What is space?

[Dr. Funkenstein]

Observations of all other space's, have a limit to what can fit into them, to a point where nothing added other, can fit in. Except astronomical space. What is this space? It seems to be a vast and endless void, where countless of solar systems can not only fit in quite comfortable, but can travel within it with relative ease. How could it be so vast that it's big enough to hold an event that hadn't taken place yet in advance, (Big bang theory). Take into account "Dark" matter/ energy which is theorized outside of traveling light being bent by it, what is it's relation to space, is it the fabric of or just another substance that popped up like we have been theorized too.

[Nicholas Kang]

I think the astronomical space and the ordinary space are the same thing. Just it is a bit hard to realize this fact because we live in it. Space have something to do with dimensions. Famous examples include string theory-11 dimensions and Relativity- 4 dimensions.

[Mordred]

Welcome to the forum in terms of cosmology the best way to think of space is simply geometric volume, space itself has no other properties other than volume that volume is simply filled with the energy-density contents of the universe.

 

as far as to what space is expanding into you may want to read this article.

 

http://www.phinds.com/balloonanalogy/ : A thorough write up on the balloon analogy used to describe expansion

[Nicholas Kang]

Dear Mr. Morderd,

 

Please allow me to ask you one question: Are you welcoming me or Dr. Funkenstein? Or both?

Do you mean I am not very experienced in terms of cosmology? I can understand that. Never mind, I won`t get angry.

 

Dear Dr. Funkenstein,

 

Trust is necessary only if somebody doesn't want to learn.

[ajb]

What is this space?

I don't think you will ever find a completely satisfactory answer to that. From a physics perspective we don't really care what it is, rather we are looking to construct and test models of nature. In that respect as long as we know how to deal with space and indeed time in our models then we are happy. Some philosophical ideas about space and time may arise from these models, but generally "what is" type questions are more philosophy than physics.

 

So, my answer to your question is that space-time is the arena of physics, it is where it all happens.

[Mordred]

Dear Mr. Morderd,

 

Please allow me to ask you one question: Are you welcoming me or Dr. Funkenstein? Or both?

Do you mean I am not very experienced in terms of cosmology? I can understand that. Never mind, I won`t get angry.

 

Dear Dr. Funkenstein,

 

Trust is necessary only if somebody doesn't want to learn.

I'm welcoming Dr Funkenstein, as it was his first post on the forum

[Nicholas Kang]

Sorry, Mr. Mordred. I am a bit suspicious. Sorry. I don`t mean to raise that problem. But to me at the first sight when I see your reply, it seems ambiguous. Maybe that is my problem. Sorry, I shall apologize anyway. It is my fault.

[Dr. Funkenstein]

To: ajb, philosophical questions are the driving force behind science, the "what is" question is paramount to understanding the phenomena. my question was scientific, I see no value in not understanding space other then how to use it, using it comes with understanding it. However maybe a answer to this question is beyond our detection.

 

To: Mr. Kang, Dimensional theories aside, your profile pic of the earth indenting onto space is the prevailing view that we have of space, this view depicts space as a foam type of substance that indents (warp) under the weight of the astronomical body, if this is true then the question is what is this substance, and upon further inquiry, would not the indention of the whole of the galaxy have a greater warp/indentation then a single astronomical body, Hubble has shown that galaxy's move through space in every angle possible, indentions therefore can not be obvious on flat views and non existence on angled realities.

Edited June 12, 2014 by Dr. Funkenstein

[Mordred]

actually his pic of space-time warping is an image of a mathematical relation between gravity and matter interactions

 

the warping of space in GR is often misunderstood, the term spacetime has special meaning in physics

"In physics, spacetime (also space–time, space time or space–time continuum) is any mathematical model that combines space and time into a single interwoven continuum".

In other words the warping is simply a mathematical descriptive used in GR to describe the geometric relations between gravity and matter.(including light paths,etc) Not space itself, GR does not state that space has a fabric or substance.

any form of physics deals with mathematical relations, even particle physics. Most of the equations used in particle physics are in actuality differential geometry equations.

 

in other words

 

GR is a theory of geometry. In GR space-time is not represented by a "fabric", but with a mathematical description known as a tensor (energy-mass tensor, stress tensor etc) that describes how the geometry of space-time will affect objects, and how objects will affect the geometry of space-time. In other words, it describes how objects interact with each other by changing the geometry of space-time.

Note that there is NO description of a fabric, sheet, or anything else analogous to a physical object. It's pure geometry.

 

The only property space itself has is geometric volume or distance.

 

 

Universe geometry is the same in that the shape of the universe is a mathematical descriptive of the energy-density relations of all contributors,(matter,dark energy,gravity, etc) will have positive or negative pressure relations with one another, if the total energy-density is the same as or close to the critical density then the universe is flat. This is essentially a pressure distribution relation.

see here for more detail on Universe geometry
http://cosmology101.wikidot.com/universe-geometry p
page 2
http://cosmology101.wikidot.com/geometry-flrw-metric/

As expansion occurs there is simply more volume, the rate of expansion depends on the energy density relations as per above, energy-density of a type (radiation, matter, dark energy etc) has a corresponding energy-density to pressure relations is determined by its equation of state.
http://en.wikipedia.org/wiki/Equatio...28cosmology%29

 

terms such as space being stretched, warped, twisted, created etc are misleading as they are only referring to the relations in the mathematical models being used. (space-time models)

Sorry, Mr. Mordred. I am a bit suspicious. Sorry. I don`t mean to raise that problem. But to me at the first sight when I see your reply, it seems ambiguous. Maybe that is my problem. Sorry, I shall apologize anyway. It is my fault.

 

no problem

Edited June 12, 2014 by Mordred

[Nicholas Kang]

Thanks, Mr. Mordred, you have taught me something new today. Now, through your explanation, I had a new vision towards space and what is space. Thanks.

[ajb]

To: ajb, philosophical questions are the driving force behind science, the "what is" question is paramount to understanding the phenomena. my question was scientific, I see no value in not understanding space other then how to use it, using it comes with understanding it. However maybe a answer to this question is beyond our detection.

Philosophical questions do of course influence science and vice versa.

 

But in physics our understanding of "what is" only really goes as far as understanding the mathematical framework in which we construct concepts, how to use them and how they relate to what we actually see.

 

So, today "what is space-time" is best described in the context of general relativity.

[Mordred]

your welcome

Thanks, Mr. Mordred, you have taught me something new today. Now, through your explanation, I had a new vision towards space and what is space. Thanks.

[derek w]

In quantum mechanics there is a concept of space as a quantum foam.

[Dr. Funkenstein]

Mr. Mordred, your explanation is indeed sound. universal geometry, while giving space no particular substance, does however defer to GR on mass and gravity on space time, So Mr. Kangs depiction stands correct, and space is thereby pliable, pliability is a hallmark of substance. It seems as if space is of no account until acted upon by mass, then it becomes tangible.

[Mordred]

actually his pic of space-time warping is an image of a mathematical relation between gravity and matter interactions

 

the warping of space in GR is often misunderstood, the term spacetime has special meaning in physics

"In physics, spacetime (also space–time, space time or space–time continuum) is any mathematical model that combines space and time into a single interwoven continuum".

In other words the warping is simply a mathematical descriptive used in GR to describe the geometric relations between gravity and matter.(including light paths,etc) Not space itself, GR does not state that space has a fabric or substance.

any form of physics deals with mathematical relations, even particle physics. Most of the equations used in particle physics are in actuality differential geometry equations.

 

in other words

 

GR is a theory of geometry. In GR space-time is not represented by a "fabric", but with a mathematical description known as a tensor (energy-mass tensor, stress tensor etc) that describes how the geometry of space-time will affect objects, and how objects will affect the geometry of space-time. In other words, it describes how objects interact with each other by changing the geometry of space-time.

Note that there is NO description of a fabric, sheet, or anything else analogous to a physical object. It's pure geometry.

 

The only property space itself has is geometric volume or distance.

 

 

 

 

read this from above, The fabric, sheet,warping terms are all just visualization aids used by GR to help others understand what is occurring much like the balloon analogy used in Cosmology. The sheet in that image is merely a 2D visualization aid, in a sense a 2D coordinate map. Doesn't mean the map itself is part of the universe. The map is only a representation of relations

 

the Calibi-Yau space is also a mathematical representation of interactions for example (string theory) doesn't mean that space at the string level has a substance itself or that the term manifold has a substance. These are all geometry relation terms

http://en.wikipedia.org/wiki/Calabi%E2%80%93Yau_manifold

Edited June 17, 2014 by Mordred

[Mordred]

In quantum mechanics there is a concept of space as a quantum foam.

"quantum foam can be used as a qualitative description of subatomic space-time turbulence at extremely small distances,"

 

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

 

again this is a visualization tool to describe the wave function turbulence at extremely small scales via virtual particle production. In essence its no different than the volume of space being filled with particles. Try to keep in mind there is plenty of empty space between particles at any level. We can only measure how particles and fields interact with each other. Space itself is volume, that volume simply is filled with energy and matter. Hence for example in Cosmology when the volume of space increases, the energy-density of matter and radiation also decreases as well as the temperature. This shows that the volume is filled as more volume becomes available

Edited June 17, 2014 by Mordred

[Dr. Funkenstein]

The terms used are acknowledged, but the fact remains, the solar system is held in place by gravity of the sun, the sun is held in place by the girth of it's mass in space, the space that holds this galaxy shows no analogy or conformity to geometric explanation. I opened the question with all of this, the question remains "what is space" not terminology or changing the rules, what is space. If defined as the home of dark matter/energy then it is of substance, if not then it has to be a thing that awakes through interaction with matter. Look here's what we know.

 

1. it surrounds all matter.

2. It haves no known trait of it's own, outside of it reaction to interaction with matter/energy/light....

3.It's capacity appears endless.

4. devoid of interaction it's static norm is cold.

 

How could such a void exist in advance of a event (big bang) that has yet to occur.

[Mordred]

You keep wanting to apply some magical attribute to space, space has no energy it has no matter, it has no property other than volume. I'm sorry if you want to believe otherwise but space itself is just volume. That volume is simply filled with everything else

 

 

1. it surrounds all matter.

2. It haves no known trait of it's own,

if it has no traits of its own then it cannot interact with anything, it is the particles that reside in the volume of space that interacts whether virtual or real

Edited June 18, 2014 by Mordred

[ajb]

You keep wanting to apply some magical attribute to space, space has no energy it has no matter, it has no property other than volume.

There are some subtleties here. We do have "pure gravitational objects" that do have energy, that is configurations of the gravitational field can carry energy. The notion of energy of a space-time is subtle, but anyway if we do include gravitational fields then space-time can have some attributes. But it is not very clear from the OP if we should be thinking of just the differential manifold as space-time or as standard we include the metric (or something equivalent) in the definition of space-time.

if it has no traits of its own then it cannot interact with anything, it is the particles that reside in the volume of space that interacts whether virtual or real

Same comment here really. Einstein's field equations are highly non-linear and so gravitational fields can interact. Again, it depends on what we mean by space and in particular space-time.

[Strange]

1. it surrounds all matter.

 

Space isn't "stuff" so it can't surround anything. It is just the physical (as opposed to temporal) distance or separation between objects and events.

[Dr. Funkenstein]

Magical attributes, what? Thought and thinking is still a proven process of discovery, although sometimes i'm inclined to believe that the educated loose the basis of inquiry in their education. Space has aspects of Volume and Distance, Thank you for the information.

[Mordred]

Magical attributes, what? Thought and thinking is still a proven process of discovery, although sometimes i'm inclined to believe that the educated loose the basis of inquiry in their education. Space has aspects of Volume and Distance, Thank you for the information.

that I agree with. As long as we all agree the only aspects space itself has is volume and distance, the space-time itself as long as were clear it also does not refer to a fabric or substance then its usage to describe relations is agreeable.

 

A term that may be handy to describe space including all its contents such as the various particles etc, is Intergalactic medium, or outside of large scale structure formation extra galactic medium. IGM for short. Its a nice science term to describe the totality of all the plasma etc that reside in space.

 

the article below is a sample of its usage, highly technical though one of my favorites

 

The Physics of the Intergalactic Medium

http://arxiv.org/abs/0711.3358

Edited June 18, 2014 by Mordred

[Dr. Funkenstein]

Upon further review I withdraw my agreement with volume and distance standing as definitions of space.

 

Distance: Under any strech of the imagination, fails miserbly as a definition of space. There are no point A's or B's or any reference points which would translate as range, which gives space parameters. Microwave emiission scientist clams, can be detected from the Big Bang. The mathematics ensue, stating the time frame and distance these emissions traveled into our detection, however any such equations would be inherently wrong, since with that computations, no point of orgin (exact space of BB is known) exsit. Light travels through space, but the traveling is the genesis, not the space itself. Therefore distance merely refers to travel within space, not a quality of space itself.

 

Universal geometry/Volume: Conceptual math to explain the unknow. As much as we rely on geometry to conceptualize phenominum, we are both corret to do so and foolish as well. correct in attempting to understand things to a particular degree, like the solar system. Foolish to then make the assumtion that our beloved math has the power to reveal everything to the bare bones. The center of this galaxy would command a curvature of space that would cancel the curvature hypothesised by the sun and this solar system in space, either way it really say's nothing about what space is, outside of our conception.

 

Definiton of space. A void which takes signifigance when interacted with.

 

 

Perhaps if we focus on the interaction's we may discover the substance of, if any.

[Mordred]

I'm not sure where you read we can detect microwaves from the BB, considering we cannot directly view the BB due to the dark ages. The dark ages is the time when the mean free path is too short for photons to avoid interaction prior to reaching us. Secondly any microwave from the BB would be red shifted to the point of being undetectable. However lets assume your talking the CMB.

 

I'm not clear on how you think that light traveling from point A to point B means that space itself has substance, that was once considered by the Ether/Aether theories. (Ether theories have been proved wrong, although nothing in physics is completely proven wrong so proposals will crop up from time to time) We can only measure interactions as they affect particles. You cannot measure the interaction of a void per se.

 

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

 

Assuming your using the definition of void as "a completely empty space" If something is completely empty (has no energy, or matter) not that energy can exist by itself. At least not in physics. Then there is nothing for a photon to interact with. How would a photon interact with something that has no substance? How would it influence nothing? Energy does not exist on its own that's one of the first things they teach physics students

 

all forces are mediates via a force carrier. Although in the case of gravity we haven't found the force carrier (graviton) but that doesn't preclude the possibility that it doesn't exist, it just means we haven't been able to produce a high enough of a temperature reaction to create a graviton.

 

"In particle physics, quantum field theories such as the Standard Model describe nature in terms of fields. Each field has a complementary description as the set of particles of a particular type. A force between two particles can be described either as the action of a force field generated by one particle on the other, or in terms of the exchange of virtual force carrier particles between them.

The energy of a wave in a field (for example, electromagnetic waves in the electromagnetic field) is quantized, and the quantum excitations of the field can be interpreted as particles. The Standard Model contains the following particles, each of which is an excitation of a particular field:

Gluons, excitations of the strong gauge field.
Photons, W bosons, and Z bosons, excitations of the electroweak gauge fields. (electro-weak field is the combination of electromagnetic force and the weak force)
Higgs bosons, excitations of one component of the Higgs field, which gives mass to fundamental particles.
Several types of fermions, described as excitations of fermionic fields.

In addition, composite particles such as mesons can be described as excitations of an effective field."

 

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

Now with everything I just stated above there is research ongoing to define the energy levels inherent in empty space as per se. Now to explain this with more clarity we need to look at a particular term. Zero point energy. Classical physics would state that zero point energy would be zero. However this isn't true in quantum mechanics. In quantum mechanics the zero point energy due to the Heisenburg uncertainty principle is

 

[latex]e=\frac{hv}{2}[/latex]

 

however as mentioned already this is essentially virtual particles popping in and out of existence

Casimer effect is one such study

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

 

so fundamentally how you define space must work at all the applicable scales of measure. There is the space between particles and there is outer space for example. I just showed that interactions is essentially particle to particle and explained that a particle must interact with another particle (cannot interact with nothing, that makes no sense)

 

so the only definition of space that applies at all levels of science and size scale is just a separation distance or volume.

Edited June 20, 2014 by Mordred

[Dr. Funkenstein]

My apologies, exchange microwave emissions for gravitational waves, and my use of the word void was meant to convey the word limitless space. Your points is sound. the Casimir effect requires more study, and a definition of space must indeed apply on all scales of measurement.