Their tiny counterparts ronto- and quecto- refer to 10 –27 and 10 –30, the way milli- refers to 10 –3, or 0.001. Until now, yotta- and yocto- (24 zeros) capped off the metric system’s range.

From Robert Checchio, Dunellen, New Jersey, US Regarding Chris Stokel-Walker’s review of Beyond Measure, opposition to the metric system hasn’t been limited to the UK (18 June, p 34).