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Gravity waves and the aether


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Dissaray

 

Well , I could be persuaded to agree with you about Gravity and wether it is an actual force or not . I must say ! During this discussion , I have been musing , how a great mass , like the earth, could do something to a small area ( where I am currently existing ) can be influenced so as to make it reasonably difficult for me to even walk up a slope , just 2 meters high. Right here , one step in front of another.

 

All I could come up with in my mind ( listening to all the curvature discussion etc ) , is that somehow with all that local concentrated mass , as opposed to me out in the open . That the mass is either pushing other movable stuff out of the way , by shear ,occupying the area below me . And the net result is this curvature , which my mass does not push much mass out of the way . So I am drawn to follow this curvature which is downward ,generally . I have felt the difference to when I do not change height at all ( very minute effort , just swinging legs alternatively . ) whereas if the slope just goes up by a few inches over each meter forward , I have to exert a reasonable quantity of effort to keep going up those few inches every meter forward. ( all because of this curvature ) . Sort of makes vague sense, rather than an invisible force coming out from the centre of the earth pulling you down ! I think ?

 

Richard Feynman was heard to say once , :- "everything is happening right next to you , right there , not from a distance ." Profound ?

 

Mike

 

 

 

me

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@ ajb

 

I don't think there is any connection between the universe expanding and things moving straightly along geodesics is there.?

 

It would help the progress of my understanding if that was the case but I think I have learned that it is not true.

Personally, I was just taking a stab in the dark.

 

Richard Feynman was heard to say once , :- "everything is happening right next to you , right there , not from a distance ." Profound ?

 

Ok, I am ashamed to say that I have not read much Feynman, despite his efforts to make physics accessible to the average person.

I don't know the context of this statement of his, but, on the other hand, I thought I had read that we are experiencing a certain degree of gravity from everything in the universe, though not sure what that would mean either.

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Personally, I was just taking a stab in the dark.

 

 

 

 

Ok, I am ashamed to say that I have not read much Feynman, despite his efforts to make physics accessible to the average person.

I don't know the context of this statement of his, but, on the other hand, I thought I had read that we are experiencing a certain degree of gravity from everything in the universe, though not sure what that would mean either.

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His example which I remember SIGNIFICANTLY . Was . An amazing show, of shoals of fish , swimming is beautiful but offset unison . One might be tempted to think there was some amazing spooky field working across the shoal amazingly keeping them swimming in offset unison .

 

No such thing . He said . Every fish keeps a rigorous, watchful , attention and response , to its neighbour . If they detect a slightest change in direction or speed by their neighbour . They respond nearly ( not quite) instantly . The EFFECT. Is this offset ( time wise ) shimmering amazing shoal dance. Response to Neighbour , repeated almost instantly , across the whole shoal . Not an overarching field . At least that was his explanation when he was alive a number of years ago . Maybe the same things happens with flocks of birds ? Or even the universe with gravity , and electro-magnetism , for that matter? Who knows?

 

Mike

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". What is making the Universe work the way it does "

 

 

Who knows.

 

Maybe it is the only way a universe can work (for reasons we don't understand).

Maybe it is one of many possibilities and chance gave us this one.

Maybe there are multiple universes that work in different ways we just happen to be here.

Maybe someone's God made it this way.

Maybe the universe doesn't exist at all and it is all a figment of your imagination (which is why it is incomprehensible :)).

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Are these fibre bundles infinitesimally small and can they be "stuck together" or perhaps "spliced" like a 4-stranded rope to give the larger picture?

No - the fibres are not small. They may be non-compact as in the case of a vector bundle where the fibres are R^n for some n.

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So each fibre is like a 4ply rope? Some are long and some are short?

A fibre is some specific manifold - all the fibres are the 'same'. A line bundle maybe the easiest to think of - here you attach the real line understood as a manifold to each point. You have to do this in a right way, but usually there are many ways you can do this - like adding twists like the Mobius band.

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I will have to give it (and you) a rest and hope that your answers have been helpful to others more able than myself to profit from them.

 

But just one last clarification. :these manifolds ,they are 4D spacetime manifolds are they ?

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But just one last clarification. :these manifolds ,they are 4D spacetime manifolds are they ?

In the context of physics, the base manifold is 4D space-time. But in general we need not have this.

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Any introductory textbooks you can recommend, AJB, to get a better grip on fibre bundle treatment of fields ?

Assume a working knowledge of diff. geometry and just a basic understanding of topology/group theory.

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Any introductory textbooks you can recommend, AJB, to get a better grip on fibre bundle treatment of fields ?

Everybody knowns that fields are sections, but this does not seem to be really used in standard physics treatments. One okay treatment is G.Sardanashvily's Five Lectures on the Jet Methods in Field Theory - you can find it on the arXiv.

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I have a huge collection of books in Cosmology/relativity and particle physics. None of the books I have or read cover Bundles. My collection is well over 150 books. Arxiv has provided the only details I know on bundle treatments

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It is becoming clear that " space -time" , far from being a totally empty void , vacuum . Is constructed, contorted , and analysed by a lot of ' seemingly complex ' geometric shapes. These must reflect in some way the real nature of ' space-time ' .' itself'

 

Without even fully understanding quite how all these , ' manifolds, cylinders, fibres, möbius ' geometric operators come together to describe the nature of space -time ,

and the interactions by the two different ingredients for waves , (1ST ELECTRO- MAGNETISM and 2nd MATTER and GRAVITY ) .

 

Some things are already clear .

1 . Space - time ..is not ..nothing and

2. Space- time is influential AS A MEDIUM

 

It would 'seem ' ? that things like :-

 

a) Electro magnetic waves( photons of light and radiation ) , travel through the medium of ' space- time ' , whose speed is dictated by ' space time itself ' . . Namely the (characteristic of 'space-time' ) .

 

B) Gravitational waves based on mass and matter , interact in a completely different way with ' the medium of ' space-time ' and so their propagation likely will have far different interaction characteristics , speed and attenuation ?

 

Is that not so ?

 

Mike

 

Ps REPORTED TONIGHT's . BBC! . China hopes to use its soon 'biggest in the world ' radio telescope , in the electromagnetic spectrum . To understand better the nature of " space time " and what is contained therein .

Here reported from the BBC :- recent photos of China's Radio Telescope being completed as we speak !

 

post-33514-0-18075600-1471812622_thumb.jpegpost-33514-0-68419900-1471812639_thumb.jpeg

Edited by Mike Smith Cosmos
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.

GRAVITY WAVES and the AETHER.

 

The thing that keeps ' popping ' up to do with this subject .

Seems to be the difference between ELECTRO-MAGNETIC WAVES and GRAVITY WAVES .

 

And in that respect,

I must come back to the difference in the relationship to the MEDIUM of both of these types of waves .

 

 

------------------------------------

The medium appears to be the FOUR DIMENSIONAL SPACE (3) - TIME (1) .

 

Could it be that ELECTRO-MAGNETIC WAVES be 3 DIMENSIONAL . ( electro- magnetic x,y (2) -TIME t (1))

 

And

 

Could it be that GRAVITY/GRAVITATIONAL WAVES be 4 DIMENTIONAL. ( Spacial x,y,z (3) -TIME (1))

 

------------------------------------

 

Of course two of the dimensions or variables in electro- magnetism are not spacial but variations in electric field and magnetic field ?

 

Mike

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Apparently there are explanations of the twin travel thought experiment (e.g., see wiki) that do not require the notion of acceleration as a key factor

 

Indeed, I recall reading somewhere that Einstein did not use the notion of acceleration with regards to time dilation in his paper on SR. I only see a discussion of "acceleration" in section 10 regarding the "Dynamics of the Slowly Accelerated Electron," which I gather was his original paper on SR.

(https://www.fourmilab.ch/etexts/einstein/specrel/www/)

 

In any case, if time dilation in the story of twin travel can be resolved without discussing acceleration, then it would seem that the Equivalence Principle, (which I gather focuses on the similarity between acceleration in the twin travel story and what one might call the "simulated acceleration" of gravity) is not needed in an explanation of time dilation with respect to gravity.

 

Indeed, there seems to be both apparent time dilation based on observation as well as real time dilation (slowing of aging process) when it comes to the twin story, while, on the other hand, there is no apparent time dilation based on observation.

 

In short, I wonder just how similar the time dilation associated with twin travel is with respect to the time dilation associated with gravity. (Indeed, I don't even see any form of the word "dilate" in Einsteins original paper, though I presume that it is implied somewhere in the formulas.)

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.

A problem that has come up on this thread , and is or has been discussed in the Philosophy Forum , the subject being

 

:- " space time " and Maths . What is reality? " something to that effect .

 

I followed the arguments put forward , and can see how the search for REALITY can become a blockage to progress quite easily .

 

Some of the arguments seem to lead to a rather daunting answer . Yet this may be a way forward with the subject of this thread concerning " space time " and the idea of the mediums for gravitational waves and Electro magnetic waves .

 

It would appear that dependable , REALITY can only apply to a sequence of causal links ( this depends upon that which depends upon another ) to a limited chain up and down . At the upper and lower end of the chain , the causal links fail to be reliable or dependable and thus if looking for a real cause or link to REALITY , it fades into the distance , up or down as NOT REALITY .

 

In other words there exists a cloud or bubble of REALITY unique to the particular area of the universe. ( not meant to be a physical region , but more a region of scientific consideration) . Which is fine within a certain region . As you reach the edges or extremities of the causal reality ( up or down , causal or predictive ) and the certainty of reality , fades away to nothing . We can move about and exist as rational , scientific , beings in our region of ' space time ' and continue to build our understanding on , real laws , set theories, etc etc . BUT .REALITY only reaches so far out . ( again more from a causal region , than a strictly physical region! )

 

How does that sound ?

 

post-33514-0-91436600-1471901160_thumb.jpeg

 

Ps .

 

This , does not exclude reality existing everywhere , but we can not have knowledge of that or even know that it exists. ( within science that is , outside of science can be another matter all together ) . It is also necessary that the patch we do know is reality , can exist it its own right .

 

But significant is it that " the most real , reality " is nearer to the centre , of the sphere of consideration .?

 

Mike

Edited by Mike Smith Cosmos
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.

GRAVITY WAVES and the AETHER.

The thing that keeps ' popping ' up to do with this subject .

Seems to be the difference between ELECTRO-MAGNETIC WAVES and GRAVITY WAVES .

And in that respect,

I must come back to the difference in the relationship to the MEDIUM of both of these types of waves .

------------------------------------

The medium appears to be the FOUR DIMENSIONAL SPACE (3) - TIME (1) .

Could it be that ELECTRO-MAGNETIC WAVES be 3 DIMENSIONAL . ( electro- magnetic x,y (2) -TIME t (1))

And

Could it be that GRAVITY/GRAVITATIONAL WAVES be 4 DIMENTIONAL. ( Spacial x,y,z (3) -TIME (1))

------------------------------------

Of course two of the dimensions or variables in electro- magnetism are not spacial but variations in electric field and magnetic field ?

Mike

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How can we connect " REALITY " to these two Mediums ?

 

One working with magnetic field , electric field (or charge) and time ,

 

The other working with

 

Matter, mass , gravitational field , 3 dimensional space , and time ?

 

Are they comparable , complimentary ,

 

or just two totally different sets of dimentions ( linked only by or in time ) ?

 

Mike

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Any introductory textbooks you can recommend, AJB, to get a better grip on fibre bundle treatment of fields ?

Assume a working knowledge of diff. geometry and just a basic understanding of topology/group theory.

 

Dodson and Poston

 

Tensor Geometry

 

Chapter VII part 3 Bundles and Fields

I keep hearing gravity waves described as ripples in space time. Does this suggest that space time is a substance like the discredited notion of the aether? It seems to me that if space time can be said to ripple then a preferred reference frame is suggested by this "ripple" I know I must be off base here but how am I mistaken?

 

 

The equations of special relativity are algebraic equations.

 

As such they have algebraic solutions ie the solutions are one or more numbers.

 

The equations of general relativity are differential equations.

 

As such they have functions or equations as solutions.

 

Some of these are equations of motion so it is not surprising that some of these solution equations of motion are a form of wave equation (which is an equation of motion)

 

 

https://en.wikipedia.org/wiki/Einstein_field_equations

 

 

The solutions of the Einstein field equations are metrics of spacetime. These metrics describe the structure of the spacetime including the inertial motion of objects in the spacetime. As the field equations are non-linear, they cannot always be completely solved

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Thanks Sudiot, I'll see if I can find it.

The lecture notes AJB recommended ( for which I thank you AJB ) may be introductory to him, as he works with these concepts everyday, but they are far from it for me.

I'm hoping your suggestion is a little more 'introductory'.

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This is all sounding like this : " ALUZA-KLEIN THEORY " which in Wikipedia shows a " compactification principle " putting electromagnetism in with general relativity and gravitational waves " manifolds, fibre bundles , etc

 

------------- WHY- O - WHY , did nobody tell me , about this , before ?

 

" We did ". I hear as a faint cry " but you did not hear us ! " ( probably AJB , amongst others ..)

 

Is this what happened ? Where was I ,? When this was said ? Asleep ?

 

Ref to Wikipedia " aluza-Klein theory" ....:- https://en.m.wikipedia.org/wiki/Kaluza%E2%80%93Klein_theory

 

Mike

 

Ps

 

To quote near end of Wikipedia quote

 

" In modern geometry, the extra fifth dimension can be understood to be the circle group U(1), as electromagnetism can essentially be formulated as a gauge theory on a fiber bundle, the circle bundle, with gauge group U(1). In KaluzaKlein theory this group suggests that gauge symmetry is the symmetry of circular compact dimensions. Once this geometrical interpretation is understood, it is relatively straightforward to replace U(1) by a general Lie group. Such generalizations are often called YangMills theories. If a distinction is drawn, then it is that YangMills theories occur on a flat space-time, whereas KaluzaKlein treats the more general case of curved spacetime. The base space of KaluzaKlein theory need not be four-dimensional space-time; it can be any (pseudo-)Riemannian manifold, or even a supersymmetric manifold or orbifold or even a noncommutative space."

 

I presume these are Examples As illustrated. Dealing with some of the points quoted here from Wikepedia . At least , to some extent , by these previously quoted images ?

 

post-33514-0-62945600-1472106773.jpeg. post-33514-0-46876900-1472106807.png

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  • 2 weeks later...

.

A quote from the latest ' New Scientist ' gives some food for thought in this matter .:- By Stuart Clark

 

Quote "

 

EVERY age in history has its own ideas about what makes up the universe. Questions about what kinds of things exist go all the way back to the earliest philosophical texts, says Jan Westerhoff, a philosopher at the University of Oxford.

 

For many ancient peoples, basic elements such as earth, air, wind and fire formed the essence of the cosmos. In the past century or so, we have concluded that matter is built from atoms, that atoms are constructed from a small set of elementary particles, and that those particles are fluctuations in a melee of quantum fields pervading empty space (see Why is there something rather than nothing).

 

So, job done reality explained? Not so fast, says Westerhoff. You need to be absolutely clear about the sense of the word reality otherwise the discussion is going to be all over the place. For a start, do only physical objects like earth or atoms count towards reality or things like minds and consciousness, too?

 

Although the scope of our definition determines the complexity of the puzzle, physics should still supply the solution, says philosopher Tim Maudlin of New York University. Physics is about just two questions, he says:

 

-- .- WHAT EXISTS ? and . - WHAT DOES IT DO ? .

 

If you answer both of those questions, then I think you have answered the question what is reality?.

 

Unquote "

 

Mike

 

Ps . This does of course beg the question ... What does it mean , quite, " TO EXIST " ?

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