How can we be sure of Planck’s constant when we have never measured anything to that accuracy?

Question

Any constant in physics or chemistry comes from experimental design and consistency in measurements. For example, if you divide multiple of pressure and volume with the multiple of moles and temperature, you will get the constant R for any ideal gas.

However, given how small planck’s constant is, how can we assume its accuracy?

In: Physics

Answer 1

There are many experiments that can be employed to determine Planck’s constant. A historic one is Milikan’s oil drop experiment. However, nowadays Planck’s constant has a fixed value the same way the speed of light does. Of course, this value is selected taking into account the available experimental data.