Old kilogram, meet new kilogram

Kilogram (kg), the base unit of mass in SI (system international; international system of units) is defined with a platinum alloy cylinder, located near Paris. The cylinder was manufactured in 1889.
After 130 years, on May 20th, 2019, the reference definition of kilogram will no longer be this physical artifact, but a physical constant.

Planck constant, defined exactly as:

6.62607015×10⁻³⁴ kg⋅m²⋅s⁻¹ 

can define the kilogram in terms of second and meter [Wikipedia], assuming we can determine Planck constant by a stable measurement. Meter is (now) defined as a time fraction of speed of light in vacuum. Therefore, kilogram can now be defined in terms of time only.

Here are the devices for the old and new definition of the kg:

 (J.L.Lee/NIST)

  (J.L.Lee/NIST)

Related articles:

• Kilogram Redefined (Wired)

Related Links:

• Kilogram (Wikipedia)
• Planck constant (W)
• Meter (W)
• International System of Units (W)