Gravity waves and the aether

[ajb]

In this case I would have thought the ' How it works ' in real terms' will lead to the Why it works the way it does ?

Maybe you are confusing 'why' and 'how'.

 

Anyway, we can give a description of how an aircraft flies based on our knowledge of physics. We can look at the mathematics more here and make some more sense of 'what pulls and what pushes'. Then you start to think about this more fundamentally. The bottom line is that I can give you various descriptions of the physics involved here - with different levels of sophistication - but that is it.

[disarray]

.But just how the Earth is pushing up against this medium of gravity field I have proposed , I am not sure . The rubber sheet model is too upside down in its modelling , it invokes more questions than answers
. I am trying to think of an alternative to a rubber sheet model ? Like large dense swarm of honey bees surrounding the earth , pressing down on us . ( joke )

 

The only theory that I have come across with respect to the earth pushing up, so to speak, is the physical expansion concept (which, I gather, is the result of the expanding universe):

 

"Beginning with the naïve idea of physical expansion as the cause of gravity, we are compelled step-by-step to the conclusion that the effective metric of spacetime must be contracting around massive bodies. If we examine in detail the requirement for the surface of an object to be accelerating outward in terms of the local inertial frames, even though the surface itself is stationary, we find that this “accelerating in place” implies that space is curved in time, and the rate of proper time is lower near massive bodies. This leads to the curved spacetime interpretation of general relativity, which of course gives a very satisfactory representation of all known gravitational phenomena."

http://www.mathpages.com/home/kmath077/kmath077.htm

 

This is an interesting article, though I don't know how sound it is.

Edited July 10, 2016 by disarray

[Strange]

One of those questions in the post you directly answered (in the preceeding post)was

 

• What property of matter **causes geodesics to curve near them?"

I thought this was a question that had not been answered. I thought Einstein had somehow figured out that if the spacetime model was curved in the presence of mass then it would correctly predict physical phenomena to an extraordinary degree of accuracy but that the actual rationale was lacking.

 

 

So mass (and energy) is the property that causes spacetime to curve.

 

Perhaps you (or Mike) will ask why it does that.

 

Well, ultimately, why anything.

 

Why do electric charges exert a force on one another?

Why do electrons obey Fermi-Dirac statistics (the Pauli exclusion principle)?

Why do photons have energy and momentum?

Why are most phenomena quantised?

Why does the universe exist?

 

I am not saying that these questions are not worth asking, but they are not really science questions.

Edited July 10, 2016 by Strange

[Mike Smith Cosmos]

So mass (and energy) is the property that causes spacetime to curve.

 

Perhaps you (or Mike) will ask why it does that.

 

Well, ultimately, why anything.

 

Why do electric charges exert a force on one another?

Why do electrons obey Fermi-Dirac statistics (the Pauli exclusion principle)?

Why do photons have energy and momentum?

Why are most phenomena quantised?

Why does the universe exist?

 

I am not saying that these questions are not worth asking, but they are not really science questions.

Yes but just putting 'why ' in front of a genuine science question , does not abdicate a scientist from exploring answers near, around or far for that matter from core proven supported fact.

 

I have moderated the tone , by placing ' how ' in front of some of these issues . As how certain phenomenon work , are possibly the gateway to new phenomenon and horizons ? Is that not a reasonable thing to do ?

 

Mike

[Strange]

So there are all sorts of speculative theories and hypotheses that might explain how space-time (and its curvature) and mass arise from something more fundamental.

 

For example:

 

 

Starting from first principles and general assumptions Newton's law of gravitation is shown to arise naturally and unavoidably in a theory in which space is emergent through a holographic scenario. Gravity is explained as an entropic force caused by changes in the information associated with the positions of material bodies. A relativistic generalization of the presented arguments directly leads to the Einstein equations. When space is emergent even Newton's law of inertia needs to be explained. The equivalence principle leads us to conclude that it is actually this law of inertia whose origin is entropic.

https://arxiv.org/abs/1001.0785

 

But that will just leave you with even more "why" questions.

[Mike Smith Cosmos]

So mass (and energy) is the property that causes spacetime to curve.

 

Perhaps you (or Mike) will ask why it does that.

 

Well, ultimately, why anything.

 

Why do electric charges exert a force on one another?

Why do electrons obey Fermi-Dirac statistics (the Pauli exclusion principle)?

Why do photons have energy and momentum?

Why are most phenomena quantised?

Why does the universe exist?

 

I am not saying that these questions are not worth asking, but they are not really science questions.

.

So at least the first three why's you list , if putting how in front puts them bang smack in current theory . Surely

 

Mike

 

Departure lounge , delay 15 mins .

Then if gravity is consistent and reliable , downwards ( not sure How ) towards the centre of the earth . Speed and wing cross section should use Lift to combat gravity. ..........I might just try that dropping a weight from my chin , just as the pilot accelerates

So there are all sorts of speculative theories and hypotheses that might explain how space-time (and its curvature) and mass arise from something more fundamental.

 

For example:

 

https://arxiv.org/abs/1001.0785

 

But that will just leave you with even more "why" questions.

.

 

 

I do not think I am being unreasonable asking questions about gravity . We seem to know precious little about it, yet the universe is full and possibly only functioning by the structure and functioning of/by gravity.

 

It is a worthwhile pursuit if all we can come up with is a " rubber sheet " , for pity sake . And even that model does not fit very well.

 

Mike

Edited July 10, 2016 by Mike Smith Cosmos

[ajb]

We seem to know precious little about it, yet the universe is full and possibly only functioning by the structure and functioning of/by gravity.

We do in fact know quite a lot - remember that GR is tested to some huge degree of accuracy.

[MigL]

Have a good time in Italy Mike.

That picture you posted looks a lot like the hills around my home town.

( S. Angelo dei Lombardi, in Campania between Avellino and Benevento )

[Mike Smith Cosmos]

Have a good time in Italy Mike.

That picture you posted looks a lot like the hills around my home town.

( S. Angelo dei Lombardi, in Campania between Avellino and Benevento )

Just landed in Italy , having defied gravity for several hours. Landed in Bologna, hire car now roaring down auto strata toward Ancona. Down the E45 toward Gubbio. Soon be in my swimming pool. Tomorrow the big think. Got some ideas while flying . I am enthused.

 

MIKE

[disarray]

I for one would stop asking questions if a scientist just said that gravity was, unexplainable beyond that it "just is", much like the electric charges between particles;.... and indeed, the equation for the degree of attraction (re distance) is virtually the same.

 

However, I did post recently a credible site that sought to actually give an answer to the "Why" it happens that was purportedly consistent with Relativity and indeed is based on the physical expansion of the universe. No comments?

 

Again, the article is at http://www.mathpages...77/kmath077.htm

Edited July 10, 2016 by disarray

[MigL]

The 'expansion simulates gravity' theory is inconsistent with observation.

How can it answer the "why masses gravitate' question ?

[disarray]

The 'expansion simulates gravity' theory is inconsistent with observation.

How can it answer the "why masses gravitate' question ?

 

The article does address this and other weaknesses of a 'basic' physical expansion concept, but comes up with a modified version that supposedly avoids these problems. Did you read the article?

Edited July 10, 2016 by disarray

[Mike Smith Cosmos]

.

Now, it has got to be explained.

 

I have looked up tonight in pitch black . From this far south the Milky Way can be seen rising from the horizon at 40 degrees leaning like a fallen tree.

 

Sitting just south but above the horizon is the constellation of Sagittarius.

 

Within this constellation is " the teapot " , with handle , lid and spout .

The spout and just beyond the funnel end is the main part of the Milky Way centre.

 

Right there are 200,000,000 stars collapsed into a black hole .

 

The gravity waves coming out of this centre of the Milky Way must be enormous !

 

The specticle , the beckoning, " I am gravity , supreme , understand me, and how I work "

 

I am in rapture !

 

Mike

 

( that was a bit poetic , somebody a few pages back , suggested that might be an avenue to explore . )

Edited July 10, 2016 by Mike Smith Cosmos

[geordief]

.

 

Right there are 200,000,000 stars collapsed into a black hole .

 

The gravity waves coming out of this centre of the Milky Way must be enormous !

 

 

I do not think that "gravity waves" as you describe them exist.

 

When I looked up "gravity waves" the term is used to describe (for example) waves caused by the moon on the oceans of the earth.

 

https://en.wikipedia.org/wiki/Gravity_wave I don't think that is what you meant by that.

 

 

Gravitational waves are seemingly caused by changes in a gravitational field and are apparently much less energetic than you would imagine.

 

I read that (perhaps I was told) even the double black hole that was recently detected was not particularly energetic even at quite a close distance.to the event

 

If you are looking up and imagining a black hole I suspect it would not be emitting much radiation at all unless it was gobbling up a large star or another black hole at the time.

 

If it was quiescent (between meals) I imagine it would be all quiet on the Western Front.

Edited July 11, 2016 by geordief

[Mike Smith Cosmos]

I do not think that "gravity waves" as you describe them exist.

 

When I looked up "gravity waves" the term is used to describe (for example) waves caused by the moon on the oceans of the earth.

 

https://en.wikipedia.org/wiki/Gravity_wave I don't think that is what you meant by that.

 

 

Gravitational waves are seemingly caused by changes in a gravitational field and are apparently much less energetic than you would imagine.

 

I read that (perhaps I was told) even the double black hole that was recently detected was not particularly energetic even at quite a close distance.to the event

 

If you are looking up and imagining a black hole I suspect it would not be emitting much radiation at all unless it was gobbling up a large star or another black hole at the time.

 

If it was quiescent (between meals) I imagine it would be all quiet on the Western Front.

.

 

What ,I have come to realise, in my time to think about GRAVITY .and its role , and condition in the Universe, is :-

 

It is ALL important to the universe . It is fundamental , and foundational . The whole universe is structured and held together by Gravity .

 

And it is probably No coincidence it was ( I believe , if I am right ) , the first Force to break , in the succession of symmetry breaking which occurred initially from the great Overarching. SUPER SYMMETRY , at the very beginning of the structuring of the four gauge forces that arose in the very early universe. Namely GRAVITY, ELECTROWEAK , THE STRONG ATOMIC, ELECTRO-MAGNETISM .

I hope I have those named right ?

 

So if Gravity was the first to break from SUPER SYMMETRY then it is foundational to the whole universe including ' WHATEVER' .... ' Structure or Substance that exists and keeps the universe held in its past, present and future state " , it is there and exists in SPACE-TIME as GRAVITY ?

 

Mike

Edited July 12, 2016 by Mike Smith Cosmos

[ajb]

So if Gravity was the first to break from SUPER SYMMETRY then it is foundational to the whole universe including whatever " Structure or Substance " , there exists in SPACE-TIME ?

Gravity must have been present in the Universe right away - it is something to do with the very nature of space-time itself. It may have been the case that supergravity was important in the early Universe. You are really getting to the limits of our knowledge now.

[geordief]

I have just a small ( theoretical) question on the side that may be relevant.

 

Is there a logical impediment on attempting to model the universe as a whole by making a model of part of it? There are always ,inevitably loose ends?(just part of the deal)

 

Is that perhaps a reframing of a question that has already been asked /anwered in different ways?

 

Btw my last post went unchallenged . So I was right? There are no "waves of gravity" emanating from objects:it is only changes in gravitational fields that produce these effects.?

 

The universal gravity field is ,so to speak "in place" and has been caused by the accumulation of countless small and large changes over time.

 

PS would that mean that the recent gravitational waves detected from the binary black hole merger caused a vanishingly minute but permanent change in the gravitational field that exists in our own little solar system?

Edited July 12, 2016 by geordief

[Strange]

Is there a logical impediment on attempting to model the universe as a whole by making a model of part of it? There are always ,inevitably loose ends?(just part of the deal)

 

I think that modelling is always an approximation and the only way we can model anything (from the behaviour of a transistor through an entire microprocessor to simulations of the evolution of the universe -- all of which are done with amazing success) is by using abstraction. In other words, you don't model an entire processor at the level of transistors, nor the entire universe at the level of atoms.

 

 

Btw my last post went unchallenged . So I was right? There are no "waves of gravity" emanating from objects:it is only changes in gravitational fields that produce these effects.?

 

Correct.

 

 

PS would that mean that the recent gravitational waves detected from the binary black hole merger caused a vanishingly minute but permanent change in the gravitational field that exists in our own little solar system?

 

I don't think so. It would have passed through and left things as they were before - like a ripple on the surface of a pond.

[Mike Smith Cosmos]

It would have passed through and left things as they were before - like a ripple on the surface of a pond.

Yes but that's what I said 100 posts ago ! " The medium for the gravitational field /wave was like ...a ripple ..in a pond "

 

 

. " Only pulling your leg ? Lol "

 

Mike

 

Ps I am hard on the heals of the originators of this scientific thought. I am stone throw from Rome , Piza , Empoli. The great universities of Bologna , Pisa . And Galileo, etc The atmosphere is thick with their Aura. Even though they have delt with their " mortal coils " their atmosphere continues .

 

Edited July 12, 2016 by Mike Smith Cosmos

[swansont]

I don't think so. It would have passed through and left things as they were before - like a ripple on the surface of a pond.

 

 

The waves carry energy, and that's a source of gravitation. The mass of the BH system deceased by ~3 solar masses in the first event, so one would expect the gravitational attraction to have decreased.

[Strange]

Che bello. Sono molto geloso!

 

 

The waves carry energy, and that's a source of gravitation. The mass of the BH system deceased by ~3 solar masses in the first event, so one would expect the gravitational attraction to have decreased.

 

Good point. I was thinking too locally!

[swansont]

Yes but that's what I said 100 posts ago ! " The medium for the gravitational field /wave was like ...a ripple ..in a pond "

 

But that's an analogy. There is no actual pond.

[geordief]

Mathematically are these gravitational waves caused by changes in a gravitational field modeled by using differential /integral calculus?

 

Are the local tensors differentiated wrt to some property of spacetime and does that produce a picture of a gravitational wave?

Edited July 12, 2016 by geordief

[ajb]

Mathematically are these gravitational waves caused by changes in a gravitational field modeled by using differential /integral calculus?

 

Are the local tensors differentiated wrt to some property of spacetime and does that produce a picture of a gravitational wave?

With no details ... you work with the linearised field equations. You think of a background metric plus a linear 'correction' g = g0 +h. You then take the 'correction' to satisfy the linearised Einstein field equations. Then you make a choice of gauge (do a little maths) and you can write the equation that h must satisfy as the wave equation.

[geordief]

With no details ... you work with the linearised field equations. You think of a background metric plus a linear 'correction' g = g0 +h. You then take the 'correction' to satisfy the linearised Einstein field equations. Then you make a choice of gauge (do a little maths) and you can write the equation that h must satisfy as the wave equation.

thanks. It is way above my pay grade. Hopefully your answer will be helpful to someone else