# Does space naturally resist mass and energy?

So I am starting to get into upper level physics classes and I was wondering, if you can imagine space like a sheet or like a set of sheets stacked on top of each other and able to be curved in any direction, just like that of 3D relativity. Doesn't the sheet have a natural resistance to the curvature it gets from mass? Space's natural state is in the opposite direction to mass so maybe it is constantly exerting some "anti-mass" or "anti-gravity", in dense regions of free space this energy might increase and lead to expansion??? I don't know just a thought

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• neb
Lv 7
2 months ago

Well, that is an interesting question. The vacuum has a kind of ‘resistance’ to electric and magnetic fields called the permeability and permitivity of space, but gravitational fields are quite a bit different than electromagnetic fields and I don’t know of any direct gravitational analog. You might argue based on the strength of the coupling constant for gravitational fields (gravity is by far the weakest ‘force’), but I think that would be a weak argument at best.

Characterizing the energy of the gravitational field might be another approach. The energy density of the electromagnetic field does depend on the permeability and permittivity of free space. However, the energy density of the gravitational field depends solely on the metric tensor (the solution to Einstein’s field equations) and there really isn’t anything there that would seem to imply a resistance to curving other than again the weak coupling constant.

As for ‘antigravity’ and expansion, the following is how it works. The source of gravity in general relativity is something called the stress-energy tensor. It has 1 component of energy density, 3 components of momentum density, 3 components of stress, and 3 components of pressure. It is the 3 components of pressure that lead to the expansion (accelerated) of the universe. This is because the 3 components of pressure can be negative, and it is believed that the 3 components of negative pressure come from dark energy (dark energy actually has a positive energy density but creates a negative pressure).

Cosmological solutions of general relativity use energy density and the 3 components of pressure in the stress-energy tensor. When the 3 components of the pressure (isotropic pressure in the 3 space dimensions) exceed the energy density, the net effect is the ‘repulsive’ gravity that is accelerating the expansion of the universe.

• 2 months ago

No. Mass and energy are interchangeable. The conversion process is inefficient because of entropy and the?randomness of Quentin mechanics. That is what E = mc^2 = hv, where v= frequency, means. Then there is the enigmatic and missing dark matter dark and dark energy.