[dleviwing]

Nobody;
Mass is a “MEASUREMENT”; so is motion; so is energy; so is time. Matter is an “ENTITY”. The question is: “Does mass truly represent a measure of the physical quantity of something?” Once you establish the absolute fundamentals, no cause can be determined beyond that point; this is where we can only say that the fundamentals have always existed and still exist today; their total quantities are the same now as they were 15 billion years ago.