TODO clear attribution source:
Some people say, "Give the customers what they want." But that's not my approach. Our job is to figure out what they're going to want before they do. I think Henry Ford once said, "If I'd asked customers what they wanted, they would have told me, 'A faster horse!'" People don't know what they want until you show it to them. That's why I never rely on market research. Our task is to read things that are not yet on the page.
Stimulated emission Updated 2025-07-16
Photon hits excited electron, makes that electron go down, and generates a new identical photon in the process, with the exact same:This is the basis of lasers.
Charging for certification is fine. Creating exams and preventing cheating has a cost.
Another thing that is fine charging for is dedicated 1-to-1 tutor time. This is something Udacity is doing as of 2022.
www.investopedia.com/articles/investing/042815/how-coursera-works-makes-money.asp has a good mention:
MOOCs were first created by people with utopian visions for the internet. This means the idea for platforms like Coursera was likely conceived without a business plan in mind. Nonetheless, Coursera has managed to monetize its platform. It is worth noting, however, that monetization has lead to the effective elimination of the original MOOC idea, which is predicated on ideals like free and open access, as well as the building of online communities.
Coursera users must pay to engage with the material in a meaningful way and take courses for individualistic purposes. This has been a consistent trend among all major online education platforms.
and it links to: www.freecodecamp.org/news/massive-open-online-courses-started-out-completely-free-but-where-are-they-now-1dd1020f59/, very good article!
That is a fundamental guiding principle of OurBigBook.com. The educational content must be licensed CC BY-SA!
Perhaps the most reliable way of reaching this state is E-learning websites must allow students to create learning content.
Bibliography:
Engine Updated 2025-07-16
Enthalpy Updated 2025-07-16
Adds up chemical energy and kinetic energy.
Wikipedia mentions however that the kinetic energy is often negligible, even for gases.
The sum is of interest when thinking about reactions because chemical reactions can change the number of molecules involved, and therefore the pressure.
To predict if a reaction is spontaneous or not, negative enthalpy is not enough, we must also consider entropy via Gibbs free energy.
Ethernet cable Updated 2025-07-16
When non-specialists say "Ethernet cable", they usually mean twisted pair for Ethernet over twisted pair.
But of course, this term is much more generic to a more specialized person, since notably fiber optics are also extensively used in Ethernet over fiber.
Fiat currency Updated 2025-07-16
A useless piece of paper (or digital version of it) that you can pay taxes with :)
As opposed to:
Lie bracket of a matrix Lie group Updated 2025-07-16
This makes it clear how the Lie bracket can be seen as a "measure of non-commutativity"
Because the Lie bracket has to be a bilinear map, all we need to do to specify it uniquely is to specify how it acts on every pair of some basis of the Lie algebra.
Then, together with the Baker-Campbell-Hausdorff formula and the Lie group-Lie algebra correspondence, this forms an exceptionally compact description of a Lie group.
Finite general linear group Updated 2025-07-16
general linear group over a finite field of order . Remember that due to the classification of finite fields, there is one single field for each prime power .
Exactly as over the real numbers, you just put the finite field elements into a matrix, and then take the invertible ones.
Flash memory Updated 2025-07-16
Video 1.
The Engineering Puzzle of Storing Trillions of Bits in your Smartphone / SSD using Quantum Mechanics by Branch Education (2020)
Source. Nice animations show how quantum tunnelling is used to set bits in flash memory.
Four Treasures of the Study Updated 2025-07-16
Video 1.
Four Treasures of Chinese Study by a journey of culture (2022)
Source. Over the top and likely without copyright.
Video 2.
Four Treasures of the Study by Li's Ink World (2021)
Source. A more realistic down to Earth one.

Unlisted articles are being shown, click here to show only listed articles.