If you try to measure the mass m of an electron, some experimental error DELTAm, and the energy-time uncertainty principle combined with the finite lifetime of the universe (at least so far...) causes a limit on the accuracy of m. So one could argue, the mass of the electron is inherently unknowable and undefined to more than a certain number of decimal places. Except, somebody could measure the mass of a million-electron blob to try to dodge that limitation. So anyhow... what are the inherent limits on how many decimal places can exist in such quantities (any further would have no meaning) and if so, estimate them. -- Warren D. Smith http://RangeVoting.org <-- add your endorsement (by clicking "endorse" as 1st step)