 More recently, Rainville et al. (2005) have published the results of what they call “A direct test of \(E = mc^2\).” Their experiments test mass-energy equivalence “directly” by comparing the difference in the rest-masses in a neutron capture reaction with the energy of the emitted \(\gamma\)-rays. Specifically, Rainville et al. examine two reactions, one involving neutron capture by Sulphur \((\S)\), the other involving neutron capture by Silicon \((\Si)\):