Gravity waves and a disapprearing sun.

[Chaos' lil bro Order]

I was thinking of a scenario where the sun suddenly disappeared into thin space as if it were blinked out of existence. Aside from this being an absurd possibility, the more interesting question is how space around the sun would react to the giant loss of mass. Would it be correct in thinking that Mercury would fly out of its orbit around the sun before the Earth flew out of its orbit? Since no force exceeds the speed of light C, gravity is still subject to propogate outwards from the sun towards the planets at a speed of C. The sun would stop emitting gravity waves and these gravity waves would no longer reach the planets and one by one the planets would be slung off into space in whatever random vector they were traveling at minus the influence of the sun's gravitational waves. What would these waves be like? Would dissappearance of the waves give a planet like Earth a instant jolt into its random vector into space or would it be somewhat smooth? Are there any good analogies that can describe how the interaction between a planet and ?

 

[disregardthat]

It is just a theory about the gravitons, or these gravity waves you are talkign about.

Gravity is a "bending" of space, where mass will attract mass. If the sun disappeared planets flying around the sun continue in the direction they were heading as the sun disappeared. If you don't add the other planets gravity into the equation (or the stars). The planets have little effect on each other in the beginning although they might crash into each other if they were heading somehoe the same direction of another planet in the same solar system...

 

[ShawnD]

Would it be correct in thinking that Mercury would fly out of its orbit around the sun before the Earth flew out of its orbit?

Correct. Well before the idea of gravitons came into play, Einstein had a theory that nothing can go faster than light, not even gravity. The gravity and light waves of this happening would be going at the same speed, and Earth would start to lose its orbit at the same time we noticed the sun is missing, which is about 10 minutes after it really happened.

 

[Chaos' lil bro Order]

If the sun disappeared planets flying around the sun continue in the direction they were heading as the sun disappeared. If you don't add the other planets gravity into the equation (or the stars). ..

You mean to say that the planets will continue in the direction they were heading minus the sun's gravitational vector component I think.

 

[Chaos' lil bro Order]

What would it look like when the final gravity wave passed through the Earth 10 minutes after the sun dissappears? Would the Earth be instantly effected or is the interaction smoother?

Furthermore, are gravity waves theorized to always travel at C, or are they subject to similar index of refraction laws like EM waves are? In other words does gravity slow down in dense regions of space and speed up in thin ones?

 

[ShawnD]

I'm not sure, but I assume the gravity effects would be instant after 10 minutes. Try to think of it like turning a light on and off. Now you see light, now you don't. Now you have gravity, now you don't.

I have no idea if gravity can slow down the way light does in other media.

 

[devino]

Newton's theory 'Action at a distance' was instantaneous gravity froce which I think works when using his equations, I might be wrong here. Later Einstein came up with 'c' or the speed limit of light. Gravity waves should not be able to travel faster then light which creates a paradox. I have read that the gravity pull toward the sun is where the sun in now but the light we see emanating from it is 8 minutes old or where the sun was 8 minutes ago. So what is Gravity then?

 

[Chaos' lil bro Order]

Newton's theory 'Action at a distance' was instantaneous gravity froce which I think works when using his equations, I might be wrong here. Later Einstein came up with 'c' or the speed limit of light. Gravity waves should not be able to travel faster then light which creates a paradox. I have read that the gravity pull toward the sun is where the sun in now but the light we see emanating from it is 8 minutes old or where the sun was 8 minutes ago. So what is Gravity then?

Not only is the light 8 minutes old, the gravity is too. Gravity's speed is bound by the upper limit of C, I'm not sure if it always travel's at C, but it surely cannot travel any faster. Therefore, gravity from the sun reaches us at least 8 minutes after its emitted, if not more.

 

[Janus]

What would it look like when the final gravity wave passed through the Earth 10 minutes after the sun dissappears? Would the Earth be instantly effected or is the interaction smoother?

Well, it wouldn't be "instant" as it would take the wave front something like 4 milliseconds to traverse the diameter of the Earth.

 

[Chaos' lil bro Order]

Well, it wouldn't be "instant" as it would take the wave front something like 4 milliseconds to traverse the diameter of the Earth.

That's an interesting point Janus. Do you think the Earth would be ripped apart by the 4 millisecond traversal of the wave? Also, are you suggesting that the wave has a front? I always thought of it as the last wave's tail traversing through the earth, not some king of wave front.

 

[billiards]

Is there a possibility that the sudden loss would have to be caused by a rarefaction (negative/repulsive anomaly) in the gravity field which would when it hits Earth could cause it to explode?

 

[Chaos' lil bro Order]

Is there a possibility that the sudden loss would have to be caused by a rarefaction (negative/repulsive anomaly) in the gravity field which would when it hits Earth could cause it to explode?

Yes that's what I was trying to get at too. If the rarefaction takes 4 milliseconds to traverse the Earth's diameter, one would think that the turbulence caused could damage the earth.

 

[billiards]

Yes that's what I was trying to get at too. If the rarefaction takes 4 milliseconds to traverse the Earth's diameter, one would think that the turbulence caused could damage the earth.

But perhaps because the Earth's gravity field is much stronger here than the effect of the sun's gravity field we would just feel lighter (assuming a rarefaction) for an instant. I don't know what would happen, maybe the Earth would jolt? but if a point in the earth, and all the other points around it are all jolted at the same time, the Earth might expand slightly which could induce long period oscillations. I don't think this would cause any damage to the earth, unless the expansion was very large in which case I'd imagine the Earth could explode.

 

[devino]

Not only is the light 8 minutes old, the gravity is too. Gravity's speed is bound by the upper limit of C, I'm not sure if it always travel's at C, but it surely cannot travel any faster. Therefore, gravity from the sun reaches us at least 8 minutes after its emitted, if not more.

A theoretical gravitational wave or perhaps a graviton probably would travel at the speed of light or less but has gravity been proven to propagate through waves or emit graviton particles? To jump to the conclusion that gravity is a wave or a particle might answer this question incorectly and then what would we learn.

What I do know for sure is that gravity is still an unknown force and we should treat it as such. Look at what the evidence shows and not try to make old theories fit.

 

[disregardthat]

First of all, I don't think gravity are any kind of waves, or particles. I think they are "bending" of space. Mass bends space, more mass bends the space more. It might be that the bending goes away as the sun disappeared in the speed of c, I don't know.

And I really doubt we on our Earth woudl take any effect of the loss of the sun thinking about gravity. Since our orbit aroudn the sun is a gravitational force, which means that we don't orbit because of any inertial force. the Earth is "freefalling" aroudn the sun. When the sun disappears the Earth might have changed acceleration but only in it's free fall. No inertial force would add to the Earth change in speed, direction or acceleration. That means that we wouldn't feel anything else than free fall (0G) if you don't add the Earth's gravity into the equation.

 

[haiha]

I have read through this topic and my vagueness about gravity comes even worst. For me it is difficult to imagine how gravitons that come from masses can pull these masses closer. The bending of space created by mass is even more difficult to understand.
Anyone who can explain that in some sentences which are clearer to me and of course to many more, please help.

 

[ranger]

haiha, you need to read up on general relativity and you will understand how spacetime is curved by the presence of mass:
http://en.wikipedia.org/wiki/General_relativity#Spacetime_as_a_curved_Lorentzian_manifold

 

[ShawnD]

For me it is difficult to imagine how gravitons that come from masses can pull these masses closer.

As long as you're not a real physicist, you can think of anything in any way you want as long as it works.
I think of gravity as being like those magnets in cartoons that had waves coming from them. The coyote points a big magnet at something metallic, a bunch of waves shoot from the magnet, and a metal object moves towards the magnet. Gravity is the same basic idea. The sun shoots out gravity waves, these waves travel at the speed of light, and the Earth moves towards the sun once these gravity waves get here, which is something like 8 minutes (I think I said 10 before).

For the sake of simplicity just ignore the idea of gravitons. As far as I know, gravitons aren't even a fact at this point. They're a product of the string theory where some guy was doing calculations and came upon the idea of a massless particle that seemed to fit with the concept of gravity. It can be shown through math, but it has never been seen in any lab test. I would really like to believe that string theory is true, but at this point in time it cannot be proven or disproven.

 

[disregardthat]

Is there any numbers of how many sceintist that tilt in the general relativity direction and those who tilt in the string theory direction? I thought that it was the general relativity that was the theory most people thought was true, and the bending of space seems quite logical, of course not fully logical. But the gravitons is kind of not possible in my mind. I'll check up on it on wikipedia

 

[ShawnD]

Physics isn't exactly black and white where one thing is wrong and one thing is right.
Newton made some theories about gravity that are basically true. Einstein added some new theories that are also thought of as true, but claimed gravity is limited to the speed of light, making Newton's theory slightly incorrect but still usable. Do the theories disagree? Yes. Are both theories correct? Pretty much. String theory sort of goes a bit farther with everything and tries to use more of a quantum mechanics approach; explain large scale things (general relativity) using small things (gravitons).

I think the answer to your question is that people who believe in string theory will also agree with general relativity.

 

[ShawnD]

But the gravitons is kind of not possible in my mind. I'll check up on it on wikipedia

Sorry to post twice in a row but this is a bit important.

In my previous post I said string theory takes a quantum look at general relativity. Quantum Mechanics states that the 3 other known forces in the universe are all caused by messenger particles.
http://en.wikipedia.org/wiki/Messenger_particle

Look under types and it says this:

Gluon - carries the strong nuclear force.
Photon - carries the electromagnetic force.
W and Z bosons - carry the weak nuclear force
Graviton - hypothetical particle which is postulated to carry either the gravitational force or (in the case of general relativity) information on changes in the gravitational field.

Then you stop and think "wait a minute, those cartoons showing the EM waves were correct?", and the answer is yes. Those cartoons are surprisingly accurate when they show how photons are responsible for magnets pulling things closer. Gravity theoretically acts in a similar way. Theoretically of course, not yet proven or disproven.

 

[devino]

I have a very limited understanding of physics but I have been doing what I can reading up on general physics, relativity theories and Newton/Kepler laws and it seems I have my work cut out for me. I think the most important thing to remember is always be open minded and objective about what is read.

Do a search on gravitons and judge for yourself if they are real or not. For me they just bring out more questions. And the same goes for http://en.wikipedia.org/wiki/Gravitational_wave" . As I read up about GW I see that only indirect evidenct has been found proving these waves and or the posibility of gravitational radiation. So my question still stands, has there been direct evidence found yet?

An objective observer would not believe in what has not been proven yet especially when there are so many problems with the explanation of gravity and planetary motion. I try not to think of gravity as waves like in the cartoons with the big magnet (I remeber them too). In fact I question if gravity is even a 'Pulling' force, but that's another topic.

Newton's laws are not complete and neither are Einsein's. The question whether the effects of gravity are bound to the speed of light is still a good question even if those far more intelligent then me quickly answer with "nothing travels faster then 'c'."

 

[disregardthat]

Well, couldn't one say that the effect of gravity on a distance would not exceed thr speed of c? I for one think that the string theory is a bit too far undescribed to me to accept. I like to think of gravity as curved space. But the space may not be curved in a presence of an object faster than c in the direction outwards.

 

[rbj]

... http://en.wikipedia.org/wiki/Gravitational_wave" . As I read up about GW I see that only indirect evidenct has been found proving these waves and or the possibility of gravitational radiation. So my question still stands, has there been direct evidence found yet?

they're working on it. http://en.wikipedia.org/wiki/Gravity_Probe_B i think that Gravity Probe B will speak to this direct evidence issue. the collection of evidence has already been done, but they haven't released any results yet but expect to in April.

An objective observer would not believe in what has not been proven yet especially when there are so many problems with the explanation of gravity and planetary motion...

but, by not "believing", that itself is a belief. with the currently developed theory and incomplete evidence we have so far, i think that 'believing" in gravitational radiation (and that the speed of propogation is c) is much less of a risk than believing that such is not true. either for or against is a belief system. you're taking something on faith.

i don't know of any astronomical observation that has not been congruent to General Relativity, which supports gravitational radiation.

Newton's laws are not complete and neither are Einsein's. The question whether the effects of gravity are bound to the speed of light is still a good question even if those far more intelligent then me quickly answer with "nothing travels faster then 'c'."

fairly recently, http://www.newscientist.com/article.ns?id=dn3232 , Sergei Kopeikin and Edward Fomalont announced that they had made an indirect measurement of the speed of gravity, having to do with the retarded position of Jupiter on its orbit during Jupiter's transit across the line-of-sight of a bright radio source and concluded that the speed of gravity is within ±20% of c.

it's not solidly proven, yet, but i have little doubt to the outcome when it is.

the way to think of it is that c is not simply the "speed of light" or the "speed of E&M" or even that it is the "speed of E&M and gravity", but that c is the speed of anything ostensibly "instantaneous". any fundamental interaction that has "instantaneous" effect on anything else propagates through space at the speed of c. whether the effect is that of a charged object disappearing (sending out an EM pulse) or a massive object disappearing (sending out a GR pulse) or some other fundamental interaction, they all have this fundamental speed of propagation that really defines the standard to measure all other speeds against (like we do with Planck units and some other systems of natural units).

 

[disregardthat]

But it's so easy to say that c is the speed of light, since it is :)

About your statement of gravity lies in the speed of 20% of c... What do they define gravity as? Curved Spacetime or particles? I would like to see the explanation of this statement. Because i find it hard to believe that geometrical curving can be that slow. ( I was surprised of that gravity didn't happen instantly (if for example the sun disappeared) )

 

[rbj]

But it's so easy to say that c is the speed of light, since it is :)

About your statement of gravity lies in the speed of 20% of c...

just to be sure, i meant to say that the result of this one experiment is that the speed of propagation of gravity is within ±20% of c or, between (0.8)c and (1.2)c. not (0.2)c.

What do they define gravity as? Curved Spacetime or particles? I would like to see the explanation of this statement. Because i find it hard to believe that geometrical curving can be that slow. ( I was surprised of that gravity didn't happen instantly (if for example the sun disappeared) )

i don't know that they define gravity in this experiment. they were measuring some tangible effect, no matter how they define it. i think when GRists think about gravity, they think of it as a curving of spacetime that is caused by masses and that changes in that curvature also propagate at c. if gravity happened instantaneously, then that would mean that instantaneous communication could conceivably be done over vast distances by somehow creating a gravitational disturbance (like blowing up a star) that would be detected before a change in light from that star was detected.

 

[disregardthat]

I understand now. Since it is between 0.8c and 1.2c you would naturally believe that it is excactly 1c, well, that is what i believe. I wonder what it would have looked like when an object appeared if you could see the 2 dimensional geometrical net curving as the object is presented. Maybe would the "ground" fall into it's position square after another, what do i know. It is difficult to imagine how the gravity works as it moves. But then again, couldn't you say it happened instantly if the gravity moved at c? Because if you rode the gravity wave time would be staning still.