nist.gov

oRKeE TIL that those plastic wall clocks in schools are actually atomic, and the reason they speed ahead when they get messed up is due to a radio signal from NIST called WWVB
NXpb8 TIL that since 1959, in the United States, the inch is based on a specific metric length. One inch is defined as being exactly 25.4 millimeters.
j6KPM TIL that Mass is the only one of 7 fundamental measurments we still use a physical example of.