# Changes to Planck constant historically [closed]

I looked all over to get the various accepted value of the Planck constant since 1900. But there is never any record about the history of this mysterious number.

• What is your question, exactly? If you are interested in the history of the measurement of Planck's constant, this question might be more suited for History of Science and Mathematics. – ACuriousMind Sep 14 '19 at 9:13
• Its more than just history. The various measured values used at different times may have scientific significance – itsme Sep 14 '19 at 9:40
• – Ben Crowell Sep 14 '19 at 13:47

I think what you are asking, in a rather poor way, is the Planck constant time-dependant over long time scales? The way you are asking this, by looking at scientific records of this measured value, is not a good approach. If you want to ask the question "are physical constants, actually constant in time?" -- which is a very good question to ask. In fact there are several experiments which want test if physical constants are actually constant; e.g. measuring the fine-structure constant $$\alpha$$ with atomic clocks.