For several months around 2024–2025, I sent weekly updates to a WhatsApp channel with friends, Semiinteresting Facts and Factoids. The aim was to find a random interesting fact, mainly from Wikipedia, and share it with some regularity. Here is a list of these random Wikipedia finds, originating from me procrastinating at work. Incomplete! I lost many posts since channel export does not return the entire set of posts, and I had to remove posts with pictures I couldn't include here. If I ever find something interesting, I will append it to the end of this document.
The last Tsar of Bulgaria (until 1946) also served as the country prime minister between 2001 and 2005, Simeon Saxe-Coburg-Gotha
When a species encounters a barrier during its population growth and forks into subpopulations circling around the obstacle from both sides, the two populations meeting at the opposite end sometimes are unable to directly interbreed anymore, while still maintaining genetic connection through a series of interbreeding neighbors: ring species
As mentioned in the yesterday post, the concept of a color space is just an approximation – it might model photosensitive cells response reasonably well, but there is more to visual signal interpretation. For instance, it is possible to perceive colors best approximated by points outside the usual colorspace – they are formed as afterimages visible after starting at certain templates, see Impossible color – Chimerical colors.
If you take two rough square slabs of metal and start lapping them (polishing their surfaces against each other), one of them will most likely end up slightly convex and the other concave, as they tend to match their curvature during polishing. However, if you take three slabs of metal and sequentially lap each pair, they will end up flat (to the point allowed by the polishing process), because zero curvature of each part is the only stable configuration: the Whitworth three plates method
There were official western spies in East Germany, and Soviet ones in West Germany: Military liaison missions
Angle trisection is not possible with ruler and compass construction, but there exist different construction systems where it is an easy task, e.g. with origami (can be proved by observing that some triangles are congruent: Mathematics of paper folding – Trisecting an angle), see also Angle trisection – With a "tomahawk").
A common OTC anti-diarrhea medication loperamide is an opioid (Loperamide) and the desired action (slowing down the large intestine muscles contractions) is in the context of medicinal or recreational use of other opioids (fentanyl, morphine, heroin) considered a side effect. The difference is that loperamide does not cross blood-brain barrier at any appreciable rate; while psychoactive effects are possible at very high doses, generally serious (some life-threatening) side effects are present in addition, making abuse rather unlikely (PMC5468105).
Suppose you'd like to connect an electric device placed on a rotating platform to a power source. You'd think that as the platform is rotated, the connecting cables will get tangled up no matter what you do, and you are forced to use something like a slip ring instead. Surprisingly, this is not necessary: rotating object can be connected to the outside world through an anti-twister mechanism – the cables never tangle up since they loop around the rotating object, negating the cumulative rotation (see also video).
Common food preservation methods, such as heating, drying, acids and preservatives, are unsuitable for some foods. In such cases other techniques of stopping any biological activity can be used: food irradiation works through breaking strong chemical bonds (in both genetic material and existing proteins), and pascalization (sterilization via application of >3000 atm pressure), which alters mostly low-energy hydrogen bonds, changing large-scale protein structure (important for its function).
Every bee has a preferred flower type which it is (almost) exclusively looking for while foraging (flower constancy). This behavior (first noted in historical record by Aristotle) is not fully understood, but it is present among different pollinators (in butterflies too), so while naively it restricts the available food sources, the insect behavior must be determined by something more complex than simplistic optimization.
Interestingly, the bumblebees visiting basil plants on my balcony enjoy both white and purple flowers - perhaps they look more similar to them?
Axons connecting the nervous systems to muscles and sensing cells (e.g. for temperature or touch) can get quite long, up to order of magnitude of a meter. To keep such long neurons alive a system transporting chemical substances back and forth exists (axonal transport). Rabies virus hijacks this system: it enters the cell at the synapse, and over the course of weeks is transported to the center of the cell, where it can replicate (Rabies virus – Infection). This property has been used to study the connections between different parts of the nervous system: if you infect one cell, after some time it will be possible to detect presence of the virus in neurons directly connected to it: viral neuronal tracing
The life cycle of eels was a mystery until early 20th century (Eel life history): it was known that they return to the ocean for breeding, but for a long time no young specimens could be found. This is because they typically travel extremely large distances for reproduction; the european eel spawning grounds are close to the atlantic coast of north America (Sci Rep 2022), and the fish take between 1-3 years to travel to mature enough so that they can live in freshwater.
It has been theorized that the Myxosporea class of tiny marine animals arose from the tumors of other Cnidaria (animals such as jellyfish, sea anemones or corals). This hypothesis, while controversial, is supported by limited genetic evidence: Myxosporea appear to lack genes necessary for apoptosis, similarly to neoplasmic cells, and their genome is much smaller than their closest relatives (PMC6343361, read also Quanta Magazine).
A tiny piece of engineering magic I realized yesterday: the sockets for CR2032 batteries (flat round ones, used e.g. in kitchen scales) are designed in such a way that wrong orientation of the batteries inserted doesn't affect the electronics it's connected to. One of the battery electrodes is a "cup", and extends from to the side area. The socket connections are on the side and bottom, which means that in the wrong orientation, they are both connected to the + battery terminal, and no current (of wrong sign) can flow to the rest of the circuit, which could damage the electronics.
As you have probably noticed, biology is full of apparent inefficiencies, and they often can't be fixed evolutionary since something important might be broken in the process. One further example: in all mammals the voice box is partially innervated by the recurrent laryngeal nerve which loops over the main artery (sitting next to the heart). Doesn't matter much in humans, but such structure is shared between all vertebrates, and this nerve in giraffes is around 5 meter long; hypothetically, in lock-necked sauropod dinosaurs this introduced a significant delay in larynx control (nerve length ~30 meters, with typical signal speed of 40-50 m/s). Topology can't be easily changed, and it seems that we are stuck with this design until the end of vertebrate life.
As Earth is not a perfect uniform ball, orbits of the satellites around the planet are continuously perturbed from their Keplerian ellipses (with stronger perturbations for lower orbits – the corrections can be described by multipole expansion of the gravitational potential, and they all fall faster than the dominant 1/r term). This can be put to use: if you want your satellite to be continuously illuminated by the sun, normally you'd need to adjust the axis of rotation with thrusters all year round, but there exists a sun-synchronous orbit for which the slight obliqueness of the Earth shape causes the orbit to precess in such a way that the Sun is never obstructed by the Earth from the satellite point of view.
Most of the white fabric and paper you have seen in your life contained blue fluorescent dyes: these materials are naturally yellowish-white (even after bleaching), and the addition of an optical brightener which transforms portion of the UV and purple radiation into (more visible) blue brings the spectrum closer to white balance. Popular dyes from the (E)-stilbene family undergo trans→cis transition in the middle double bound upon long UV irradiation, which makes paper exposed to the sun yellow back again.
Fluorite is a natural form of calcium fluoride (CaF₂), and like most fluorides, in the pure form is remarkably transparent in wide range of wavelengths – because of this, mixtures of fluorides are used as fluoride glass for optical fibers and specialized windows in experiments. However, radioactive inclusions may degrade the crystal structure over time, resulting in opaque antozonite. Surprisingly, this mineral has a distinctive smell (hence its other name, Stinkspar): fluorine element released from the crystal structure accumulates in the material, reacts with other substances creating odorous chemicals (with the overall smell similar to ozone): doi:10.1016/0009-2541(77)90047-X
(The other hypothesis is the presence of tholins, common in other places in the solar system. By the way, if you're ever in the US, you can buy irradiated NaCl for science demonstration at Walmart: Energy Transformations With Irradiated Salt Kit)
Finally, lattice defects caused by irradiation can potentially cause nuclear accidents. Graphite moderators are especially prone to this due to their weakly bound crystal structure, and the stored energy (called the Wigner effect) needs to be released periodically by annealing (heating above a certain temperature). Otherwise, it could do so without control, potentially reaching several hundreds ℃ and igniting.
One of my favourite categories of artificial satellites are the completely passive reflecting spheres, are today I present a gallery of various designs.
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Project Echo was one of the first ones, a sphere (30 m in diameter) of metallized PET designed to reflect radio waves.
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Most of them were actually intended to be used in research (e.g. atmospheric drag radar measurements) or early space communication (since they can reflect a radio wave `over the horizon'), but the first example was meant to be of purely artistic value. Unfortunately, Orbital Reflector could not unfold itself due to politics: US government shutdown during the Trump rule prevented the museum employees from ordering the satellite to open.
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Lincoln Calibration Sphere 1, as the name suggests, is meant to be used by radars for callibration. Placed in middle Earth orbit, it isn't subject to much drag, and is still used up to this day since 1965.
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PAGEOS goal is to serve as a surveying tool: a reflective target visible by multiple stations around the globe allowed for very precise (for the time period) position measurements, which were (apart from more practical purposes) in the study of continental drifts.
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Next in line was OV1-8: a grid of aluminum wires attached on a sphere of thin plastic. Upon launch, the plastic was intended to disintegrate in the strong solar UV radiation environment, leaving only the thin mesh behind (which would still reflect radio waves, but be less susceptible to atmospheric drag in the low Earth orbit).
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Humanity Star intention was to reflect light intentionally, creating an oscillatory flare. It performed according to the plan, and was universally hated by astronomers due to this fact (who welcomed the news about its 2018 atmospheric reentry).
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Honorary mention, since this satellite is neither passive nor spherical. However, just as the previous one, its goal was to reflect light; Znamya was supposedly able to illuminate 5 km patch of Earth in the night with luminosity equivalent to a full moon. Unfortunately, the mirror deorbited only after several hours, and, quoting the Wikipedia article, "although clouds covered much of Europe that morning, a few ground observers reported seeing a flash of light as the beam swept by.[4]" Now a similar idea is proposed by Reflect Orbital for commercial purposes (at least they claim so, I don't believe their story).
The word for tungsten in many languages – Wolfram – comes from the fact that the early technique to isolate it consumed a lot of tin, "like the wolf eats the sheep" (vanderkrogt.net). This follows a long tradition of naming minerals originating from Erzgebirge: Nickel – History apparently refers to a mischevious spirit (like Old Nick – the devil – in English), and supposedly Cobalt – Etymology is cognate with Kobold. Ores of both were reminiscent of other minerals, but one couldn't obtain any metal with the technology available back then, or ruined smelting if present in the mix.
The first computer tomography scanners were developed in the labs of EMI company, the same as the distributor of The Beatles records in 1960s. Some claim (Nobel Prize 1979 – Perspectives) that it is thanks to the success of the band that we have the CT scanners; the early devices were even called EMI scanners (doi:10.1098/rspb.1977.0008).
Ciabatta was invented in 1980s by Italian bakers concerned with the popularity of the French baguette: it is made of similar kind of dough (large gluten and water content), the main difference being the shape, better adapted for making sandwiches (which was the original application of this bread).
For some metals, if you bring two pieces to contact they may fuse (the process is known as cold welding) because of strong interactions between the atoms in the two parts. The flatter the surface, the stronger the bond, and it is more prominent in vacuum, which led to some problems on satellites (although indium is able to cold weld in air: video). Gauge block – Wringing is similar, but enhanced by surface oil.
Common cold is a description of symptoms rather than a disease caused by a single infectious agent and in fact hundreds of only very distantly viruses can cause it. One of those is Human coronavirus OC43: interestingly, there is some data to suggest (rather speculatively) that it caused the 1889–1890 pandemic during which COVID-like symptoms (like loss of smell) and mortality patterns (children less affected) were reported. One of the closest relatives of OC43 is Murine hepatitis virus – as the name suggests, despite genetic familiarity, it causes a completely different disease (in mice), infecting internal organs and not the respiratory tract.
Iapetus is an icy body orbiting Saturn and tidally locked to it: just like our Moon, one hemisphere always points towards the planet. If you imagine the movement of the moon on its orbit, one of the hemispheres always points towards the orbit direction (the leading hemisphere), while the other (trailing) always points away from it. Turns out that in the case of Iapetus they have completely different colors: the leading hemisphere is much darker than the trailing one.
Another (even more surprising and not understood at all) feature is the presence of the equatorial ridge, 13 km high range of ice mountains sitting perfectly on the moon's equator and almost encircling it.
When a sheet of ice breaks from a larger surface and water flow underneath makes it turn and grind against neighboring objects, an ice circle may form. Similar thing may also happen to floating islands: El Ojo is a natural perfectly circular island which was created via the same mechanism.
Syncytiotrophoblast is a thin (one cell thick) barrier between fetus and uterus; it is formed by joining a large group of cells into a giant (diameter ~10cm) flat one with multiple nuclei. Its role is to prevent immune reactions between the two organisms through blocking white blood cells movement: typically they "squeeze between other cells" searching for threats, but here it's a huge flat disk without any cell junctions. Curiously, the protein syncytin-1 used in the cell fusion is repurposed from an extinct virus embedded in our genome.
The vanes in modern turbines must withstand enormous mechanical and thermal loads: some of them operate in temperature higher than the melting point of their material. To make this possible, the blades in critical section of the engine are often casted as monocrystals. If you just poured the metal in the mold, it would be composed of multiple small grains of crystals with different orientations; but if you attach a "pigtail"/helix at one end, and start the crystallisation across it, only one crystal orientation will be selected (crystals grow with varying speeds in different directions, and the helix geometry makes one take over all the rest). Read more on: Each Blade a Single Crystal
If you've ever seen a piece of sodium being thrown in the water, you know that it often pops into tiny pieces. This has a surprising origin: maybe you remember the heurestic that alkali metals "want to donate electrons", and this hold true here; the metal pushes its electrons directly to the water, and subsequently explodes due to electrostatic forces (Nat Chem 2015). You can actually see the electrons dissolved in water (as any other anion, albeit quite light): it is a deep blue haze visible in ultrafast videos of the reaction. The same deep blue color of electrons is visible when dissolving alkali metals in ammonia: video, later in the video (around 6:11), when the experimenter adds even more metal, there are enough electrons to give ammonia a metallic sheen.
One semiinteresting consequence of tidal locking is that from the Moon, the Earth is always seen at the same point in the sky (+ some small wobble due to the elliptical orbit); in a long recording taken at the the Moon, it would just appear to rotate around its own axis.
Ammonia (NH₃) has strong affinity to water: both are polar molecules which can ionize, and bind to each other through hydrogen interactions. This can be used in several ways: if you ever dissolved ammonium salt in water you know that the process absorbs huge amount of heat and the solution becomes cold very quickly. Instant cold packs use ammonium salts exactly for this reason. A related absorption refrigerator used water as a sort of compressor without moving parts: it can absorb gaseous NH₃ (hence the name) and release it when the solution is heated. They were quite popular for a long time in cases where no reliable electricity was available, exactly because only heat is required for operation (which was frequently provided by a small flame fueled by camping gas). The main operation is similar to a normal compressor refrigerator: hot ammonia is cooled and liquifies (4 of this image), is allowed to decompress (7) during which time it absorbs heat and evaporates (8). The difference is that instead of compressor to complete the cycle, the ammonia dissolves in water (9), and is controllably driven out of solution by heat (1) as its solubility decreases with temperature. (As far as I understand, hydrogen is there to make the (7,8) steps more effective.)
The classic ammonia fountain experiment (video) shows the same principle: ammonia (stored in the upper flask initially) dissolves in water really well (lower container, squirted into the upper flask to initiate the process), and in doing so lowers the pressure in the upper flask enough to suck the water to a large height.
If you have one of your nostrils congested right now, take a moment to note which one is it and create a reminder in about 2 hours to check again. Chances are the opposite one will be blocked: this is a normal behavior of the nose known as the nasal cycle. Some potential benefits are mentioned in the article (the inhaled air is better moisturized and it seems that it makes smell detection easier), but in the end it's such a minute detail of how our organism work that we simply don't know how beneficial is it or not. Quick search shows that dogs experience it as well: doi:10.1111/vru.12115