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#55752 03/29/16 09:40 PM
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Bill S. Offline OP
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We had a thread in which we were discussing run-away gravity. We didn’t really reach a conclusion, and the thread drifted to a point far from gravity. Rather than try to resurrect that thread, I am proposing this as a possible conclusion, and would be interested to know if it makes sense to others.

If M is the original mass/energy that creates gravity,
And G is the gravity (curvature) created by M,
Then, although G carries energy, the total mass/energy of M + G cannot be greater than the original mass/energy of M, because the energy contained in G does not appear from nowhere.

We might continue this line of thought by saying that the energy in G gives rise to more gravity (G2), but the total still remains the same: the mass/energy of M + G1 + G2cannot be greater than the mass/energy of M.

There is, therefore, no run-away gravity.


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Originally Posted By: Bill S.
There is, therefore, no run-away gravity.

Or as per your original interchange of gravity <=> curvature there is no runaway curvature. You are actually on the same argument as Einstein.

Note here you have used the conservation of energy to formulate the constraint. I am not saying that is wrong or right just making you very aware of what your argument relies on. Always remember to outline what underpins your idea.

The idea also precludes energy going into the "structure of the curvature". If you imagine bending an everyday material some of the energy goes into heat, and atomic adjustment. This is the layman way of saying the stress energy tensor of space always disappears locally to zero AKA you can't build up energy in the structure of space itself. You are on good solid ground with that because of the detection of gravity waves which match Einsteins prediction. This is an example of how experimental results can rule things in and out.

Ok I am going to make a rare thing a statement, to see if we can get you to bring it all together into a field theory. So lets assume there is a field which is our curvature (again be clear we have a concept underpinning our idea). You have in the above got to the point the gravitational field's potential energy itself contributes to the gravitational field. So if we turn the curvature into a field you have now reached the point where you should be asking yourself can the energy of other fields create the curvature in spacetime?

As a start point we use a simple proton which is three quarks bound together. Those quarks have very little mass but when they bind together the mass of the proton is 80–100 times greater than the individual masses. So here we energy in a non gravitational field doing something interesting. The more detailed background is given in the section "Quarks and the mass of a proton" in here (https://en.wikipedia.org/wiki/Proton). As discussed on the page QCD just so happens to give the right answer to what you measure experimentally as it will everywhere it has been tested.

Inbuilt into all that you now have a new interchange to get happy with "spacetime curvature" <=> "gravitational field". If you aren't happy with the interchange then you have a new problem you can't reconcile Gravity with Atomic theory and you will have to adapt or change one or both.

So you can reject the idea if you like but go and fix up the poor atomic theory and your world falling apart smile

I probably should also highlight a fact that got lost in all the GW150914 discussion is that wave of Einstein’s theory are those of a spin-two classical field. Remember there are multiple solutions to Einstein's theory and one can extend the standard model in certain ways. The detected wave is one of the few options that is compatible with both frameworks and sets the only valid value of a graviton mass to pretty much zero. It is covered losely in the section "Speed of gravitational waves and limit on possible mass of graviton" in here (https://en.wikipedia.org/wiki/First_observation_of_gravitational_waves) and no dispersion was observed and the max mass limit is very very low. It basically was last nail in coffin to theories like MOND but also the first step to joining QM and GR.

This is one of the big problems with science media communication, they don't consistently use the same terms. For a scientist the words "gravity","spacetime curvature" and "gravitational field" are interchangeable but that is not obvious to a layman.

Last edited by Orac; 03/30/16 04:44 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Orac #55775 04/02/16 09:04 PM
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Originally Posted By: Orac
The idea also precludes energy going into the "structure of the curvature"


Originally Posted By: Chris Baird
Curved spacetime can indeed hold energy, in addition to the energy of the mass itself, but this energy is not created by gravity. It is held in the spacetime curvature, but it is not created by the curvature. The energy held in a spacetime curvature is created by the thing that created the curvature: the original mass/energy.”

Just trying to “distil” the essence of these two quotes.


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Your second statement about curvature isn't considering spacetime itself might have internal structure and be inefficient. It has like 100% efficiency built into that statement which Chris has made. There are multiple solutions to GR and that was not a guarantee and one of the reasons we may not have seen gravitational waves if things were a bit different. Einstein modelled it as a PERFECT FLUID (Chris used that definition) and our detection seems to confirm that was right.

Go back to the example of the flexing say a piece of metal or wood. The flexure in that case holds energy as well but you lose some of the energy to internal and other effects ... the flexure is not 100% efficient and you know the story with metal flexing too many times.

Ignore the flexure itself think about possible inefficiences that may bleed energy from the conversion. The detected gravitational wave showed no dispersion effect that was measurable. So it's like a wave rolling across the ocean with no loss other than the energy fading due to larger volume.

So the statements aren't in conflict just looking at totally different level of accuracy. The second statement is basically now proved correct by GW150914 within certain tight limits which will be something like 99.9999xxx% efficiency at the moment.

Does that help?

Last edited by Orac; 04/03/16 09:34 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.
Orac #55779 04/05/16 08:29 AM
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INVERSE SQUARE LAW = PROBLEM FOR EINSTEIN



BIG BIG ROCKET EXAMPLE !


rocket is accelrating .....accelerating ...accelerating

1 year .... 100 years ..XXX years ..later !

HOW BIG INTENSITY IS REGISTERING PERSON ?
Q is CONSTANT or NOT ?
ACCELERATION = GRAVITION ?


A] rocket is moving constant speed Q is constant
B]rocket is accelerating.... Q is not constant




Marosz's conclusion
gravitation it is not acceleration we are not able simulate
Inverse Square Law if A TRUE => B False , If B True => A False


Last edited by newton; 04/05/16 08:33 AM.
newton #55783 04/06/16 01:46 AM
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Rose as per usual Marosz's post is completely off topic spam feel free to deal with it.

It definitely wasn't worth the notification e-mail and I have turned notifications off now.

Last edited by Orac; 04/06/16 02:02 AM.

I believe in "Evil, Bad, Ungodly fantasy science and maths", so I am undoubtedly wrong to you.

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