Education – Page 7 – Hi, I'm Rauf Aliev.

Childhood Curiosity and the Mysteries of Soviet Electrical Engineering | September 23 2025, 17:00

I remember being puzzled as a child by who the idiot was that decided to make the radio plug exactly the same as the one for 220 volts. This radio plug was supposed to go into a radio socket.

As a child, I used to disassemble and “improve” almost everything electrical in the house (I hadn’t graduated to electronics yet). Of course, I got shocked many times by the outlet, but to my surprise, the old Soviet phone could also give a shock. When a call came in, the voltage in the line would jump from 12-60 volts to 120 volts 🙂

I also had an interesting experience with Christmas lights. For a younger schoolchild, it was unclear why Christmas lights could shock you since they used the same bulbs that I connected to a flat “Planeta” battery. I had to learn the technicalities 🙂 By the way, those square flat batteries have disappeared; they used to be everywhere.

Inside the High-Tech World of USB-C Cables: More Than Just Wires | September 22 2025, 22:50

It turns out USB-C cables are sometimes whole computers inside the odd form factor of a wire. Watching a video where guys from Adam Savage’s dissected an Apple Thunderbolt 4 cable ($130) using a CT scanner, explaining its internals, and comparing it to a similar cable for $12.

The cable connector contains a complex system that includes a full-fledged processor, two power supplies, and many other components. The processor splits data into multiple parallel streams and converts them into differential signals that travel through twisted, intertwined pairs of wires. The system sends two signals simultaneously, but in mirror-opposite directions. This helps protect the signal from interference (from vacuum cleaners, mobile phones, etc.). Indeed, the circuit board inside is nine-layered.

On the internal circuit board, there are interesting serpentine/wavy tracks with sizes in fractions of a millimeter. It turns out, Apple engineers intentionally made them longer to match the overall length with the neighboring longer tracks (because they include turns). This is necessary for the signals to reach the processor absolutely simultaneously, down to the nanosecond.

The cable itself inside is made up of many individually shielded smaller coaxial cables. There are more than a dozen of them.

The cheap cable lacks this smart electronics, no active components inside. It just has connectors and wires.

But the coolest thing – the guys post such scans in the video description as a link to a viewing program. There you can rotate and examine everything on your own. I’ll put it in the comments

From Opera to Oblivion: The Fascinating Journey of Lorenzo Da Ponte | September 22 2025, 18:53

We just finished watching Le Nozze di Figaro with Nadezhda in a serialized mode and today we’ll continue with Don Giovanni, also in a serialized mode, because no one has the time. So, both of these operas were written by an American 🙂 I mean the librettos. Turns out, Lorenzo Da Ponte, an Italian librettist, emigrated, naturalized in the U.S., lived here 33 years, taught Italian literature at Columbia University in New York, founded an opera theater in the USA, which became the precursor to the New York Academy of Music and the New York Metropolitan Opera. Really an interesting dude. His real name was Emanuel Conegliano. A Jew by birth, who became a Catholic priest, a friend of Casanova, and a supporter of Rousseau’s ideas. Before moving to the U.S., Da Ponte successfully juggled teaching and a small business, earning not so much from lectures as from owning a brothel for aristocrats which he maintained. In the U.S., he kept a grocery store in New Jersey and tried selling medicines in Pennsylvania. Lorenzo Da Ponte died on August 17, 1838, in humiliating poverty, a few blocks away from the boarded-up building of his theater. His grave in one of the New York cemeteries, which was not marked, eventually got lost. Essentially, the same post-mortem fate befell his friend Mozart.

Solar Simplicity: How Turkey’s Homes Heat Water with the Sun | September 11 2025, 06:44

I constantly see such panels on almost every house in Turkey. Of course, my first thought was that these were solar photovoltaic panels for generating electricity. But the second thought — they are expensive, there shouldn’t be so many of them, plus typically just two panels on a roof seems too few. I started googling.

It turned out, these are solar water heaters, more precisely, flat-plate solar collectors. The system is simple, reliable, and inexpensive — that’s why they are installed on every other house.

The principle of operation: the panels consist of an absorber (usually copper or aluminum plates with a black coating), a transparent cover (low-iron glass for greenhouse effect), and thermal insulation (glass wool or stone wool). A heat-carrying fluid circulates in the tubes — either water or antifreeze (glycol).

Solar rays heat the absorber up to 60-90°C, the heat transfers to the fluid, which by the principle of thermosiphon (natural convection, without a pump) rises to the tank, which is usually nearby. The tank is a thermos of 100-300 liters, with insulation, so the water stays hot for 2-3 days.

This too was a surprise. I actually thought the tanks were just metal and heated up in the sun by themselves. That’s how it was in Baku. It turns out, no, and so they are white here, not black.

In Turkey, with over 2000+ hours of sunshine a year, such a system covers 70-90% of the hot water needs for a home. The efficiency of the collector is 40-60% (depending on the model and angle of installation, optimally 30-45° to the horizon for the latitude of Antalya). For a family, this costs from 500-1500 euros, with a payback period of 3-5 years due to savings on gas/electricity. Electricity is expensive in Turkey. Plus, government subsidies and tax incentives encourage installation.

Probably, there are also electric panels, but I haven’t seen them yet.

Debunking Kelvin: The Dynamics of Wake Angles at Different Speeds | September 10 2025, 12:03

I look from the boat at the water and wonder whether the divergence angle of the waves depends on speed or not? Started Googling. Turns out, according to Kelvin, it’s constant at any speed, and amounts to 39 degrees (or 19.47 =arcsin(1/3) from the axis). But then I found a paper where the authors studied satellite images and disproved Kelvin, stating that with increasing speed, the wedge indeed narrows slightly (“Ship wakes: Kelvin or Mach angle?”, authors: Marc Rabaud and Frédéric Moisy)

Exploring Airport Security: How Baggage Scanners Work | September 02 2025, 20:29

The day after tomorrow, I am flying to Amsterdam (and then to Turkey), and I remembered that I had an unanswered question to myself about how baggage scanners work at the airport. Of course, I knew that it was essentially computer tomography, X-rays and all that, but I wanted more details. And below is the response as to why they ask you to take out water, and why sometimes they do not.

It turns out that modern scanners can not only see the shape of objects but also determine what material they are made of. How does a regular scanner work? Dense materials (such as metal) absorb a lot of radiation and appear bright or opaque in images. Less dense materials absorb little radiation and appear dark. Hence laptops, for example, had to be taken out — not because the scanner couldn’t recognize them, but because their dense components (battery, boards) could be used to hide other prohibited items behind them. So, it has long been not just scanners, but computer tomography — in essence, the bag or suitcase is scanned from all sides, then a 3D image is created. It seems like everyone knows this.

But I mentioned that they understand the materials items are made from. How?

It turns out that the scanner uses dual-energy X-ray technology. It scans the object with two beams of rays of different energy levels (high and low). Since materials absorb radiation differently depending on the energy of the ray and their atomic composition, the system analyzes this difference. Based on the absorption ratio of the two beams, the effective atomic number Z — a key characteristic, a kind of “elemental fingerprint” of the substance, is calculated.

The problem is that this “fingerprint” of water (~7.4) and many explosives are almost identical. This is precisely why water was banned. Relying only on this parameter would mean receiving a huge number of false alarms.

Here is where computer tomography (CT) comes into play. The scanner creates an accurate three-dimensional (3D) model of the contents of the bag. From the 3D model, the system obtains the exact volume (V) of each object. Based on data on the absorption of X-rays, its mass (m) is calculated. Then it’s simple: ρ=m/V.

That is, the system does not make a decision based on one parameter. It plots each detected substance on a two-dimensional graph with axes “Z — density.” On this graph, water and explosives, having almost the same atomic number, occupy completely different positions due to different densities.

And that’s precisely why water can sometimes be carried through. Smart machines simply do not mark it as something significant, but still identify it as water. Then procedures follow. If the airport has updated the machines, but not the procedures, they will ask to dispose of the water. But also, not all machines are updated everywhere, and at the same airport, it depends on which line is open at the moment.

The cost of such a scanner is $300-400 thousand.

The scanners for people work differently. They use millimeter waves. They pass through clothing and reflect back from the skin. Water absorbs them significantly, so they penetrate only a couple of millimeters. The system registers the reflected signal and constructs a three-dimensional map of the body surface and objects under the clothing. But it does not show this — instead, it displays a simplified contour of a person and shows on it what ML found unusual. Therefore, by the way, many try to carry various items inside themselves, knowing that such a scanner absolutely cannot see it.

Cracking Codes: Interactive Adventures at the Spy Museum | September 01 2025, 18:15

In the spy museum yesterday, one of the devastatingly informative terminals, where you had to crack the code, allowed you to hack into it too

Beijing Parade Marks 80 Years Since China’s WWII Victory | August 31 2025, 14:02

On September 3rd in Beijing, a military parade dedicated to the 80th anniversary of China’s victory in World War II will take place. Apparently, I did not pay enough attention during history lessons at school: it turns out that China’s losses during WWII were almost comparable to those of the USSR, considering the official figures (in both cases, they are significantly lower than the actual ones). However, there is a catch – the war between China and Japan began in 1937, and later merged with World War II when Japan attacked the USA and its allies in 1941, officially making China part of the anti-Hitler coalition. Germany in 1937 was just preparing: a year later, in 1938, the Anschluss of Austria began, and another year later (1939) – the invasion of Poland, and at the same time the USSR attacked Finland.

Meanwhile, in Germany, it is considered that the precision of German accounting was incomparably higher, and the cumulative losses of the aggressors, together with Japan, turned out to be four times less than the cumulative losses of the defenders.

The figure of China’s losses mainly consists of civilian population. Their military losses were 3-4 million, while 12-17 million suffered from bombings, punitive actions, diseases (remembering Japanese Unit 731 and biological warfare) and other war consequences.

—–

Below I quote my post from January 25th of this year – just relevant and timely:

Who won the Second World War? Interestingly, note that no one paid attention to Trump’s words about the Second World War in his recent tweet-ultimatum.

He writes “Russia helped us win the Second World War” — everyone noted the incorrect figure of 60 million losses, but somehow not this.

I found an interesting study from 2017. It was a survey (1,338 people) from 11 countries including 8 allied countries and 3 Axis countries.

It showed significant differences in how the former Soviet Union and 10 other countries remember the war.

Events marked by representatives of the Soviet Union were almost completely different from those mentioned in other countries. Besides, Russians stated a greater responsibility for the victory in the war (75% of military efforts), than representatives of any other nation (although the USA and Great Britain also estimated their contribution as more than 50%).

However, when people from each country assessed the contribution of other countries to the war, they attributed a greater role to the USA than to the former Soviet Union.

An interesting finding is that, when asked why the USA dropped atomic bombs on Japan, most people from ten countries responded that it was to win the war, except for Russians.

Moreover, the older the respondents were in 7 of these countries, the more often they agreed with the statement that the USA dropped the bombs to end the war.

Russia (USSR) in the survey results demonstrates a unique narrative centered on the Eastern Front, unlike Western countries.

Most countries (including former Axis countries) focus on events related to the USA and Great Britain, such as Pearl Harbor, the Normandy landing, the atomic bombings of Japan, and the Holocaust.

USSR holds a central place in the Russian narrative (75% contribution to victory). The USA and Great Britain also overestimate their evaluations, stating their contribution exceeds 50%, focusing on the Western Front and the Pacific Campaign. The total estimates of the contribution of the eight allied countries amount to 309%, showing the effect of “national narcissism”. Most countries prioritize the USA (27%), while the USSR — 20%.

Four events gained the status of “key” (mentioned by more than 50% of respondents): the attack on Pearl Harbor, the atomic bombings of Japan, the Normandy landing, and the Holocaust. The Russian narrative concentrates on events termed in Soviet and contemporary Russian historiography as the Great Patriotic War (1941–1945). Russians highlighted unique events: battles near Stalingrad, Kursk, Moscow, Berlin, and the blockade of Leningrad. Thus, although the USA and Russia fought together as allies, research shows that there is almost no overlap in which events are remembered as most important. Members of each group mainly remembered those events related to their own country. However, this is not surprising.

On the subject of atomic bombings, most respondents believe that the purpose of the bombings was to end the war. Russians see this event as an act of intimidating the USSR. Opinions within countries vary by age: older generations are more likely to support the official version of ending the war.

In France in 1945, 57% of the population considered the USSR the main victor. By 2004, this figure had dropped to 20%, while the share of the USA increased to 58%.

The reasons are clear: history textbooks and popular culture reinforce national emphasis. In the USA and Great Britain, films and books praising their role in the war predominate. The USSR and the USA fought on different fronts and represent different ideological systems, which determined the narratives. And of course, all countries overstate their role in historical events.

Exploring the Boundless Spectrum: The World of Animal Hearing | August 29 2025, 17:56

From my notes as I read Ed Yong’s Immense World—

“..It is known that the range of audible frequencies for animals is different from that of humans, but I didn’t realize just how different. Imagine the highest pitch in the world—it would be just under 20 kHz, as it’s considered the upper limit of the audible range. Both the upper and lower limits tend to decrease with age. Most adults can’t hear sounds over 16 kHz. Anything above 20 kHz we call ultrasound.

So, it turns out that our closest relatives, chimpanzees, can hear up to 30 kHz, dogs up to 45 kHz, cats up to 85 kHz, mice up to 100 kHz, and moths even up to 300 kHz. Imagine, there are so many high-frequency sounds around us, and how rich their sound world is compared to our limited one. It would be interesting to wear headphones that compress the range from 20-40000 Hz to 20-15000 Hz. Many animals, such as mice, actively use ultrasound for internal communication, beyond the hearing range of their predators.

And when the topic of ultrasound comes up, it’s impossible not to mention bats with their echolocation. Turns out, it’s a wildly interesting topic.”

Probably everyone knows that bats successfully hunt in caves, where no light penetrates at all, and they don’t crash into stalactites and stalagmites. There’s an English saying, blind as a bat, but actually, they can see. Some species see better, others worse. But let’s talk about echolocation.

In general, it’s just radar. The bat screams, the sound bounces off a tree, comes back into its ears, and it gets information about how far away the tree is and whether to slow down or not. But the devil, as they say, is in the details. “Engineering” ones.

Firstly, high-frequency sound attenuates quickly, so you need to shout very loudly for something to bounce back from a few meters away. Beyond that, bats simply don’t “see.” So, they do indeed shout very loudly, and it’s a directed scream. Specifically, they measured 138 decibels, the sound level of a jet engine if you stand next to it. But in the ultrasonic range.

Secondly, when they scream so loudly, they need to plug their own ears so as not to kill their sensitive apparatus. It turned out that they have special muscles that block the inner ear during the scream.

Thirdly, both they and their prey are on the move, very fast and erratic. Meanwhile, the speed of sound is about 343 meters per second. The bat’s brain must calculate the difference between the signal and the echo, taking into account both its own movement through space and the movement of the prey. It turned out that the bat’s vocal muscles can contract up to 200 times a second. Moreover, the frequency depends on the phase of the hunt. 200 times—that’s the final phase, when the moth is right in front of the nose, and tiny movements need to be tracked.

Fourthly, the bat’s brain also has to cope with creating interference between what was shouted out two moments ago and what was shouted out a moment ago. Considering that the sound can echo off the far wall and the near branch. Plus there are waves from the cries of other bats, and they’re usually very numerous in caves. To manage this, they seem to throw a bit different modulation, plus this musculature allows them to “fire” very short pulses—a few milliseconds—and to renew pulses at their own frequency through very short intervals. Imagine what kind of computer in their brains performs the inverse Fourier transform.”

So, all this works pretty well in small groups. But for example, the Brazilian free-tailed bats live in groups of millions. Really, together 20 million mouths shout something and wait for their echo from the walls and each other. You can’t just pick modulation and frequencies that easily, but somehow they manage. Not perfectly, and if they gather in a really big bunch in the cave, then they perform their commute to the hunt and back to the cave “by memory” – probably due to issues with echolocation. When a “door” was placed at the entrance to the cave, a bunch of bats crashed into it.

Fifth, consider how they determine distance. It’s necessary to calculate the difference between the signal sent and the signal received (amid a bunch of noise from other bats), and for hunting, it needs to be calculated very precisely. And sound of course isn’t light, but 343 meters per second is also a lot. So studies have shown that bats can recognize differences as little as 1-2 millionths of a second, which allows them to determine distance to fractions of a millimeter. In other words, our eyes are significantly less accurate than their ears.

Plus, a moth is actually a fairly complex 3D creation that reflects sound differently with its different parts. Otherwise, bats would eat everything that moves. They recognize. In complete darkness. A mouse’s scream contains a whole palette of frequencies, which reflect differently off parts of a moth, and the mouse’s brain somehow manages to translate this into a coherent picture. Moreover, for each of the constituent frequencies, the delay will be its own.

Then, all this information is layered over time. Roughly speaking, a snapshot from one point is combined with a snapshot from a point a half meter to the right, then from a point half a meter forward, and so on many, many times, which enhances “sharpness” and detail. Overall, it’s the same with us – we only see the spot in front of us clearly while the rest is constructed by the brain. But the brain of a bat weighs 1-2 grams against our half kilogram.

Think about it, you’re flying with such a built-in radar, and in front of you are two branches at the same distance, which produce essentially the same echo for their ears. And to distinguish them and understand that it’s not one object but two, you really need an advanced brain.

So, they send pulses lasting 1-20 ms, plus longer pauses between pulses. The pulses are complex in terms of frequencies, so such bats are called frequency modulation (FM) bats. But there are about 160 species that have a much longer cry—many tens of milliseconds but with short pauses, and instead of a complex gamma of frequencies, these use a pure “note.” These bats are called CF—constant frequency. So here’s the thing with these bats—there’s a problem with the Doppler effect, which is an increase in frequency as the distance decreases. Since their brain is tuned to a strict frequency, like 87 kHz for example, they might lose their prey if the echo that reaches their ears is shifted in frequency. And what they do—they shout at a sound speed lower, so that after the Doppler effect it arrives at the correct frequency for the brain.”

Incidentally, their radar has two modes—forward and downward, the echoes from which are processed separately. The downward radar provides information about position in space, and the forward radar—about the position in space of the prey.

When I researched the subject, I found that yes, after 20 kHz humans hear nothing, with one exception—frequencies of 2.4 GHz and 10 GHz, which actually belong to the microwave range. Yes, humans can “hear” these frequencies, but not with the ear, but “hear.” This phenomenon is called the microwave auditory effect or the Frey effect. Initially, this effect was registered by people working near radars during World War II, and the sounds they perceived were not heard by others. It turned out that when pulsed or modulated microwave radiation was applied to areas around the cochlea, it was absorbed by the tissues of the inner ear, accompanied by their thermal expansion. In the course of this process, shockwaves are produced, perceived by humans as sound, which no one else hears. It was also discovered that with the appropriate choice of the modulating signal, it is possible to transmit information to a person in the form of individual words, phrases, and other sounds. Depending on the radiation parameters, the sound created in the head can be irritating, cause nausea, and even disable. The volume of the perceived sound can be changed, but acoustic trauma is not possible, as the eardrum does not participate in the process at all. Generally speaking, the method of specifically transmitting sonic messages that are absolutely inaudible to others opens up a whole bouquet of possibilities. I wonder if research is still being conducted on this topic. Google shows that they used to be pretty intense.”

I once published this along with a video, and Facebook reckons that if you publish a video, the text should be one, at most two lines. And in the end, almost no one saw this text. Everyone just watched the video of a bat flying around my apartment 🙂

Exploring a Conditional Investment-Based U.S. Visa Program | August 21 2025, 21:23

I wonder if a U.S. visa program would work where specially authorized American investing organizations collectively invest, say, $500,000 in each candidate who files a petition and is ready to pay a hypothetical $20-50K. The money goes to the government, but it returns it monthly with interest. Then, he moves to the U.S., gets a job, and pays back the “investors” from legally earned money, like a student loan. “Investors” help him find a job. If he loses his job, and can’t find another, he can pay from savings for some time, but afterward — he must return home. No savings — go back home. Violated the law (criminal) — go back home. But each such negative case affects whether the “investor” will have the opportunity to invest in new ones.

Investors help with job finding if needed, but there’s no coercion or serfdom, because it doesn’t matter what kind of job the person has, as long as it’s legitimate, and the debt is deducted from the salary. Until the debt is paid, a person’s profile affects the “investor’s” performance indicators, and in case of poor indicators, the investor loses their license or priority.

It’s assumed that, given existing quotas, the “investor” has an interest in finding the smartest and most hardworking people worldwide and subsequently placing them in the local market. If they perform poorly, they simply can’t operate.

After full repayment, he gets the right to citizenship. This could attract talented individuals, support the economy, and ensure responsibility. What do you think?