Just wondering, how do you know it's purple? ;-)

You'll have to take my word for it.... :P

You seem to be a very trustworthy person, so I'll believe you! But don't bring him out for a walk!!!!! ;-)

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http://www.therageclub.com

... I had always liked the mass curving space-time model, as in the simple bowling ball on a trampoline analogy.

That analogy is nice for 'showing' lines of gravitational equipotential. However, there is a very strong anthropomorphic temptation to assume a 'global gravity' acting 'downwards' in viewing the analogy to explain things rolling around on the analogy's 'surface'. Rather misleading... But nicely 'cinematic' for pop-TV science.

Which leads to a strong argument against the geometric view of gravitation: What is it in the geodesic view that imparts an acceleration on bodies on a "geodesic slope"? (There is no 'global gravity acting downwards' to impart a lateral force vector for anything on a 'slope' in that view.)

What this means to me in terms of propagation, is that for an observer on the moving mass (bowling ball) the observable effect on a distant object will be effectively at "time plus 2*(C/distance)", whereas for the observer situated at the distant 'edge' of the field will see the space-time (trampoline) curve change before the light of the visible movement of the mass reaches it, or "time minus C/distance", So maybe we have a hypothetical external observer where the effect would appear to be an instantaneous one, as only a hypothetical observer could be, with practical observers 'seeing' the change either long after or before the observable event.

That is part of the discussions. Taking the first part of your view and the orbital mechanics just don't work. Yet, taking your 'external observer' view invalidates causality.

Now to me space-time curvature implies tension, and tension implies 'fabric', which I guess also allows for the propagation of waves in similar fashion to the slapping of the trampoline.

Using that analogy, the fabric is the gravitational field, and the 'slapping' and 'ripples' are light speed gravitational waves.

The question is whether or how that fabric 'moves' with the source mass.

The hypothesis I'm favouring from my previous post is that the fabric has a sort of 'momentum' and settles to follow linear motion. Hence, for sources that move linearly, the fabric (gravity) is already in place at all distances.

The light speed part is for when the source mass is displaced from a linear path by some acceleration. The 'fabric' is stretched by the source displacement from the linear path and that displacement and the new (linear) vector for the continued motion of the 'fabric' is what propagate out at light speed.

Bearing in mind the fabric is expanding, how might that alter the simplistic analogy? Might the expansion be significant enough to stretch the moving mass local observed round trip time even further, and the remote observation see the effect even further before the event [keeping speed of light as constant, just as it's s'posed to be]? or would they stay in equilibrium, stretching speed of light with the fabric.

Good question. It's a question whether the effects of that cancels out in the maths or whether that could be something to be measured.

Will frequencies practical for propagation of such gravitational waves be dependant on localised 'tension', or mass density, as it is with the perhaps overly simplistic trampoline analogy, by the spring tension and objects placed on the fabric?

When the various LIGOs et al find something, we can then start looking in greater detail. Who knows yet?!

Too many questions, good fun though :D

Very much so.

Another good question is what is or might be whatever 'fabric'?


Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

I could not let this go any longer and had to let you guys know your all wrong. Gravity is ... singularity ... zero volume and infinite density ... tears a hole in the dimensional barrier ... infinite density ... infinite gravity ... Infinite density = an infinite number of graviton particles. The gravitons just want to go home...

Sorry, there's too many infinities and discontinuities in there for anything 'sensible'.

Infinites and division by zero usually imply in the maths that some assumption is wrong and so the description is invalid.

A pan-dimensional view is entirely possible, but it must be something seen (testable) to be proven.


Keep searchin',
Martin

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

Just wondering, how do you know it's purple? ;-)

You'll have to take my word for it.... :P

You seem to be a very trustworthy person, so I'll believe you! But don't bring him out for a walk!!!!! ;-)

Sorry, that is merely belief and not Science.

I can equally believe the colour to be orange merely because I might like orange.

And thus a new religion is laid down.

[ Crescendo of a booming base voice: ]
And Yea! Let these Forums be [ insert magic pause here ] The Bible!!!

(Cue almighty crash of thunder and the flash of an old incandescent light bulb going 'ping' :-p )


Keep searchin',
Martin

(Please see the other thread for "Intelligent Design".)

---

See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

There is no test as yet for gravitons such as your talking about. I do know the experiment your talking about where it was demonstrated that light is both a particle and a "wave". Quantum superposition is the cause of this effect. Its a particle while your watching it and a "wave" when your not watching it. When I say "wave" that means its not actually a wave but it exhibits properties of a wave. A single photon can interact with itself because it exists in more than one place at the same time. By observing the photon you collapse it into a single particle. I know for some of you this might not make sense but it is true. For a demonstration there is a very simply put video on the double slit experiment @ youtube.com. Just search double slit experiment. That particular test uses electrons but a similar test using photons will and has yielded the same results.

I'm not talking about a test at all. I am not saying that they did a test like they did to find out that light was both particles and waves! I am simply saying that it has been theorized mathematically.

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How does this sound to you guys?:

http://www.youtube.com/watch?v=v1tkM_f5B9s

General Relativity: gravitational waves

"Matter tells space how to curve, and space tells matter how to move."
-- John Wheeler (physicist)

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"Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind." - Dr. Seuss

How does this sound to you guys?:

http://www.youtube.com/watch?v=v1tkM_f5B9s

General Relativity: gravitational waves

"Matter tells space how to curve, and space tells matter how to move."
-- John Wheeler (physicist)

Good but it does not mention Einstein@home, in whose message boards you can find many informations on the research actually going on in USA, Japan and Europe.
Tullio

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How does this sound to you guys?:

http://www.youtube.com/watch?v=v1tkM_f5B9s

General Relativity: gravitational waves

"Matter tells space how to curve, and space tells matter how to move."
-- John Wheeler (physicist)

Good but it does not mention Einstein@home, in whose message boards you can find many informations on the research actually going on in USA, Japan and Europe.
Tullio

Can you link us Tullio?


Thanks!


.

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"Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind." - Dr. Seuss

Here it is:
Einstein@home
Tullio

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I thought you might guide us a little closer to a forum section or something but I guess we can look for it for ourselves.

Looks like this is the place:

http://einstein.phys.uwm.edu/forum_forum.php?id=4

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"Be who you are and say what you feel, because those who mind don't matter and those who matter don't mind." - Dr. Seuss

I thought you might guide us a little closer to a forum section or something but I guess we can look for it for ourselves.

Looks like this is the place:

http://einstein.phys.uwm.edu/forum_forum.php?id=4

Well, yes, but the whole home page is interesting and has also a link to a game.
Tullio

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... General Relativity: gravitational waves

"Matter tells space how to curve, and space tells matter how to move."
-- John Wheeler (physicist)

The questions are:

How does the "how" and "telling" work?

What is the mechanism and mediation?

And how 'fast'?

Most importantly: Can the properties of the assumed "space-time 'fabric'" be measured and probed?


To my reading around so far, there seem to be a few too many holes.

Keep searchin',
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

Most importantly: Can the properties of the assumed "space-time 'fabric'" be measured and probed?


To my reading around so far, there seem to be a few too many holes.

Keep searchin',
Martin

Gravity Probe B has measured the geodetic effect foreseen by GR with great accuracy. The much smaller frame dragging has been also measured with lesser accuracy and NASA has not financed the data analysis needed to do so. Gravity Probe B has taken forty years from design to launch and is probably the most sophisticated scientific satellite ever. It's a shame that Stanford University does not start a BOINC application to perform the data analysis.
Tullio

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I have heard that Gravity waves, or the effect of same, has no propagation delay.
Is this true?
Light from the sun takes 8 minutes to reach us.
If the sun was snuffed out of existence, it would be 8 minutes before the light went out.
If the sun was snuffed out of existence, we would immediately leave our orbit and fly off into space.

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*** Those who know, don't speak,
those who speak, don't know ***

I have heard that Gravity waves, or the effect of same, has no propagation delay.
Is this true?
Light from the sun takes 8 minutes to reach us.
If the sun was snuffed out of existence, it would be 8 minutes before the light went out.
If the sun was snuffed out of existence, we would immediately leave our orbit and fly off into space.

This would violate relativity. I do not believe it to be true.
Tullio

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...Is this true?
Light from the sun takes 8 minutes to reach us.
If the sun was snuffed out of existence, it would be 8 minutes before the light went out.
If the sun was snuffed out of existence, we would immediately leave our orbit and fly off into space.

This would violate relativity. I do not believe it to be true.

That is pretty much the basis for the start of my questions about the propagation and action of gravity.

One aspect is that there is a lot of confusion over what the phrases "gravity wave" and "gravity propagation" actually mean.

A vital aspect is that for orbital calculations to accurately describe reality, you must assume an instantaneous position for all the gravitational sources. And yet those sources themselves are moving and accelerating.

Hence the offered hypothesis that a gravitational field can move linearly with it's source, and that it is the positional displacement due to any acceleration that has effects that propagate out at a finite speed...

Or is it indeed that gravity has some aspects that are "faster than light".

Keep searchin',

Regards,
Martin

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See new freedom: Mageia Linux
Take a look for yourself: Linux Format
The Future is what We all make IT (GPLv3)

A vital aspect is that for orbital calculations to accurately describe reality, you must assume an instantaneous position for all the gravitational sources. And yet those sources themselves are moving and accelerating.

Hence the offered hypothesis that a gravitational field can move linearly with it's source, and that it is the positional displacement due to any acceleration that has effects that propagate out at a finite speed...

Or is it indeed that gravity has some aspects that are "faster than light".

Keep searchin',

Regards,
Martin

You make me try to remember the difference between newtonian mechanics, which is still used in astronomy and astronautics if we forget extreme cases like black holes. In newtonian mechanics, where speeds are much lower than the speed of light and masses are not extremely large one can forget relativistic corrections of the order of v square over c square and can imagine the propagation speed of static gravitational field as practically infinite with no significant error. The case if different if we have a rotating neutron star with some asymmetry and in this case one cannot consider its gravitational field as a static field but as a dynamic quadrupole field (the electromagnetic field is a dipolar field, which corresponds to a spin 1 particle, the photon) whose hypothetic particle, the graviton, has spin 2. The associated wave of such a field is the gravitational wave we are looking for.
Tullio

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Here's a thought. Everyone seems to agree EM & Gravity waves are not "the same" or at least seem to resist unification with the EM, weak and strong forces. Just a thought.. what if they are similar in form but of vastly differing magintude [which they are..] - by this I mean that EM also causes/is a result of a warping of spacetime, just like gravity, but at such a tiny scale [amplitude]/high freqiency as to be detected as EM whereas low frequency large scale [orders of magintude beyond the longest radio] could be felt as GW - Or to think of it another way, it's essentially the same waves that make a tennis ball bob about on a pool as those which throw supertankers about on the open ocean.. Just a thought .. about to be shot down no doubt..

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I just watched the History Channel's "Universe" episode on gravity. Nice series, but I still like Sagan's "Cosmos" series better. Anyway, "Gravity" was good even though they stuck with Newton for the first 40 minutes before Einstein. Those two massive G-Wave detector projects got me thinking: phase modulation of intelligence using a G-Wave carrier?

I hear you. I personally believe that advanced civilizations would prefer to use gravitational waves, not EM waves, as a method of interstellar communication.
I had the pleasure of presenting this idea in a poster session at the AbSciCon 2008 conference last April. The reasons ETs would use gravitational waves as their preferred mode of communication, are as follows:
1. They can be monitored 24 hours a day, 365 days a year, regardless of weather conditions.
2. Gravitational waves are more like sound waves, which can be detected (or heard), regardless of detector orientation.
3. Gravitational waves are not impeded by interstellar dust.
4. Gravitational waves produced by natural sources have a relatively low frequency (< 5 kHz). Intelligent signals are likely to be much higher.
5. Only the most advanced civilizations would have the technology to receive gravitational waves.
6. Currently, there are no terrestrial sources of gravitational waves that we know of.
7. Since the demand for wireless (EM) services is constantly growing, radio interference will become more and more of a problem. Satellites orbiting the earth also cause major interference. For this reason, advanced civilizations will be forced to use gravitational waves as a method of extraterrestrial communication and reserve EM waves for terrestrial communication. I predict that once we develop the technology to transmit and receive gravitational waves, we will also use it for interplanetary communication.
You can go to: http://www3.telus.net/foamyether/seti/seti.htm to view my poster and also watch a video of my presentation.

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Here's a thought. Everyone seems to agree EM & Gravity waves are not "the same" or at least seem to resist unification with the EM, weak and strong forces. Just a thought.. what if they are similar in form but of vastly differing magintude [which they are..] - by this I mean that EM also causes/is a result of a warping of spacetime, just like gravity, but at such a tiny scale [amplitude]/high freqiency as to be detected as EM whereas low frequency large scale [orders of magintude beyond the longest radio] could be felt as GW - Or to think of it another way, it's essentially the same waves that make a tennis ball bob about on a pool as those which throw supertankers about on the open ocean.. Just a thought .. about to be shot down no doubt..

The difference is a bit deeper. EM stuff one particle effects one particle. In gravity one particle effects the rest of the universe. If you launch a photon, it has a direction. Gravity doesn't have a direction. When you toss the bowling ball the rest of the universe feels it. Ripples on a pond is the way it works.

BTW photons are warped by spacetime. They have a rest mass.

Gary

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