## Is there a Gravitational Effect Which is Analogous to Electrodynamic Induction?

This is the title taken from a little known (perhaps intentionally!) of a 1912 article of Einstein to show that the mass of a system is modified by the presence of other matter by an amount $GMm/Rc_0^2$, where $m$ is within a hollow sphere of mass $M$ of radius $R$, and $c_0$ is the speed of light at infinity. This is the amount of increase in mass independently of whether we are considering $m$ or $M$. Instead of the electrodynamic repulsion between two circuits, embodies in Ampere's law, Einstein always comes out with an attraction between the masses.