I’ve wondered for a long time why Planck’s constant is called, ‘h’. I know, as a physics guy, Planck is going to be all into the math. Clever reasoning in letter selection for a constant is probably not something Planck would focus on. He studied with Helmholtz, and Hermes is a speedy god, but it just doesn’t seem like Planck would waste his time with this sort of planning for his constant’s name. I don’t know German. Maybe a german word starting with ‘h’ is behind this? Could it be just a random letter he chose?
Here’s my guess, backed up with absolutely no citations.
Planck needed a symbol for a constant of proportionality, but k was taken by Boltzmann’s constant (German: “konstant”). h is nearby, distinct, and unused (contrast i and l). I doubt it came from any particular word. Indeed, there was no good physical interpretation of h when it was first written down.
This paper claims that Planck used h for the German word Hilfsgrösse. My German is nicht sie gut, but as far as I can tell this means “auxiliary quantity”.
Good find. It would be interesting to see if anyone can find an independent mention of this etymology. The citation given in that unrefereed document doesn’t warm the heart with confidence:
Who?
A quote from Planck himself (or perhaps one of Planck’s contemporaries) might be required on this one (at least for me to believe it)…
which translates to: Max Planck introduced the constant h (from Hilfsgröße) in 1900 …
No direct quote from Max Planck himself, but maybe a little more confirmation for the origin.
As far as I can determine from a quick browse, Planck in no way mentions any reasoning for chosing the letter h, but just introduces it as a natural constant fitting the formula. But my German is rusty and it was a quick browse, so I might have missed something.
A google search for Hilfsgröße Planck yields 1,330 results, most of them - unsurprisingly - in German. My German is not good, but from the snippets on the first couple of pages of search results, most of them seem to be affirming that this is the etymology of ‘h’. So it seems that this understanding is at least widespread.
Of course, if you used another word, and got even more results (1,330 is piddly on Google), that might be better. I used the “English Only” feature, and I found the 34 results agreed, but that is definitely a small number.
Apparently Planck used the letter “b” in his paper. So it could have been German physicists that decided that “h” was a good choice.
But I thought it was because mathematicians like to use the letter “h” for the small quantity in limits (since at least Cauchy). In Planck’s analysis “h” was supposed to go to zero in the limit, but instead a finite value corresponded to physical reality.
Now why Cauchy chose “h” I don’t know. Presumably it corresponds to some word in French or Latin.
While I’m not discounting this possibility, I find it a little suspicious that this statement about Mr. Hayward was only added to the Wikipedia article earlier today, without any citation. I’ll dig around online a little more and see if I can find any proof of it, though.
ETA: The same wiki user also added this claim to the page on areal momentum. There’s a citation there, which I’m looking over now.
The citation in the “areal momentum” article just talks about angular momentum; it seems to only be a coincidence that Hayward used the symbol h to denote it, and it’s fairly clear that he viewed h (the angular momentum as a continuous quantity rather than a discrete one (since he takes derivatives with respect to it. Moreover, Planck’s initial paper had nothing to do with angular momentum; he was concerned with the energies of oscillators in a blackbody.
All in all, I remain unconvinced that Hayward had anything to do with Planck’s constant as we understand it today.
Looking at the talk page for Planck’s constant, it seems that I’m not the only one who is unconvinced. (For the record, I’m “Johnny Assay” over there.)
Wow… Yep, I understand your suspicion, but for the record: I haven’t edited that page, nor did I know of this. Giving my Wikipedia login (my real name) wouldn’t help, since there’s sock-puppet accusations afloat now…
Anyway, that was weird timing. I got to this page, and thence that article, from a recent article about an experiment that (supposedly) validated a new (2003) formulation of the Heisenberg Uncertainty Formula. Naturally, I can’t find the damned article now, but here’s a referenceto the reformulation.
What continues to boggle my mind is that there’s a sudden edit storm on Wikipedia (nothing odd yet…) about the HUP (OK, a bit odd) the very day I cite it. :smack:
No worries, I believe you that it was just a strange coincidence. In any event, it drew additional eyes to the article, and so it got corrected more quickly.
