Question about LIGO's big step in gravity wave astronomy

I don't think LIGO has positively detected gravitational waves yet, other than man-made ones used to test it.

I am pretty sure it would have made headlines if it had detected them.

You're right about the failure to detect such waves: it brings into question whether something like LIGO really can detect such waves, whether the objects in question actually emit such waves, whether the objects emit them but they deteriorate with distance to the point where we can't detect them with LIGO, or whether their amplitude is so small we can't detect them even with very much better technology.

There certainly are many unknowns in this quest. That's why it's classified as "discovery science."

I happened to come accross this thread when doing some searching on LIGO. I know very little about the theory behind gravity waves, but here's my question. Why are we trying to detect gravity waves from objects so far away? I know that ultimately, the goal is to learn more about the distant cosmos, but if we are just trying to discover the gravity waves themselves, then why don't they try to detect them from nearby objects like the moon or our sun? Wouldn't those waves be MUCH stronger and easier to detect? If gravity from the moon is strong enough to cause tides on Earth why can't we measure/detect its gravity waves (if they exist). Am I missing something here?

I believe they are looking for the gravity waves that actually distort space / time. These waves are hypothesized to be created in massive events, as in two neutron stars colliding / merging.  

Advanced LIGO

Its my understanding that any object with mass distorts space-time however big or small, in that it exerts a force on another object and thus caused it to accelerate in space and thus distorts space-time. I know it would be far more interesting to detect start colliding, but if gravity waves do exist, there should also be waves from teh moon, sun and other onjects, right?

The effects that LIGO is attempting to detect are quite dissimilar from the localized ones we associate with massive bodies like the sun, moon, etc. These effects are well understood and predictable. A basic understanding of physics, and the ability to plug a few constants into equations is all that is required to get consistent results that match observations to a fine degree of tolerance. The effects caused by local celestial objects are all related to their gravitational fields.

 The mission of LIGO is to detect gravitational radiation effects, as predicted by the General Theory of Relativity. These have to do with the distortion of space time in which one direction of space-time, while it is compressed in another. These effects have yet to be observed.

As with other aspects of Relativity (such as Einstein's cosmological constant-which he later dismissed as his biggest blunder, but is now being used to explain dark energy), the implications for gravitational waves have yet to be fully realized. The success, or failure, of LIGO will be a step in the direction of better understanding our universe.

chipdatajeffB ! In accordance with some people( excluding me) on this thread that think gravity can escape places where electromagnetic energy can't . I can understand why LIGO wouldn't detect Gravitational waves, because some people think, they(Gravitational waves) exceed the speed of light, in which case they(Gravitational waves) could have passed us several thousands, or millions of year in the past, however I think a more logical answer is , because of the time dilation in the location of the event , the event is ELONGATED( as in shift energy to lower frequencies in the event) relative to our observations, for which would reduce the transition time of both the leading and trailing edge of the Gravitational wave pulse, making it much lower in energy and less likly detected.

The trouble I'm having with this discussion is that local gravity from near by bodies seem to be caused by geometry correct? Gravity is a bending of space time caused by mass not a force or wave that emanates from massive body.

The LIGO experiments are trying to detect "waves" and this does not seem to be the same concept as geometry.

Far as I can see there trying detect something that may not be there.

 
Is this an attempt to detect quantum radiational effects  "caused" by the warping of space time?

 Eh? Lol

test,
 

Test4echo ! Ithink the Gravity wave they are trying to detect is the merging vector resultant generated by two strong gravitational fields.

Far as I know M theory predicts the exsistence of the graviton, a closed looped string responsible for transmiting the force/effect of what we call gravity.  Just as the photon carriers the electromagnetic effect/force the graviton would be for gravity.

 So these experiments may be trying to prove the exsistence of the partical/string deemed the graviton and if shown to exsist, would go a long way exciting M theorists even more.

 But M Theory also predicts 10 space dimensions and one of time, it also predicts N dimensional P branes, a possibility exsists where if photons are open ended strings attached to these P branes and gravitons are closed looped strings, the gravition would not be restricted to our familar dimensions and thus would become harder to detect as it can dissapate/travel in many more ways.

M theory, I think, says this is also way gravity is so weak compared to the other forces.

Ste ! I like your idea of gravitons, If gravitons convey the interaction of gravity and gravity propagates at the velocity of light, the same velocity as the photons, how would you explain the reason the photon can not escape the black hole while the graviton does it with ease?

Well they aren't my Ideas.  Im just reciting things I have learned by reading alot.

Gravitons escaping black holes, interesting that you bring it up, because it would raise the question of if gravitions can affect other gravitons or if they can even affect themselves.  That is to say, we know blackholes have an event horizen, and they are the strongest gravitational field we know of, but by transmiting gravity could that in itself prevent its own emision?  So in affect it is like asking if the black hole can prevent its own gravity?

My guess is and I am by no means an expert, is that gravitons do not affect each other, so perhaps that is why gravitons can escape the event horizen of a black hole because they are the transmiting force responsible for the event horizen in the first place. 

Or it may have something to do with that postulation that gravitons are closed looped strings and photons are open ended, so even if they may travel at the same velocity as each other they may not interact the same with our familar dimensions or like I said above, may not interact with other gravitons at all. 

So maybe this means that gravitons do not directly interact or affect each other because they are not restricted to any particular nth dimensional P brane, or perhaps it is because the second emision of the gravition occurs from matter and energy in our dimension it already disapates or impeeds on the higher dimensions not in contact or affected by how matter and energy interacts near and at the event horizen. 

In the end I have no idea,.this is all just speculation, At best..

Ste ! Thanks for your responce. It does look a little like cutting your nose off to stop the itch.

Hi!

I know that LIGO still hasn't detected any Gravitational Waves.   They are VERY difficult to detect.  But I also read that it is currently not operating as they are upgrading it and increasing it's sensitivity by about 10-fold.   Even so, I think we may need that LISA Space Mission to detect them.

According to General Relativity, Gravitational Waves do travel at the speed of light.   So the two facilities may just not have been operating when the Gravitational Waves of GRB070201 passed by, or they were not sensitive enough to detect them.     These GRBs are very far away. 

James3D

James3D : There are other factors, such as how does dark matter react to gravitational waves, after all, it may be necessary for it to travel through much more dark matter than visible matter to reach us, who knows, how dark matter reacts to gravity. I have found most people on these threads think gravity instantaneously moves through out all space-time. That's the main reason I can't get the idea of gravity having the same limitation, when it comes to traversing the event horizon of a black hole, as does light. I personally see gravitational changes propagating through space-time much like electromagnetic waves, one reacts (light) with the permittivity and permability of space-time, and the other (gravity) with changes of relative magnetude of space-time.