of physics

whether all the events exist objectively, or they're created is a bit of an open question (determinism)

hmm, this is hard to tease apart

 

If you want the ontology of it (what is it, rather than what is it isomorphic to) I can't really help you.

My ontology broke down just as I got past quantum town and be damned if I can get the parts to fix it.

[DrRocket]

If we want to talk about the "origin of space" or the "emergence of space" as a first principle - before we introduce anything inside it ... what is it that we are actually referring to ?

 

Sometimes the simplest questions are the hardest:

 

"What do we mean by 'space' ?"

 

 

In any theory there are some things that are taken as "primitive" and understood without definition. You cannot write a dictionary starting from the initial premise that no words are understood.

 

"Space" (or "distance") and "time" are such terms.

 

The best that we have are the operational definitions "distance is what rulers measure" and "time is what clocks measure". No better definition currently exists. Philosophers tend to obfuscate rather than illuminate when they address the issue.

 

More fundamental definitions could be very valuable. but I am not going to hold my breath in anticipation.

[Schrödinger's hat]

Agreed, DrRocket. I'd also assumed this thread was in philosophy without looking. Could it be moved? I think this is more of a philosophical question than physical.

I don't think philosophy is worthless regarding these questions, sometimes it provides useful insights. It's a good idea to stop the science every now and again, look at the fundamentals and see if you can make progress in this regard.

In the same way, philosophising for too long is useful without spending a while on the science.

[DrRocket]

 

I don't think philosophy is worthless regarding these questions,....

 

 

http://depts.washington.edu/ssnet/Weinberg_SSN_1_14.pdf

[michel123456]

There is a physical relation between distance and time. Physical I mean, not philosophic.

[Schrödinger's hat]

http://depts.washing...rg_SSN_1_14.pdf

Of course philosophers are useless!

I said philosophy, not philosophers.

I agree that the science and maths should lead the way, but sometimes we should sit and ponder afterwards.

Make up stories to help teach it to others and make it more understandable. There's something both comforting and helpful to the intuition about having ontological objects to work with. Be they little ball-like particles, wiggling electrons, or universe-permeating fields.

Maybe even break down some concepts, find a little crack that we can wedge open with more maths and experiment.

 

I guess that in many ways, this is indistinguishable from doing more physics.

It's certainly not the thing that philosophers do (for the most part).

I used the word because I wanted to distinguish between These two things:

Breaking down or creating new assumptions and predicates. Along with finding new representations, stories and ontologies for theories which do not add any predictive power, merely make them easier to use. I call this philosophy for want of a better word. The kind of philosophy done by someone who is very familiar with physics.

and

Finding new mathematical objects, making new assumptions, combining predicates and assumptions, making predictions and doing experiments. I call this science.

 

I'm not quite sure where to put the making new assumptions part, it fits in both to a degree, although better in the latter. Perhaps this is why we shouldn't draw these sharp distinctions and accept that there is a continuum.

Edited March 3, 2011 by Schrödinger's hat

[DrRocket]

Of course philosophers are useless!

I said philosophy, not philosophers.

I agree that the science and maths should lead the way, but sometimes we should sit and ponder afterwards.

Make up stories to help teach it to others and make it more understandable. There's something both comforting and helpful to the intuition about having ontological objects to work with. Be they little ball-like particles, wiggling electrons, or universe-permeating fields.

Maybe even break down some concepts, find a little crack that we can wedge open with more maths and experiment.

 

I guess that in many ways, this is indistinguishable from doing more physics.

It's certainly not the thing that philosophers do (for the most part).

I used the word because I wanted to distinguish between These two things:

Breaking down or creating new assumptions and predicates. Along with finding new representations, stories and ontologies for theories which do not add any predictive power, merely make them easier to use. I call this philosophy for want of a better word. The kind of philosophy done by someone who is very familiar with physics.

and

Finding new mathematical objects, making new assumptions, combining predicates and assumptions, making predictions and doing experiments. I call this science.

 

I'm not quite sure where to put the making new assumptions part, it fits in both to a degree, although better in the latter. Perhaps this is why we shouldn't draw these sharp distinctions and accept that there is a continuum.

 

agreed

[TaoRich]

Morning folks,

 

Brain a bit clearer now, and the first thing I noticed was my botching of the topic question:

What do we men by space ?

Should actually have been:

What do we mean by space ?

Now on to the responses - thanks again to all who have commented.

I must make it clear, I am asking about science here and not philosophy.

I'm stepping backwards in first principles, right down to the "zero'th" principle.

 

My starting point(s) for my question here (and for the paper I am working on) is this/are these:

 

• nothing exists
• no-thing exists
• no space exists
• time has not yet begun

I'm working on defining the physical nature, behaviour, characteristics and properties of the very first elemental fundamental space to emerge from the nothingness.

• It emerges out of no-where.
• Prior to its emergence, there is no other space
• It does not expand into an existing space
• It does not expand within any existing framework

As it expands, it creates the very first space.

As it expands, it does so over time, and hence space-time emerges from the emergence of this fundamental space.

 

- - -

Revisiting my initial "definition" I think this might be slightly better:

 

We define "space" to be a fundamental field with properties of:

• dimension
• volume

Again, to repeat myself, I'm not musing philosophically.

I'm setting out to:

• define a formal mathematical and physical model of an fundamental self-emergent quantum space "cell"
• where the "space cell" is comprised of interacting "elemental spaces"
• from which I derive a (dynamic) field density equation across the profile of the interacting spaces
• which I believe will provide insight into a basis for quantum gravity

Edited March 3, 2011 by TaoRich

[ajb]

In special and general relativity space-time means the collection of "all possible events". Mathematically we model this by understanding "all possible events" as points on a Riemannian manifold (pseudo-Riemannian technically).

 

By "space cell" it sounds like you are flirting with noncommutative geometry. You treat a noncommutative algebra as if it were the algebra of functions on some "noncommutative space". The trouble I think really lies in what replaces the smooth structure: what is a "noncommutative differential manifold"? I think that is a story to be told another time.

Edited March 3, 2011 by ajb

[lemur]

It's a way of sorting events.

Without spacetime there'd just be events, no order to them. No system or way of interacting to anything.

It is a conceptual basis for various forms of social power/domination/control. By delineating it according to boundaries, the concept of territory is created along with territorial "belonging" or "misplacement." This, in turn, allows for the projection of natural-legitimation for removal or retention of certain elements/objects/people/etc. in order to "relegate" things to "their proper places." This bounding and separation of space into multiple "spaces" (areas/regions/territories) then allows for differentiation between inside and outside. These are used as basic concepts for psychological associations with behavioral rewards and punishments, including that of ego-identification ("my" or "our" territory as "insiders," "the place where I belong," etc.) This, in turn, is connected with psychological/cultural differentiations between public and private "spaces" where different activities are allowed or resisted with the effect of generating general psychological partitioning and differentiation between plural regions/spaces, which have come to seem naturally distinct and different.

 

Free of spatial-containment cognition, people would have to directly interact with other people and objects without reliance on assumptions about super-individual authority. They would also have to commit actions directly and actively instead of being able to engage in indirectness and passive-reactionism. These are some social-political implications of spatial sorting, which are somewhat derived from or associated with physical science's use of spatial ontology but of course applied in rather different contexts and discourses.

 

 

[TaoRich]

In any theory there are some things that are taken as "primitive" and understood without definition.

<snip>

"Space" (or "distance") and "time" are such terms.

 

Back in my University days - during Maths I and Physics I - for some reason I was deeply uncomfortable with the "foundation on which the higher-level arguments" were built.

 

I always felt there was something missing - that there was something "shaky" at the root.

 

Somehow I had this (intuitive) feeling that I was being led into a house of cards, but I could never quite work out from whence exactly my discomfort stemmed.

 

That's what started me off on this 15 year track of investigation.

 

"What if these primitives that we take for granted shouldn't be taken for granted. Do they bear further investigation ?"

 

In my exploration of this "topic" I often feel like a janitor in a Physics Lab lifting up the carpet to see what is underneath.

 

I'm not saying that any of Physics has it wrong - it's just that I resent anything I can't understand.

 

I'm not content to walk on the carpet and take it for granted - I need to understand for myself what supports it.

[Schrödinger's hat]

Your sentiment reflects what I understand to be that of the main thrust of quantum gravity and string theory research.

 

It all gets very abstract before we even make it as far as the standard model/symmetry, we can build comforting stories and ontologies for everything up to QFT and GR (in fact, the story is a lot easier to understand than the theory), but eventually our analogies get stretched too fair. I feel the reason for this is twofold:

We are starting to get to concepts that are very alien to our every day experience, and the language we use will be quite alien and seem very abstract as a result.

These are the newest theories for the world, so we haven't had time to think of good stories (as relativity was a good story for the Lorentz transforms and the strangeness of Maxwell's equations) yet. Or find good ways of explaining the stories (most undergraduates today can understand the rockets-tied-by-string scenario, whereas it allegedly confounded a room full of researchers when first presented).

[DrRocket]

"What if these primitives that we take for granted shouldn't be taken for granted. Do they bear further investigation ?"

 

 

Sure.

 

But in the meantime taking time and space as primitive is the best that we can do.

 

Any more fundamental, and useful (not a bunch of philosphical mumbo jumbo), definitions would be a great step forward.

 

 

My understanding is that lattice (discrete) theories have been attempted but have failed.

 

If you can build better predictive theories than GR and QFT on some new concept of time and space that would be terrific. People are trying. Results thus far are underwhelming. Ver Linde has a pre-print in which he sees "space" as emergent from information -- but I see way too much vague hand waving in his "logic", and it has been awfully quiet since he gave his talk..

[ajb]

My understanding is that lattice (discrete) theories have been attempted but have failed.

 

Like causal set theory. I remember Fay Dowker giving a talk about in Sussex, must have been about 2005. I have no idea what the current status is.

[michel123456]

But in the meantime taking time and space as primitive is the best that we can do.

 

As stated before, there is relation between space & time. They may be considered "primitives", but they are related.

 

It has been established that mass cannot move through space without spending time.

 

There is a reverse statement that has not been established yet: mass cannot move through time without spending space.

 

Read it three times.

[DrRocket]

As stated before, there is relation between space & time. They may be considered "primitives", but they are related.

 

It has been established that mass cannot move through space without spending time.

 

There is a reverse statement that has not been established yet: mass cannot move through time without spending space.

 

Read it three times.

 

Three is not eough,

 

Whar in the world is that supposed to mean ? Any of it.

[michel123456]

As stated before, there is relation between space & time.

 

That is speed.

 

They may be considered "primitives", but they are related.

 

That is spacetime.

 

It has been established that mass cannot move through space without spending time.

 

That is the barrier of speed of light.

 

There is a reverse statement that has not been established yet: mass cannot move through time without spending space.

 

That is new*.

It should mean that massive bodies in some manner must move through space continuously. It has been observed.

 

"everything in the universe is moving.", Wikipedia 21st Century

Τα Πάντα ῥεῖ, (Ta Panta rhei, everything flows) Heraclitus 535–475 BC

 

*New from 3000 years ago.

[jajrussel]

I am a little late to this thread...

I agree that there is a relationship between time, distance and speed; but why do you imply that distance and space are the same thing?

[michel123456]

I am a little late to this thread...

I agree that there is a relationship between time, distance and speed; but why do you imply that distance and space are the same thing?

 

Wiki's definition is

Distance is a numerical description of how far apart objects are. In physics or everyday discussion, distance may refer to a physical length, or an estimation based on other criteria (e.g. "two counties over"). In mathematics, a distance function or metric is a generalization of the concept of physical distance. A metric is a function that behaves according to a specific set of rules, and provides a concrete way of describing what it means for elements of some space to be "close to" or "far away from" each other.

 

"numerical description" means "measurement".(description has a broader meaning, but they are basically the same)

 

My definition would go like this:

Distance is a one dimensional measurement of space.

 

If you accept the above, you can say that distance is the measurement of space reduced to one dimension.

 

And if you accept the above, the next step consists at saying that measurement coincides with reality.

 

Then you obtain distance = [one dimensional] space.

 

This is my syllogism.

Edited March 29, 2011 by michel123456

[lemur]

Wiki's definition is

 

 

"numerical description" means "measurement".(description has a broader meaning, but they are basically the same)

 

My definition would go like this:

Distance is a one dimensional measurement of space.

 

If you accept the above, you can say that distance is the measurement of space reduced to one dimension.

 

And if you accept the above, the next step consists at saying that measurement coincides with reality.

 

Then you obtain distance = [one dimensional] space.

 

This is my syllogism.

I'm not so sure that dimensionality is the same thing as "space." E.g. if you travel in a straight line in any direction on a sphere, you eventually end up where you started. If all space worked like this, what would that imply about "space/volume?" Further, if spatial dimensionality on the surface of a sphere can be deconstructed by recognition of the sphere as the dominant reality, who is to say there's not yet another level that is even more dominant, which renders sphericism itself a function of some other "truer form?"

[jajrussel]

Distance is a physical measurement. Point A to point B. Point A and point B can always be said to have a physical relationship even though as separate systems they may seemingly act independent of each other. There is their synchronic relationship to time; there is their gravitational relationship, etc… Space though difficult to define is to some degree defined. We expect certain things of it. It shares a synchronic relationship to time; it takes shape or is shaped by matter. It is as much a thing, as point A and point B is, in that it is independent of A and B, but is so correlated to A and B that either A or B would not exist except for space. I will grant that most of spaces properties, if not all, are implied, but most of those implications are accepted and generally expected. We say that space is expanding and accept the statement as fact, because we can not conceive matter moving through an area where there isn’t space. More important for this discussion, we can measure sections of space using the same system we use for matter, and we express the measurement as distance.

Your argument concludes that one dimensional space exists; there would be no measurement.

 

I apologize for the statement that there would be no measurement. I tend to see a line as a string of multiple points. I forget that most people see a line as a representation of a single dimension.

 

I still question if one dimensional space exist?

Edited March 29, 2011 by jajrussel

[Mike Smith Cosmos]

Back in my University days - during Maths I and Physics I - for some reason I was deeply uncomfortable with the "foundation on which the higher-level arguments" were built.

 

I always felt there was something missing - that there was something "shaky" at the root.

 

Somehow I had this (intuitive) feeling that I was being led into a house of cards, but I could never quite work out from whence exactly my discomfort stemmed.

 

That's what started me off on this 15 year track of investigation.

 

 

 

 

 

I am sure you have probably come across Lee Smolin A lecturer ( Prof or Dr ) at the Peninsular Institute Canada ( an offshute of Princetown University ) He came up with Loop quantum gravity as a link from/between quantum mechanics and relativity. He found that space rather than being a backdrop to " things" came out of, and with, the loops and knots . See The road to reality by Lee Smolin

 

 

 

Edited March 30, 2011 by Mike Smith Cosmos

[lemur]

I am sure you have probably come across Lee Smolin A lecturer ( Prof or Dr ) at the Peninsular Institute Canada ( an offshute of Princetown University ) He came up with Loop quantum gravity as a link from/between quantum mechanics and relativity. He found that space rather than being a backdrop to " things" came out of, and with, the loops and knots . See The road to reality by Lee Smolin

Thanks for posting this reference. I googled it and read the Amazon preview pages. There is a nice quote that I'd like to copy and paste but I can't. I don't want to retype it word for word so I can just paraphrase it as basically comparing space to a sentence where if you would take all the words and phrases and subject-predicate-object relationships out of it, you wouldn't be left with an empty sentence - you'd be left with nothing. That's a pretty good (and original) analogy for space, I think.

Edited March 31, 2011 by lemur