Gravity waves and the aether

[ajb]

Okay, you can think of gravitational waves as small changes in the background geometry. These are described using the wave equation - hense gravitational wave.

[geordief]

Is it possible (in theory) to "subtract" one geometry from another (the changed from the pre-existing) and arrive at those diagrams that showed the signature of the BH merger that we all saw recently?

 

Am I even close?

[ajb]

Is it possible (in theory) to "subtract" one geometry from another (the changed from the pre-existing) and arrive at those diagrams that showed the signature of the BH merger that we all saw recently?

In general no - you cannot add or subtarct solutions to the field equations and get another solution. What is often done is add this small linear correction and in an approximate sense the sum of the background and the correction satisfy the field equations

[geordief]

In general no - you cannot add or subtarct solutions to the field equations and get another solution. What is often done is add this small linear correction and in an approximate sense the sum of the background and the correction satisfy the field equations

Is that a principle that stretches right across mathematics? Is there ever a situation where non-linear equations can ever be translated into linear equations? (if I am making sense)

[ajb]

Is that a principle that stretches right across mathematics?

If the equations are non-linear then you cannot usually add solutions to get another solution.

 

Is there ever a situation where non-linear equations can ever be translated into linear equations? (if I am making sense)

It depends what you mean - for sure there are some equations that a change of variables can make them linear. But more generally, we can always (or just about always?) linearise a differnetial equation. This gives us an approximation to the original equation, which more or may not be a reliable thing to do.

[geordief]

If the equations are non-linear then you cannot usually add solutions to get another solution.

 

 

It depends what you mean - for sure there are some equations that a change of variables can make them linear. But more generally, we can always (or just about always?) linearise a differnetial equation. This gives us an approximation to the original equation, which more or may not be a reliable thing to do.

I am only "fishing" but (perhaps I am asking the same question) is there ever a physical situation where the same circumstance can be exactly described by either a linear or a non-linear equation?

 

I appreciate(I think) that the equations are perhaps by definition approximations to the physical reality in the first place (unless it is the other way round and the physical reality is an approximation to the equations )

[ajb]

I am only "fishing" but (perhaps I am asking the same question) is there ever a physical situation where the same circumstance can be exactly described by either a linear or a non-linear equation?

Only if the non-linear effects are small. I am sure there are such examples, but I can't think of anything off the top of my head.

[blue89]

image.jpegimage.gif

 

I think we might be able to find some new clues. but not via using the same methods like traditional.

I believe ,the perspective approach would be required.

Edited July 12, 2016 by blue89

[Mike Smith Cosmos]

I think we might be able to find some new clues. but not via using the same methods like traditional.

I believe ,the perspective approach would be required.

.

Well you seem to have an interesting background .

What are you proposing ? That we can discuss .

 

As AJB said we are right up against the very start and unexplored area of the " Birth of the Universe " , particularly how :-

Gravity may be one of the fundamental Constructions and backbone of the Universe.

 

I appreciate we are getting nearer And nearer the start zone .

 

Here you have to chose between ' all sorts of 'way out ' solutions for the start of the universe ,

 

as it includes GRAVITY ? And the nature of GRAVITY .

 

It would be appropriate to say that :- Whoever or whatever set the 'whole ball rolling ' with the universe , would have had to get there original calculations or processes right , such that , we would end up with what we have today ?

 

 

Mike

Edited July 12, 2016 by Mike Smith Cosmos

[swansont]

Only if the non-linear effects are small.

 

 

To be a bit nit-picky, that would give you good approximations, but not exact solutions.

 

The concept ajb describes is easy enough to see; there are plenty of example of solutions that are expansions where we drop the higher-order terms because they make a very small contribution. But strictly speaking, a solution of the form kx is not the same as a solution that's kx + k'x^3. For small x, the difference can typically be ignored. But kx would not be an exact solution. The solution for a simple pendulum might fit here. We use the small angle approximation and get a linear solution, but it fails for larger angle displacements.

[ajb]

To be a bit nit-picky, that would give you good approximations, but not exact solutions.

Of course. I had in mind physical situations where these non-linear effects are too small to be detected.

Edited July 12, 2016 by ajb

[Mike Smith Cosmos]

.

I have come across an Italian Institution , who are looking at the region of research ,dealing with the Quantum nature of Gravity and Space-Time . They are encountering the difference between this and the General Relativity Version of Gravity.

 

On the quantum side they are finding a 'granular ' nature to gravity/Spacetime . It would appear that time is contained , to within the granular form , and has no presence outside the grains . ( granular )

 

Mike

 

 

 

The Italian Coordinator of the research project is Carlo Rovelli . Link http://www.cpt.univ-mrs.fr/?lang=fr

 

Carlow Rovelli Link :- http://www.cpt.univ-mrs.fr/~rovelli/

 

Ref ( Uk. ) http://www.city.ac.uk/news/2016/april/city-researcher-and-academic-collaborators-to-host-prestigious-theoretical-physics-workshop-in-florence,-italy

Edited July 13, 2016 by Mike Smith Cosmos

[Strange]

.

I have come across an Italian Institution , who are looking at the region of research ,dealing with the Quantum nature of Gravity and Space-Time . They are encountering the difference between this and the General Relativity Version of Gravity.

 

On the quantum side they are finding a 'granular ' nature to gravity/Spacetime . It would appear that time is contained , to within the granular form , and has no presence outside the grains . ( granular )

 

There are a large number of such research projects (all under the general heading of "quantum gravity"). I am not familiar with this one but there is also "causal dynamical triangulation", "loop quantum gravity", various types of string theory and so on.

 

All of these suggest some lower-level structure out of which space-time emerges at the large scale.

 

All of these will simply move your question from "what is the medium of space-time made of?" to "what are the simplexes/loops/strings made of?" And the answer is: nothing. They are all purely mathematical models.

 

So none of them will satisfy you ...

[ajb]

Rovelli is well known - but he is in France at the moment?

 

Another well known Italian here is Giovanni Landi.

[Mike Smith Cosmos]

Rovelli is well known - but he is in France at the moment?Another well known Italian here is Giovanni Landi.

.

Wherever he is , the institute seems to have come up with some pretty interesting research ,

 

as to the nature of " quantum gravity "

 

To me , it is encouraging that gravity , possibly has such a start in life, around 'here' somewhere.

But obviously , like everybody else , people are trying to reconcile this with Geneal Relativities role in Gravity .

 

It is rather Fun !

Staring into the caldron of creation , whoever or whatever is responsible . It is surely here or hereabouts is the origin of mass, gravity and ( space-time ) ? Is that not so ?

 

Mike

Edited July 13, 2016 by Mike Smith Cosmos

[ajb]

as to the nature of " quantum gravity "

 

But obviously , like everybody else , people are trying to reconcile this with Geneal Relativities role in Gravity .

However, the vast majority of people working in physics are not looking into quantum gravity.

 

Anyway, Rovelli is know for loop quantum gravity. This approach interests you?

[blue89]

.

Well you seem to have an interesting background .

What are you proposing ? That we can discuss .

 

 

actually I have some sort of solutions,but unfortunately I can/would not to propose there. because normally I would protect at least some of them , not as ordinarily discussed , I only imply that need to offer some evidences to some associations in order to prove some of my allegements.I ask your understandings, I have stated that it was required having perspective sight and not traditional ways.

 

the thing what I would/am able to suggest you is that we required to try something interdisciplinary.I do not mean clearly this is compulsory ,but I saw generally great scientists were not studying/being interested only to their main discipline. for instance sir issac newton was not only interested in physics ,he also was a mathematician. plato was also mathematician , but we commonly see him at philosophic literatıures,too.

 

these days the last one is generally extraordinary thing,it is being thought that the last example is generally unlike.

 

however,unfortunately the system is own supports that idea and also make it very difficult to do. but I believe that in spite of everything, surely,it should not be impossible or unlike .

 

probably it would be better to comply the universal truths. (not subjective ones! ,like thinking that it was required to be young to be interested in science).the universal truth: there should be given no margin relevant age to learn something)

Edited July 13, 2016 by blue89

[Mike Smith Cosmos]

However, the vast majority of people working in physics are not looking into quantum gravity.Anyway, Rovelli is know for loop quantum gravity. This approach interests you?

.

 

Well yes, very much so ! I can not pretend to be an expert, but I have very much followed the thought processes of Prof Lee Smolin over the years. I think it would be fair to say , he developed the idea of loop quantum gravity ( although I suppose nobody can claim anything . ). Similarly he has been responsible for the moving ideas on " Time " .( over in the Perimeter Institute in Canada).

 

Now Rovelli , seems to be taking up the, mantle! Of both loop quantum gravity , and the perceptions of time

 

This diagram from CARLO ROVELLI , Illustrates his interest in quantum gravity . He also talks about NO TIME , within the quantum particle responsible for gravity . ! That is quite incredible !

 

 

Mike

Edited July 13, 2016 by Mike Smith Cosmos

[ajb]

Smolin had publsihed works on loop quantum gravity for sure. Loop quantum gravity is not something I know much about.

[Mike Smith Cosmos]

Smolin had publsihed works on loop quantum gravity for sure. Loop quantum gravity is not something I know much about.

To quote ' Carlo Rovelli

 

" the central result of Loop Quantum Gravity is indeed that space is not continuous, that it is not infinitely divisible but made up of grains or ' atoms of space ' . These are extremely minute: a billion billion times smaller than the smallest atomic nuclei. The theory describes these ' atoms of space ' in mathematical form and provides equations which determine their evolution.

They are called 'loops' or rings , because they are linked to each other, form a network of relations which weaves the texture of space"

 

They are not in space because they are in themselves space ... The equations of space and matter no longer contain the variable .'time'

Each process dances independently of its neighbour . .. The illusion of space and time which continues around us is a blurred vision of this swarming of elementary processes.. "

 

unquote

 

Mike

[ajb]

The illusion of space and time which continues around us is a blurred vision of this swarming of elementary processes..

At least that is the general thinking - showing this carefully has proved to be tricky. It is not properly understood if one can get general relativity as a limit of loop quantum gravity. The last time I spoke so someone on that they said there are some results in this direction.

[Mike Smith Cosmos]

At least that is the general thinking - showing this carefully has proved to be tricky. It is not properly understood if one can get general relativity as a limit of loop quantum gravity. The last time I spoke so someone on that they said there are some results in this direction.

Two quotes from Carlo Rovelli .

 

 

 

 

Mike

Edited July 13, 2016 by Mike Smith Cosmos

[ajb]

Loop quantum gravity has given some nice results about the entropy of black holes - which agree with calculations via string theory. It seems that either both theories agree on something or one is unable to say something where the other can.

[swansont]

Loop quantum gravity has given some nice results about the entropy of black holes - which agree with calculations via string theory. It seems that either both theories agree on something or one is unable to say something where the other can.

 

 

But how much of this has been experimentally confirmed? MSC's post implies none of it. Which means this all has to be taken with a large grain of salt.

[ajb]

But how much of this has been experimentally confirmed? MSC's post implies none of it. Which means this all has to be taken with a large grain of salt.

Nothing in loop quantum gravity has been experimentally confirmed. It is not even clear that classical gravity really comes out of this - string theory at least has that

Edited July 13, 2016 by ajb