Speed Of Gravity

harry · Post by **harry** » Wed Apr 26, 2006 8:20 am

Hello Marc

Doubt what?

makc · Post by **makc** » Wed Apr 26, 2006 11:01 am

That "Galileo" experiment and "Michaelson" experiment results are correct.

harry · Post by **harry** » Wed Apr 26, 2006 12:19 pm

Hello Makc

I have read "Galileo" experiment
It has very little info.

Unable to open "Michaelson" experiment its a wikpedia thing.

I may have to use my wifes comp,,,,,,,,,,,,,hers opens all.

My settings on my comp are wrong,,,,,,,,,,,,,,,,,,my comp man will fix it soon.

Pete · Post by **Pete** » Wed Apr 26, 2006 4:25 pm

makc wrote:And that's all to it, everything else is logical consequence, including "speed of gravity propagation". Now, what reasons, in the name of ***, you have to doubt it?? I just don't get it.

I don't believe anybody intended to doubt GR directly; the questions asked so far seem to be along the lines of "Okay, I understand that the photon is a massless particle that quantizes the electromagnetic field. Is there an analogous quantization of the gravitational field? If so, what is its nature and how do we know it exists? If not, how and how fast do changes in the gravitational field propagate?"

If you understand the 'logical consequences' by which GR implies that gravity travels at speed c (and it does sound like you do), please try to enlighten us...

Pete · Post by **Pete** » Wed Apr 26, 2006 4:31 pm

makc wrote:That "Galileo" experiment and "Michaelson" experiment results are correct.

Galileo's experiment showed that mass is independent of gravitational acceleration. The Michaelson-Morley experiment showed that light does not travel relative to any fixed medium, or 'luminiferous aether'. Neither of these experiments address the speed of gravity.

ta152h0 · Post by **ta152h0** » Wed Apr 26, 2006 4:36 pm

speed of gravity is an invention of the original poster, possibly due to having entirely too much time on his hands. However, it does provoke serious considerations. may I suggest a new unit to quantify this mistycal quantity ?

Sg = X kilojoules / cubic parsec

there, pass on the ice cold one

makc · Post by **makc** » Thu Apr 27, 2006 8:57 am

Pete wrote:Is there an analogous quantization of the gravitational field? If so, what is its nature and how do we know it exists? If not, how and how fast do changes in the gravitational field propagate?"

If you understand the 'logical consequences' by which GR implies that gravity travels at speed c (and it does sound like you do), please try to enlighten us...

...Neither of these experiments address the speed of gravity.

1) Ok-kay, now I see you point. The thing is that in GRT there is no gravity quantums to begin with, and hence the question, "what is speed of graviton", is meaningless.

Here's why I asked about your definition of "speed". With GRT, changes in space-time curvature do not really "propagate" anywhere. 4D space-time is completely static. Solution of GRT equation gives us metric tensor g (for example, g(x,y,z,t)) which is simply set of numbers, and the only thing that can be associated with "speed of gravity", therefore, is partial derivative dg/dt. Clearly, it depends on coordinate system (i.e., who measures time, where and how he does it) and, finally on g itself (i.e., on mass configuration). For typical layouts, solutions are well-known, and I'm sure you can calculate dg/dt yourself. Note, however, that units for this thing are Hz, and not m/s, so it is not "speed" as that in the "speed of light".

2) Experiments are important in that they are experimental basis for GRT.

harry · Post by **harry** » Thu Apr 27, 2006 2:14 pm

Hello

Someone asked me what is gravity

see link

http://hyperphysics.phy-astr.gsu.edu/hb ... .html#grav
and
http://hyperphysics.phy-astr.gsu.edu/hb ... or.html#c2

http://metaresearch.org/publications/CD ... ntents.asp

http://metaresearch.org/media%20and%20l ... peikin.asp
http://metaresearch.org/cosmology/gravi ... ravity.asp
http://metaresearch.org/cosmology/speed_of_gravity.asp

If thats not enough let me know

makc · Post by **makc** » Thu Apr 27, 2006 2:42 pm

yes, that's not enough, could you please copy/paste next hundred of google search results, thank you.

ta152h0 · Post by **ta152h0** » Thu Apr 27, 2006 3:35 pm

Don't egg him on, he might believe you

kovil · Post by **kovil** » Thu Apr 27, 2006 4:50 pm

For the Canadian viewpoint on this subject;

As gravity is thought to be a reactionary event, whereby two objects react to each other's inertial mass by a gravitational attraction equivalent; the question comes up of how is the inertial mass equivalent communicated between the two objects ? There must be some kind of communication between massive objects, because as mass changes from a variety of reasons, gravitational attraction changes commensurately.

The question is, Makc, how fast do these masses communicate their inertial or gravitational status? Or even how do they communicate at all.

Speed is just the common word to describe the time lag in communication.

A variety of metaphores to describe what is taking place have been suggested, and none of them are sufficient to answer all questions about the subject.

The fact that Inertial Mass and Gravitational Mass are equivalent is a huge clue in the direction of a correct solution. This is the direction of my summer homework ! Inerita is the subject I'm studying first.
Ernst Mach is the main character in this quest at the moment. His studies and thoughts during the 1800's are still at the forefront of our present inquiries.

As Vedanta was making itself known in the 1800's to scientists, it likewise holds a key to the solution of inertia/gravitation equivalency, tho it seems no one is looking in that direction. Science and Religion is always a difficult marriage !

What is the cause of Inertia ?
This leads to the answer of how does gravity work.

Talley Ho; the Quest Awaits.

makc · Post by **makc** » Fri Apr 28, 2006 7:02 am

well, Einstein has put forward his answer: you feel gravity when you move wrong way. I can't help if it's not good for you.

harry · Post by **harry** » Fri Apr 28, 2006 8:42 am

Hello Makc

My comp will not search google,,,,,,or anyother.
These links have been collecting over time.

I usually give these links not for brownie points but for info to others.
If in the future people do not want them than I will stop posting links.

makc · Post by **makc** » Fri Apr 28, 2006 11:43 am

If you'd ask me, what I'd suggest is to buy a site, let's call it HarrySpace.com, then add a page, let's say Links.html, and finally change your signature to contain http://harryspace.com/links.html ...so when it comes to posting links, you could just say, "click that nice link in my sig, and scroll down to where it sais in bold, GRAVITY".

That's it.

Qev · Post by **Qev** » Sat Apr 29, 2006 3:36 am

makc wrote:well, Einstein has put forward his answer: you feel gravity when you move wrong way. I can't help if it's not good for you.

Well, according to relativity, gravity is simply the curvature of spacetime caused by the presence of mass. The question here is, how 'fast' do changes in this spacetime curvature propagate?

A simple example, you have to heavy masses interacting through gravity, and they're one light-minute apart. One of these masses is suddenly moved relative to the other. When does the 'stationary' mass feel the change in the gravitational pull from the 'moving' mass due to its change of position? Instantly? Exactly one minute later (when it sees the other mass move, due to light-speed delay)? Some other length of time? That's the question of the 'speed of gravity'.

ta152h0 · Post by **ta152h0** » Sat Apr 29, 2006 4:14 am

you would have two timed events with sensors exactly one light minute apart talking to each other at the speed of light. Great topic for a Friday night discussion in a college dorm. Gravity is just a number, no units. this number changes as a function of distance, totally dependent upon the velocity of the mass used to measure the gravity. Newton stated that an object remains at rest( or constant speed and direction ) until acted upon by an expernal force.. Let us say an object rotates once every 24 hours with gravity=1 at the surface. Let us say a force acts on this planet increasing the rotation, resulting in g=1 to be 1000 miles further up. The velocity of this change is directly related to the speed of the change, not plus any particular " flavor " of the gravity.
See, I did learn somethingh on a Friday night.

and i bet I am about to learn a whole bunch more in a few minutes.

astroton · Post by **astroton** » Sat Apr 29, 2006 4:18 am

makc wrote:well, Einstein has put forward his answer: you feel gravity when you move wrong way. I can't help if it's not good for you.

Newton's equation for gravitational force was replaced by Einstein with set of field equations to show how spacetime curvature works under the influence of massive body. The equations were much ahead of their time. Some Super Comps can create models using these field equations today.

These days, a lot of goofy arguments are dedicated to Einstein. Beware,,,,,,,,,,,,

harry · Post by **harry** » Sat Apr 29, 2006 5:22 am

Hello All

Makc that is really funny.

---------------------------------------------------------------
if you notice no more links,,,,,,,,,,,,

---------------------------------------------------------------
its like smoking,,,,,,,,,,,,,cut the habit out
---------------------------------------------------------------

So! has someone come up with the speed of gravity so to speak.

So far
I have been told that
its equal to that of light
others have said 10 times c
others 20 times c
some say infinite.

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

If gravity is 20 times c
Imagine no longer we shall be held back by the speed of light.
New communication skills can be applied.

makc · Post by **makc** » Tue May 09, 2006 10:23 am

Qev wrote:One of these masses is suddenly moved relative to the other. When does the 'stationary' mass feel the change in the gravitational pull from the 'moving' mass due to its change of position? Instantly? Exactly one minute later (when it sees the other mass move, due to light-speed delay)? Some other length of time? That's the question of the 'speed of gravity'.

Qev, I will look into your setup and see if my math skills are enough for this.

EDIT. Off the top of my head, without much of computation it is possible to show that your 'speed of gravity' cannot be greater than c, unless you'll be comfortable with peculiar phenomenon.

Let us designate 'speed of gravity' by w. We dont know if it changes on coordinates, but it has to have some value everywhere. In relation to very distant observer, two locations, R and R+dR, will

Qev wrote:feel the change

in times T and T+dT, correspondingly, so that dR = w*dT there. Now, another observer moving outwards with speed v would see these events separated by time dt = (dT - dR* v/c^2)/sqrt(1-(v/c)^2). Solving inequality dt < 0 (when dT > 0), we end up with v > c^2/w. In other words, an observer with v > c^2/w would see location R+dR 'feeling the change' before location R. That would be pretty weird - don't you think - and the only way to exclude such peculiar possibility is to conclude that w <= c.

Pete · Post by **Pete** » Tue May 09, 2006 11:06 pm

Your math looks correct, makc. One small thing bugs me, though: the derivation of the Lorentz transformations requires the assumption that light travels at speed c. Lorentz transforming the two events cannot result in the speed of a causal influence w being greater than c, which is exactly as expected, if changes in the gravitational field travel at speed c - which is the whole question.

Let me know if I'm off my rocker on any of this. My relativity-fu is weak.

dcmcp · Post by **dcmcp** » Wed May 10, 2006 2:37 am

Dunno if anyone's posted this link (I've only skimmed the thread):
http://en.wikipedia.org/wiki/Speed_of_gravity
According to wikipedia spd of Gravity = c

makc · Post by **makc** » Wed May 10, 2006 6:13 am

Pete wrote:One small thing bugs me, though: the derivation of the Lorentz transformations requires the assumption that light travels at speed c.

Well yes but that's just light, and whole this question assumes there's no direct connection between light and gravity "propagation". This assumption should be true for "very distant observer", as well as that gravity still "propagates" at some speed w around that observer, and not just "stops" at some r<R.

harry · Post by **harry** » Wed May 10, 2006 7:53 am

Hello All

Wikipedia is not always right.

The resluts of the speed or propagation of gravity will not be resolved for another few more years.

I wander if we can read gravity before the light.

Like the speed of sound and light from a thunder bolt.

Starship Asterisk*

Speed Of Gravity

speed of gravity

google

Is space-time flexable or stoic ?

impossible to prove