Black Body 11 Stefan Boltzmann Law

This video shows a fascinating application of the black body theory.

Stefan Boltzmann's law describes what happens when the black body container has a leak. The measurement and theory were pivotal in the development of modern science.

An interesting historical note is that Dr. Boltzmann derived a T to the forth law in 1884 before Planck's quantum theory. He did this by assuming that the radiation pressure in an enclosed vessel is 1/3 the energy density of the radiation. Of course, the classical radiation energy density is infinite as we know from the ultraviolet catastrophe. Boltzmann's derivation ignored this fact and essentially used a feature of Planck's quantum theory before Planck. It should be noted that Boltzmann knew that the experimentalists had already found a T to the forth law. Boltzmann was unable to give a theoretical derivation of the Stefan-Boltzmann constant.

Jean Baptiste Perrin received the Nobel prize in 1926 for measuring Avogadro's number. His Nobel lecture shows all the elements that went into his measurement. By 1926, black body radiation was augmented by many other types of experiments.

[dochollowood]

Well this is the one to watch - it begins to show the circular usage of measuring and guessing to arrive at a "constant" used to calculate other numbers related to counting theoretical physical items.

[AviVajpeyi]

I am confused as to why Boltzmann's constant k would have been needed in the Millikan experiment to measure the charge of an electron - can you elaborate on this?

[abubardewa]

Please continue ... I love all your videos .

[das]

That is a fantastic story .. Truly . What is a shame is that many people get bogged down into the formulas and not the connections between the observations and discoveries . Example being how spectroscopy has allowed us to put the cosmic puzzle together . I need to replay this series a few times over because I want to thoroughly understand it . I have a real issue with light being viewed as a wave and then a particle . It has no mass yet bends in Gravity even though newtons laws need mass . The double slit is the reason I am still digging through all this material .. Because light seems to indicate that we have adequate models but not the required model . It seems to indicate that space must bend to accommodate it's speed and that it can communicate when tangled faster that it's speed of travel . This really causes me to question our notion of time and or distance . I have a feeling this story is not complete .. Based on this last video, if space is expanding does this not imply that.

[tomdrowry]

Amazing, I'd always wondered how they solved Avogadro's number

[bobbyt]

It's amazing that people so brilliant can also be so clueless. The photons are emitted by the inside of the container, not the gas itself. Yet today, you have so-called physicists applying these theories to gases. Gases are not blackbodies, they do not emit photons proportional to T^4.