Tag: science

Hyperinflation Memories: Collecting Zimbabwe’s Trillion Dollar Notes on Etsy and eBay | September 27 2025, 21:20

On Etsy, you can buy five billion Zimbabwean dollars for a billion times less (minus one cent)

And a 50 trillion note can be bought for 30 dollars (minus two cents)

And there is also a 100 trillion note

Crafting the Future of Recommender Systems: A Deep Dive into Algorithms and Implementation | September 26 2025, 21:17

I decided a while ago to write a book on recommendation algorithms. With mathematics, code examples, a repository, etc. English, of course.

Accordingly, I am looking for volunteer reviewers who are knowledgeable in the field. Also those who have experience with print-on-demand on Amazon.

There’s already about 200 pages of content. About three months of work left. Working title Recommender Algorithms in 2026: A Practitioner’s Guide. Roughly half of it is still in draft form, with the first 80 pages about 80% complete.

I’ve built a mechanism to publish in HTML and PDF simultaneously. The HTML version is fully functional, with navigation. The navigation block reflects the current section, and as you scroll, it shifts to the one in front of the reader. Clicking on a section, of course, teleports you to what you clicked on. It’s all completely automatic.

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

Living in the Valley of Data Centers: The NSA’s Gigantic Utah Facility | September 20 2025, 20:06

I live right in the valley of data centers, like 80% of internet traffic goes through us (a dangerous place!). I drove by one of them today, and later at home, while Googling stuff about data centers, stumbled upon the NSA’s data center in Bluffdale, Utah.

It serves as a data repository for the U.S. intelligence community. Capacity — something like 5 trillion terabytes. 5,000,000,000,000,000 gigabytes. Back in 2013, it was 100-1000 times less, but 12 years have passed, Moore’s Law and all that. Hard drives in data centers usually have a lifespan of 3-5 years. Meaning, since the launch of the data center, they have all been replaced several times with obviously greater capacity.

It is expected that the data center will be able to process “all types of communications, including the full content of private emails, mobile phone conversations, internet browsing, as well as all types of personal data: parking receipts, travel itineraries, purchases in bookstores, and data of other transactions made using digital technologies.”

The amount of data this facility is able to store is, of course, classified, but estimates “several yottabytes”. Yottabyte = 1000 zettabytes = 1,000,000 exabytes = 1 trillion terabytes. To store all the books ever written in any language would require just 400 terabytes.

In 2013 it consumed no less than 65 MW with a potential of 100 MW. Water — ~1.5–1.7 million gallons (5.7–6.4 million liters) per day for cooling servers. The water is treated with chemicals (to prevent corrosion) and discharged, leading to criticism in arid Utah — especially amid the record heat from 2022–2025 and the shortage of fresh water. There’s no closed-loop system, and it remains a “hot” topic in local discussions.

The Maunder Minimum’s Impact on Stradivari’s Unique Violins | September 18 2025, 21:20

I stumbled upon an interesting scientific hypothesis from 2003 regarding why Stradivari violins (and those of his contemporaries) are so unique. Traditional hypotheses—about the secrets of the varnish or the aging of the wood—prove insufficient. According to this hypothesis, the entire blame lies with the Maunder Minimum, a period of reduced solar activity occurring from 1645–1715, during which the tree growth rate slowed down due to the climate, meaning the wood was denser. The hypothesis suggests that amidst the perfect combination of altitude, humidity, and temperature, this environmental shift provided material with unique properties, ideal for resonant soundboards.

Stradivari was born a year before the Maunder Minimum began. His “Amati Period” (1666–1690), “Experimentation Period” (1690–1700), and “Golden Period” (1700–1720), during which he perfected and produced his best instruments (see Henley 1961), all coincided with the Maunder Minimum. Cremona’s craftsmen during this period used the only wood available to them, i.e., from trees growing during the Maunder Minimum. Neither before nor after this period was such wood available. And, probably, it is nowhere to be found in the world even now.

But really, modern violins are also quite something. Two-three hundred years ago, musicians extracted the maximum from an instrument through trial and error, whereas now it is done through meticulous calculation of sound. It is almost impossible to differentiate violins by their sound anymore, and the difference lies in the realm of individual preferences, rather than an undisputed objective worse-better.

Seeing Shapes and Shadows: How Portrait Drawing Changes Our View of Faces | September 12 2025, 15:44

It’s interesting that even a little experience in drawing portraits makes one see patterns in other people’s faces that you wouldn’t think about otherwise. For example, you look at someone’s face, and some points on the face converge into an equilateral triangle. Or the shadow from the sun forms a notable pattern. Or some lines are strictly parallel or perpendicular. And at that moment, you feel like grabbing a pencil and trying to sketch it. At this point, it seems that achieving a likeness is a piece of cake.

Or you notice that a silvery dress is the darkest thing in the picture and probably needs to be depicted almost in black. With highlights, of course. This contradicts the notion that “a silvery dress is just a shiny white.”

Sometimes you look at someone’s face, reassured that the typical proportions are maintained, or, conversely, that they are not. There are also optical illusions. They are the most interesting. It’s when it seems that some point exactly divides a segment in half, but as soon as you measure, it turns out not to be the case.

It’s also interesting that our eyes deceive us about what lines are and what are not lines. Here, it would be more correct not to use the word line” but edge.”

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)