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Planck constant
Angular momentumexact by definition
The Planck constant is exactly 6.62607015 × 10⁻³⁴ joule seconds, fixed by definition since 20 May 2019. It is the quantum of action, and it is now the constant through which the kilogram itself is defined, so its exactness is not a rounding convenience but the foundation of the SI mass scale.
| 1 h | 6.6260701e-34 kg·m²/s |
Where the unit came from
Planck introduced it in 1900 as a fitting parameter that made the blackbody spectrum come out right, and described it as an act of desperation. It turned out to be the constant that separates classical from quantum physics.
Solvers that use angular momentum