2021-01-28: used this show for the first time after wearing dhb Dorica MTB Shoe (2020-12) exclusively for a while. It felt much much more comfortable, the Dorica is too narrow. Also this one is much more recessed, and walking with it is much easier. Also, I notice that the intentional asymmetry I had put on cleats is not necessary anymore now that my saddle height is not way too high
It is not possible to do long walks with this, unlike some websites suggests, especially on hard surfaces like rock, that would be very dangerous because the cleat area will slip. But it is good for shorter walks on grass/mud, and that does open up some good short walk exploration possibilities compared to a road shoe.
Color "Black/Red 20" (but it's actually orange), size 46 www.wiggle.co.uk/giro-rumble-vr-off-road-shoe (archive). Manual says to use Loctite 243 medium strength, first 2.4 Nm bolt torque to test it out and find good position, and then final bolt torque 5-6 Nm unless cleat says less. Starting with Shimano SM-SH56 cleats (archive), which also says provisional torque 2.5 Nm, tightening torque 5-6 Nm.
BB84 by Ciro Santilli 37 Updated 2025-07-16
Does not require entangled particles, unlike E91 which does.
en.wikipedia.org/w/index.php?title=Quantum_key_distribution&oldid=1079513227#BB84_protocol:_Charles_H._Bennett_and_Gilles_Brassard_(1984) explains it well. Basically:
  • Alice and Bob randomly select a measurement basis of either 90 degrees and 45 degrees for each photon
  • Alice measures each photon. There are two possible results to either measurement basis: parallel or perpendicular, representing values 0 or 1. TODO understand better: weren't the possible results supposed to be pass or non-pass? She writes down the results, and sends the (now collapsed) photons forward to Bob.
  • Bob measures the photons and writes down the results
  • Alice and Bob communicate to one another their randomly chosen measurement bases over the unencrypted classic channel.
    This channel must be authenticated to prevent man-in-the-middle. The only way to do this authentication that makes sense is to use a pre-shared key to create message authentication codes. Using public-key cryptography for a digital signature would be pointless, since the only advantage of QKD is to avoid using public-key cryptography in the first place.
  • they drop all photons for which they picked different basis. The measurements of those which were in the same basis are the key. Because they are in the same basis, their results must always be the same in an ideal system.
  • if there is an eavesdropper on the line, the results of measurements on the same basis can differ.
    Unfortunately, this can also happen due to imperfections in the system.
    Alice and Bob must decide what level of error is above the system's imperfections and implies that an attacker is listening.
Electron microscope by Ciro Santilli 37 Updated 2025-07-16
All of them need a vacuum because you can't shoot elecrons through air, as mentioned at Video "50,000,000x Magnification by AlphaPhoenix (2022)".
Busy beaver scale by Ciro Santilli 37 Updated 2025-07-16
The Busy beaver scale allows us to gauge the difficulty of proving certain (yet unproven!) mathematical conjectures!
To to this, people have reduced certain mathematical problems to deciding the halting problem of a specific Turing machine.
A good example is perhaps the Goldbach's conjecture. We just make a Turing machine that successively checks for each even number of it is a sum of two primes by naively looping down and trying every possible pair. Let the machine halt if the check fails. So this machine halts iff the Goldbach's conjecture is false! See also Conjecture reduction to a halting problem.
Therefore, if we were able to compute , we would be able to prove those conjectures automatically, by letting the machine run up to , and if it hadn't halted by then, we would know that it would never halt.
Of course, in practice, is generally uncomputable, so we will never know it. And furthermore, even if it were computable, it would take a lot longer than the age of the universe to compute any of it, so it would be useless.
However, philosophically speaking at least, the number of states of the equivalent Turing machine gives us a philosophical idea of the complexity of the problem.
The busy beaver scale is likely mostly useless, since we are able to prove that many non-trivial Turing machines do halt, often by reducing problems to simpler known cases. But still, it is cute.
But maybe, just maybe, reduction to Turing machine form could be useful. E.g. The Busy Beaver Challenge and other attempts to solve BB(5) have come up with large number of automated (usually parametrized up to a certain threshold) Turing machine decider programs that automatically determine if certain (often large numbers of) Turing machines run forever.
So it it not impossible that after some reduction to a standard Turing machine form, some conjecture just gets automatically brute-forced by one of the deciders, this is a path to
Sonicator by Ciro Santilli 37 Updated 2025-07-16
These can be used to break cells apart from tissue, and also break up larger DNA or RNA molecules into smaller ones, suitable for sequencing.
As of 2020s and much earlier, Ciro Santilli believes that undergrad studies were fundamentally broken (considering the Information Age which completely changed what would be possible) because university had only two goals, with the exception of a few enlightened professors:
  • rank students from worse to best so they can get into PhD programs.
    For regular jobs grades didn't even matter as much compared the prestige of your university (and therefore, university entry exam grades) and your ability to stand the stress of exams to get minimal passing grade.
    In particular, being able to rank requires setting the difficulty level at a point where you can see a normal distribution in grades, and not have everyone at either 0 nor 100%.
    Also, this split could be caused by either shitty learning materials/conditions, or by mere volume. It doesn't matter.
  • get money from the students. Of course, in countries where university is "free", this means reporting how many students you had to some government office so they can give you a corresponding budget. But you still have an incentive to enroll as many as possible.
As a result, most students, who would not go on to do a PhD essentially do a simple trade: all their time, and possibly some money, in exchange for imbuing themselves with the incredible name of a respected institution so they can get better jobs later on.
Beauty, deep understanding, and learning awesome things comes basically as a second thought.

Pinned article: 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 2.
    You can publish local OurBigBook lightweight markup files to either https://OurBigBook.com or as a static website
    .
    Figure 3.
    Visual Studio Code extension installation
    .
    Figure 4.
    Visual Studio Code extension tree navigation
    .
    Figure 5.
    Web editor
    . 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