Gravity

[science worm]

Every force needs a energy ? What is the energy source of gravity ? how is it made?

Edited August 28, 2011 by science worm

[DrRocket]

Every force needs a energy ?

 

What in the world is that supposed to mean ?

 

What is the energy source of gravity ? how is it made?

 

All forms of energy, except gravitational energy enter into the stress-energy tensor of general relativity, which determines spacetime curvature, which is gravity. Gravity also plays a role through the nonlinearities in the field equations, so in the words of Wheeler, "gravity gravitates".

[csmyth3025]

...All forms of energy, except gravitational energy enter into the stress-energy tensor of general relativity, which determines spacetime curvature, which is gravity. Gravity also plays a role through the nonlinearities in the field equations, so in the words of Wheeler, "gravity gravitates".

I'm a bit confused about the "gravity gravitates" concept. If the energy of gravity (I'm guessing that this would be the gravitational binding energy of the object) doesn't contribute to the stress-energy-momentum tensor of general relativity, in what way does it contribute to the nonlinearities in the field equations?

 

I hope the explanation isn't too involved - my grasp of differential equations is, at best, rudimentary.

 

Chris

[DrRocket]

I'm a bit confused about the "gravity gravitates" concept. If the energy of gravity (I'm guessing that this would be the gravitational binding energy of the object) doesn't contribute to the stress-energy-momentum tensor of general relativity, in what way does it contribute to the nonlinearities in the field equations?

 

I hope the explanation isn't too involved - my grasp of differential equations is, at best, rudimentary.

 

Chris

 

There is no simple explanation.

 

Gravitational energy is not explicitly included in general relativity. Among other things this is what makes "conservation of energy" a bit of a problem in GR.

 

http://math.ucr.edu/home/baez/physics/Relativity/GR/energy_gr.html

[swansont]

Every force needs a energy ? What is the energy source of gravity ? how is it made?

At a more basic level (i.e Newtonian), it's because masses attract. You could ask the same thing about Electrostatics — the answer is that charges attract. I think painting this as "every force needs a energy" misses a basic point. We have interactions. Force, energy, momentum, etc. are convenient ways of describing those interactions and the behaviors resulting from them. There will be an energy associated with a force because they are related concepts. Similarly with force and momentum.

 

You don't need a source of energy in the way that you need fuel for your car. Energy is conserved.

[csmyth3025]

There is no simple explanation.

 

Gravitational energy is not explicitly included in general relativity. Among other things this is what makes "conservation of energy" a bit of a problem in GR.

 

http://math.ucr.edu/.../energy_gr.html

Thanks for the link DrR.

 

I'm afraid it's a bit over my head, though. I'll keep working on the basic concepts (and the math). Hopefully, one day a light will go off in hy head and I'll finally "get it".

 

Chris

[Nobel okelekele]

Gravity itself@is a natural occurring energy.but if you want to trace the energy source of gravity,you would first ask your self of the chemical combination of the substances present in the core of the earth,other planet and stars,before you can arrive at it's power source.because you know gravity pulls us to the core of earth.

So the questions we should ask is what is pulling us before we can answer the question of how it gets it's energy.

But if you ask me.the continuous heating of magma in the earth 's core emits the energy that pulls us to the ground.

[swansont]

!

Moderator Note

Posts on pushing gravity have been split http://www.scienceforums.net/topic/59583-pushing-gravity

Nobel okelekele, if you want to discuss your hypotheses, the appropriate place is the Speculations forum

[csmyth3025]

There is no simple explanation.

 

Gravitational energy is not explicitly included in general relativity. Among other things this is what makes "conservation of energy" a bit of a problem in GR.

 

http://math.ucr.edu/.../energy_gr.html

As an object gravitationally contracts, the internal pressure of the object increases. Is this the mechanism by which "...Gravity also plays a role through the nonlinearities in the field equations..."?

 

Chris