The first application of mobile phones was in motor vehicles by Ciro Santilli 35 Updated +Created
Early models were heavy and not practical for people to carry them, so the main niche they initially filled was being carried in motor vehicles, notably trucks where drivers are commercially driving all day long.
It also helps in the case of trucks that you only need to cover a one-dimensional region of the main roads.
For example, this niche was the original entry point of companies such as:
History of mobile phone by Ciro Santilli 35 Updated +Created
Ethernet physical layer by Ciro Santilli 35 Updated +Created
Lifting electromagnet by Ciro Santilli 35 Updated +Created
Video 1.
Easy-to-Build Electromagnet lifts over 50 lbs by Dorian McIntire
. Source. Fun, but zero reproducibility.
Solenoid by Ciro Santilli 35 Updated +Created
Solenoids are a type of electromagnet coil of helical shape.
Solenoid means "tubular" in Greek.
Solenoids are simpler to build as they don't require insulated wire as in modern electrical cable because as the electromagnetic coils don't touch one another.
As such it is perhaps the reason why some early electromagnetism experiments were carried out with solenoids, which André-Marie Ampère named in 1823.
But the downside of this is that the magnetic field they can generate is less strong.
Figure 1.
Illustration of a solenoid
.
Figure 2.
Magnetic field lines around a solenoid cross-section
. TODO accurate simulation or not?
Picturephone by Ciro Santilli 35 Updated +Created
ethw.org/Picturephone good article!
Video 1.
AT&T Picturephone Model 2
. 1969
Public domain in the United States by Ciro Santilli 35 Updated +Created
Oscilloscope XY mode by Ciro Santilli 35 Updated +Created
Electromagnet by Ciro Santilli 35 Updated +Created
Electromagnets allow us to create controllable magnetic fields, i.e.: they act as magnets that we can turn on and off as we please but controlling an input voltage.
Compare them to permanent magnet: on a magnet, you always have a fixed generated magnetic field. But with an electromagnet you can control the field, and even turn it off entirely.
This type of "useful looking thing that can be controlled by a voltage" tends to be of huge importance in electrical engineering, the transistor being another example.
Laser spectrum vs LED spectrum by Ciro Santilli 35 Updated +Created
electronics.stackexchange.com/questions/477264/spectrum-of-leds claims cheap LEDs have 20 nm width at 50% from peak, and cheap lasers can be 1 nm or much less
Phases of ice by Ciro Santilli 35 Updated +Created
Telegrapher's equations by Ciro Santilli 35 Updated +Created
Expert system by Ciro Santilli 35 Updated +Created
These were the earlier attempts at decision making systems that could replace intellectual jobs.
Their main problem is that it is very costly to acquire data, which is kind of the main issue that large language models address with their ability to consume natural language input.
Why aren't LEDs monochromatic by Ciro Santilli 35 Updated +Created
www.reddit.com/r/Optics/comments/18f6bdt/comment/kcsiook/ mentions:
LEDs are broadband by nature, since the spontaneous emission broadly speaking reflects the overlap of the Fermi distribution and the density of states
Water molecule by Ciro Santilli 35 Updated +Created
Videotelephony by Ciro Santilli 35 Updated +Created
Emile, or On Education by Ciro Santilli 35 Updated +Created
Figure 1.
Front cover of the first edition of Emile, or On Education.
Source.
Good summary on the defunct Encyclopedia Britannica: www.britannica.com/topic/Emile-or-On-Education
it is not specifically about schooling but about the upbringing of a rich man’s son, Émile, by a tutor who is given unlimited authority over him. Rousseau’s aim throughout Émile is to show how a natural education, unlike the artificial and formal education of society, enables Émile to become social, moral, and rational while remaining true to his original nature
Also:
He learns a trade, among other things. He studies science, not by receiving instruction in its facts but by making the instruments necessary to solve scientific problems of a practical sort.
Book 1:
I do not consider these laughable establishments called Colleges as a public institution.
There are in several schools, and especially in the University of Paris, Professors whom I like, whom I esteem very much, and whom I believe very capable of instructing young people well, if they were not forced to follow established usage. I urge one of them to publish the reform project he designed. We will perhaps finally be tempted to cure the illness by seeing that it is not without a remedy.
Source:
Je n’envisage pas comme une institution publique ces risibles établissements qu’on appelle Colleges
Il y a dans plusieurs écoles, & surtout dans l’Université de Paris, des Professeurs que j’aime, que j’estime beaucoup, & que je crois très capables de bien instruire la jeunesse, s’ils n’étoient forcés de suivre l’usage établi. J’exhorte l’un d’entre eux à publier le projet de réforme qu’il a conçu. L’on sera peut-être enfin tenté de guérir le mal en voyant qu’il n’est pas sans remède.
Oscilloscope mode by Ciro Santilli 35 Updated +Created
Publish Notion content by Ciro Santilli 35 Updated +Created
But non-paid plan currently disables "Search engine indexing" of that sharing, so it's useless. There's an "Allow duplicate as template" button though which is nice.
URLs are horrendous however, e.g.: lofty-flower-be4.notion.site/aa-2274c59a06124d5b974b781a67340670 Only the aa in that came from us. They don't even have the guts for a fixed subdomain.
Also it does not work without JavaScript, no SSR, everything is dynamic.
They don't show multiple input pages on the same render, e.g.: lofty-flower-be4.notion.site/aa-2274c59a06124d5b974b781a67340670 does not contain the child lofty-flower-be4.notion.site/bb-45df7212a2e14e04b3f9604035c7acf4 as already implemented on OurBigBook Web Dynamic Article Tree.
Cross page links to work fine. But you don't link to explicit IDs, only internal hidden IDs. This can be even slightly confusing to users as multiple identical options can show up when you start creating a link. They do try to disambiguate with the parent page however.
So this is a reasonable single-person publishing platform for your notes.
Someone made and sold a helper for it:
Pinned article: ourbigbook/introduction-to-the-ourbigbook-project
Welcome to the OurBigBook Project! Our goal is to create the perfect publishing platform for STEM subjects, and get university-level students to write the best free STEM tutorials ever.
Everyone is welcome to create an account and play with the site: ourbigbook.com/go/register. We belive that students themselves can write amazing tutorials, but teachers are welcome too. You can write about anything you want, it doesn't have to be STEM or even educational. Silly test content is very welcome and you won't be penalized in any way. Just keep it legal!
Video 1.
Intro to OurBigBook
. Source.
We have two killer features:
  1. topics: topics group articles by different users with the same title, e.g. here is the topic for the "Fundamental Theorem of Calculus" ourbigbook.com/go/topic/fundamental-theorem-of-calculus
    Articles of different users are sorted by upvote within each article page. This feature is a bit like:
    • a Wikipedia where each user can have their own version of each article
    • a Q&A website like Stack Overflow, where multiple people can give their views on a given topic, and the best ones are sorted by upvote. Except you don't need to wait for someone to ask first, and any topic goes, no matter how narrow or broad
    This feature makes it possible for readers to find better explanations of any topic created by other writers. And it allows writers to create an explanation in a place that readers might actually find it.
    Figure 1.
    Screenshot of the "Derivative" topic page
    . View it live at: ourbigbook.com/go/topic/derivative
    Video 2.
    OurBigBook Web topics demo
    . Source.
  2. local editing: you can store all your personal knowledge base content locally in a plaintext markup format that can be edited locally and published either:
    • to OurBigBook.com to get awesome multi-user features like topics and likes
    • as HTML files to a static website, which you can host yourself for free on many external providers like GitHub Pages, and remain in full control
    This way you can be sure that even if OurBigBook.com were to go down one day (which we have no plans to do as it is quite cheap to host!), your content will still be perfectly readable as a static site.
    Figure 5. . You can also edit articles on the Web editor without installing anything locally.
    Video 3.
    Edit locally and publish demo
    . Source. This shows editing OurBigBook Markup and publishing it using the Visual Studio Code extension.
    Video 4.
    OurBigBook Visual Studio Code extension editing and navigation demo
    . Source.
  3. https://raw.githubusercontent.com/ourbigbook/ourbigbook-media/master/feature/x/hilbert-space-arrow.png
  4. Infinitely deep tables of contents:
    Figure 6.
    Dynamic article tree with infinitely deep table of contents
    .
    Descendant pages can also show up as toplevel e.g.: ourbigbook.com/cirosantilli/chordate-subclade
All our software is open source and hosted at: github.com/ourbigbook/ourbigbook
Further documentation can be found at: docs.ourbigbook.com
Feel free to reach our to us for any help or suggestions: docs.ourbigbook.com/#contact