"Gravity Waves"

[frobozz]

These came up in a previous thread. I have a few questions concerning them and wasn't sure if they directly belonged to the thread in question.<br /><br />(1) What exactly are gravity waves? Are they akin to normal waves? Can one use Harmonic Analysis to represent such a wave as sum of simpler waves?<br /><br />(2) Assuming the last part of question (1) holds, has anyone attempted to build a filter to perhaps "filter" out gravity waves eminating from one object from another. (insofar as that makes sense or is even possible)

 

[yevaud]

This is not the same as big "G" gravity.<br /><br />With respect to Atmospheric Physics, Gravity waves are oscillations caused by a number of factors. In the case I'd made mention of, it works as follows:<br /><br />Air can be perturned upwards in the presence of unstable weather. It can oscillate upwards, lose it's moisture, descend, do it again...and again...and again.<br /><br />Look at it as a sort of atmospheric harmonic.<br /><br />If you note the examples I used in that thread, the manifestation of gravity waves was on the periphery of a thunderstorm that was highly active. E.g., highly disturbed, moisture-laden air.<br /><br />There are other forms of this effect, but it manifests quite visibly in this sort of situation. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[frobozz]

Thank you for the explanation. The topic came up in a discussion on the theoretical black hole at the centre of our galaxy as a response to my question in regards to it's shape. I am afraid I am not quite seeing the connection between what you have explained and what was explained to me earlier, if in fact such a connection is to be found.

 

[yevaud]

I see what you mean. This is atmospherics, and a known effect - they're talking gravitation, and an effect that's unknown and as yet hypothetical. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[frobozz]

By the way, what you did describe does sound familar, is it perhaps related to, or equivalent to, the model on which the lorenz equations (note the lack of t in the name <img src="/images/icons/wink.gif" /> ) were devolped from? I remember the model only briefly when my prof was giving an introduction to chaotic dynamical systems as the highlight of the d.e. course he was teaching. What you have looks very similar to what how he described it, only he used water , ice, and bunson burner in his example.

 

[yevaud]

Well, it *is* a chaotic and dynamic system, sure. Usually, what occurs in this is convection (caused, as I'd mentioned, by several different possible factors) cause uplift, and gravity the dampening.<br /><br />It really is just an oscillatory effect. <div class="Discussion_UserSignature"> <p><em>Differential Diagnosis:  </em>"<strong><em>I am both amused and annoyed that you think I should be less stubborn than you are</em></strong>."<br /> </p> </div>

 

[tmccort]

Gravitational waves are ripples in spacetime caused by the acceleration of mass.<br /><br />The problem is that the effect is very, VERY weak and we haven't been able to detect any yet. Probably one of the best hopes of detecting them will be the LISA spacecraft ( http://lisa.jpl.nasa.gov/ )

 

[frobozz]

Thanks for your response and the link. I believe that the link contains enough information to actually answer my entire question completely.

 

[j_rankin]

To give a simple example of why gravity comes in waves, we need to look back to Einstein.<br /><br />Newton believed that if the sun was to suddenly disappear, then the Earth would immediately have no mass drawing it in and would therefore fly off into space. Einstein predicted that wouldn't be the case. It would take roughly 8 minutes (the speed of light) for the sun's disappearance to have any effect on the motion of the earth. Therefore gravity must affect it's surroundings in 'waves'. A 'wave' of difference, if you will.<br /><br />I am not entirely satisfied with this, however, because in 1984 an experiment was conducted where they observed a change in the amount of light entering a cylinder changing instantaneously at the far end of the cylinder (faster-than-light). The same may happen regarding gravity.

 

[CalliArcale]

The question depends on whether spacetime would instantly spring back into shape or whether it takes time for it to do so (going with Einstein's universe-as-a-rubber-sheet analogy; rubber sheets of course *do* take time to spring back). It's part of a larger question as to whether or not information can be transmitted instantaneously across space. <div class="Discussion_UserSignature"> <p> </p><p><font color="#666699"><em>"People assume that time is a strict progression of cause to effect, but actually from a non-linear, non-subjective viewpoint it's more like a big ball of wibbly wobbly . . . timey wimey . . . stuff."</em>  -- The Tenth Doctor, "Blink"</font></p> </div>

 

[igorsboss]

I going to state the obvious here, not to detract from the many correct and valuable posts on this thread: There are several correct but different definitions for the term "gravity waves", depending on context.<br /><br />If you throw a stone into a pond, the ripples on the surface of the pond may also be called gravity waves.<br /><br />I really liked the definition "Gravitational waves are ripples in spacetime caused by the acceleration of mass."<br /><br />The speed of gravitational waves has not been measured, but is predicted to be the same as the speed of light.<br /><br />I wonder: Mass may only "dissapear" by converting it to an energy, according to e=mc^2. This energy is in the form of photons, which are massless, and therefore gravitationless. Later, that same quantity of gravitiationless energy could reassemble itself back into the same mass, with the same gravitational properties.<br /><br />This sounds like a silly question, but where did the gravity go? Might gravity actually be conserved in the matter-to-energy conversion?

 

[najab]

><i>It's part of a larger question as to whether or not information can be transmitted instantaneously across space. </i><p>What do you mean "whether or not" - how else does my wife know exactly what I'm thinking when another hot-looking lady walks by?</p>

 

[robnissen]

" This energy is in the form of photons, which are massless, and therefore gravitationless. Later, that same quantity of gravitiationless energy could reassemble itself back into the same mass, with the same gravitational properties. <br /><br />This sounds like a silly question, but where did the gravity go? Might gravity actually be conserved in the matter-to-energy conversion?"<br /><br />IMHO that is not a silly question at all, I sure hope someone here has the answer because I sure don't.

 

[igorsboss]

<font color="yellow">>It's part of a larger question as to whether or not information can be transmitted instantaneously across space.<br /><br />What do you mean "whether or not" - how else does my wife know exactly what I'm thinking when another hot-looking lady walks by? </font><br /><br />Because c is pretty quick.

 

[jatslo]

If gravity is pressure, like I know it is <img src="/images/icons/wink.gif" />: Then, when converting matter to energy, you will most definitely feel a pressure wave, which will first rip the air from your lungs before it annihilates every atom in your body in the worse case, and of course, your atoms would annihilate in the primary implosion first (worst case). If I were working on gravity, I might prefer to work with a reactor (low pressure), and/or helium which I think I can convert to high pressure in a cold fission process.<br /><br />..." <font color="yellow">but where did the gravity go</font>"...

 

[j_rankin]

Pressure is a result of gravity, not the other way round.

 

[tmccort]

<font color="yellow">I wonder: Mass may only "dissapear" by converting it to an energy, according to e=mc^2. This energy is in the form of photons, which are massless, and therefore gravitationless. Later, that same quantity of gravitiationless energy could reassemble itself back into the same mass, with the same gravitational properties.<br /><br />This sounds like a silly question, but where did the gravity go? Might gravity actually be conserved in the matter-to-energy conversion?</font><br /><br />igorsboss, you use the equation E = mc^2 and at the same time you say that light doesn't have mass. Sounds like you have some confusion over the correct definition of "mass".<br /><br />More info: http://math.ucr.edu/home/baez/physics/Relativity/SR/mass.html<br /><br />

 

[jatslo]

I said gravity and pressure are the same thing, and nothing will change my mind, because I am certain that I am right. <font color="yellow">Pressure is a result of gravity, not the other way round.</font>/safety_wrapper>

 

[tmccort]

<br /><font color="yellow">and nothing will change my mind, because I am certain that I am right.</font><br /><br />How absurd...

 

[frobozz]

In regards to your link, specifically calling attention to this line:<br /><br />"The equation E = mc2 was only meant to be applied in the rest frame of the particle"<br /><br />I seem to recall that their is no rest frame for a photon, hence it is perfectly acceptable to proclaim that photons are massless. <br /><br />http://en.wikipedia.org/wiki/Photon <br /><br />Specifically one would be looking for the paragraph containing the line:<br /><br />" Because the (rest) mass is zero, such a frame does not exist, according to the theory of relativity."

 

[jatslo]

<font color="yellow">How absurd...</font>With no counter argument, which is absurd. There was an old lady who swallowed a bird; how absurd to swallow a bird. She swallowed the bird to catch the spider that wiggled, wriggled, and wiggled inside her.

 

[tmccort]

You are correct to say that the photon has zero mass (invariant), but it does have a relativistic mass because m = E / c^2

 

[frobozz]

Again, not according to what you have provided.<br /><br />The photon does not have a rest state, i.e. you can't apply E=mc^2 and your equation is not valid in this case and hence you cannot conclude that m = E / c^2 in the case of a photon.<br />

 

[frobozz]

I really want to know sometime what it is that you drink or smoke and where can the rest us get some? Can you cut us a deal <img src="/images/icons/wink.gif" />

 

[jatslo]

It is obvious to me that you are trying to make a connection, like me; however, you are blinded by politics and fear reprisals. I do not give a hoot, and that is the difference between you and me. Gravity waves are pressure waves, plain and simple. If you work in nuclear physics, then you have access to a reactor; therefore you can most definitely prove that gravity is, in fact, pressure.