What is space?

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Offline Firelark

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What is space?
« on: 17/08/2011 07:55:25 »
I was watching a program on TV the other day about the big bang which was very interesting. In the show they explained that time and space began with the big bang.

That made me start to think about what space (and time) is and whether it can be created. I've been looking around on internet about this, and most people, when they explain what space is; they explain what it contains: matter, energy, radiation, vaccum. But I'm interested in what space it self is. Even though space doesn't seem to be made of anything, it clearly exists because it allows me to put my coffie cup (for example [:)]) over here, or over there, or way over there. In other words what is this it that provides this "space" that allows other things to exist whitin it? If space (and time) is not a physical thing, can it be created (by the big bang) and does that allow space (and time) to be infinite and eternal?

I often like to ponder these philosophical questions. I realize the answers to these questions are out of our reach at the moment but I still like to here peoples thoughts about this. People around me usually don't like to talk about these things, and probably think of me a bit of a nerd [;D].

Karl Hansson

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Offline neilep

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What is space?
« Reply #1 on: 17/08/2011 10:21:49 »
Great question !...and welcome to the site Karl!

You're right of course when people cite 'space' as the unlimited expanse in which everything is located...but what is it ?...I want to know too !...I hope you get some good answers !

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Offline graham.d

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What is space?
« Reply #2 on: 17/08/2011 10:25:48 »
It's OK. We're all nerds here  [;D] In answer to "What is space?" I was tempted to put "the final frontier" which speaks for itself.

As you say, really nobody knows what space-time is but just that it has certain properties, as described, for example, in general relativity. In trying to reconcile gravity within quantum mechanics, there have arisen other theories which quantise space-time or which have space-time existing on a 4D "surface" (a brane) in a 5D universe. These theories tend to give a "structure" to space-time and reserve the concept of "nothingness" to something outside of (or before) space-time. That is space-time IS a physical thing. I don't think our brains are capable of understanding this except by analogy, mathematics or perhaps some new language yet to be devised.

Whether space-time is infinite and eternal is another difficult one. From our perspective it seems to have a definite start and may (or may not) have a definite end. But this may be only part of some greater universe or part of a multiverse. I don't think these issues will get resolved any time soon and may never be. It leaves lots of room for speculation though.

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Offline Soul Surfer

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What is space?
« Reply #3 on: 17/08/2011 10:40:42 »
Space can be explained in a similar way to time (which is what stops everything happening at once) that is, it is what stops everything happening in the same place!  The real fundamental components of the universe are energy and momentum and these in effect create time and space as things happen.  we actually infer the existence of time and space from the way that the energy and mometum behaves.   

For a more detailed explanation of this vital principle see   New Scientist  6th August issue  Page 34  "Beyond space-time". also my reply in  15/08/2011 17:23:34 »  to  http://www.thenakedscientists.com/forum/index.php?topic=40515.0

« Last Edit: 17/08/2011 10:43:41 by Soul Surfer »
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Offline Don_1

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What is space?
« Reply #4 on: 17/08/2011 15:25:39 »
There's no 'space' here on our planet, just swing your arms around in an 'empty' room and you can feel something. The air around us. So if you put your coffee cup down here, you will not be filling a space so much as displacing the air that was there before. Also, you'll find I'll nick your coffee!

But outside the confines of our atmosphere, there seems to be 'space', ie the apparent emptiness between the bodies of the cosmos. The question is, what is this 'space'? Is there actually something there? Perhaps gravity, repulsion, time???? Perhaps a particle we are unaware of, a particle which does not conform to the physics we understand.

An even bigger question is, if the universe is expanding, expanding into what? If there is 'space' between the bodies of the cosmos, can 'space' expand? What is 'space' expanding in to? Could there be something which is 'spaceless'? A true void? (Like the inside of my cranium!) A void which has no 'space' and no time and is truly infinite.
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Offline neilep

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What is space?
« Reply #5 on: 18/08/2011 00:52:00 »
Firelark wants to know what the nothingness in space is ?..what the void is made from....I want to know too !..I'm going to ask my cat !
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Offline Firelark

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What is space?
« Reply #6 on: 18/08/2011 07:10:24 »
Thanks Neilep. I love the radio shows.

Graham, thats a great post. I've heard about the brane theories and they are definitely interesting, I need to read up on this though. I guess it would be like a character living in a 2D universe trying to visualize a 3D universe, he would have no concept how it would look. And if this 2D universe was curled up into a sphere it would appear that his universe is infinate or at least feeding back on it self.

Is space concidered to be part of the universe or is the universe a part of space? When people say that the universe is expanding do they mean that actual space is expanding or just that the matter inside of the space is flying appart? If they mean that the actual 3D space is expanding; what are the arguments for this? If the space it self is expanding wouldn't everything (including my coffiecup [;D]) then be flying apart not just galaxies?

The questions of what space is, also involves the questions of what is non-space, i.e. what lies outside the realm of space. There seems to be a structure to space, at least in 3 dimentions (4 if you count time), does this structure not exist outside of space? I imagine that infinity must exist at some plane, because if something lies outside of our space, something must lie outside of this something (at least our own space does), and something must lie outside of that and so on into infinity. Instead of imagening some alien non-space(s) laying outside of space what is there to stop us from believing that it is just ordinary space that is stretching into infinity and that our universe is just a collection of parts that is flying away from each other inside this space?

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Offline Phractality

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What is space?
« Reply #7 on: 18/08/2011 08:01:25 »
Since you posted this question in the mainstream physics section, we're only allowed to give mainstream physics answers. The idea that empty space has substance was mainstream until about a century ago. In his Leyden address, Einstein expressed his dislike of the idea that there is no æther, but he reluctantly conceded that the existence of æther is a moot point, since there appears to be no way of distinguishing it from any other reference frame. Since then, the mainstream of physics has falsely attributed to Einstein the conclusion that there is no æther.

Absent a theory of æther, space is nothing, and light is a wave which propagates without a medium. If that answer does not satisfy you, then you need to look outside the mainstream of physics.

There is a certain moderator, here, who is in the habit of hiding my posts for merely mentioning æther in the mainstream physics section. So that's all dare say about it, here. If you want to learn about æther theories, you should ask again in the new theories section.
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Offline graham.d

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What is space?
« Reply #8 on: 18/08/2011 08:57:01 »
When it comes to the expansion of the universe it is that thought that space is expanding and not matter flying apart. Again there are theories about this but the one that holds most traction is that space is being created or, looking at it another way, more space is being encompassed within our universe; this is consistant (at least qualitatively) with the concept of Dark Energy.

For accessable discussions on Brane theories look at lectures by Prof. Lisa Randall (MIT)
For work on Space-Time structure look at work on "Loop Quantum Cosmology"

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Offline Firelark

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What is space?
« Reply #9 on: 18/08/2011 09:23:07 »
I don't know much about the aether theories but I'm not sure it is the same thing I'm looking for. I'm basically looking for what is it that allows something to have a position and orientation. In my mind I see a basic 3D euclidian space structure, but how come this structure (or which ever structure space has) exist in reality, it doesn't seem at all obvious why that has to be.

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Offline graham.d

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What is space?
« Reply #10 on: 18/08/2011 12:51:41 »
Firelark, try reading the overview in the wiki page on Loop Quantum Gravity:
http://en.wikipedia.org/wiki/Loop_quantum_gravity

I think it's quite good as a simple intro to the subject. I am definitely no expert on this although I know someone who is. The trouble is it takes a long time to even get to understand the terminology, let alone the maths. And really the maths is essential for a good understanding I think. For a very thorough study on the subject works by Martin Bojowald are good but it's hard unless well beyond degree standard physics:

http://relativity.livingreviews.org/Articles/lrr-2008-4/

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Offline Firelark

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What is space?
« Reply #11 on: 18/08/2011 14:06:28 »
Thanks Graham I'll check these sites out [:)]. I'm also currently reading Roger Penrose book "The Road To Reality". I've only just started reading it and it's a huge book, so it will probably take me some time to read through it (I'm a slow reader [:)]). But I hope and I think it will cover some of this stuff as well. I'm not a mathwizz either but I do have some understanding of it [::)], and I'm generally fairly confident with vector math.

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Offline Firelark

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What is space?
« Reply #12 on: 19/08/2011 07:35:04 »
Graham That Loop Quantum Gravity theory is very interersting! I've only really read the wiki page yet but I'll also have a look at the other link.

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Offline graham.d

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What is space?
« Reply #13 on: 19/08/2011 09:47:49 »
The other link is a complete summary of all the work on the subject. I'm afraid it is very heavy going :-)

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Offline yor_on

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What is space?
« Reply #14 on: 21/08/2011 19:28:48 »
Space is defined through gravity. and depending on your motion relative the 'gravity gradient' you can magically make it disappear. Motion is defined in two categories, accelerating (aka 'gravity') and uniform (aka 'geodesics').

Motion is a description of something having a distance and a duration of 'travel'. The duration of travel falls under 'clocks'. Clocks is a definition of 'time' and also of a 'arrow', that is that linear causality chain we observe, also making it possible for us to define repeatable sequences and experiments.

But motion is also a description of something changing depending on from where you observe it. Time is also a subject of change, as observed from your own unchanging 'frame of reference' time-wise. So the room can shrink, others time can compress, or become 'elongated' in durations relative you, conceptually that is, but your own 'time durations' will always be the same, relative your clock.

Space exist, time exist, but inter connected, and the description you find will be yours, mine will be slightly different. What connects it all though is the conceptual definitions we can find in joining a same 'frame of reference', as Earth becomes to us. From there we experience ourselves as being together, having the same durations, and definition of distance.

But SpaceTime?
« Last Edit: 21/08/2011 19:31:27 by yor_on »
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Offline lightarrow

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What is space?
« Reply #15 on: 21/08/2011 20:23:46 »
Forget space or spacetime.
We live in an 8-dimensional "phase space":
http://www.newscientist.com/article/mg21128241.700-beyond-spacetime-welcome-to-phase-space.html

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Offline granpa

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What is space?
« Reply #16 on: 22/08/2011 04:54:16 »
space is filled with events interacting in a space-like way.

however, through entanglement some events interact in non space-like ways.

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Offline MikeS

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What is space?
« Reply #17 on: 22/08/2011 10:50:05 »
Does light require a medium through which to propagate? 

The only thing we know of that fills all of space is the gravitational field.
Or the gravitational and time field.

Could the gravitational field be the 'medium' through which light propagates?
Or perhaps the gravitational and/or time field?
Time, by itself would appear to have no features through which light could propagate but light does propagate over time.

Just a thought.


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Offline yor_on

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What is space?
« Reply #18 on: 23/08/2011 02:17:20 »
I agree in one thing Lightarrow. Smolin is one of the most interesting thinkers I know of. But it still has to be proven.

But Smolin does not ignore relativity, neither in Loop quantum gravity, nor here. And does not assume that relativity is wrong either, even thought the author from Nature seems to angle it that way?

He's continuing an idea that Max Born had 1938 in where he "saw that several key equations in quantum mechanics remain the same whether expressed in spacetime coordinates or in momentum space coordinates. He wondered about a union of general relativity and quantum mechanics. Born reciprocity suggests that if spacetime can be curved by mass then so can momentum space."

As for if it really is this way? I don't know, but his idea of looking at as a momentum space makes sense to me, and assuming that it can 'bend? Even though we do not know why it would, you might assume it as a sort of symmetry, possibly?

He's interesting.
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Offline yor_on

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What is space?
« Reply #19 on: 23/08/2011 02:34:40 »
The point here is 'bend'. If it does, then you can still assume light as a 'constant'. If it on the other hand would be dependent only on the photon 'energy' and so have different 'velocities' then light as a constant will fail, and with that a worst case scenario would be that we needed a new theory of Einsteins SpaceTime. Against that is all those experiments we found validating it.
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Offline Robro

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What is space?
« Reply #20 on: 23/08/2011 18:45:10 »
I tend to think that the very volume of "space" is made of all the electromagnetic phenomena that is observed in nature. To back up my thoughts on this, consider that nothing has EVER been observed in this Universe to be comprised of anything other than electromagnetic energy. So, in light of this, perhaps the question is as void as the answer here, and maybe "space" is an illusion of volume brought on by electromagnetism, the only thing ever observed so far in nature.
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Offline yor_on

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What is space?
« Reply #21 on: 24/08/2011 02:52:45 »
So atoms are electromagnetic now?
And gravity too :)
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Offline imatfaal

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What is space?
« Reply #22 on: 24/08/2011 11:01:04 »
So atoms are electromagnetic now?
And gravity too :)

Not sure how many observations you will be able to list that aren't mediated at one point through the electromagnetic force/photons
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Offline MikeS

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What is space?
« Reply #23 on: 24/08/2011 16:53:21 »
quote
What is space?

Nothing.

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Offline yor_on

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What is space?
« Reply #24 on: 24/08/2011 20:27:25 »

Gravity.
HUP. I know, one can argue about that one, but to me it is HUP that lays the ground for QM. And sort of find some own remarkable definition of 'time' from assuming a possible superposition of all states before the measurement, where statistics and matrices will define the probability of a outcome. You could see is as we have time, like a surface moving forward, where that surface has passed you will have classical outcomes, but inside that surface at 90 degrees to existence you don't have a 'time' at all, at least not a 'arrow'. Instead you have it all, coexisting on a very small plane, and as we can't define a arrow to it, without classical motion.

What we see after that is 'forces' under a arrow with a direction. The more confusing way is to discuss it as 'seething with possibilities' and 'fluctuation' which both imply a 'motion' to it.

Amongst others.
But radiation is a seriously weird subject.

So yes, assuming that a photons is a 'wave' in a electromagnetic field, it is something defined by electromagnetism. But photons are not 'gravity', and they are not diverged by a electrical or magnetic field.
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Offline yor_on

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What is space?
« Reply #25 on: 24/08/2011 20:41:16 »
And to be perfectly correct, what seems to be the primeval 'carriers' are the, so called, 'virtual particles', those that we can't measure inside our arrow. I see it as a matter of personal taste how you define them, inside Planck time or outside. Defining them inside should give them a 'motion', as they then will be inside our definitions sensible. Thinking as I though, they are 'outside' Planck Time, which then makes them outside of our definitions of 'motion' too.
==

And they are, as I see it, creatures of HUP.
« Last Edit: 24/08/2011 20:43:08 by yor_on »
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Offline lightarrow

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What is space?
« Reply #26 on: 24/08/2011 23:37:26 »
I agree in one thing Lightarrow. Smolin is one of the most interesting thinkers I know of. But it still has to be proven.

But Smolin does not ignore relativity, neither in Loop quantum gravity, nor here. And does not assume that relativity is wrong either, even thought the author from Nature seems to angle it that way?
The idea is that General Relativity is not wrong, but it's just a sort of approximation of a reality which is also quantistic, at smaller levels.

In this context, the 4-dimensional spacetime is just one face of the coin, the other being the 4-dimensional momentum space; both would be non-absolute, while, putting them together in a 8-dimensional "something", it would become absolute (invariant). So the theory would like to be even a... generalization of General Relativity  [:)]

Have you ever thought to the fact that the Heisenberg principle, in the form Δx*Δpxh, means that there exist a minimum "area" = h, in a coordinate system where one axis is x and the other px?
That is space phase.

Using all the three spatial coordinates and time, you have an eight-dimensional phase space.
The Heisenberg principle is nothing than the fact "phase space" has an element of "volume" equal to
(Δx*Δpx)*(Δy*Δpy)*(Δz*Δpz)*(ΔE*Δt) = h4

Things become to be more clear in phase space, isnt'it?
« Last Edit: 24/08/2011 23:40:28 by lightarrow »

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Offline Robro

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What is space?
« Reply #27 on: 25/08/2011 05:33:01 »
Not sure about any "virtual particles". Consider that the photon, whatever type it may be, always migrates toward increasing field strength. Massive objects "bend" light waves of photons, and what do massive objects pour out into space, "Electromagnetic Fields"! I do not think that gravity is a mysterious force propagated by any special unobserved phantom particles such as gravitons. I do think however that photons reach their maximum amplitude of, and  between, their electric and magnetic oscillations in the direction that they travel, this is the point of the photon most forward in association to the electric and magnetic fields that emanate from it. As the photon encounters electromagnetic fields through it's journeys, it reaches maximum saturation for it's specific wavelength in an offset toward increasing field strength, causing it to "curve" toward that increase in field strength.

Consider that a photon produces two distinct things, an electric field and a magnetic field. Something happens at the tip of the photon between these two entities. Perhaps it is a vortex of sorts, where these two fields fold around each other, like the spike of energy in a wave. And the rate at which this takes place governs the total amount of energy the photon exhibits.

It is difficult for me to visualize gravity as a "pulling" function. I tend to think of gravity as a "propagating" phenomenon.
« Last Edit: 25/08/2011 05:41:20 by Robro »
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Offline yor_on

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What is space?
« Reply #28 on: 29/08/2011 04:50:06 »
Hm, you're putting together HUP and phase space :)
Wish I knew Lightarrow? (Seem to write that a lot those days, don't I.)

But I don't know, if we assume that there are photons, and that they are propagating, then they must have a motion. What exactly are you imagining as a momentum space? To me it must be those particles propagation. They are what will consist of a measurable momentum, at any point defined, under their propagation.

And to then split the 'particle' from its momentum? In a way I can think of it as only being momentum, everything being translated into that, but that's no different to me than thinking of it as we see it 'normally'. It's just a shifting of gears. I could as easily describe it all in form of changing densities with space then becoming some sort of limit for our observation.

Another one that I really like, as it fits my ideas better, is to see it all as a numberspace. In that space nothing 'moves', but the numbers change their value. And from that you can get a 'motion' too as I think of it. But the honest truth is that I don't know, but wished that I did :)

But maybe I'm missing the point here. You will have to explain to me how a momentum space becomes something new in physics?
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