The need for a smaller, more transportable version of ANSTO's 1,500-liter atmospheric radon-222 monitor, and with a calibration traceable to the International System of Units, prompted the team to ...

Every measurement we make, be it for length, time, temperature, or electric current, needs a standard unit so that results ...

In addition to other scientific units, the kilogram also is now defined by a natural constant. This is made possible by single crystals grown from highly enriched silicon-28. In addition to Ampere, ...

If scientists had sacred objects, this would be one of them: a single, closely guarded 137-year-old cylinder of metal, housed in a vault outside of Paris. It is a prototype that precisely defines a ...