Planck Units: How Did He Know What We Don't?

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    Planck Units
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Discussion Overview

The discussion revolves around the origins and significance of Planck units, particularly how Max Planck derived these units prior to the establishment of quantum theory and the Planck constant. Participants explore the historical context and implications of Planck's work in relation to blackbody radiation and the development of physical constants.

Discussion Character

  • Exploratory
  • Historical
  • Debate/contested

Main Points Raised

  • Some participants express confusion about how Planck could derive his units before the discovery of the Planck constant and quantum mechanics.
  • Others clarify that Planck's determination of the Planck constant was empirical and derived from his work on the blackbody spectrum.
  • A participant notes that Planck introduced two physical constants in his 1899 paper, which were later replaced by the Planck constant and the Boltzmann constant.
  • There is a suggestion that some Planck units can be derived without the Planck constant, indicating a nuanced understanding of their origins.
  • One participant challenges the notion that Planck units preceded the Planck constant, comparing it to saying a car preceded the wheel.
  • Another participant questions why the derivation of Planck units is portrayed as a mystery, suggesting that it may not be as unresolved as implied.
  • There is a request for an online version of Planck's original 1899 paper, indicating interest in primary sources.

Areas of Agreement / Disagreement

Participants do not reach a consensus on the implications of Planck's work or the characterization of the derivation of Planck units. Multiple competing views remain regarding the historical context and the clarity of Planck's contributions.

Contextual Notes

There are limitations in understanding the assumptions made in Planck's original work, as well as the dependence on definitions of physical constants that were not fully established at the time.

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I was reading about the Planck units, and they said that Planck came up with them before his quantum theory of blackbady radiation, and before the constant h had been discovered. They said it's unclear how he found these units. This seems pretty weird to me. How did he come up with these numbers? Did he know something we still don't?
 
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Plancks determination of the Planck constant was the result of his work on blackbody spectrum. It is empirical, which is to say it is directly measured. All Planck units are derived from the Planck constant. See here for a more:
http://physicsweb.org/articles/world/13/12/8
 
http://en.wikipedia.org/wiki/Natural_units

The above site says:

"At the time he presented the units, quantum mechanics had not been invented. He himself had not yet discovered the theory of black-body radiation (first published December 1900) in which the Planck's Constant made its first appearance and for which Planck was later awarded the Nobel prize. The relevant parts of Planck's 1899 paper leave some confusion as to how he managed to come up with the units of time, length, mass, temperature etc. which today we define using Dirac's Constant and motivate by references to quantum physics before things like [tex]\hbar[/tex] and quantum physics were known. "
 
To say that Planck units preceded Planck's constant is to say that the car preceded the wheel. What are your sources for any other ideas about this?
 
In the 1899 paper, Planck introduced two physical constants, a and b, which he had calculated from experimental data. In 1900, he replaced b with the now better known letter h. He also replaced the 'a', with the letter b [Boltzmann constant]. To correct my earler statement, there are a few Planck units that can be derived without knowing the Planck constant.
 
ok thanks. I don't know why they acted like it was some unsolved mystery.
 
Errata: the constant 'a' was replaced by the letter 'k' [Boltzmann's constant]. That was bugging me and it was too late to edit the typo.
 
Chronos said:
In the 1899 paper, Planck introduced two physical constants, a and b, which he had calculated from experimental data. In 1900, he replaced b with the now better known letter h. He also replaced the 'a', with the letter b [Boltzmann constant]. To correct my earler statement, there are a few Planck units that can be derived without knowing the Planck constant.

is there an online version of his original 1899 paper?? i know he (and others) thought his quantum 'leap' was nothing more than a mathematical fudge to solve the analytics and numerics
 

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