Putting to Rest Mass Misconceptions
From Putting to Rest Mass Misconceptions, Wolfgang Rindler, Physics Today, May 1990, page 13
I am disturbed by the harm that Lev Okun’s earnest tirade (June 1989 page 31) against the use of relativistic mass (“It is our duty … to stop this process”) might do to the teaching of relativity. It might suggest to some who have not thought these matters through that there are unresolved logical difficulties in elementary relativity or that if they use the quantity m = gm0 they commit some physical blunder, whereas in fact this entire ado is about terminology. There are perhaps 40% of us who find it useful occasionally to write m for E/c2 and 60% who don’t. But why the latter should try to coerce the former beats me.
One can perhaps understand a desire that everyone should use the term “mass” in the same sense. I myself have never found this a stumbling block, since the context tells me which mass the author means. Nevertheless, if I am told by the particle physicists � and they are the largest user group of special relativity these days � that henceforth I must use the symbol m for rest mass and call it mass, so be it. But I refuse to stop using the concept of relativistic mass, which I would then denote by mr.
I know a man who can drive a shift car without ever using the clutch � it’s a question of timing. The ingenious Ernest Vincent Wright in 1939 wrote a 50 000 - word novel, called Gadsby, in all of which the letter e never occurs. Its sentences look like this: “A busy day’s traffic had had its noisy run.” Sure, such feats can be performed. But to what end? I like using my clutch, the letter e and relativistic mass.
To me, m = gm0 is a useful heuristic concept. It gives me a feeling for the magnitude of the momentum p = mv at various speeds. The formula E = mc2 reminds me that energy has mass-like properties such as inertia and gravity, and it tells me how energy varies with speed. I will confess to even occasionally using the heuristic concepts of longitudinal mass g 3m0 and transverse mass g m0 to predict how a particle will move in a given field of force
Wolfgang Rindler
University of Texas at Dallas