 where \(K\) is merely an additive factor that fixes the zero-point of energy and is conventionally set to zero and \(q\) is also routinely set to zero. However, unlike the convention to set \(K\) to zero, setting \(q = 0\) involves a hypothesis concerning the nature of matter, because it rules out the possibility that there exists matter that has mass but which is such that some of its mass can never be “converted” into energy.