&gt; That physical quantities such as mass are forever increasing<p>I think that&#x27;s a little uncharitable. In classical terms you could say that each &quot;universe&quot; is associated with some weight or probability, and those probabilities always sum to one.<p>I guess you could say that the &quot;number&quot; of things increases (provided that number is countable and finite, I guess, which seems a bit silly), but the probability-weighted mass of things going on stays the same.<p>Of course, it isn&#x27;t terribly useful to talk about all of the inaccessible universes taking up the majority of the probability, so we condition on our observations (i.e., we do a Bayesian update, or &quot;collapse the wavefunction&quot;.)<p>Then if we talk about &quot;our universe&quot; having probability 1 given our observations, and surmise that people in another parallel, inacessible universe would also say that theirs has probability 1, we might say &quot;Aha! There is now a total of 2, where once there was a total of 1!&quot; It should be clear how this is an error, though.