KentuckyFC writes "A team of physicists has measured the smallest force ever recorded, at 174 yoctonewtons (yocto=10^-24), beating the previous best by three orders of magnitude. Their measurement device consists of a few dozen beryllium ions trapped in magnetic and electric fields using a device called a Penning trap. These ions vibrate at between a few mega and kilohertz, frequencies that can be accurately measured by bouncing laser light off the ions and measuring any Doppler shift they cause. Being charged, the ions are highly susceptible to the tiny forces associated with stray magnetic and electric fields, which change the frequency at which the ions vibrate. Hence the super-sensitive measurements. They team says that straightforward modifications should allow them to measure single yoctonewtons in the near future. This sudden leap in sensitivity could cause a problem for the system of SI prefixes, which don't yet come any smaller than yocto."