Heinrich Hertz's main initial experiment used a spark-gap transmitter. It is not something that transmits recorded sounds like voice: it only transmits noisy beeps. And as such was used for wireless telegraphy.
Video 1.
Hertz Experiment on Electromagnetic Waves by Ludic Science (2015)
Source. Simplified recreation with cheap modern equipment. Uses as transmitter power source both:and the signal is observed on the receiver with a neon lamp
Video 2.
Hertz and Radio waves Explained by PhysicsHigh (2016)
Source. Simple schematics showing the basics of the experiments. No choice of components rationale.
Gram-negative bacteria by Ciro Santilli 37 Updated 2025-07-16
Notable examples:
Figure 1.
Structure of a Gram-negative bacteria
. Source.
The Supermen: The Story of Seymour Cray by Charles J. Murray (1997) page 4 mentions:
Cray wanted his new machine to employ circuits made from a material called gallium arsenide. Gallium arsenide had achieved limited success, particularly in satellite communications and military electronics. But no one had succeeded with it in anything so complicated as a computer. In the computer industry, engineers had developed a saying: "Gallium arsenide is the technology of the future," they would say. "And it always will be."
University of Paris by Ciro Santilli 37 Updated 2025-07-16
Their split in 1970 was a huge fuck up. If it were a single entity, the university would likely be in the top 10 university rankings, undoubtedly top 20. But as of 2020 French universities only appear instead in the top 40s or 50s.
For a quick and dirty introduction to the format, see: ELF Hello World Tutorial.
Plant by Ciro Santilli 37 Updated 2025-07-16
Formal name: "plantae".
Matrix mechanics by Ciro Santilli 37 Updated 2025-07-16
It is apparently more closely related to the ladder operator method, which is a more algebraic than the more analytical Schrödinger equation.
It appears that this formulation makes the importance of the Poisson bracket clear, and explains why physicists are so obsessed with talking about position and momentum space. This point of view also apparently makes it clearer that quantum mechanics can be seen as a generalization of classical mechanics through the Hamiltonian.
Inward Bound by Abraham Pais (1988) chapter 12 "Quantum mechanics, an essay" part (c) "A chronology" has some ultra brief, but worthwhile mentions of matrix mechanics and the commutator.

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