# Classical Planck Spectrum for Relative Thermal Radiation, Classical Zero-Point Radiation, and Scale Parameter

## TL;DR

This paper derives Planck's blackbody spectrum within a classical framework by linking thermal scalar radiation and zero-point electromagnetic radiation, revealing a scale parameter related to experimental Casimir force measurements.

## Contribution

It presents a classical derivation of the Planck spectrum incorporating zero-point radiation and introduces a scale parameter connected to cavity geometry and experimental data.

## Key findings

- Classical derivation of Planck spectrum from scalar and zero-point radiation.
- The scale parameter aligns with known physical constants like Planck's constant.
- The approach connects theoretical classical physics with experimental Casimir force measurements.

## Abstract

In this work we obtain Planck's blackbody spectrum from the thermal scalar radiation contained in a resonant cavity of volume V in the context of classical mechanics, which provides the classical zero-point electromagnetic radiation in terms of a scale parameter that depends on geometric properties of the enclosure and electrical magnitudes. The scale parameter of the classical zero-point electromagnetic radiation is associated to experimental measurements of Casimir forces, but we show that theoretically its value for known radiant cavities that approach a blackbody has a numerical value of the order of Planck's constant.