Let us now consider two such gas samples S1 and S2 that are spaced some distance apart in a vacuum. Let us further suppose that all of the energy ΔE emitted by S1 is absorbed by S2. In this configuration, the mass M1 of S1 will decrease by an amount ΔE/c2. As S2 absorbs the amount of energy ΔE, its mass increases by an equal amount ΔE/c2. There is a sense, then, in which it can be said that the radiation that “carried” the energy ΔE from S1 to S2 had the effect of transferring some of the inertial mass from S1 to S2, or as Einstein put it “If the theory agrees with the facts, then radiation transmits inertia between emitting and absorbing bodies” (1905b, p. 174).