플랑크 상수
‘불변의 단위’ 시대 열린다…질량 등 4개 단위 재정의
http://www.hani.co.kr/arti/science/science_general/870623.html?fbclid=IwAR1retk8aAw3VAY47N1tyGyr3jnWFFNigCCXkI5A4HSmZ-b4stg6yl2XvOkThe world just redefined the kilogram
https://www.vox.com/science-and-health/2018/11/14/18072368/kilogram-kibble-redefine-weight-science