Okay, I am not a physicist but I am wondering about where Planck's constant came from? I understand that he was attempting to explain "black body radiation" and that he got frustrated with the math of this endeavor. So in a stroke of genius, he introduced a number $6.55×10^{−34}$ J⋅s and it made sense of the "Black Body Radiation" and worked perfectly, great. My question is, where or how did he derive this number and does it affect us?


closed as too broad by Norbert Schuch, Emilio Pisanty, Jon Custer, Daniel Griscom, Rory Alsop Aug 11 '17 at 23:56

Please edit the question to limit it to a specific problem with enough detail to identify an adequate answer. Avoid asking multiple distinct questions at once. See the How to Ask page for help clarifying this question. If this question can be reworded to fit the rules in the help center, please edit the question.

  • 1
    $\begingroup$ also it's $6.63\times 10^{-34}$, not $6.55$. Well if you want to be a constant nerd it's $6.62607004081\times 10^{-34}$, but who's experiment is that accurate anyway. $\endgroup$ – CooperCape Aug 11 '17 at 18:45
  • 1
    $\begingroup$ Which books or articles, there are lots (and lots) of them, have you read relating to this? Then you can create a better question regarding which aspect of the topic you would like to pin down as a problem in understanding it. $\endgroup$ – user163104 Aug 11 '17 at 18:48
  • $\begingroup$ The size of atoms, based on the Bohr radius, goes like the square of the Planck constant. So yes, it affects the size of your and everything else's atoms... and... and... $\endgroup$ – Cosmas Zachos Aug 11 '17 at 19:30
  • $\begingroup$ Is there some specific part of the corresponding Wikipedia article that you find confusing? $\endgroup$ – Emilio Pisanty Aug 11 '17 at 19:51
  • 1
    $\begingroup$ @Countto10 Of course I have nothing to say about Panck himself and what he thought or didn't. I am "reminding" the OP of the evident in his "does it affect us" dangler. It is not about Planck, really. $\endgroup$ – Cosmas Zachos Aug 11 '17 at 22:38

The experimental black body radiation curve

black body

followed the quantum curve ( named a posteriori) in the above diagram. Classical calculations could not fit the data for intensity of radiation versus frequency.

Planck had the out of the box idea to model black body radiation as a cavity with discrete energy oscillators, since continuous ones of classical electromagnetism led to the ultraviolet catastrophe..

class versus quantum

The h is a proportionality constant between energy of the mode ( we now call photon) and frequency. I.e., since continuous frequencies did not fit the data, he tried discrete, and fitted them with just a constant measured from data and in the end given Plack's name.

The success of solving the ultraviolet catastrophy for black body radiation is one of the basic reasons that quantum mechanics was discovered to be necessary to explain the data in the microcosm of atoms..

  • $\begingroup$ Thank you, I now understand, it was not a guess but derived. That's what I was looking for! $\endgroup$ – Dick Patton Aug 13 '17 at 18:30

Not the answer you're looking for? Browse other questions tagged or ask your own question.