Significant Figures

The digits reported in a measured (or calculated) value are not all equally trustworthy -- some are known reliably, and exactly one more is a reasonable estimate; the rest are meaningless noise a calculator happily prints but physics should never quote. Significant figures formalise exactly which digits in a number carry real information, and this section builds the rules for counting them (1.7.1), rounding a long decimal down to the right nu …