Abstract

Measured values of the electron mass and Compton wavelength yield a value of Planck’s constant with a relative standard
uncertainty of 3 × 10−10. This is only slightly larger than the 1.3 × 10−10 relative standard uncertainty in measurements
performed using the Kibble balance. Compton scattering presents an alternative pathway for improving the value of
Planck’s constant.
Natural units of length, mass, and time offer viable solutions for improving the values of physical constants. While
extensive values of the Planck units lie beyond the reach of present-day instrumentation, certain product and quotient
pairs of Planck units such as the speed of light can be measured with relatively high precision. Better measurements of
certain unit pairs will improve the value of the gravitational constant.

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