All base units of measurement now tied to defined constants rather than physical objects

Scales aren't changing and the weather won't be noticeably different, but on May 20 the definitions that underlie what your scale and thermometer report—along with standard definitions used in chemistry and electronics—are undergoing a major overhaul. That's the date that a more-than-centuries-long process of standardizing measurements reaches its conclusion.

Physical kilogram is officially dead

Nature, Published online: 20 May 2019; doi:10.1038/d41586-019-01614-8Definitions of four basic scientific units, including the kilogram and the kelvin, now rely on fundamental ...

Mon 20 May 19 from Nature News

These are the top 10 landmarks in the history of making measurements

Little appreciated but vastly important, metrology celebrates a long history with the adoption of new definitions for key units.

Mon 20 May 19 from ScienceNews

The kilogram just got a revamp. A unit of time might be next

After years of preparation, new definitions for the basic units of mass, temperature and more have now gone into effect.

Mon 20 May 19 from ScienceNews

Adieu, Le Grand K: The kilogram to be redefined for the first time in 130 years

In a subterranean vault in a suburb of Paris lies a small, rarely seen metal cylinder known as Le Grand K.

Mon 20 May 19 from

Definition of kilogram, amp, and kelvin set to change forever

A shift from physical artefact to natural constant marks a huge shake-up in how the world defines units of measurement. Andrew Masterson reports.

Wed 15 May 19 from Cosmos Magazine

There's a Brand-New Kilogram, And It's Based on Quantum Physics

The kilogram isn't a thing anymore. Instead, it's an abstract idea about light and energy and fundamental universal constants.

Tue 21 May 19 from

There's a Brand-New Kilogram, And It's Based on Quantum Physics, Mon 20 May 19 from Livescience

Total number of sources: 20


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