Ciro Santilli @cirosantilli  40

This shows that viewing electromagnetism as gauge theory does have experimentally observable consequences. TODO understand what that means.

In more understandable terms, it shows that the magnetic vector potential matters where the magnetic field is 0.

Classic theory predicts that the output frequency must be the same as the input one since the electromagnetic wave makes the electron vibrate with same frequency as itself, which then irradiates further waves.

But the output waves are longer because photons are discrete and energy is proportional to frequency:

The formula is exactly that of two relativistic billiard balls colliding.

Therefore this is evidence that photons exist and have momentum.

No matter how hight the wave intensity, if it the frequency is small, no photons are removed from the material.

This is different from classic waves where energy is proportional to intensity, and coherent with the existence of photons and the Planck-Einstein relation.

cat-v.org/ by Rob Pike, co-creator of Go, looong time Unixer, and some kind of leader of a 9p resurrection cult. That one's spicy. E.g.: harmful.cat-v.org/, Ciro's version: good and evil.

Created by Dr. Rod Nave from Georgia State University, where he worked from 1968 after his post-doc in North Wales on molecular spectroscopy.

While there is value to that website, it always feels like it falls a bit too short as too "encyclopedic" and too little "tutorial-like". Most notably, it has very little on the history of physics/experiments.

Ciro Santilli likes this Rod, he really practices some good braindumping, just look at how he documented his life in the pre-social media Internet dark ages: hyperphysics.phy-astr.gsu.edu/Nave-html/nave.html

The website evolved from a HyperCard stack, as suggested by the website name, mentioned at: hyperphysics.phy-astr.gsu.edu/hbase/index.html.

Shame he was too old for CC BY-SA, see "Please respect the Copyright" at hyperphysics.phy-astr.gsu.edu/hbase/index.html.

exhibits.library.gsu.edu/kell/exhibits/show/nave-kell-hall/capturing-a-career has some good photo selection focused on showing the department, and has an interview.

Kell hall is a building of GSU that was demolished in 2019: atlanta.curbed.com/2020/1/31/21115980/gsu-georgia-state-atlanta-kell-hall-demolition-park-library-north

A linear map $A$ can be seen as a (1,1) tensor because:is a number, $v\ast$. is a dual vector, and W is a vector. Furthermoe, $T$ is linear in both $v\ast$ and $w$. All of this makes $T$ fullfill the definition of a (1,1) tensor.

Bibliography:

The Wikipedia page of this article is basically a masterclass why Wikipedia is useless for learning technical subjects. They are not even able to teach such a simple subject properly there!

Bibliography:

Naming taxonomic ranks like genus, domain, etc. is a fucking waste of time, only useful before we developed molecular biology.

All that matters is the tree of clades with examples of species in each clade, and common characteristics shared by the clade.

And with molecular biology, we can build those trees incredibly well for extant species. When extinct species are involved however, things get more complicated.