Limit (mathematics) by Ciro Santilli 37 Updated 2025-07-16
The fundamental concept of calculus!
The reason why the epsilon delta definition is so venerated is that it fits directly into well known methods of the formalization of mathematics, making the notion completely precise.
Fourier series by Ciro Santilli 37 Updated 2025-07-16
Approximates an original function by sines. If the function is "well behaved enough", the approximation is to arbitrary precision.
Fourier's original motivation, and a key application, is solving partial differential equations with the Fourier series.
The Fourier series behaves really nicely in , where it always exists and converges pointwise to the function: Carleson's theorem.
Video 1.
But what is a Fourier series? by 3Blue1Brown (2019)
Source. Amazing 2D visualization of the decomposition of complex functions.
ASCII porn by Ciro Santilli 37 Updated 2025-07-16
Collections and overviews:
You just couldn't resist Googling it and clicking this page, could you? You naughty, naughty bearded programmer nerd. Yes, I'm talking to you.
TODO it is quite hard to actually find non-automatically generated ASCII art of people fucking, most of them are just sexy/horny women drawn by bearded nerds, likely and based on sticky physical paper porn magazines from the 80's, good old days.
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   Tank Man                         |
   by Ciro Santilli          00     |
   2021 CC-BY-SA 4.0          \\  +-|-+
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Code 1.
Tank man ASCII art by Ciro Santilli (2021)
This image depicts the Chinese government fucking 1 million Chinese people in the ass during the Tiananmen Square Protests, which was undoubtedly one of the largest gang bangs of the late 20th century:
Video 1.
The IBM 1401 mainframe runs "Edith" by CuriousMarc
. Source. 1960's punched card ASCII porn. Vintage. EDITH is also mentioned e.g. at: www.threedee.com/jcm/aaa/index.html. No ASCII uploads found however: www.reddit.com/r/programming/comments/a2pser/the_ibm_1401_mainframe_runs_edith/.
Power engineering by Ciro Santilli 37 Updated 2025-07-16
Applications of power, we have to remember it is there to notice how awesome it is!
Popular science by Ciro Santilli 37 Updated 2025-07-16
On one hand, yes, we need knowledge at all levels, and it is fine to start top-to-bottom with an overview.
The problem is, however, that there is a huge knowledge gap between the one liner "this is the truth" and the much more important "this is how we know it, these are the experiments" as mentioned at how to teach and learn physics.
Therefore, if you have that extremely rare knowledge, you should be writing that in addition to the dumbed down version with an open knowledge license. It takes time, but that's what really changes the world.
Ciro Santilli has always felt that there is a huge gap between "the very basic" and "the very advanced", as mentioned at: Section "The missing link between basic and advanced", which existing scientific vulgarization is not doing enough to address. In a sense, filling out this "middle path" is the main goal of OurBigBook.com.
Ciro really enjoyed the description of the "Arindam Kumar Chatterjee" YouTube channel:
Theoretical/mathematical physics at the graduate level and above. This is NOT a popular science channel. Here you find real theoretical physicists doing real theoretical physics. We think it is important for people to get a taste of the real deal, and for aspiring theoretical physicists to see what they are working towards, i.e., to provide the public with something beyond the ubiquitous Michio Kaku and Brian Cox.
One thing must be said however: there seems to be an actual bias against researchers tho try to create vulgarization material: How To Get Tenure at a Major Research University by Sean Carroll (2011), and that is terrible.
There is often more value in a tutorial by a beginner who is trying to fully learn and explain a subject, than by an expert who is trying to "dumb it down" too much.
Video 1.
Pop Science And The Limitations Of Infotainment by Coffee Break (2019)
Source.
You start with a very small list of:
Using those rules, you choose a target string that you want to reach, and then try to reach it. Before the target string is reached, mathematicians call it a "conjecture".
Mathematicians call the list of transformation rules used to reach a string a "proof".
Since every step of the proof is very simple and can be verified by a computer automatically, the entire proof can also be automatically verified by a computer very easily.
Finding proofs however is undoubtedly an uncomputable problem.
Most mathematicians can't code or deal with the real world in general however, so they haven't created the obviously necessary: website front-end for a mathematical formal proof system.
The fact that Mathematics happens to be the best way to describe physics and that humans can use physical intuition heuristics to reach the NP-hard proofs of mathematics is one of the great miracles of the universe.
Once we have mathematics formally modelled, one of the coolest results is Gödel's incompleteness theorems, which states that for any reasonable proof system, there are necessarily theorems that cannot be proven neither true nor false starting from any given set of axioms: those theorems are independent from those axioms. Therefore, there are three possible outcomes for any hypothesis: true, false or independent!
Some famous theorems have even been proven to be independent of some famous axioms. One of the most notable is that the Continuum Hypothesis is independent from Zermelo-Fraenkel set theory! Such independence proofs rely on modelling the proof system inside another proof system, and forcing is one of the main techniques used for this.
Figure 1.
The landscape of modern Mathematics comic by Abstruse Goose
. Source. This comic shows that Mathematics is one of the most diversified areas of useless human knowledge.
Ciro Santilli is actively looking for donations and contracts so he can continue to work full time on OurBigBook.com sustainably, and develop free hardcore university-level STEM education for all ages!
For 300k USD I will quit my job or not get a new job and work on OurBigBook full time for a second year to try and kickstart The Higher Education Revolution. Status: ~44k / 300k USD. At 2M USD I retire and work on open STEM forever.
I first quit my job 1st June 2024 to work on the project for 1 year after I reached my initial 100k goal mostly via a 1000 Monero donation. In this first year I improved project tech, but didn't go and solve university courses to create super targeted content, and didn't obtain a single contributing user except myself, see a summary at Section "OurBigBook Project Update March 2024".
For a followup, it would be an interesting experiment to spend on year full time solving as many courses as I can from a world class university in the city where I live in the UK, and adding that as content to the platform to see if that would attract interest, and reaching out directly to course takers at their university environment to try and help them. I intended to do that in year one but my got distracted by tech. It is quite possible that no one has ever done that before in history: a highly motivated technical person with the time and opportunity to do one single thing: help top university students learn their STEM courses better and have more fun doing so. I have in particular identified one course where this would be particularly feasible: the mathematics course, given that much of their course materials, and also their building are quite open. I do sometimes wonder if doing this would be just a waste of my life. But part of me tells me it could generate big interest and is worth a try.
For a second follow up year, I increased my requirement to 300k USD to give me more peace of mind. So the total donation so far is 244k, and if I reach a total of 300k USD, then I'll work on the project for a second year.
At 2M USD I retire and work on open STEM projects forever. At these timelines, I can't guarantee it will be specifically on education technology specifically all the way, but I guarantee that whatever it is it will be open and extremely well explained as usual.
It's necessary to be slightly underemployed if you are to do something significant - James Watson
Total donations to date ~244k USD. Donation breakdown:
More details: Section "Accounting method"
How to give:
And if you have a different preferred payment mechanism not listed above, please contact Ciro, and he will set it up.
Ciro's current ambitions require him to remain in developed countries, because Ciro wants to document advanced science and technology by liaising with top universities, and there is not nearly as much high technology in poor countries. Remaining in developed countries is also a required due to family reasons.
Note to potential anonymous crypto donors: I live in the UK, and after some messy back and forth that included freezing my account at one point, Barclays finally decided that they do not allow me to receive anonymous donations. And I'm pretty sure that the same would happen on any other British bank sooner or later. Therefore, while I continue to accept anonymous donations, they will not count towards my "if I get X I do Y"-type donation goals, since I can't reliably spend that money. If you want to donate in crypto, and clearly give me your real identity and an explanation of how you got the money, then that is fine, it can count. Just be warned that I will need to give that information to my bank and clear it with them beforehand, and if they are still not happy with it, I'll just give it all back. Your identity does not have to be publicly disclosed, only the dates and amounts. But my bank has to know.
If you would like public acknowledgement for your support, Ciro will very gladly give it, just let Ciro know how you'd prefer it. Due to Ciro Santilli's campaign for freedom of speech in China, many supporters have chosen to be anonymous, and that is totally fine, not everyone is interested in politics, or has a situation where going public is acceptable, so we don't have a standard setup yet, let's build it together. A acknowledgement section at the bottom of this page would be a minimum, but I for larger donations we could add a your advertisement in a locations such as:
100k USD/year is a semi arbitrary amount that sounds nice. My last day job total compensation as of 2024 was about 150k USD/year.
Video 1.
Intro to the OurBigBook Project
. Source.
Video 2.
OpenGL GPU GLSL fragment shader real time v4l2 Linux webcam computer vision box blur vs CPU
. Source.
Figure 1.
Ciro Santilli playing with a pipette at the University of Cambridge circa 2017
. Although totally disqualified for it, Ciro would really like to understand and explain cool scientific experiments in insane detail much as he does with computer software, related:Maybe if he ever gets enough credibility, such opportunities would actually materialize. It could be a bit like Periodic Videos, but for molecular biology and physics, and backed by OurBigBook text/tree with minimal openly licensed videos. The fact that such opportunities are essentially impossible outside of the boredom of the university system is something we should really change about education.
Ciro Santilli is very happy to meet people with related interests, he really loves his like-minded online friends. Even if you don't have something a specific goal in mind for the contact, please just say hi.
To contact Ciro publicly about any general subject that is not covered in a more specific GitHub repository, including saying hi or suggestions about his website either:
Publicly viewable contact is preferred if possible to more effectively share Ciro's wisdom with the world.
But if you feel more comfortable with private contact, no problem, either:
For other less good methods that will also likely work, use direct messages of the following profiles from under Section "Accounts controlled by Ciro Santilli":Ciro's Twitter DMs are also open, but note that Ciro receives endless Chinese language SPAM there which Twitter is doing nothing to combat, so it's not as reliable.
If you are a privacy freak or are going to tell Ciro state secrets Ciro has this GNU Privacy Guard public key: pubkey.gpg, but it's not something that he has ever really used.
Disqus comments were removed from his website in 2019-05-04, a manual dump is available here, removal rationale at: why Ciro Santilli removed Disqus comments from his website in 2019-05-04.
Firstly, in 2012, while he was at École Polytechnique, Ciro Santilli was introduced to LaTeX (thank God for French mathematical obsession), and his mind was blown:
Ha, so I can write my own books, and so can anyone, for free?
he though. Why isn't everyone doing that!
One particular event stood out: Ciro made a small change to his teacher's course material, who blessed be him (dude's a legend, Ciro just noticed he has some Chinese publications with another French dude, e.g. www.amazon.co.uk/高效算法-应试与提高必修128例-克里斯托弗-Christoph-Durr/dp/B078SJQPVK "High-efficiency algorithm competitions 128 examples", did he write it the Chinese himself?? Must be of course to complement the notoriously low French professor salaries), made it available, and then Ciro gave him back the .tex file. Ciro was just a bit worried about how the teacher would be able to tell what he had changed in the file to validate the change. The teacher just said of course, "no problem, I'll just use diff". Ciro had never heard of diff. Let alone Git of course, though yes, this was a bit early in Git's history version control systems had been around since forever of course. This was 2011 or 2012, about 4 or 5 years into a superior education curricula with various courses involving computers, some requiring quite a lot of "fill these empty functions" style programming. Education is a joke. Anyways, this was a prelude to exactly what Ciro wanted to do in OurBigBook.com. This might have been the one actually: webia.lip6.fr/~durrc/Iut/Notes580.pdf
Not long afterwards, Ciro started playing with Linux. Until then, Ciro had had some contacts with the mysterious operating system at university, and was a bit puzzled what the point of it was! He clearly remembers:
University should be forced to use only open source software and hardware in undergrad teaching courses by law BTW.
Then came an Ubuntu live disk on his own machine, and finally a measly 40GB dual book partition in a Microsoft Windows machine on a laptop. At first, it took a lot of time to learn all the crazy new terminal stuff! Yes, at this point, Ubuntu was already usable enough without the terminal, an accomplishment actually. But as a programmer, Ciro felt obliged to learn. Many hours were spent reading man pages at the library. But it all just felt so right, and sometimes powerful... true wizardry.
And ten years later, Ciro was seriously considering buying a computer without Windows pre-installed. He had not used Windows a single tie on a personal machine even once in those ten years!
Finally, to finish things off Ciro found two websites that changed his life forever, and made be believe that there was an alternative: Stack Overflow and GitHub.
The brutal openness of it all. The raw high quality content. Ugliness and uselessness too no doubt. But definitely spark in a sea of darkness.

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