 Electromagnetic stress–energy tensor

For metric signature $(-,+,+,+)$,In particular, $T^{00}=\frac{1}{2}({ϵ}_0{E}^2+B^2/{\mu }_0)$.

The electromagnetic stress-energy tensor is a mathematical object that describes the density and flux of energy and momentum in an electromagnetic field. In the context of general relativity and field theory, it encapsulates how electromagnetic fields contribute to the gravitational field via their energy and momentum distribution.