# Shouldn't the mass of an electron be uncertain?

1. May 26, 2013

### gamow99

How is the mass of an electron known down to 31 orders of magnitude? Shouldn't the mass be uncertain beyond a few decimal places?

2. May 26, 2013

### dextercioby

It is, the $10^{-31}$ is certain, the 9 something number at the front isn't.