High flying bird vs gophers Updated 2025-07-16
Ciro once read that there are two types of mathematicians/scientists (he thinks it was comparing Einstein to some Jack of all trades polymath who didn't do any new discoveries):
  • high flying birds, who know a bit of everything, feel the beauty of each field, but never dig deep in any of them
  • gophers, who dig all the way down, on a single subject, until they either get the Nobel Prize, or work on the wrong problem and waste their lives
TODO long after Ciro forgot where he had read this from originally, someone later pointed him to: www.ams.org/notices/200902/rtx090200212p.pdf Birds and Frogs by Freeman Dyson (2009), which is analogous but about Birds and Frogs. So did Ciro's memory play a trick on him, or is there also a variant; of this metaphor with a gopher?
Ciro is without a doubt the bird type. Perhaps the ultimate scientist is the one who can combine both aspects in the right amount?
Ciro gets bored of things very quickly.
Once he understands the general principles, if the thing is not the next big thing, Ciro considers himself satisfied without all the nitty gritty detail, and moves on to the next attempt.
In the field of mathematics for example, Ciro is generally content with understanding cool theorem statements. More generally, one of Ciro's desires is for example to understand the significance of each physics Nobel Prize.
This is also very clear for example after Ciro achieved Linux Kernel Module Cheat: he now had the perfect setup to learn all the Linux kernel shady details but at the same time after all those years he finally felt that "he could do it, so that was enough", and soon moved to other projects.
If Ciro had become a scientist, he would write the best review papers ever, just like in the current reality he writes amazing programming tutorials on Stack Overflow.
Ciro has in his mind an overly large list of subjects that "he feels he should know the basics of", and whenever he finds something in one of those topics that he does not know enough about, he uncontrollably learns it, even if it is not the most urgent thing to be done. Or at least he puts a mention on his "list of sources" about the subject. Maybe everyone is like that. But Ciro feels that he feels this urge particularly strongly. Correspondingly, if a subject is not in that list, Ciro ignores it without thinking twice.
Ciro believes that high flying birds are the type of people better suited for venture capital investment management: you know a bit of what is hot on several fields to enough depth to decide where to place your bets and how to guide them. But you don't have the patience to actually go deeply into any one of them and deal with each individual shit that comes up.
Cosmos: A Personal Voyage (1980) episode 1 mentions as quoted by the Wikipedia page for Eratosthenes:
According to an entry in the Suda (a 10th-century encyclopedia), his critics scorned him, calling him beta (the second letter of the Greek alphabet) because he always came in second in all his endeavors.
That's Ciro.
Searching by th epart name "GF03FC" leads to other sellers besides Elica however, which could reduce shipping costs: www.cookerhoodsupplies.co.uk/filters-and-lamps/188-metal-grease-filter-gf03fc.html
Brand on extractor glass: Elica: elica.com
Dimensions: 45.9cm x 17.6cm on the exterior. Too long to fit into any container that we have.
Brand on filter itself: "ARMA Filtre a.s." based on markings: www.armafiltre.com.tr/uygulamalar/7/3/en/Home-Appliances.html Cannot find any model on website however... looks like Elica's B2B supplier only.
Marker inside after removing filter: 12NC: 208298104403 Model: CIAK GR/A/56.
2018: noticed that it was unbearably greasy, tried to clean, but even boiling water didn't help.
July 2019 message:
Aluminium extractor filter for 208298104403
Hi there,
I'm trying to buy a spare aluminium extractor filter for an Elica extractor, but I can't find the right size on the website.
My 12NC is : 208298104403
My filter looks a lot like this: shop.elica.com/en/accessori/filtro-grassi-in-alluminio-cod-GRI0077330A.html but the dimensions are different: I measured 45.9cm x 17.6cm on my old one.
Do you have that for sale?
Kitchen: 2021-04: nine-volt battery battery at 8.79V. Not sounding.
Maxwell's equations Updated 2025-07-16
Unified all previous electro-magnetism theories into one equation.
Explains the propagation of light as a wave, and matches the previously known relationship between the speed of light and electromagnetic constants.
The equations are a limit case of the more complete quantum electrodynamics, and unlike that more general theory account for the quantization of photon.
The system consists of 6 unknown functions that map 4 variables: time t and the x, y and z positions in space, to a real number:
  • , , : directions of the electric field
  • , , : directions of the magnetic field
and two known input functions:
  • : density of charges in space
  • : current vector in space. This represents the strength of moving charges in space.
Due to the conservation of charge however, those input functions have the following restriction:
Equation 1.
Charge conservation
.
Also consider the following cases:
  • if a spherical charge is moving, then this of course means that is changing with time, and at the same time that a current exists
  • in an ideal infinite cylindrical wire however, we can have constant in the wire, but there can still be a current because those charges are moving
    Such infinite cylindrical wire is of course an ideal case, but one which is a good approximation to the huge number of electrons that travel in a actual wire.
The goal of finding and is that those fields allow us to determine the force that gets applied to a charge via the Equation "Lorentz force", and then to find the force we just need to integrate over the entire body.
Finally, now that we have defined all terms involved in the Maxwell equations, let's see the equations:
Equation 2.
Gauss' law
.
Equation 3.
Gauss's law for magnetism
.
Equation 4.
Faraday's law
.
Equation 5.
Ampere's circuital law
.
You should also review the intuitive interpretation of divergence and curl.
Reference mark Updated 2025-07-16
Ciro Santilli had to see this in a few separate places, until he underestood: that little pictur emust be a thing! Examples:
2020-12: buying Miele SF AP 50 AirClean Plus filter www.miele.co.uk/e/airclean-plus-filter-sf-ap-50-10107860-p. Once it arrived, changed the filter, which fit comes with plastic casing and accordion shaped filter. Also changed bag. But the bag full meter still goes to red on carpet even with everything new while vacuuming. Is it supposed to be checked while not vacuuming?
Takes two AAA rechargeable batteries.
2021-08: rechargeable battery charges were in, nominal marked 1.2V nickel metal hydride, measured as 1.38V and 1.42V.
Reflections of the Moon on Erquan Updated 2025-07-16
Composed by Abing in 1949[ref]
Video 1.
Reflections of the Moon on Erquan with erhu solo performed Song Fei
. Source.
Although quotients look a bit real number division, there are some important differences with the "group analog of multiplication" of direct product of groups.
If a group is isomorphic to the direct product of groups, we can take a quotient of the product to retrieve one of the groups, which is somewhat analogous to division: math.stackexchange.com/questions/723707/how-is-the-quotient-group-related-to-the-direct-product-group
The "converse" is not always true however: a group does not need to be isomorphic to the product of one of its normal subgroups and the associated quotient group. The wiki page provides an example:
Given G and a normal subgroup N, then G is a group extension of G/N by N. One could ask whether this extension is trivial or split; in other words, one could ask whether G is a direct product or semidirect product of N and G/N. This is a special case of the extension problem. An example where the extension is not split is as follows: Let , and which is isomorphic to Z2. Then G/N is also isomorphic to Z2. But Z2 has only the trivial automorphism, so the only semi-direct product of N and G/N is the direct product. Since Z4 is different from Z2 × Z2, we conclude that G is not a semi-direct product of N and G/N.
TODO find a less minimal but possibly more important example.
I think this might be equivalent to why the group extension problem is hard. If this relation were true, then taking the direct product would be the only way to make larger groups from normal subgroups/quotients. But it's not.
Made four blisters on back of foot on first two days after walking a few hours on them, but then put on some tape on foot, and stopped hurting after that, so the shoe broke quickly.
Meal deal Updated 2025-07-16
x.com/Birdyword/status/1777591446612193667
A while ago a Singaporean taxi driver asked me what a UK hawker centre lunch might cost. I explained that there aren't any. He asked what office workers ate, and I explained the concept of Meal deals. And he looked at me with such a powerful combination of pity and revulsion.
Singaporean taxi drivers are the cutest.
Measure theory Updated 2025-07-16
Main motivation: Lebesgue integral.
The key idea, is that we can't define a measure for the power set of R. Rather, we must select a large measurable subset, and the Borel sigma algebra is a good choice that matches intuitions.

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