Gravity waves and the aether

[disarray]

What I do need to know in this instance is " what exactly ( in reality terms ) is Space or Space - Time that it can be bent or curved or what ever . Is it a field , if so what sort of field , grit field , rubber field , electromagnetic field . Atomic field ,

 

I agree that from a strictly semantic standpoint, the degree of "nothingness" that we presume that space (or should I say 'spacetime' ) has can not be very high if it contains properties such as time dilation and curvature, so that we intuitively assume that it must have a degree of "somethingness." If it is indeed, a field of some sort, as ones intuition seems to suggest, then it would seem that scientists either have not detected what sort of field it might be, or else categorically deny that it is a such a "spatial field" (for lack of a better term) that "is somehow involved with" the properties, directly or indirectly, associated with time dilation and curvature.

 

Similalry (I think), Lawrence Krauss remarked that there could not have been absolute nothingness originally, since there would not be the necessary ingredients for a Big Bang to take place if that were the case....that is, there was a sort of partial nothingess.

 

He also is quoted as stating that "If you removed all of the particles, all of the radiation, absolutely everything from space and all that remained was nothing, that nothing would weigh something."

 

Article on Krauss's views on multiverse and types of Nothingness: http://www.nytimes.com/2012/02/21/science/space/cosmologists-try-to-explain-a-universe-springing-from-nothing.html

 

Edited July 7, 2016 by disarray

[Mike Smith Cosmos]

You have not measured anything tangible. Is 1 mile tangible? Is 1 second tangible?

 

Space is just the distances between things. Why do you expect it to be "made of" something?

Because in the subject we are discussing , space time is supposed to be getting curved , by the general state of gravity relevant at this particular location .

 

I want to know " what is actually getting ' curved ' " . Not its name ' Space Time ' . What it actually IS .?

 

 

 

It is not too much to ask for surely ? If you said and offered me " do you want one of these? I would reply " one of what ?

 

Here I am asking " what it is " ?

 

What is this Space - Time , that is getting Curved ? What is it ?

 

Mike

 

Ps and you can't just say , " Space is Space and Time is Time " that does not count !

 

What I do need to know in this instance is " what exactly ( in reality terms ) is Space or Space - Time that it can be bent or curved or what ever . Is it a field , if so what sort of field , grit field , rubber field , electromagnetic field . Atomic field ,

 

I think the answer is that no one actually knows. I agree that from a strictly semantic standpoint, the degree of "nothingness" that we presume that space (or should I say 'spacetime' ) has can not be very high if it contains properties such as time dilation and curvature, so that we intuitively assume that it must have a degree of "somethingness." If it is indeed, a field of some sort, as ones intuition seems to suggest, then it would seem that scientists either have not detected what sort of field it might be, or else categorically deny that it is a such a "spatial field" (for lack of a better term) that "is responsible for" the properties, directly or indirectly, associated with time dilation and curvature.

 

Similalry (I think), Lawrence Krauss remarked that there could not have been absolute nothingness originally, since there would not be the necessary ingredients for a Big Bang to take place if that were the case....that is, there was a sort of partial nothingess.

 

He also is quoted as stating that "If you removed all of the particles, all of the radiation, absolutely everything from space and all that remained was nothing, that nothing would weigh something."

 

Article on Krauss's views on multiverse and types of Nothingness: http://www.nytimes.com/2012/02/21/science/space/cosmologists-try-to-explain-a-universe-springing-from-nothing.html

 

I just suddenly got my sanity back , I was just about to reach for the phone , and sign myself into a mental institution. You have rescued me from the edge of lunacy !

 

Even though that is not the answer to " what is space time " , at least I know I am not alone ! I need to go and lay down ! Phew , so near the edge !

 

 

The top of the glass looks like the universe . The bottom of the glass is the space time in the universe .

They both look fairly similar . BUT the bottom is water , substantial, refreshing . The top is nothing ! Yet both look and sound similar . One is real , the other is nothing !

 

 

The big question is . What IS the real bit ?

 

Mike

Edited July 8, 2016 by Mike Smith Cosmos

[MigL]

Space-time is the co-ordinate map that we use to model the universe.

It is akin to a flat Cartesian map of the Earth as opposed to a globe map, such that the points on the far right side identify with the points on the far left. If you go off the right hand side of the map, you re-appear on the left. This is called intrinsic curvature, it is not embedded in a higher dimension.

The globe map on the other hand, has what's normally considered 'curvature', as you have to circumnavigate around the globe to get to the other side.

This is called extrinsic curvature, and requires an embedding dimension.

 

 

Mike you keep asking " Is there something tangible 'there' ? "

And people keep telling you "No".

Yet you cannot accept that, and keep repeating the question.

I don't think this is getting any of us anywhere and its time you started adjusting your thinking regarding this requirement to have something tangible.

 

Oh, and please don't shoot yourself.

Edited July 8, 2016 by MigL

[disarray]

I think a key question is whether nature really does abhor a vacuum (apart from the mathematical speculations) so that one does not know whether time exists in a vacuum in pure spacetime without matter. Since Einstein predicted that we'd be able to tell gravity was present during those early moments, thanks to gravitational waves (or changes in a gravitational field), I wonder whether, just as you can't have one without the other when it comes to love and marriage according to the old pop song, you can't have time without space as well as, perhaps, gravity and matter. If so, perhaps one can't say whether one is more basic or precedes the other, or whether they are all inevitably interwoven as one.

 

Relevant quotes:

"if the universe can't curve (because gravity doesn't exist), then there can be no matter or energy within it."

http://www.livescience.com/17809-gravity.html

"The spacetime structure of the metric field is shaped by what it contains. This may mean that space and time would not exist if there were not matter or energy in the universe."

http://www.thestargarden.co.uk/General-relativity.html from Norton, J. D., 'The Hole Argument', Stanford Encyclopedia of Philosophy, last accessed 15-02-16.

[MigL]

Space-time is a mathematical construct.

Why is there such a need to assign a 'tangibility' to it ?

Think of the extremely curved space-time around a Black Hole. Can you touch the event horizon ? Can you feel it ? Can you see it ? Can you hear or taste it ( just being goofy now ) ? can you even tell in any way, other than with a test mass, that it is curved ?

 

And there are solutions for an 'empty' universe.

Edited July 8, 2016 by MigL

[disarray]

Space-time is the co-ordinate map that we use to model the universe.

It is akin to a flat Cartesian map of the Earth as opposed to a globe map, such that the points on the far right side identify with the points on the far left. If you go off the right hand side of the map, you re-appear on the left. This is called intrinsic curvature, it is not embedded in a higher dimension.

The globe map on the other hand, has what's normally considered 'curvature', as you have to circumnavigate around the globe to get to the other side.

This is called extrinsic curvature, and requires an embedding dimension.

Mike you keep asking " Is there something tangible 'there' ? "

And people keep telling you "No".

Yet you cannot accept that, and keep repeating the question.

I don't think this is getting any of us anywhere and its time you started adjusting your thinking regarding this requirement to have something tangible.

 

It seems that you are suggesting that we shouldn't search for something tangible about spacetime (with its own brand of 'curvature') because, unlike the tangible earth (which is perhaps just mass/energy anyway), there is no higher dimension for the universe. However, the fact that there may be no higher dimension in itself does not negate the possibility that spacetime is, if not as tangible as a spade, something more than nothing (particularly given its specific 'qualities' such as gravity, time dilation, and curvature). Indeed, could one not suggest that the backdrop of the multiverse (that some physicists propose) provides such a higher dimension? However, I do take the point that space-time is a sort of trade off and that this has something to do with gravity (with the role of mass seeming less clear). Indeed, it is amazing that math of Relativity fits 'reality' so well, as Einstein himself quipped, given that, in his own case, he penciled the math all out in his room in a couple of weeks without any particular appeal to data or empirical verification (while his poor wife was instructed to leave him alone except to leave his food on a tray outside his door).

 

But no, it would be nice to understand a little bit more about the "why" of spacetime than just that we can map it out....that does not mean that one wants to understand it in such a literally "tangible" manner that one can see or touch it.

 

Personally, I don't think that there is anything wrong with being Socratically persistent in pursuing a question. Of course, it is good to rephrase the question or perhaps give an illustration or to suggest possible answers, etc. Whether people want to continue to explain or not is up to them. Indeed, Einstein stated that he asked some pretty simple questions about the nature of light for years in order to galvanize his thinking, despite the fact that few if any could give him any answers at all. Also, I don't think one should ever give up trying to explain things in different ways to people who have different types of intelligence (in accordance with multiple intelligence theory). Even if images are misleading in some respects, such as spheres rolling around on the net of space time (even though the spheres are a part of spacetime themselves), they can be an immense comfort and initial help to those who are not particularly mathematically minded, such as myself.

 

 

 

Edited July 8, 2016 by disarray

[Markus Hanke]

I want to know " what is actually getting ' curved ' "

 

 

Nothing is "getting curved", that is the point. It just so happens that the relationships between measurements taken at different events in spacetime are the same relationships as those between points on an appropriately curved manifold. Hence, curved manifolds are good models to describe gravity. There is no "fabric" here that gets mechanically distorted in any way.

[Mike Smith Cosmos]

You could look at the path a photon takes as it passes by. You would notice that it doesn't follow what we would consider to be a straight line. The source of the light wouldn't be where the straight-line travel projection of the light would indicate.

.

Now that is a sensible , answer . It is some form of test. Like I did a test while zooming down the runway in a plane , before take off and dropped an object that curved into my chest . So maybe it is something like that ? ( the test I mean ) . Now for that to happen there was quite a lot going on ( materially , substance, movement ) . There was the plane, me, the weight, a lot of accelerated movement, of tangible things like dropping mass , my body, an accelerating aircraft .

 

So if we are talking about a spot , halfway to Jupiter , would we have any of these tangible things ? Perhaps no ? So would there be any curvature , possibly no. That curvature would only be a suppose ? Only if we put a photon there , would there be any curvature . Only if I was there in an aircraft and dropped a weight , would there be any curvature .

 

It begs the question ? How is that state of affairs communicated to be there , ready for a passing photon , or man in a space ship/ aircraft . Is it that there is some long distance communication of curving , or is there something actually there in substance , all over space which is intrinsically curved ?

 

It is as if the water in a goldfish bowl is intrinsically curved . So that when it starts to swim what it thinks is straight forward the curved water automatically makes the straight swimming of the fish " go curved " .

If this analogy has any merit we are looking for the equivalent of curved inducing water , or curve inducing space.

 

There must be 'something there' or some inducing field permeating all of space like some supermassive mechanical Tesla experiment . Or a distribution of matter ( or the equivalent of matter ) , dark or otherwise , everywhere across space , which gets amplified when concentrated matter is near , ( eg stars and planets ) .

 

So , if this is correct, we are getting a picture here , of NOT an empty void of space ! With isolated stars , galaxies , and planets . With huge space of nothingness in between .

 

But rather one whole sea of ' stuff' in various concentrations . From one side of the universe to the other . The curving in proportion to the concentration of ' stuff'

Stars and planets reasonable concentrations , in between fairly thin concentrations . But all concentrations of ' stuff' say 'matter ' . All curved to a greater or lesser extent. All curved " stuff " ?

 

Mike

 

I still wonder if there is not a lot of ' spinning ' , going on here somewhere , somehow ?

Edited July 8, 2016 by Mike Smith Cosmos

[ajb]

Our best model of gravity tells us that space-time is curved - but as a model it does not tell us what space-time 'is' or if it is 'real' in any metaphysical meaning of these words. We know how to mathematically work with this and we have matched the theory very well to observations.

 

To detect this curvature, one can look at the motion of test particles or light beams (as Swansont says). The curvature can then be seen as something to do with the rate at which initinally parallel beams diverge or converge. However, our models treat space-time curvature as independent of presence of these test particles - we think that curvature is there with or without these particles. Or at least that is how we treat it.

Edited July 8, 2016 by ajb

[Mike Smith Cosmos]

Nothing is "getting curved", that is the point. It just so happens that the relationships between measurements taken at different events in spacetime are the same relationships as those between points on an appropriately curved manifold. Hence, curved manifolds are good models to describe gravity. There is no "fabric" here that gets mechanically distorted in any way.

.

Are you absolutely CERTAIN, immovably CERTAIN , that there is not a lossless medium there called ' lossless distributed matter ' across all of space and time , like the Higgs field or some other distributed gravitational field ( unless these ARE descriptions of a curved manifold - whatever that is exactly in reality -)

 

Mike

Edited July 8, 2016 by Mike Smith Cosmos

[Strange]

Because in the subject we are discussing , space time is supposed to be getting curved , by the general state of gravity relevant at this particular location .

 

I want to know " what is actually getting ' curved ' " . Not its name ' Space Time ' . What it actually IS .?

 

 

Distance. You measure a straight line between two points. You can measure a non-straight line between two points. Neither of those distances need to be made of something.

 

 

 

It is not too much to ask for surely ?

 

Yes, it is.

[Mike Smith Cosmos]

Distance. You measure a straight line between two points. You can measure a non-straight line between two points. Neither of those distances need to be made of something.

 

The distances , true do not need to be 'made of something ' . But the pegs , stuck in the ground , to give you the points to measure . These are made of something . Soil and a couple of sticks . Or if you don't like the sticks . Two stones protruding out of the soil. So as to know what you are measuring .

 

So I am asking what the equivalent of the soil and the marker points. This must be the " stuff "or " substance " of space time . There must be something to measure ? Surely .

 

All surveyors put down markers . Then make a measurement . You can't just put a ruler in the air and say I just measured 10 cm . Of air . You would need to mark a molecule or two either end of the 10 cm . Then measure the two markers a minute later , and see where the markers are now , and make a second measurement .

 

So what is the 'air equivalent ' in space that we are measuring . To see if it is changing length.

 

Mike

[ajb]

There must be something to measure ? Surely .

Abstractly, we call these 'events' - space-time is 'made up' of possible loctions and times of physical events.

 

In practice one needs two events to measure anything - say, the sending and receiving of a light signal.

[Strange]

The distances , true do not need to be 'made of something ' . But the pegs , stuck in the ground , to give you the points to measure . These are made of something . Soil and a couple of sticks . Or if you don't like the sticks . Two stones protruding out of the soil. So as to know what you are measuring .

 

So I am asking what the equivalent of the soil and the marker points. This must be the " stuff "or " substance " of space time . There must be something to measure ? Surely .

 

 

You have the markers at the end points. There is no need to anything in between.

[geordief]

Do massless particles follow the geodesics in spacetime?

 

What happens to them when they meet a black hole?

 

Can they be used in theory to carry information in a way not limited by the curvature of space?

[disarray]

Again, I don't think that scientists generally presume to have all the answers as to the accuracy of Relativity, e.g., :

"Mass is linked to space in a way that physicists today still do not completely understand." http://hubblesite.org/reference_desk/faq/answer.php.id=58&cat=exotic

Of course, the equivalence principle states that gravity gives virtually the same effects as acceleration (hence, time dilation). But how does one get from that principle to an explanation for light curving (either literally or just as a measurement of events?) as it passes the sun?

 

One theory is that it is caused by universal expansion:

 

"This acceleration can only result from the linear expansion of the matter comprising the earth. It is this universal expansion of matter that is the

simple and local cause of gravity.

.....It is this constant upward velocity at the surface of matter that is the universal constant for gravity." http://www.circlon.com/living-universe/015-cause-of-gravity.html

 

But it seems we are talking small amounts and for very fast moving things:

 

"The curvature of space alone has almost no effect on the movement of objects until they are moving really fast...the total stretching of space due to

the Earth amounts to less than 1cm."

 

Other scientists, while also admitting that they don't fully understand gravity, suggest that a greater understanding of dark matter will some day provide more clues:

 

"We think we understand gravity in most situations," he says "but when we look at galaxies and, on much larger scales, at galaxy clusters, we see

things happening that we don’t understand using our familiar equations, like Newton’s equation of gravity or even Einstein’s gravity. So we have to

assume there’s this mysterious form of matter, which we call dark matter, which we cannot see."

http://www.dailygalaxy.com/my_weblog/2013/11/our-understanding-of-gravity-is-fundamentally-wrong-two-conflicting-theories-of-the-universe.html

 

So no, I am guessing that few scientists would claim that Einstein's theory of GR gives a complete picture of gravity.

 

 

 

 

Edited July 8, 2016 by disarray

[ajb]

Do massless particles follow the geodesics in spacetime?

Yes - they follow what we call null geodesics. These path have zero 'length'!

 

What happens to them when they meet a black hole?

They pass the event horizon and eventually hit the singularity. But we do not understand what is really happening at the classical singularity - we expect quantum effects to 'smear out' the singularity.

 

Can they be used in theory to carry information in a way not limited by the curvature of space?

I don't quite follow the question.

 

 

So no, I am guessing that few scientists would claim that Einstein's theory of Relativity is complete in that it gives a complete picture of gravity.

Nobody thinks that general relativity is the final say on gravity. In part this is because it does not fit with the standard model of particle physics and there is no full quantum theory of gravity as of yet. Other reasons are the presence of singularites which are quite generic and the existsnce of CTCs. All this suggest that we have to treat general relativity as an effective theory - that is at some energy scale new physics takes over.

[geordief]

 

 

I don't quite follow the question.

If the universe is "folded in on itself" naturally can the neutrino pass from one region of space to another cutting across the contour lines ?

 

So if there was any way to encode information into a neutrino it would in theory allow for instantaneous(ish) transfer of information....between regions that would be otherwise far distant if one had to follow the geodesics in the normal way with massive particles.

 

The practicalities of that do occur to me

 

EDIT: when we detect the odd neutrino do we have any idea what part of the cosmos they emanated from?

Edited July 8, 2016 by geordief

[disarray]

Ajb: So do we even have an explanation for the basic equation, viz., that the gravitational force one object exerts on another is related to the mass of the two objects and the distance between them.

 

(Apparently, to be more precise, increasing the size or radius and keeping the mass the same will cause gravity to decrease. On the other hand if one decreases the radius and keeps the mass same, gravity would increase. But if the density is constant i.e. the mass to volume ratio is constant, then the gravity will increase if one increases the radius.)

 

In terms of relativity, 'heavier' objects (e.g., the heavier planets in our solar system as opposed to the lighter ones) have a greater impact on the spacetime fabric (as the usual spheres on a net illustrate). But does Relativity give an explanation above and beyond this description as to why this is so.

Edited July 8, 2016 by disarray

[swansont]

.

Now that is a sensible , answer . It is some form of test. Like I did a test while zooming down the runway in a plane , before take off and dropped an object that curved into my chest . So maybe it is something like that ? ( the test I mean ) . Now for that to happen there was quite a lot going on ( materially , substance, movement ) . There was the plane, me, the weight, a lot of accelerated movement, of tangible things like dropping mass , my body, an accelerating aircraft .

 

So if we are talking about a spot , halfway to Jupiter , would we have any of these tangible things ? Perhaps no ? So would there be any curvature , possibly no. That curvature would only be a suppose ? Only if we put a photon there , would there be any curvature . Only if I was there in an aircraft and dropped a weight , would there be any curvature .

 

It begs the question ? How is that state of affairs communicated to be there , ready for a passing photon , or man in a space ship/ aircraft . Is it that there is some long distance communication of curving , or is there something actually there in substance , all over space which is intrinsically curved ?

 

It is as if the water in a goldfish bowl is intrinsically curved . So that when it starts to swim what it thinks is straight forward the curved water automatically makes the straight swimming of the fish " go curved " .

If this analogy has any merit we are looking for the equivalent of curved inducing water , or curve inducing space.

 

There must be 'something there' or some inducing field permeating all of space like some supermassive mechanical Tesla experiment . Or a distribution of matter ( or the equivalent of matter ) , dark or otherwise , everywhere across space , which gets amplified when concentrated matter is near , ( eg stars and planets ) .

 

So , if this is correct, we are getting a picture here , of NOT an empty void of space ! With isolated stars , galaxies , and planets . With huge space of nothingness in between .

 

But rather one whole sea of ' stuff' in various concentrations . From one side of the universe to the other . The curving in proportion to the concentration of ' stuff'

Stars and planets reasonable concentrations , in between fairly thin concentrations . But all concentrations of ' stuff' say 'matter ' . All curved to a greater or lesser extent. All curved " stuff " ?

 

Mike

 

I still wonder if there is not a lot of ' spinning ' , going on here somewhere , somehow ?

 

 

The spot wouldn't be halfway to Jupiter; that would have a minimal amount of curvature. The deviation would happen in the vicinity of large masses. Like a star visible just off the edge of some body, even though a straight line extrapolated from us puts it behind the sun, or some planet. The light follows what we would call a curved path as it passes near.

.

Are you absolutely CERTAIN, immovably CERTAIN , that there is not a lossless medium there called ' lossless distributed matter ' across all of space and time , like the Higgs field or some other distributed gravitational field ( unless these ARE descriptions of a curved manifold - whatever that is exactly in reality -)

 

 

Absolutely certain? No, of course not. This is science it's always subject to modification given new evidence.

 

But the current state of science is that there is no evidence of any tangible medium and the models we have — which agree with experiment to great precision — do not require one.

The distances , true do not need to be 'made of something ' . But the pegs , stuck in the ground , to give you the points to measure . These are made of something . Soil and a couple of sticks . Or if you don't like the sticks . Two stones protruding out of the soil. So as to know what you are measuring .

 

So I am asking what the equivalent of the soil and the marker points. This must be the " stuff "or " substance " of space time . There must be something to measure ? Surely .

 

 

No, you aren't, unless you've been doing a horrible job of it. By all reasonable interpretation, you have been asking about what's between those marker points. Or, if the markers are casting a shadow, what the shadow is made of.

[geordief]

 

 

They pass the event horizon and eventually hit the singularity. But we do not understand what is really happening at the classical singularity - we expect quantum effects to 'smear out' the singularity.

 

 

 

Why do they hit the singularity (no one can say the singularity actually exists can they? ) if they are not affected by gravity. Why don't they just pass through?

 

Do they interact with matter even though they have no mass themselves?

[ajb]

If the universe is "folded in on itself" naturally can the neutrino pass from one region of space to another cutting across the contour lines ?

In principle it is possible to beat the local speed limit of c by taking other paths. For example, through a wormhole. If that is what you mean?

 

Ajb: So do we even have an explanation for the basic equation, viz., that the gravitational force one object exerts on another is related to the mass of the two objects and the distance between them.

We have some general arguments about the form of the action for general relativity, for example. The geodesic equation is added on as an equation of motion for test particles - it is a natural assumption but it is an assumption.

 

If you are looking for deeper philosophical reasons, then I have no idea.

 

 

Why do they hit the singularity (no one can say the singularity actually exists can they? ) if they are not affected by gravity. Why don't they just pass through?

Massless particles are effected by gravity - they follow null geodesics and these are not in general straight lines.

 

Classically they hit the singularity as that is what the classical equations tell us.

[geordief]

In principle it is possible to beat the local speed limit of c by taking other paths. For example, through a wormhole. If that is what you mean?

 

 

 

I looks like that . I seem to be getting a fixation on massless particles. Are they especially relevant in the context of wormholes?

 

I wonder how they interact with massive objects if they are not massive themselves.

 

 

EDIT: i have just realized that photons are also massless . So neutrinos can be treated more or less the same way as photons?

 

They are not as exotic as I thought they were and don't just naturally "cut across" spacetime contours as I was imagining

Edited July 8, 2016 by geordief

[ajb]

Are they especially relevant in the context of wormholes?

I don't think they are special in this context.

 

I wonder how they interact with massive objects if they are not massive themselves.

Massless particle still carry energy-momentum and so can act as a source of gravity.

[geordief]

I don't think they are special in this context.

 

 

Massless particle still carry energy-momentum and so can act as a source of gravity.

Thanks . That makes sense to me now.