## 7 Great Videos! "New SI"

Part 1: My System of Units
by Michael de Podesta, NPL

Part 2: The International System of Units

Part 3: The Kilogram Problem

Veritasium (with NIST) : How We're Redefining the Kilogram

Veritasium (with CSIRO) : World's Roundest Object

NIST : Measuring Planck's Constant

How to Build Your NIST D.I.Y. Watt Balance

## The New "SI"

Measurement Science Professionals
Redefining the (SI) is creating Great Conversation!
Join the conversation by understanding the changes to come...  ## Redefining the International System of Units (SI) in 2018

In the "New SI" four of the SI base units – namely the kilogram, the ampere, the kelvin and the mole – will be redefined in terms of constants; the new definitions will be based on fixed numerical values of the Planck constant (h), the elementary charge (e), the Boltzmann constant (kB), and the Avogadro constant (NA), respectively. Further, the definitions of all seven base units of the SI will also be uniformly expressed using the explicit-constant formulation, and specific mises en pratique will be drawn up to explain the realization of the definitions of each of the base units in a practical way.

Key to SI Definition Constants:
Δν = the unperturbed ground state hyperfine transition frequency of the caesium-133 atom ΔνCs is 9,192,631,770 hertz
c = the speed of light in vacuum c is exactly 299,792,458  metres per second
h = the Planck constant h is exactly 6.626 070 15 x 10–34 joule seconds
e = the elementary charge e is exactly 1.602 176 634 x 10–19 coulombs
kB = the Boltzmann constant kB is exactly 1.380 649 x 10–23 joules per kelvin
NA = the Avogadro constant NA is exactly 6.022 140 76 x 1023 reciprocal moles
Kcd = the luminous efficacy Kcd of monochromatic radiation of frequency 540 x 1012 Hz is exactly 683 lumens per watt

## The New "SI" in the Media

What the Media is talking about...

"Quantum physics to the rescue after the kilogram develops a weight problem"