Pleistocene by Ciro Santilli 35 Updated +Created
Agriculture is not the official definition of the age. But it is good enough. Likely related to the official end of glaciations thing.
Poincaré conjecture by Ciro Santilli 35 Updated +Created
Poincaré group by Ciro Santilli 35 Updated +Created
In simple and concrete terms. Suppose you observe N particles following different trajectories in Spacetime.
There are two observers traveling at constant speed relative to each other, and so they see different trajectories for those particles:
Note that the first two types of transformation are exactly the non-relativistic Galilean transformations.
The Poincare group is the set of all matrices such that such a relationship like this exists between two frames of reference.
Point-contact transistor by Ciro Santilli 35 Updated +Created
The first working one in 1947 by John Bardeen and walter Brattain in Bell Labs Murray Hill.
People had already patented a lot of stuff before without being able to make them work. Nonsense.
As the name suggests, this is not very sturdy, and was quickly replaced by bipolar junction transistor.
Point groups in three dimensions by Ciro Santilli 35 Updated +Created
Bacterial cell structure by Ciro Santilli 35 Updated +Created
Pokemon Mania by Ciro Santilli 35 Updated +Created
Video 1.
Pokemania Comes to America by ABC News (1999)
Source. Ciro Santilli was a part of it! Especially during Ciro Santilli's 10 month stay in Coventry, United Kingdom, in the year 2000!
.
Polarization of light by Ciro Santilli 35 Updated +Created
This section discusses the pre-photon understanding of the polarization of light. For the photon one see: photon polarization.
People were a bit confused when experiments started to show that light might be polarized. How could a wave that propages through a 3D homgenous material like luminiferous aether have polarization?? Light would presumably be understood to be analogous to a sound wave in 3D medium, which cannot have polarization. This was before Maxwell's equations, in the early 19th century, so there was no way to know.
Politics of France by Ciro Santilli 35 Updated +Created
Cell biology (field) by Ciro Santilli 35 Updated +Created
The science that studies cell.
Politics of the United States by Ciro Santilli 35 Updated +Created
Polonium by Ciro Santilli 35 Updated +Created
Discovered by Marie Curie, published July 1999.
Polymorphism (computer science) by Ciro Santilli 35 Updated +Created
Polymorphism (materials science) by Ciro Santilli 35 Updated +Created
TODO definition. Appears to be isomers
Example:
Polynomial over a field by Ciro Santilli 35 Updated +Created
By default, we think of polynomials over the real numbers or complex numbers.
However, a polynomial can be defined over any other field just as well, the most notable example being that of a polynomial over a finite field.
For example, given the finite field of order 9, and with elements , we can denote polynomials over that ring as
where is the variable name.
For example, one such polynomial could be:
and another one:
Note how all the coefficients are members of the finite field we chose.
Given this, we could evaluate the polynomial for any element of the field, e.g.:
and so on.
We can also add polynomials as usual over the field:
and multiplication works analogously.
Porn meme by Ciro Santilli 35 Updated +Created
Positive definite matrix by Ciro Santilli 35 Updated +Created
The dot product is a positive definite matrix, and so we see that those will have an important link to familiar geometry.

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!
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
  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:
    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.
  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