In a landmark decision, representatives from 60 countries voted to redefine the International System of Units (SI), changing the world's definition of the kilogram, the ampere, the kelvin and the mole ...

SI Unit: Every measurement we make, be it for length, time, temperature, or electric current, needs a standard unit so that results are understood universally. To maintain uniformity worldwide, ...

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, ...

The NIST-4 Kibble balance, an electromagnetic weighing machine that is used to measure Planck's constant, and in turn, redefine the kilogram. Jennifer Lauren Lee / NIST Locked in a vault that requires ...

We measure stuff all the time – how long, how heavy, how hot, and so on – because we need to for things such as trade, health and knowledge. But making sure our measurements compare apples with apples ...

The kilogram — anywhere in the world, for any purpose — is based on the exact weight of a golf-ball-sized chunk of platinum and iridium stored under three glass bell jars in a vault in an ornate ...

As ever more digital data is created and stored, the world needs more unit measurements to keep up with the ever-expanding numbers. To do so, the 27th General Conference on Weights and Measures on ...

Meet the metric system’s newest prefixes: ronna-, quetta-, ronto- and quecto-. Science News spoke with Richard Brown, head of metrology at the National Physical Laboratory in Teddington, England, ...

In addition to Ampere, Kelvin, Mol and Co., the kilogram also is now defined by a natural constant. In concrete terms, this means that the original kilogram, which has been the measure of all things ...