Speed Of Gravity

[imported_Ziggy]

GRAVITY, NOT SPACE-TIME! I've got an idea for a new kind of interstellar drive and am planning to do a report/article/sci fi story on it. But in order to to give my drive some possibility to it, I need people's opinons on it. Please vote and replie! :)

[Fraser_Abel]

You have to realize that talking about the speed of gravity and the speed of gravitons are essentially two different things. Gravitons might have a constant spped, true, but gravity itself always varies. Earth has a semi-weak gravity, the moon has weak gravity,the sun strong gravity, and blacholes have a gravitational effect far surpassing C.

GRAVITY, NOT SPACE-TIME!
You have to recognize C for each of these.
For spacetime, v=c.
For gravity, v always varies in relation to C.

[zephyr46]

Speed of gravity (http://www.ldolphin.org/vanFlandern/gravityspeed.html), you would have seen this site?

I think gravity is instantanious, it moves as fast as the generating body. That is if gravity is only thought of as a feild.

There are a lot of sites on this subject.

[kashi]

Ziggy I have a major problem with people voting on science. It kind of misses the point. It's a fascinating question that you raised, but could you please stop the polls. Afterall, this isn't Who Wants to be a Millionaire.

[imported_Ziggy]

I think the speed of gravity varies too. Maybe in a perfect vacum gravity travels at infinite speed. If light can't escape a blackhole, then a blackholes gravity is faster then light. The "far out physicts" in a blackhole only occur in the singularity. As soon as you pass the event horizon theres no going back and in a event horizon the physicts are still the same. But Enstein was still right. Nothing going "through" space-time moves faster-then-light.

[John L]

The problem with equating gravity with light when discussing escape velocities is that we don't what gravity is made of. Is gravity a particle that would be affected by itself? Is gravity literally the curvature of spacetime caused by any mass, and therefore independent of the speed of light limit? Does it depend on the medium, or is the fabric of spacetime itself the medium, and therefore idependent of what is in spacetime? Of course, if you could answer those questions you'd be up there in the history books with Kepler, Newton, Maxwell, Einstein, and Hawking...

[spedmen]

I agreee with John, in a way. The only way to study gravity is to isolate a graviton, if that is even possible, and only then will we be able to study the true and complete nature of gravity.

[kodakball]

Here is another site that says, they finally measured the speed of gravity.
http://www.newscientist.com/news/news.jsp?...p?id=ns99993232 (http://www.newscientist.com/news/news.jsp?id=ns99993232)

Well they just say the speed of light and gravity travel at the same speed.

[Cygnus X-1]

We must always question the unknown. If gravity can "move" faster than C, why couldn't it take matter with it? Poll, question; I see them as the same.

[John L]

Originally posted by Cygnus X-1@May 26 2004, 12:15 AM
We must always question the unknown. If gravity can "move" faster than C, why couldn't it take matter with it? Poll, question; I see them as the same.
YES! We must always question the unknown. One of the defining characteristics of the human species is our unquenchable curiosity. If we weren't this way we'd still be wandering the savannah scrounging for a little food, or sitting a caves picking fleas off our neighbors, or even still in the jungles of Africa hoping a big cat doesn't decide we'd make a tasty snack. All human advancement has come about because someone questioned not only the unknown but what we thought was the known.

[tarajee]

Originally posted by Ziggy@May 25 2004, 12:50 AM
GRAVITY, NOT SPACE-TIME! I've got an idea for a new kind of interstellar drive and am planning to do a report/article/sci fi story on it. But in order to to give my drive some possibility to it, I need people's opinons on it. Please vote and replie! :)
Hello all reders, Will you please contact me . There is no gravity. Some other system is working. You can call me :- tarajee20@hotmail.com[COLOR=blue]

[StarLab]

To say there is no presence or existence of gravity is to say there is no such thing as electrons and photons, spacetime, etc. Maybe if you mean there is no strong "pulling" force in the universe, I'd agree with you, because in almost all scenarios planets fall in stars and stars in blackholes of their own accord. When a photon travels along spacetime in a straight line, a blackhole may be in its path, stopping the photon and the photon ends up disappearing as soon as it reaches the blackhole.

Some other system is working.
In your other post, Tar, you said something that gave me an idea: what if gravitons and photons are the same thing, except gravitons carried zero energy? It's like an "energy" particle, but without the energy!

[Jan]

ok.....

first of all i would like to say hello to all the participants i am from Slovenia

I have a theory abaut how and why univers is expanding....

lets say that we can travel faster than light...
so lets say einstain was kind of wrong...(but he was write ,just watching from a pointless prospective) my theory is that space is expanding because there is a force beetwen two blackholes that is making the blackholes getting away from each other....but blackholes have a great mass that collects all the material and even light that pass her buy...so more that a blackhole eats more (let me call it antigravity (but this isnt the exact term)) more geeting-away-from-each-other-force) accumulates...........

so there is this force that is pozitive-(black-hole) and negative-(all things that are not black-holes) that obviously atract each other (obviously black-hole attracks the the lighter "things*) and black-hole and another blackhole that do just the opposite...because they are lets call them positve...



the most fascinating thing is that it hacs been measured that galaxies are getting away from each other and speeding ....but i would like to know if (because we can measure the mass of galaxies ) if maybe the largest galaxies are getting away with greater speed...(why u ask?......well many people has said that there is a high posibility that there is a black hole in every galaxy

there is another thing that i would like to comment.
a galaxy looks like a tornado in space so what happens if we take a tornado and we place another tornado near him (what will be the affect that one tornado will make at the other) ....

what do you all think abaut my theory


Jan

P.S. a apologize if i have made some grammar mistakes (i am not english)...
:)

[StarLab]

so there is this force that is pozitive-(black-hole) and negative-(all things that are not black-holes) that obviously atract each other (obviously black-hole attracks the the lighter "things*) and black-hole and another blackhole that do just the opposite...because they are lets call them positve...
I like what you are saying here: that if blackholes are positive and everything else is negative, blackholes attract everything but other blackholes, which they repel. But since the repulsion force btwn. blackholes is so strong, the universe is being pushed apart! I llllike it!

[John L]

Black holes don't repel each other. Black holes, like everything else in the universe, is made of matter and is attracted by gravity. That is how black hole attract matter and , yes, black holes do attract each other.

[Jan]

if black holes do atract each other how come galaxies get awy from each other...

[StarLab]

So...black holes attract everything...
Well, that's one thing I hate about gravity. I'd prefer it if gravity acted just a weeny bit like electromagnetism.

[Jan]

my theory can be tested...

[Jan]

are u 100% sure that one black hole can eat another?

[John L]

Originally posted by Jan@Jun 1 2004, 04:07 PM
if black holes do atract each other how come galaxies get awy from each other...
Jan,

There are numerous beautiful images from the Hubble and other space and ground telescope that clearly show two or more galaxies in the process of colliding with each other. Most galaxies are in fact members of gravitationally bound clusters. From the perspective of our galaxy, most distant galaxies are moving away from us due to the expansion of space between us and them (that's the theory), but not all of them are. The Andromeda galaxy is moving directly towards us and should collide with us in 2 billion years. Our galaxy is currently absorbing the dwarf galaxy Sagitarius. There are several satelite galaxies to the Milky Way such as the Magelanic Clouds that will be one day absorbed into our galaxy, and the galaxies known as the Local Group are not moving away, but part of our local cluster of galaxies. Those that are moving away are not members of the Local Group, our cluster, but are members of much more distant clusters.

[Jan]

i can easaly solve that problem....

what if ther were sevarel bigbangs all over the space then surely more galaxies with a bigbang speed woiuld overcome the speed of blackholes antigravity

[StarLab]

bigbang speed
:blink: :huh:

the speed of blackholes antigravity
:huh: :blink:

[katz3200]

Jan,
I like your theory. I think you have some valid ideas.

I believe there is a magnetism positive and negative, and on earth we only see one type. And that this magnetism is the same as we call "gravity". Even the atom has it - both positive and negative. (+4, -4)

But since we only see one, call it positive, we cant picture the other force.

The more advanced physicists here will not accept new ideas. Even tho modern science is lately pointing out that physics could be entirely mistaken up till now...they dont want to learn everything again. Dont let that opinion make you think any less, keep working on it.

The man who says he knows all about black holes, is speaking purely of ideas, not fact. There is energy in black holes, heat we can see, but that is simply all we know. Taking pictures still tells you nothing of WHY things are happening, what is their basis, etc. We can only assume from pictures, and space is not earth.

When we say two magnets same pole repel each other, that is fine. I think there are two COMPLETELY different types of magnetisms. And that this example is using Positive Magnetism only.....negative magnetism would be dark matter, black holes, and possibly stars that we have no real understanding of.

There is a page about the galaxy here, with a new theory that is interesting.

http://www.geocities.com/canasha2001/universe.html

It sounds like it would interest you. Happy theorizing!

:)

[imported_Nexus]

Greetings all,

I have been reading with great enjoyment all the posts in this forum, and i must say, its very interesting.

Staying consistent with my other posts in other forums, i would like to remind those that are here of the difference between observation and theory. It has been observed by great scientific minds of the past and present that gravity is a result of curvature in space caused by a presence of mass. The greater the mass the greater the curvature.

Newton fomularised the laws of motion that are widely used today in deriving answers as to the movement of things through spacetime. Taking the question of the speed of gravity to light, you will notice that when you try and measure the speed at which an object falls to the ground, you will have to use a gravitational constant (g) which on earth is (9ms to the power of minus two), this value is denotes the acceleration of an object towards a gravitational center. So the greater the curvature of space time, the greater the acceleration, you can than use this as your starting point.

All bodies of mass in the universe attract each other, not because they are positive or negative, its because of gravity, how strong is the effect of each bodies gravity towards the other (taking to account its proximity). Even our bodies cause some curvature in space, but its too weak to be taken into serious account.

The above have been proven and are being used in today's world. What has been theorised is that it is possible that since all sorts of radiation and submolecular emotions are associated with a form of particle or another, is it possible that gravity has a particle associated with it (the graviton). Then scientists went on to investigating the possibilities caused by the existence in our universe set against past and current observations. So far, the graviton has not been found, but i think they are close. Until then, i think anyone who values their credibility would side with what has been proven - or correct theory.

As for blackholes contributing to the expansion of the universe, i would like to say that black holes are theorised to not be that many that they would so draqmatically affect the expansion of the universe. As for black holes being made of matter, unfortunatelly, this premise is based on a false understanding of the general nature of black holes. There are typed of blackholes made of super massive planets and stars, but the kind of blackholes that shame light as the univer's untouchable are initially made from ultra massive collapses that in turn create an anomaly in space time, which in turn comes through as so massive as to bend space time in such a way that light would take gazilions of years to escape it, unfortunaly ending un in the anomaly before the idea of escape is formulated (so to speak).

If black holes were made of matter, then they would callapse into themselves in a huge blaze of glory. Through Stephen Hawking Radiation, black holes have been observed to decrease in strength as they radiate their energy through this radiation, thus dying forever (slowly though, seriously slowly...).

I like the idea of a gravity drive, but i seem to remember Star Trek using the warp field as a form of gravity drive. As far they their theory says, they have core systems that use anti matter as a source of energy used in the bending and collapsing of space. Space expands at the rear of the ship and collapses at the front end of the ship, thus sending it hurtling forward. The key here is that one can never have enough energy to cause an object of significant mass to surpass the speed of light, but if you manipulate gravity to throw you in the direction you want (consistently) then all the energy you need to provide is the one that is used in th expanding and collapsing of space in the respective part of the ship, the moving of the ship will be taken care of by the universe (with it having access to vast oceans of zero-point energy fields to do this with). That is how the Star Trek warp drive works.

I heard some scientist saying that if you wanted to move as fast as one of the star trek ships, then you would have to carry a black hole on your back. The fact of thetheory is that you created something like a blackhole, the strength of which was determined by your warp drive (which curves spacetime by creating its own singularity). The scientist missed that point, mineature black holes is what the creators of star trek were arguing, not the natural variety. If you take a close look at warp 9 = 257x speed of light, you will come to understand just how powerful the effect of a mineature black hole is (if it existed at all). When the warp drive is up, you would notice that you would have created your own gravitational buggle that cancels out your the external enertial effects, thus protecting you from the sudden speed changes. The other nice effect that the warp drive would cause is that all objects of lesser gravity than yours would be pushed aside (deflected) as you move through space, but will be pushed back as you pass (that is why the deflector dish is needed in the star treck ships, its just an overgrown particle accelerator/emmiter.

I hope that is enough info for you who is theorising on using gravity as a form of engine core. I am looking 4ward to replys

[StarLab]

Katz, your website literally just highlighted every single "idea" that posters have come up with over the past few months...and I regret to say, not many people have been happy about it. I'm sorry, but whomever made that website has got his/her brain thinking backwards. I'm not aware of any credentials of the person who made that website. Mainly, and most sadly, that site is mostly about a Nova-ing sun...while that might be a possibility, the author of the site (who wrote it?) tries to expand this idea to say such things of heresy, such as the Nova was responsible for the death of the dinosaurs, and for the eventual climb of primates on earth, and actually rebukes Darwinian theory...so, I'm sorry, but that website has gone too far. Don't pay any attention to it!

[bob338]

Nexxus,
For you to be referring to Star Trek is questionable in the area of credibility.

:)

[bob338]

Starlab,

"heresy" is a religious word not belonging in science.

"Darwinian Theory" is already rejected by many schools teaching our children.

"Relativity" is the only government project not having its funding pulled this budget, and will be put to the test now in outer space, which will determine its validity. 70 years is long enough to not have tested that theory.

Whether or not the results of that test pass or fail, remains to be seen. But should it fail, not many scientists will be very "happy" about it either. This matters not, it simply is. Oh well!

So whats your point?

[bob338]

And Starlab

While credentials are very nice, have you realized yet that Einstein was a dropout without credentials?

Cheers

[John L]

Originally posted by bob338@Jun 11 2004, 09:27 AM
"Relativity" is the only government project not having its funding pulled this budget, and will be put to the test now in outer space, which will determine its validity. 70 years is long enough to not have tested that theory.
The precision with which it is being tested is being increased with the GPB. This isn't the first test, and it won't be the last.

[Atomic Mojo]

what ever happened to gravity probe b

[antoniseb]

Originally posted by Atomic Mojo@Jun 11 2004, 11:12 PM
what ever happened to gravity probe b
Take a look at this site for weekly updates on Gravity Probe B
Gravity Probe B (http://einstein.stanford.edu/)

[Jan]

thank you all for the comments and critics of my theory......


now i realise that maybe i have had misteaken myself.....

but one thing is sure ....

if there is a force that is making the space expand it must be opposite of the gravity....but i am not even sure if that is thrue since we know that the world is full of surprises.....

i am eager to try an experiment but i dont know how to make it dine properly....
listen------has anyone ever asked himself how do two tornados efect on eachother....or how would two forces of watter being sucked in a hole influence on the movement of the two holes.....

if anyone has an idea how to test that reply me please....

i think that the answer could give us important informations abaut space and galaxies interacting with eachother.......


jan



jan

[StarLab]

Well, space and galaxies might not do as much sucking as we think. :P :lol: ;) :D

[Jan]

i didnt argument my theory well...
sorry

i thought because there is a BH in the center of galaxy the BH influence gives to the galaxy a look of a tornado (looking from above) a spiral


jan

[BettysFetish]

<_< Hummm,- - I wonder how to best exemplify this? Is it not true that if one produces an electrical field in the vicinity of a compass the magnetic field causes the needle to fluctuate wildly? AND, when the current is shut off isn&#39;t an electrical impulse discharged? Wouldn&#39;t these radiations propagate at the speed of light?
This should be the speed of gravity as well. If the earth were suddenly "not here" there shurely would not be any delay in the moon going on it&#39;s path in a straight line.
The universal expansion someone mentioned is most likely due to the natural opposite attraction between the negitive state of virtual energys present, pre- big bang, and the positive energys produced upon the creation of matter. That void should still surround our expanding universe and may provide a constant pull on all matter - i.e., gravity.
L8R B)
P.S. black holes can merge, it just makes a bigger black hole.

[madman]

the speed of light depends upon the medium it is traversing....c is the top speed of light when travelling in a perfect? vacuum.

do you think gravity could travel at different speeds too?...and what could cause it&#39;s variation in speed?

*************************

does anyone know if the strong and weak forces travel at the speed of light too?

otherwise, why is it assumed that gravity must have a "travelling property" to it&#39;s nature..is it just because einstein said so?

maybe gravity is a stationary field effect?

[antoniseb]

Originally posted by madman@Jun 28 2004, 02:24 AM
maybe gravity is a stationary field effect?
Imagine two black holes [assume two masive stars if you don&#39;t believe in black holes] of equal mass are moving directly towards ech other, so that they will unite into one object. There is a smaller object near where these two larger will meet [offset by a few hundred million kilometers]. The two objects meet, and the smaller object begins falling towards them [or perhaps orbiting them depending on its velocity at the time of the merger]. The gravity of this new massive object is not stationary. The force felt in the hours leading up to the joining of the larger bodies by the small object depends on the speed of gravity. This would result in a single pulse gravity wave.

[madman]

"The gravity of this new massive object is not stationary."

yes, the gravity field effect moves with the massive object...mergers make larger fields.

"The force felt in the hours leading up to the joining of the larger bodies by the small object depends on the speed of gravity."

which is assumed to be at the speed of light?...if it is, and if you haven&#39;t detected gravitons yet, and the only outward journeying waves are light, then perhaps it is an effect of light...what is the proof that a wave of gravity has occured?

"This would result in a single pulse gravity wave."

please show us an example (if there is one)......how many gravitons in that wave?..why only one wave?

[antoniseb]

Originally posted by madman@Jun 29 2004, 05:55 AM
the gravity field effect moves with the massive object...mergers make larger fields.
In this case the field changes can vary suddenly and non-cyclicly if the two black holes are travelling at relativistic speed towards each other.

which is assumed to be at the speed of light?...if it is, and if you haven&#39;t detected gravitons yet, and the only outward journeying waves are light, then perhaps it is an effect of light...what is the proof that a wave of gravity has occured?
It is whatever the speed of gravity is. Personally, I think the speed of gravity might be 71% of the speed of light, but it might be the speed of light. Perhaps its instantaneous&#33; [I doubt it]. We haven&#39;t measured it very accurately, or with an undisputed experiment. Look at the pages about the LISA experiment for a good description about what gravity waves are thought to be, and how they might be detected.

please show us an example (if there is one)......how many gravitons in that wave?..why only one wave?
I have said in a previous post that I don&#39;t take for granted that there is some particle that conveys the force of gravity. How could such a particle escape a black hole? If it can&#39;t escape, would a black hole seem massless? My guess is that there&#39;s zero gravitons in this wave; also zero magnetic monopoles, and zero tachyons.

The reason it would be a single wave is that the change happens once. The more expected wave form for detectable gravity waves is going to be when two neutron stars or black holes [or one of each] spiral into each other, losing orbital energy from the radiating gravity waves. These waves will be roughly sinusoidal, slowly increasing in frequency and amplitude until the final merger [when they will stop]. This is what the gravity wave experiments currently being developed hope to observe.

[blueshift]

If the speed of gravitational waves are infinite then all of the gravitational waves from everything in the universe is affecting everythiing else immediatley.

Along our line of sight in many directions will be gravitational waves from many very distant black holes forming this very instant. A percentage of those waves should be in phase and, if so, their amplitudes should be additive...

Need more be said? We should be sucked right out of our orbit into a chaotic
oscillation and our motion should, along with everything else that steps into phase
at precise points should pulled out of galaxies...in fact, galaxies should not exist.

blueshift

[antoniseb]

Originally posted by blueshift@Jun 29 2004, 07:30 PM
Along our line of sight in many directions will be gravitational waves from many very distant black holes forming this very instant. A percentage of those waves should be in phase and, if so, their amplitudes should be additive...
You are assuming that the universe is infinite and that gravity waves fall off in intensity by the inverse square law [or less]. This is sort of a gravitational Olber&#39;s Paradox. But gravitational waves may be quadrapole and fall off in intensity faster than inverse square. Also, the universe may not be infinite.

None-the-less, like you, I do not think that the speed of gravity is infinite.

[blueshift]

Thanks again for a response..I did use a bad example akin to the Olber&#39;s
Paradox explanation and shouldn&#39;t have. Simple constructive wave interference akin to Young&#39;s 2 slit experiemnt should suffice..I don&#39;t buy the static state universe idea. I was thinking of a number of black holes being formed that would be additive.

However, to place another perspective here, is it possible that no wave movement
occurs with infinite speed but a shape that is immediate and influences at great distances immediately without information moving?

I&#39;m thinking of something similar to the advance mechanism that is in the distributor of an automobile..Acceleration coupled with the geometry of the auto
spark advance system does not send a message from A to B but is directly linked
from A to B..Could space geometry behave in this manner?

blueshift

[antoniseb]

Originally posted by blueshift@Jun 30 2004, 03:40 AM
I&#39;m thinking of something similar to the advance mechanism that is in the distributor of an automobile..Acceleration coupled with the geometry of the auto
spark advance system does not send a message from A to B but is directly linked
from A to B..Could space geometry behave in this manner?
Your automobile distributor model seems a little far-fetched to me, but perhaps I am not understanding what it is you are trying to explain.

Keep in mind that gravity waves that go through the Earth from cosmic sources are so weak [if they exist at all] that we have never been certain that we detected one. [See the LIGO experiment].

[blueshift]

It is far fetched and I don&#39;t see waves exceeding speed c..I am familiar with LIGO
and its attempts to realize gravitational wave measurement..

We use metaphors and similes to describe what doesn&#39;t make sense and if measurements were to prove that Earth does not respond to what the Sun was doing 8 minutes ago, but where it is going to be 16 minutes into the future, then we
introduce such terminology...Yet, experiments need more data than what gets tossed out on a few websites..

.In quantum physics we don&#39;t comprehend why the collapse of a probability wave seems to be instantaneous. Metaphors have popped out trying to explain why.In this case it is experimental results that force us to realize that we can&#39;t make sense out of it.

Experiments with gravity need to reveal a larger amount of data than what is present..I guess that, in practice, I don&#39;t always adhere to the Copanhagen
school of reasoning. It might have to do with the fact that I&#39;m a sci-fi poet and have built up a lot of inertia using metphoric description..

Further, when it comes to this subject of measuring gravitational waves, I did once blow my cool in a response to someone on another site who claimed he could measure gravitational waves right near the San Andreas fault..He insisted he had made sound measurement and had invested his own money into such a project..
Now, just where did someone get the chump change to do that and find enough free time to sit on a site pouring this on? And where was the press?

I&#39;ve heard some self delusions in my life and that one ranked right up there.

blueshift

[GOURDHEAD]

is it possible that no wave movementn occurs with infinite speed but a shape that is immediate and influences at great distances immediately without information moving?

An influence at great distances is information moving..if the influence is detectable.

I have been unable to imagine how a gravitational deformation of spacetime can be made to sufficiently change sufficiently fast to be detectable at or beyond several radii of the sphere enclosing the change event.

[madman]

"Now, just where did someone get the chump change to do that and find enough free time to sit on a site pouring this on?"


it could have been something like Gregory Hodowanecs solid state gravity wave detectors....i tried making one, it acted like a theremin.

[spedmen]

So, basiclly from what i understood, if we could figure out teh speed of gravity and exceed it, we would be able to escape a black hole with ease? <_< im probebly wrong so please correct me :D

[dann]

Instead of gravity being stronger or weaker, in relation to a Blackhole, what is the possibility that gravity is denser because of the mass of the Blackhole?

[StarLab]

what is the possibility that gravity is denser because of the mass of the Blackhole?
Density is always infinite, because volume is always zero; remember, d=m/v

[StarLab]

This seemed like a hot topic in its heyday...I&#39;m bringing it back to life. ;)

[antoniseb]

Originally posted by StarLab@Jan 5 2005, 06:53 PM
This seemed like a hot topic in its heyday...I&#39;m bringing it back to life. ;)
Why, do you have something new to add? Just to recap, until we have several gravity wave experiments set up in various places across the solar system, we have little chance of learning the speed of gravity by direct experimentation. The Jupiter occultation thing was poorly thought out, and didn&#39;t actually measure the speed of gravity to any precision at all. GR says that changes in a gravitional field should move at the speed of light.

[StarLab]

GR says that changes in a gravitional field should move at the speed of light. And, do you agree with this? (really, take a side this time.)

[antoniseb]

Originally posted by StarLab@Jan 6 2005, 04:01 AM

GR says that changes in a gravitional field should move at the speed of light. And, do you agree with this? (really, take a side this time.)
Until I see some good evidence to the contrary, I&#39;d say this is a good bet, but I really don&#39;t need to take a side since some gravity-wave experiment in the next ten or twenty years will be sensitive enough to give a meaningful result here.

On the other hand, why do you think its important to take a side?

[StarLab]

Because constantly remaining neutral would slowly isolate me from the field of research and discovery. In picking a side, I must prove it and thus the discovery, whether it proves me right or wrong, is discovered much sooner.

[Nereid]

Just read this thread for the first time ... a couple of items to clarify things that were left open ...

1) The Tom Van Flandern site needs to taken with a tonne or three of salt, much of what&#39;s there is quite misleading, some downright wrong, and his own ideas wildly speculative.

2) The graviton is a hypothetical particle, which would be the &#39;force carrier&#39; for the gravitational force if gravity could be formulated in a structure similar to that of QFT ... as the other three forces are (electromagnetism, weak and strong). Unfortunately, there is not even a hint of what such a theory of gravity would look like, so the graviton will remain hypothetical for a while yet.

3) In principle, the Kopeikin experiment could measure the speed of gravity. However, if GR is a good theory of gravity (more later), then the effect would be far too small for the 2002 experiment to detect (Kopeikin got his sums wrong).

4) General Relativity (GR) is a very successful theory of gravity ... it has passed all tests so far with flying colours (including some to 1 part in 20,000). In GR, gravity propogates at c, via gravitational waves. In the sense that GR is consistent with ALL good observational and experimental results so far, we can say that &#39;gravity travels at c&#39;. However, gravitational radiation hasn&#39;t been directly observed yet, though LIGO and LISA should detect it sometime in the next 20 years or so (esp if there is a nearby asymmetric supernova, or the SMBH of two galaxies collide/merge ... let&#39;s hope if this happens, it&#39;s not as close as M31&#33;)

IMHO, &#39;picking sides&#39; - on its own - is pretty silly. The best ways to progress on questions such as these include a) working through the theory to see if there&#39;s an effect which could be detected with today&#39;s capabilities (and that has previously been overlooked), b ) racking your brains to come up with an experimental/observational setup that ingeniously allows a prediction of theory to be put the test, c) exploring new &#39;spaces&#39; (energy, distance, time, mass, density, ... whatever regimes that haven&#39;t previously been examined); in most cases new phenomena are discovered, some of which may relate directly to &#39;the speed of gravity&#39;. An example of the last point might be GRBs, or UHE cosmic rays.

[Duane]

Unfortunately, there is not even a hint of what such a theory of gravity would look like, so the graviton will remain hypothetical for a while yet.

Just a quick comment, you are actually talking about the Higgs Boson (http://www.e-paranoids.com/e/el/elementary_particle.html#Higgs%20boson) which they are hoping to find with CERN (http://public.web.cern.ch/Public/Welcome.html) once it gets up and running.

[Nereid]

Hi Duane.

The Higgs Boson, according to the page you provided a link to: "Through the process of spontaneous symmetry breaking, the Higgs selects a special direction in electroweak space that causes three electroweak particles to become very heavy (the weak bosons) and one to remain massless (the electromagnetic photon). Although the Higgs mechanism has become an accepted part of the Standard Model, the boson itself has never been observed in detectors."

From further down the same page: "String theory also predicts the existence of gravitons." IOW, in one (vast number of) theory which unifies QFT and GR, a particle force carrier for gravity has an existence, and is called a graviton. Different approaches to unifying QFT and GR (such as LQG) do not, necessarily, require a &#39;graviton&#39;.

[Duane]

Hmm, should have read that closer, sorry. Try here instead:

http://www.phy.uct.ac.za/courses/phy400w/p...ticle/higgs.htm (http://www.phy.uct.ac.za/courses/phy400w/particle/higgs.htm)

Cheers&#33;

[ngeo]

Is not our perception of gravitational attraction a motion (change in space-time co-ordinates) within a constantly altering space-time co-ordinate system (curved space-time)? In that case whatever &#39;speed&#39; we observed for &#39;gravity&#39; would be relative to ourselves (our constantly-altered co-ordinate system) only. (I think Einstein said "rays of light are propagated curvilinearly in a gravitational field".) In the universe as a whole, there is no &#39;absolute&#39; speed because there is no &#39;absolute&#39; space or time. The &#39;speed&#39; of gravity in a constantly altering space-time system can only be the measurement we make of the acceleration of objects in the gravitational field. So if we shoot an arrow in the air and watch its path, the path we see it taking describes the curvature of space-time in our gravitational system. &#39;Gravity&#39; then &#39;travels&#39; at the same speed as the light by which we observe its &#39;effect&#39;.

I wonder if anyone has read the paper by Abhay Ashtekar which can be reached through

http://arxiv.org/abs/gr-qc/0410054

[antoniseb]

Hi ngeo,

That&#39;s a nice paper for explaining a lot of GR stuff to non-professionals, thanks.

Concerning your statements about the speed of gravity, I have a question for you. If two nearby neutron stars were to spiral into each other and energetically "merge", there would over a period of time, gravity waves, which would suddenly end.

If we had space based gravity wave detectors at Jupiter&#39;s L4 & L5 points, as well as in a near Earth orbit, would we be able to observe one consistant speed for the gravity waves? What speed do you think we&#39;d observe it to be? Or, if not, how would we see these waves?

[ngeo]

Hi Antoniseb,

You wrote, "If two nearby neutron stars were to spiral into each other and energetically "merge", there would over a period of time, gravity waves, which would suddenly end.

"If we had space based gravity wave detectors at Jupiter&#39;s L4 & L5 points, as well as in a near Earth orbit, would we be able to observe one consistant speed for the gravity waves? What speed do you think we&#39;d observe it to be? Or, if not, how would we see these waves?"

The way I see the merging is that the gravitational field around the two stars has a certain &#39;shape&#39; around their common center of gravity, which changes as the two stars converge. So when they collide, the shape of the gravitational field changes (and the overall strength of the field would also change according to the density of the new mass, ejection of matter, etc.). The changes in the gravitational field would be observable, but again by way of the path of the light by which they were observed. So I am not sure the changing field could be directly observed as waves. It would have to be implied through a haze of changes in the pattern of radiation from the collided body, which could easily be lost in the overall radiation from the collision.

If we measure the changes in Earth&#39;s gravitational field we may see &#39;waves&#39; in patterns of change, and that is the only kind of wave I can imagine being detected.

Alll the observations we make depend on light transmitted through gravitational fields, which - if we think of a graph on paper - constantly change the dimensions of the lines on the graph, although we cannot see the changes. So once again I think the speed of the &#39;gravity&#39; we observe is exactly that of the light rays which carry the invormation about the gravitational field to us. In the example you gave, if we are able to measure different patterns of light in different locations, the gravitational &#39;wave&#39; would be measurable by comparing the different patterns of light (due to the difference in the path of light between the event and the different locations). We would have to find a &#39;synchronizing event&#39; for the comparison between the locations. We would also have to take into account the local distortion in the curvature of the graph produced by the Earth&#39;s rotation which I believe has been measured by the Gravity B probe, the distortion produced by the Sun, Jupiter, etc. So it gets to be really complicated.

I diligently read that paper by Ashtekar - I even understood one or two of the words.
I was informed by email that the LQG space-time geometry resembles a kind of &#39;energized medium&#39; - the medium is also a dynamic &#39;actor&#39;. It is also speculated that the LQG geometry may give rise to matter. (This leads to my scenario in which the universe is an expanding energy field in which &#39;matter&#39; is produced by the field, which means there is an ever-increasing &#39;amount&#39; of energy - and matter - in the universe.)

In light of the apparent success in tackling &#39;quantum gravity&#39; in that paper, in which it is space-time geometry which is quantized (rather than a quantum &#39;graviton&#39;), I think the search for a gravity wave (or a graviton) may not be necessary.