I think what you're describing is called the stress-energy tensor, which as I understand it is a generalization of mass. https://en.wikipedia.org/wiki/Stress%E

I think what you're describing is called the stress-energy tensor, which as I understand it is a generalization of mass. https://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor https://en.wikipedia.org/wiki/Stress%E2%80%93energy_tensor