Commonplace

S.S. Stevens’ scales of measurement classifies data into four hierarchical levels—Nominal, Ordinal, Interval, and Ratio (NOIR).

Categorical (or qualitative) variables describe kinds rather than amounts:

• Nominal categorical variables are pure labels with no inherent order (e.g., blood type, country, product category).
• Binary variables are a special case of nominal with exactly two categories, often encoding a yes/no condition.
• Ordinal categorical variables impose a ranking without guaranteeing equal spacing between levels (e.g., high/medium/low, good/fair/poor, education levels).

Numerical (quantitative) variables measure amounts and support arithmetic to varying degrees:

• Interval numerical variables have equal, measurable spacing but no true zero, so ratios are meaningless, (e.g., 40° C is not “twice as hot” as 20° C because 0° is arbitrary).
• Ratio (or cardinal) numerical variables have both equal intervals and a true zero, enabling all arithmetic.

Historically, producing clear glass required careful management of iron content in the raw sand, as even trace amounts introduce a greenish tint. Truly colorless cristallo was achieved around 1450 in Murano (near Venice) by combining purified soda ash with finely ground Alpine quartz pebbles; the recipe was a state secret punishable by death to disclose. For scientific instruments, homogeneity (consistent optical density) mattered more than color, but the drive for purer raw materials incidentally delivered both, and clear glass in microscopes and telescopes enabled the Scientific Revolution.

Greenland ice cores provide an indirect proxy for Roman economic activity: lead pollution from smelting and mining, carried atmosphetically and deposited in Arctic ice, tracks closely with the empire’s fortunes. The record suggests Roman economic output peaked in the first century AD, declined through the crisis of the third century, and largely collapsed after the Western Empire fell.

Sedentarism preceded agriculture — people settled into permanent or semi-permanent communities before they began cultivating crops, inverting the intuitive assumption that farming drove people to settle down. The archaeological record suggests that abundance of wild resources, not farming, first enabled and incentivized fixed settlement.

At the end of the Younger Dryas (~9600 BC), Greenland temperatures rose roughly 10°C within a decade or two. This event marks one of the sharpest climate transitions in the ice core record and is widely regarded as the climatic catalyst that made sedentary agriculture suddenly viable across much of the world.

Terminal value is the estimated value of a business’s cash flows beyond an explicit forecast period in a discounted cash flow (DCF) model. It typically captures the majority of total valuation by assuming the company continues generating cash indefinitely at a stable growth rate.

The UAE’s oil wealth belongs to the individual emirates, with ~96% in Abu Dhabi. Dubai has little oil and diversified into trade, tourism, and finance — oil is now under 1% of its GDP. Financial transfers between emirates (including a 2008 Dubai bailout) are informal and constitutionally discretionary.

Call options are the right to buy and are profitable when the spot price rises above the strike price. Put options are the right to sell at the strike (profitable when spot falls below strike). Options are dated: American options can be exercised anytime before their expiration, European only at that date. The premium is the price paid for the option contract itself.

Options are described as in-the-money (ITM) or out-of-the-money (OTM) based on the relative spot vs strike values. Common strategies include covered calls (owning the underlying and selling a call against it; this caps upside but generates income), protective puts (owning the underlying and buying a put as insurance against downside), straddles (buying a call and put at the same strike and profiting from large moves in either direction), and spreads (buying one option and selling another at a different strike/expiry to reduce premium cost).

Contango is the normal state where futures prices exceed spot (reflecting carry costs), while backwardation is the inverted state where spot exceeds futures, signaling near-term scarcity or exceptional demand for immediate delivery.

Spot is immediate delivery at today’s price (e.g., buying physical silver or an ETF). Linear derivatives move 1:1 with the underlying asset (e.g., futures and forwards), while non-linear derivatives can produce a disproportionately large or small gain depending on where you are relative to the strike price.

Sexed semen technology allows dairy farmers to breed beef-on-dairy crossbred calves after they have bred enough replacement heifers. These crosses can qualify for premium labels like Certified Angus Beef, perform competitively in feedlots, and are indistinguishable to consumers from conventional beef, making them worth significantly more than purebred dairy bull calves. Dairies are now supplying premium cuts, not just ground beef: beef-on-dairy crosses may represent ~15% of total U.S. cattle slaughter in 2026.

Many Ashkenazi Jews adopted permanent surnames in the late 1700s–1800s as required by the Habsburg Empire and Prussia for administrative records. Before this, they typically used patronymics (e.g., Baruch Spinoza, whose Hebrew name was Baruch ben Michael). These surnames were usually German “ornamental” compounds made from pleasant nature or value words (Gold-, Rosen-, Silber-) combined with endings such as -berg (mountain), -blum (flower), -stein (stone), -thal/tal (valley), or -baum (tree). Because millions of Jews adopted such German-style names within a short historical period, these combinations became statistically associated with Jewish surnames even though the words themselves are ordinary German.

Ashkenazi Jews came from Central/Eastern Europe and represent the largest group (~75% of modern world Jewry). Sephardi Jews were expelled from the Iberian Peninsula in 1492 and settled in the Ottoman Empire, North Africa, and Netherlands. Mizrahi Jews never left the ancient diaspora and were indigenous to Middle East and North Africa (Iraq, Iran, Yemen, Egypt, etc.).

The U.S. freight rail system is much more dominant than Europe’s, moving much more cargo per capita at a much lower cost. This is because privately-owned railways optimized for profit with bulk commodity movement across continental distances where rail has no cost-effective competitor. State-owned European railways were optimized instead for politically visible passenger service across shorter, denser corridors where high fuel taxes and city-center-to-city-center travel times made rail competitive with both cars and planes.

After the Meiji Restoration (1868), the samurai class was quickly dismantled. Samurai lost their stipends, status symbols, and social roles virtually overnight, and they and their sons flooded missionary schools seeking Westernized educations. Because missionaries were initially confined to cities and barred from preaching, the first Japanese Christians were overwhelmingly students at these language schools, and almost all were jobless samurai, who often found that Christianity’s emphasis on personal ethics and self-sacrifice mapped naturally onto bushido values. This cemented a lasting association between Japanese Christianity and a highly educated elite: in a country that is less than 1% Christian, 7 of Japan’s 35 post-WWII Prime Ministers have been Christian.

Stalin prioritized Soviet state interests over international communist solidarity, directing the Chinese Communist Party (CCP) to subordinate itself to Chiang Kai-shek’s Nationalist Kuomintang (KMT) in a United Front strategy during the 1920s. This proved catastrophic when Chiang turned on his communist allies in the 1927 Shanghai Massacre, slaughtering thousands of CCP members who had been ordered not to arm themselves or resist. Stalin later reversed course but continued to hedge his bets, consistently treating the CCP as a bargaining chip in Soviet geopolitical dealings rather than a revolutionary movement worth protecting.

Cleisthenes was an Athenian statesman who, around 508–507 BCE, overhauled Athens’ political structure after helping expel the tyrant Hippias. He reorganized citizens into ten new tribes based on geography rather than kinship, diluting aristocratic clan power and creating a more representative Council of 500 (Boule). His reforms established the foundation of Athenian democracy, giving ordinary citizens unprecedented political participation and introducing the concept of equality under the law, or isonomia - from isos (equal) + nomos (law/custom).

Gold and silver production is often a byproduct of base metal mining. While 70–75% of gold is “primary” gold, the world’s largest gold mine (Grasberg in Indonesia) is primarily a copper operation, producing over a million ounces of gold annually purely as a byproduct. Silver is the inverse and is largely captive to base metal cycles: 70–75% comes as a byproduct of lead-zinc, copper, and gold mining, so supply barely responds to silver price signals. This makes silver supply structurally inelastic compared to gold, amplifying price moves when demand shocks hit.

Hay is forage (typically grasses or legumes like alfalfa) that has been cut and field-dried to roughly 15–20% moisture before baling. Hay is shelf-stable and does not need to be wrapped. Haylage is cut forage baled and wrapped in plastic at a higher moisture content (40–60%). Anaerobic fermentation preserves the crop, and it retains more digestible energy, protein, and vitamins than dry hay. Hay silage (or simply silage when referring to ensiled hay-type crops) is cut and wrapped at even higher moisture levels of (60–70+%), which allows for more rapid and thorough anaerobic fermentation and better long-term stability when sealed.

Ensiling preserves nutritional quality better than field-drying but requires airtight storage infrastructure and carries risk of spoilage if improperly sealed. Silos store silage in anaerobic conditions, while grain bins store dry, low-moisture grain aerobically with ventilation to prevent spoilage. With the advent of plastic, the traditional tower silo became largely obsolete for many operations, replaced by wrapped and bagged silage that requires far less capital investment, offers more flexibility in field location, and scales better for smaller farms.

Xerxes couldn’t contain his ambitions while Artabanus couldn’t conquer his fears; both yielded, if in different ways, to intemperance. Pericles shifted from tolerance to repression in a single speech, and Athens soon followed. Octavian rose by teaching himself self-control; Antony sank by forgetting it. Augustine and Machiavelli bequeathed the heavy and light hands with which Philip and Elizabeth shaped different new worlds. Napoleon lost his empire by confusing aspirations with capabilities; Lincoln saved his country by not doing so. Wilson the builder disappointed his generation; Roosevelt the juggler surpassed the expectations of his.

— John Lewis Gaddis, “On Grand Strategy”

In finance, a beat refers to a company exceeding analyst expectations for either revenue or earnings per share (EPS). A double beat occurs when a company surpasses consensus estimates for both revenue and earnings.

The price return of an investment refers to returns from the change in the market price of the asset only, while total return encompasses the full economic return to an investor, including dividends and distributions (usually assumed to be reinvested). For example, if an index starts at $1,000 and ends at $1,080, the price return would be 8%, but if $30 of dividends were paid, the total return would be ≈11%.

During and after the Neolithic transition (roughly 6000–2000 BC), several skin-lightening alleles rose in frequency among European populations, likely due to a combination of low sunlight levels and dietary changes (shifting from fish and meat to cereals) that reduced vitamin D intake.

Retrieval-Augmented Generation (RAG) is a technique that enhances AI models by combining them with external information retrieval - e.g., querying a database or document repository. This can give an AI access to current, specific, or private information beyond its training data, reducing hallucinations by grounding responses in real sources and enabling source citation.

The ouroboros is an ancient symbol of a snake or dragon eating its own tail, representing the eternal cycle of death and rebirth, wholeness, and infinity. In modern usage, it also refers to anything that forms a self-consuming, circular process.

Diocese is a leftover term from an administrative unit established by the emperor Diocletian

The Common Language Effect Size (CLES) quantifies the probability that a randomly selected observation from one group will be greater than a randomly selected observation from another group, expressing the difference in understandable, plain language. For example, a CLES of 0.8 means that in 80% of random pairings, the observation from the first group will be higher.

Vinegar is made when bacteria (called Acetobacter) convert alcohol into acetic acid.

Japanese shipboard anti-aircraft fire was very ineffective in WW2 - their doctrine relied on maneuver, and the primitive fire computers of the time could not recompute quickly enough to keep up with changing headings. Of the roughly 150 US aircraft lost at Midway, only 2 were confirmed AA kills.

The Chilean earthquake of 1960 released more than a quarter of all the earthquake energy released in the 20th century.

Infrared, although it carries ~49% of solar energy, plays a relatively small role in ocean heating because it is absorbed so quickly. IR warms only the ocean skin layer, and the heat is immediately re-radiated or lost to evaporation. Visible light—still a large fraction of sunlight—heats water down to tens of meters and is primarily responsible for warming the bulk of the upper ocean.

Stochastic, or aleatoric uncertainty represents the inherent randomness in a system or process. This uncertainty exists because the world itself contains genuine randomness that cannot be reduced, no matter how much data is collected. Epistemic uncertainty comes from having incomplete information, limited data, or imperfect models. Unlike stochastic uncertainty, epistemic uncertainty can be reduced by gathering more data, improving models, or gaining better understanding of underlying processes.

Corruptio optimi pessima is a Latin phrase that translates to “the corruption of the best is the worst”.

The USSR cooperated with Germany to skirt the Treaty of Versailles beginning in the early 1920s - long before the Molotov-Ribbentrop Pact.

Dogs pant at their lungs’ resonance rate, breathing quickly and shallowly to push air back and forth across their airways.

Thunder starts as a sharp crack and gradually gets lower because the higher frequency sounds are absorbed more quickly by the atmosphere. The initial sound is from the closest (and usually lowest) part of the lightning column, and subsequent sound waves come from higher up.

The ouzo effect happens when a strongly hydrophobic essential oil is dissolved in high-alcohol solution, then mixed with more water. Once the concentration of ethanol gets below a certain point, the oil precipitates from the solution and spontaneously forms an emulsion with the remaining ethanol-water mixture. When this happens, the mixture transforms from a clear appearance to cloudy.

Many antireflective coatings consist of transparent thin film structures with alternating layers of contrasting refractive index. Layer thicknesses are chosen to produce destructive interference in the beams reflected from the interfaces, and constructive interference in the corresponding transmitted beams. This improves the efficiency since less light is lost due to reflection and improves the contrast of the image by elimination of stray light. The coating’s performance changes with wavelength and incident angle, so that color effects often appear at oblique angles.

Gerunds look like participles but are different in that gerunds are nouns while participles are used in verbs. Participle: I have been thinking about you. Gerund: Thinking about you makes me happy.

— Kevin D. Williamson

During the Holocaust, many countries sent large numbers of rural, unassimilated Jews to Nazi Germany, while urban Jews were more likely to be protected.

The worm-like structures that drop from pine and oak trees in the spring are male cones, called catkins.

Autoencoders are neural network architectures that learn efficient data encodings in an unsupervised manner. They consist of two main parts: an encoder that compresses input data into a lower-dimensional representation, and a decoder that attempts to reconstruct the original input from this representation. The network is trained to minimize the difference between the input and its reconstruction.

One-hot encoding is a machine learning technique that converts categorical data into a numerical format suitable for algorithms by creating a binary column for each unique category.

The weak Federalists of 1812 and 1820 and the proper Whigs of the 1830s and 1840s too often would seem to oppose the frontier, westward expansion, and war, a collectively unappealing platform. Slaveholders, by contrast, made the frontier an ally. … During the early decades of the nineteenth century, the Democratic Party, usually southern-led, was Indian-fighting, anti-British, and strongly favorable to U.S. expansion. This put it in tune with popular opinion and slavery hitched a thirty-year ride.

In Britain, expansionism was imperial, Tory, and aristocraric-led. In the United States, the embrace of manifest destiny was republican, egalitarian, and Democratic-led in its politics.

The Federalist North was largely opposed to the War of 1812, and the war resolutions passed somewhat narrowly and along partisan lines.

Tories who stayed in the new United States tended strongly towards the Federalists, lending credence to the notion that it was a monarchist party.

The acquisition of India and the loss of America both helped to strengthen the class system in Britain: the former made status more numinous; the latter made middle-class radicalism unpatriotic.

— J. H. Plumb

More than half of Harvard graduates from the 1640s went to England during the English Civil War.

The word company is derived from Latin roots com (with) and pan (bread), referring to people you break bread with.

Peak hunting efficiency generally occurs around age 40 - old enough to take advantage of learned skills, but not too old to lose strength.

Only 3 percent of the Soviet 18-year-olds mobilized in 1941 were still alive in 1945.

A takfir is a declaration of apostacy against a Muslim (the accuser is called a takfiri). While most Muslims regard this as extremely weighty (an ill-founded takfir is haram), radical Islamists have used them extravagantly as rationalizations for killing any Muslims who disagree with them.

In Islamic jurisprudence, the five rulings are:

• fardh (فرض) – compulsory
• mustahabb (مستحب) – desirable
• mubah (مباح) – permissible
• makruh (مكروه) – discouraged
• haram (حرام) – prohibited

Sayyid Qutb was an Egyptian writer and influential Islamist. He was critical of secularism and materialism in the West but rejected Communism as an alternative. He saw Sharia law as the only solution and argued that any secular government was jahiliyyah (an Arabic word roughly equivalent to “ignorance” and referring to the period before Islam). Qutb’s writings were very influential for later Islamists, and he has been called “the father of Salafi jihadism”.

Osama bin Laden made himself odious in Sudan and was forced out and ended up in Afghanistan, where the Taliban had taken over (with significant help from the Saudi and Pakistani governments). When he arrived, the Taliban asked Saudi Arabia what they should do with him and were told to keep him there and keep him quiet.

Arab mujahideen were relatively minor players in the Soviet invasion of Afghanistan (though Osama bin Laden’s somewhat shambolic experience was later mythologized), and nearly twice as many Arabs took part in the Afghan Civil War after the Soviets left.

When [Churchill] first met with Stalin, in August 1942, he tried to justify his focus on the Mediterranean by telling the Soviet dictator that it would open up new areas from which to attack German air power, including the strategic bombing of German production. By the second half of 1943, however, this argument had mostly disappeared and he talked almost entirely in a battle-centric manner about the need to divert German divisions from the Eastern Front and France.

— Phillips Payson O'Brien, “How the War Was Won”

So Churchill’s different planning was not nearly as erratic as it seemed to those around him. He was looking for campaigns that Britain could fight with air and sea weaponry primarily. If the ideas seemed disconnected, it was in their location and number, not their intention.

— Phillips Payson O'Brien, “How the War Was Won”

By early 1943, the Allies had developed FIDO, an acoustic homing torpedo that could be dropped from low-flying aircraft. Though referred to as a mine to conceal its fire-and-forget capability, it had a very high success rate - 204 torpedoes fired sank or damaged 55 enemy submarines.

Marbury v. Madison was not the first case in which SCOTUS reviewed the constitutionality of a law: Hylton v. United States upheld the constitutionality of a tax on carriages.

When whale populations crashed in the mid-20th century due to commercial whaling, krill populations also declined - the phytoplankton they feed on relies on essential nutrients like iron that whales recirculate to the surface.

About 1/3 of recent sea level rise is from the thermal expansion of the oceans, the rest from melting freshwater.

The SOFAR (SOund Fixing And Ranging) channel is a layer of the ocean where the speed of sound is at its minimum. The speed of sound increases with temperature (in the warmer water above this layer) and pressure (in the deeper water below the layer). These speed differences cause near-horizontal sound waves generated inside the SOFAR channel to refract towards the center of the channel, which allows them to travel great distances with minimal loss, especially at low frequencies.

The Heard Island Feasibility Test was an experiment in 1991 that transmitted very low frequency sound from a point in the southern Indian Ocean that had a “line of sight” to both coasts of the US. A network of listening stations was able to use precise measurements of the speed of sound to estimate the water temperature. The experiment is was stopped due to equipment failure and concerns about marine mammals, which were poorly understood at the time.

The Arctic Ocean has more than enough thermal energy to melt its sea ice, but the water does not mix enough for this to happen.

Sound does not efficiently travel from water to air or vice versa. The human inner ear is optimized for air, so underwater sounds (especially high frequencies) are muffled. When humans hear underwater, much of the sound is transmitted through their bones.

The name Pakistan is an acronym for the names of several regions, combined with the suffix -stan which means “land”:

• Punjab
• Afghania
• Kashmir
• Indus-Sind
• Baluchistan

The name was coined in 1933 by Choudhry Rahmat Ali, a young Muslim student and activist in the Pakistan Movement, in his pamphlet Now or Never, Are We to Live or Perish Forever?. In Persian and Urdu, Pakistan can also be translated as “the land of the pure”. The word pak means “pure” in Persian or Pashto, while the Persian suffix -stan means “place of” or “country”.

A phatic word or phrase is one which adds little meaning and is mainly used for social purposes.

In a siege, a circumvallation is a fortification that faces inwards towards the focus of the siege, as opposed to a contravallation, which faces outwards to defend the besiegers against relief attempts.

After steam passes through the turbine in a power plant, it is not reused directly, but is condensed back into water. This is because compressing the “cool” steam back up to the boiler inlet pressure requires much more energy than pumping water to the same pressure and heating it.

The three-fifths formulation was first proposed by James Madison in an amendment to the Articles of Confederation and was an implicit recognition of the fact that free labor was much more productive than slave labor.

Cash flow hedges smooth out variations in cash flow. For example, if a company issues debt with a floating interest rate, they might set up a swap with a counterparty in which they purchase debt at that same floating rate in exchange for fixed rate debt. Other examples include buying futures contracts to hedge against fluctuating commodity prices or entering into an interest rate swap to lock in a fixed interest rate for expected future debt issuance. Net investment hedges mitigate exposure to changes in the value of a foreign investment from exchange rate fluctuations.

In medieval England, bakers were strictly regulated on the price and weight of loaves and were subject to harsh penalties, including flogging. As bread dried, it constantly lost moisture and thus weight. To ensure that they were selling the correct weight of bread, bakers would often throw in an extra loaf - the origin of the term baker’s dozen.

Specie scarcity in 18th-century Massachusetts led first to taxes being paid in-kind with agricultural commodities, then to the creation of the Land Bank, which issued paper notes backed by mortgages on the land of the holders. Hundreds of people subscribed - among them Samuel Adams Sr. - and were ruined when the bank was dissolved by an act of parliament.

If you believe that God is the Creator and sustainer of life, then death is simply what happens to the body when we run away from God, and hell is what happens to the soul.

Classical Liberalism means minimal social and economic regimentation. Fascism means social and economic regimentation with pre-Christian moral vibes. Socialism means social and economic regimentation with post-Christian moral vibes.

Handicap comes from the old English arbitration game Hand-in-cap. When two players want to trade possessions, an umpire determines the difference in value, if any. Both players and the umpire then put some forfeit money in a cap. The players put their hands in the cap, then simultaneously remove them either open (to signal agreement with the valuation) or closed (to signal disagreement). If both players agree, the difference in valuation is paid, the items are traded, and the umpire collects the forfeit. If both players disagree, the items are not traded, and the umpire collects the forfeit. If one player agrees and the other does not, the items are not traded, and the player who agreed to the valuation collects the forfeit.

A pidgin language is one that has been stripped down, usually for use in trade, and sometimes consisting of a blend of multiple parent languages. If spoken natively, a pidgin language will evolve into a creole, with more grammar and room for subtlety.

And so a big part of the bank’s financial engineering operation is optimizing risk-based capital. For instance: If a bank has $100 of stuff that gets a 100% risk weight, and can somehow split it into $80 of stuff with a 0% risk weight and $20 of stuff with a 300% risk weight, then that’s good, that’s what it wants, that reduces its risk-weighted assets from $100 to $60, which reduces its capital requirements, which increases its ability to return money to shareholders. And this is the explanation for capital relief trades, and also in some loose sense the explanation for the 2008 financial crisis: If you slice your risky thing exactly right, you will end up with a collection of new things that look less risky, to capital regulators, than the original thing.

— Matt Levine, “Money Stuff: Financial Engineering for Green Energy”, 1/29/24

Nearly all citrus fruits grown today are hybridized blends of three ancestral species: the citron, the mandarin orange, and the pomelo.

Andrew Jackson was intensely patriotic (opposing nullification and hints of secession) and identified himself and his agenda with the will of the people. He significantly expanded executive power through use of the veto and personal domination of his cabinet. His opponents denounced this as monarchical and formed the Whig party, named for the British faction that opposed absolute monarchy.

Horses, unlike cows, will break through a crust of snow to forage in the winter. Thus horses are better suited to colder grassland climates, and were originally domesticated on the Eurasian steppe as an easily maintained source of meat.

Mace and nutmeg come from the same plant - mace is the protective husk around the nutmeg seed.

Before the Russian Revolution, most crop surpluses came from the landed estates, so land redistribution meant returning land to peasants who generally farmed at subsistence levels. During the period of War Communism, all surpluses were confiscated, leading to even further drops in yields.

After the Norman Invasion, laws were written in Latin and most nobles spoke French, but by the time French was used for law, most nobles were speaking English.

At the Battle of Pulo Aura during the Napoleonic Wars, Commodore Nathaniel Dance commanded a large convoy of unescorted EIC merchant ships that was surprised by a powerful French naval squadron. He arranged his ships in a line of battle, bluffing that they were in fact ships of the line. When the French force retreated, Dance pursued them to keep up the charade until his ships were out of danger. His convoy arrived safely with an intact cargo of tea, silk and porcelain worth over £8 million, and Dance was knighted.

Marx reasoned that since profits come out of the sale price of goods and services, the wage earners who produce the goods and services can’t afford, in the aggregate, to buy all they produce. This inexorably leads to overproduction, he said, followed by collapse of both prices and employment. He thought the built-in discrepancy between wages and prices, by creating a demand gap, led to periodic cyclic crises of unemployment and price collapse, and must also lead before long to a final insurmountable crisis of capitalism, to be followed by socialism, which would eliminate the demand gap by eliminating private profits.

— Jane Jacobs, “Cities and the Wealth of Nations”

A bullet loan or balloon loan is one that does not amortize fully over the length of the loan term, such that most of the principle is repaid in a large payment due at the end.

Effective Translational Lift (ETL) happens in helicopters when forward movement (“translation”) brings the rotors in contact with undisturbed air. At 16 to 24 knots, the rotor system outruns the recirculation of old vortices and begins to work in undisturbed air. This effect can allow overloaded helicopters to take off by accelerating forward on the ground, then lifting off once ETL is achieved.

Kerogen is solid, insoluble organic matter in sedimentary rocks. Labile kerogen breaks down to generate principally liquid hydrocarbons (i.e., oil), refractory kerogen breaks down to generate principally gaseous hydrocarbons, and inert kerogen generates no hydrocarbons but forms graphite.

The earliest known wheel was locked to its axle and the entire assembly rotated in a groove in the bottom of a cart. Later woodworking advances enabled fixed axles, which improved steering by allowing left and right wheels to rotate independently.

Coppicing is the practice of cutting down a tree while leaving the stump to regrow shoots. This regrowth is more efficient than seedlings because it uses the mature root system. When the cuts are performed above grazing height, it is known as pollarding.

As wood burns, flames are produced as large polymers break down into smaller molecules - these evaporate around 600°F and glow before combusting. When these small molecules are gone, only the carbon structure (charcoal) remains, which does not evaporate and merely glows as it combusts around 900°F. Charcoal can be manufactured by limiting a wood fire’s oxygen supply to keep it between 600-900°F.

When a tree is struck by lightning, the damage is done by the instant boiling of the water inside, which causes a steam explosion that tears the tree apart.

A greenstick fracture occurs when a child breaks a long bone and the fracture travels up and down the center of the bone rather than continuing through, reminiscent of the way green tree branches break.

In the wake of the Crusades and the growing influence of the Church, knighthood was reformed - codes of chivalry began replacing violent and thuggish behavior. Priests began administering knighting ceremonies rather than other knights, and knights (previously a class of upwardly mobile warriors) became more closely entwined with the nobility.

Pliny the Younger wrote to Trajan about his persecution of Christians, who were an unsanctioned club. Other clubs were typically burial societies (social groups with regular meals and rules for providing proper burials for their members) and cults devoted to the worship of specific deities.

Roman piety was very externally oriented and civically focused - a common criticism of early Christians was that they were unsocial because they did not participate in civic ritual. This sort of belief was seen as a superstition (and seen as inferior to true, civic religion) because it detracted from public unity and order.

Galen treated Christianity as a philosophy rather than a superstition because of the way it led Christians to live lives of virtue, and was the first pagan author to do so. He criticized Christianity for expecting adherents to take teachings on faith, rather than thinking through syllogisms. He also (like most philosophers of his day) took issue with the idea of a god pre-existing the natural world and not himself bound by laws. This doctrine of creation ex nihilo became central to Christian teaching as an differentiator from pagan philosophy.

The custom of putting one’s hands together began as an element of the homage ceremony in which proto-feudal lords and vassals bound themselves together, and it was only later borrowed as a symbol of prayer.

A corps includes two to five divisions with anywhere between 20,000 and 45,000 soldiers. A lieutenant general is in command. The current active corps are I Corps at Fort Lewis, Washington; III Corps at Fort Hood, Texas; and XVIII Airborne Corps at Fort Bragg, North Carolina. Levels of command higher than corps are concerned with administration rather than operations.

A division is made up of three or four brigades and includes 10,000 to 15,000 soldiers, usually commanded by a major general. There are currently 15 infantry, 3 airborne, 1 armored, 1 cavalry, and 1 mountain divisions. Each can conduct major tactical operations and sustained battlefield operations.

A brigade consists of a few battalions and anywhere from 3,000 to 5,000 soldiers, generally commanded by a colonel. An equivalent armor or Ranger unit is called a regiment, and an equivalent Special Forces unit is called a group.

A battalion consists of four to six companies and can include up to about 1,000 soldiers, usually commanded by a lieutenant colonel. An armor or air cavalry unit of equivalent size is known as a squadron.

A company consists of three or four platoons and is generally commanded by a captain. It can also go by different names, depending on the function: Company-sized artillery units are called batteries, while in armor and air cavalry units, they are called troops.

Potash is a general term for potassium salts (and the source of the word potassium), historically produced from wood ashes by a process of leaching and evaporation.

Lime is a general term for inorganic substances that are high in calcium. Quicklime (calcium oxide) is produced by burning (calcinating) limestone, chalk, and other calcium-rich minerals.

-Thorp, -thwait, -by, -kirk, and -dale are place name suffixes (predominantly in the old Danelaw) derived from Old Norse

In a machine learning context, a regressor model predicts the value of a continuous variable, while a classifier model predicts the probability of a binary outcome.

The F1 Score of a model is the harmonic mean of Precision (true positives / predicted positives) and Recall (true positives / total positives), given by: 2 * (precision * recall) / (precision + recall)

Monoclonal antibodies fall into four categories (murine, chimeric, humanized and human)

• Murine antibodies (suffix -omab) are from mice or rats, and have largely been replaced.
• Chimeric antibodies (suffix -ximab) are composed of murine variable regions fused onto human constant regions. This reduces immunogenicity (i.e., trigger less immune response in humans), and thus increases serum half-life.
• Humanized antibodies (suffix -zumab) are produced by grafting murine hypervariable regions on amino acid domains into human antibodies. This results in a molecule of approximately 95% human origin.
• Human antibodies (suffix -umab) are produced using transgenic mice - mice with human immunoglobulin genes. When these mice are vaccinated against the desired antigen, they produce fully human antibodies.

Lyophilization is the technical term for freeze drying, whereby a product is frozen, subjected to very low pressures to sublimate the water content, then brought back to room temperatures.

Ye as in ye olde comes from a typographic substitute for the Old English letter thorn (þ). Thorn fell out of use (replaced by the digraph th) and when printers began using movable type imported from Belgium and the Netherlands, their type sets did not include thorn, so they used Y instead.

Thorn (Þ, þ), along with Eth (Ð ð) were often used in Old English instead of the digraph Th. Eth was associated with ___ and largely died out by the Middle English period

The words pupil, puppy, and puppet all derive from Latin word for doll - pupa. The pupil of an eye referred to the small (doll-like) reflection of a person you saw when looking into someone’s eyes.

Infant and infantry come from the same root - infantry once being thought of as youthful or inexperienced.

The Spanish Civil War started as a military coup against the newly established Second Spanish Republic. The coup was partially successful, setting the stage for a civil war. Germany and Italy quickly aligned with the Nationalists, while western European democracies (fearful of widening the conflict) enforced a neutrality agreement that effectively embargoed Republican Spain. Anarchists and Communists joined the Republicans in an uneasy coalition, while foreign volunteers (relatively few in number, but widely publicized) flocked to join.

Anti-Catholic and anti-Nationalist atrocities and purges, often exaggerated, were mirrored and exceeded by nationalist massacres, including Guernica, and helped frame the war as a battle of communism against fascism.

While Soviet military sales were a major lifeline to the Republicans (financed by the 73% of Spain’s gold reserves that were absconded to Moscow - the Moscow Gold), Communist maneuvering behind the scenes helped fragment support for the Republic. Multiple major offensives were pushed on after obvious failure because of propaganda commitments, and many successes stalled out when Republicans stopped to besiege small strongholds rather than sustaining momentum.

The word clue originally referred to a ball of yarn - it acquired the modern usage in reference to the legend of Theseus, who used a ball of thread to find his way through the Labyrinth. The original meaning survives as the (archaic) spelling clew.

The word posh is popularly believed to have originated as an acronym for port out, starboard home, referring to the more desirable cabins (which got morning sun and afternoon shade) on ocean liners travelling from Britain to the Indian Ocean.

The in-law suffix is short for in Canon law, referring to the Catholic Church’s prohibitions on incest, the definition of which was gradually expanded beginning in the 4th century.

In the Ancien Régime of France, the noblesse de robe (Nobles of the Robe) held purchased titles, generally attached to a function or office for which they had studied, while noblesse d’épée (Nobles of the Sword) held titles earned by their ancestors for military service and generally attached to a fiefdom.

In typography, the x height is the top of a typical lowercase letter, while the cap height is the typical height of an uppercase letter. When rendering on screen, higher x heights allocate more pixels for the more distinctive portions of a glyph, increasing legibility at small sizes.

Infidel is a catch all term for non believers, while heathen or pagan refer specifically to followers of non-Abrahamic religions

The term opiate refers to naturally derived narcotics, while opioid can be used either for synthetic narcotics or as an umbrella term to encompass both categories.

Original Antigenic Sin refers to the human body’s tendency to deploy existing immune responses when re-infected with a pathogen, even when the re-infection comes from a mutated version of the pathogen that could be more effectively fought by a new, different response. This “memory” can cause the immune response to be “trapped” in a sub-optimal immune response.

After Sumter, a few slave states (including Virginia) seemed poised to remain in the Union, but Lincoln issued a strong call to arms that convinced many Southerners that he was ready to invade, not merely to hold Federal forts. Many contemporaries blamed this order for prompting Virginia’s secession.

Eskimo is an umbrella term used to refer to two groups of indigenous peoples: the Inuit (of northern Alaska, Nunavut, and Greenland) and the Yupik (of eastern Siberia and southern Alaska). The term appears to come from the Innu-aimun (of eastern Quebec and Labrador) word ayas̆kimew, meaning “a person who laces a snowshoe”, and shares an etymology with the husky dog breed.

The term Eskimo was once speculated to derive from an Algonquian phrase meaning “eaters of raw meat”. Eskimo is now seen by many Canadians as offensive due to this speculative etymology, and Canada has adopted the term Inuit (the plural form of inuk, meaning “human being”) instead, and Eskimo is now seen by many Canadians as offensive due to this speculative etymology. The usage of Inuit to refer to both Inuit and Yupik is less common in Alaska, where Yup’ik people predominate.

In divided Germany, Checkpoint Alpha was between West and East Germany, Checkpoint Bravo was between East Germany and West Berlin, and the famous Checkpoint Charlie was between West and East Berlin

The Art of War argues for professional control of the military, rather than letting noblemen command

Piles of sand come in 2 distinct size regimes: small ripples and massive dunes, with little in between. Ripples are the result of thin boundary layers of air moving over sand, whereas dunes are the result of large piles of sand “catching” airborne sand and becoming even larger.

English common law relied on juries to convict of crimes, while Roman law required 2 witnesses (often impossible) or a confession. This led to the use of torture to coerce confession in jurisdictions that used Roman law.

When a rocket flies above its optimal altitude, the exhaust exits the nozzle at a higher pressure than ambient air (under-expanded), so the exhaust forms a widening cone behind the rocket as it spreads out. If a rocket is flying below its optimal altitude, the exhaust is exiting the nozzle at a lower pressure than the surrounding air (over-expanded), so the exhaust forms a narrowing cone behind the rocket as it is pushed back down to local pressure. This also causes the appearance of shock diamonds as the exhaust repeatedly bounces back outwards and collapses back in.

Rocket engine nozzles accelerate exhaust gasses and direct them straight back so that they are parallel to the flight path of the rocket. Each nozzle’s shape and size is optimized for a specific altitude - large nozzles for higher altitudes (lower pressure), small nozzles for lower altitudes (higher pressure).

A rocket’s throat constricts the flow of high-pressure gas to accelerate it up to the local speed of sound (at high temperature, this can be much higher than sea level). Any further constriction would begin to limit flow.

The philosopher Karl Popper held that any scientific proposition must be falsifiable, in other words it must at least be possible to imagine some reproducible experiment or observation whose outcome would disprove the hypothesis.

— Wikipedia

In 19th-century Germany, the Napoleonic conquests led to a cultural defensiveness associated with Romanticism. Instead of universal values, and French rationalism, people chose to value the German “spirit”—the beauty of the native soil, the soul of the German language, and so on. It was quite deliberately a provincial reaction to a global conceit.

— Ian Buruma, “Racism & Enlightenment”, Persuasion, Feb 22, 2021

The [interest coverage] ratio is calculated by dividing a company’s earnings before interest and taxes (EBIT) by the company’s interest expenses for the same period. The lower the ratio, the more the company is burdened by debt expense. When a company’s interest coverage ratio is only 1.5 or lower, its ability to meet interest expenses may be questionable.

A widely accepted definition of a zombie is a business with an interest coverage ratio of less than 1 for three years.

— Investopedia

Tanzania comes from Tanganyika and Zanzibar, which were independent states that merged in the 1960s shortly after gaining independence (from Britain and the Sultanate of Zanzibar, respectively).

The Articles of Confederation were drafted shortly after the Declaration of Independence but were not approved by all states until much later, in part because Maryland and other states objected to the territorial claims of the colonies carrying over to the United States. Large territorial claims were a significant source of revenue for the states, as commonly-held land was sold off to individual landowners.

Brazil does not have a coastal plain, so much of the produce from the interior is shipped down to the Río de la Plata and reaches harbor at Buenos Aires in Argentina

As rulers of the Ottoman Empire the Turks saw a rugged, mountainous area dominated by Kurds, then, as the mountains fell away into the flatlands leading toward Baghdad and west to what is now Syria, they saw a place where the majority of people were Sunni Arabs. Finally, after the two great rivers of the Tigris and the Euphrates merged and ran down to the Shatt al-Arab waterway, the marsh lands, and the city of Basra, they saw more Arabs, most of whom were Shia. They ruled this space accordingly, dividing it into three administrative regions: Mosul, Baghdad, and Basra. In antiquity, the regions very roughly corresponding to the above were known as Assyria, Babylonia, and Sumer. When the Persians controlled the space they divide it in a similar way, as did Alexander the Great, and later the Umayyad dynasty.

— “Prisoners of Geography”, pp. 146–7

Sensitivity and Specificity: when meaning the performance of binary classification tests, Sensitivity measures the proportion of positives that are correctly identified (e.g., the percentage of sick people who are correctly identified as having some illness), and Specificity measures the proportion of negatives that are correctly identified (e.g., the percentage of healthy people who are correctly identified as not having some illness).

In 1956, Kruschev denounced Stalin in a 4-hour speech that was distributed around the world

Switzerland’s international abbreviations (CH and CHE) are derived from its Latin name: Confoederatio Helvetica

Alpha (α) is the amount of a fund’s return that can not be attributed to the overall movement of the market. Beta (β) is the correlation of a fund’s return that is attributable to the market movements

The narthex of traditional Christian churches is the end closest to the entrance and opposite the altar.

Uncopyrightable is the longest English word that does not repeat letters, along with dermatoglyphics

Because church and state were separated in the US, political turnover didn’t directly discredit the church

The Roman Catholic Church is just one of 24 sui iuris churches contained in 6 rites, all under the pastoral government of the Roman Pontiff:

The Latin Rite (containing the Latin/Roman Catholic Church), Alexandrian Rite (Coptic, Eritrean, and Ethiopian), West Syrian/Antiochene Rite (Maronite, Syriac, and Syro-Malankara), Armenian Rite (Armenian), East Syrian/Chaldean Rite (Chaldean and Syro-Malabar), and Constantinopolitan/Byzantine Rite (Albanian)

Peter the great grabbed a port and named it after himself

In the early 600s, decades-long war between the Byzantines and Sassanids (itself coming a few decades after the Plague of Justinian) left both empires exhausted and ripe for takeover. Arab warriors, traditionally mercenaries hired by the superpowers, quickly turned the tables to establish the first caliphate.

Shiites emerged as a district branch by rebelling against the Umayyad caliphate about 120 years after Muhammad. Their holdings were roughly analogous to the old Persian/Sassanid empires, with a new capital founded at Baghdad.

Muhammad and the Quran were not universally reverenced by Arabs after his death, and the forging of the Muslim faith was undertaken by ibn alzubayr and abd al-malik

The original orientation of mosques was shifted from Jordan? To mecca

The dome of the rock originally marked the spot where god himself has ascended to heaven. This was changed to Mohamed in the eleventh century

Samaritan articles of faith begin with the statements Allah Wahid (God is one), Musa Nabiyah (Moses is His prophet).

Freud did not see sexual repression as a purely negative thing - he saw sublimated sexual desires as responsible (and necessary) for civilization itself, and he viewed everything from art to music to politics as expressions of these desires. However, he viewed the repression of his day as excessive, and argued in his most famous essay, Civilization and Its Discontents, that (inevitable) unfulfilled sexual desires led to unhappiness.

Rousseau theorized that amour de soi-meme (self love) was the basic instincts and simple desires of man, but that society imposed status and competition, leading to amore propre, which corrupts by complicating desires and causing people mask their feelings in search of status. Returning to the simpler, natural state involves peeling back the layers of civilization that have corrupted man’s fundamentally good and pure nature.

Wordsworth argued that poetry, by directly imparting emotions from author to reader, was superior to prose, and that the objective of such poetry was to connect readers with the long-forgotten reality of their authentic emotions. He often chose rural subjects and themes, contrasting them with artificial, mechanical, prosaic city life.

Shelley believed the use of poetry for moral refinement in its readers. By directly engaging emotion and imagination rather than reason, poetry can cultivate empathy and thus, ethical improvement. In describing their role in shaping cultural morality through aesthetics, Shelley called poets “the unacknowledged legislators of the World”.

The shape of an ECG wave is broken into 5 points: P is the top of the first gentle upward bump, Q is the bottom of the first downward spike, R is the top of the large upward spike, S is the bottom of the second downward spike, and T is the top of the second gentle upward bump.

Wealthy Romans were expected to give back to their cities in lavish displays of ("" love for one’s city) civic generosity, in the form of public works, monuments, and games. The citizens of each city (populus) did not think of themselves as beggars receiving charity - they jealously guarded their status and the proofs of their citizenship (only citizens were eligible for grain doles, for example). To skip over the populus and give to the truly destitute and immigrants, as Christian charity demanded, was an affront to the social order.

After Muhammed, the Rashidun (“rightly guided”) Caliphate ruled, first by Muhammad’s longtime general Abu Bakr, then his brother in law Umar, then son in law Uthman, and finally cousin (and first male convert) Ali ibn Abi Talib.

The statute of pleading (1364?) established English as the language of the courts of England, in order to make proceedings intelligible to the people. Many legal terms and phrases in English (and later, American) law are derived from pairing newly mandated English translations with the corresponding French terms previously in use, eg: law and order, breaking and entering, fit and proper, free and clear, and sale and transfer

Ultramontane means pope-centered, an attitude toward church affairs characterized by extraordinary deference to the pope and his prerogatives. (Ultramontanism was born in France, from which point of view the Vatican is “beyond the mountains,” hence ultramontane.)

— Kevin D. Williamson, “Against Fanaticism”, National Review Online, August 16, 2022

Orthonasal olfaction is the standard way we smell things (e.g., by sniffing), gustation is tasting, and retronasal olfaction is when scents pass through the oral cavity and are sensed in the back of the nasal cavity

The decision to break up the Soviet Union was taken by the leaders of the individual soviet republics without broad popular support

Immediately after the breakup, much of Russia’s industrial property was divided into shares, which tended to be bought up by the people with money

Yeltsin’s government allowed state-owned businesses to be sold for fractions of their market value in exchange for loans

Pottery can be made impermeable to water by glazing or by vitrification, the partial fusion of the clay by firing at high temperatures. Earthenware refers to unvitrified pottery, Stoneware may be vitrified or semi-vitrified, and Porcelain is vitrified and impermeable even without glaze. All ancient Greek and Roman pottery was earthenware, as vitrification requires much higher temperatures than their potters used.

Algiers was invaded in 1830 as a campaign stunt

In Old English, man was the generic term for a human, with wif and wer designating women and men, respectively. While wif-man mutated into woman, wer disappeared (surviving in the word werewolf), and men came to be referred to with the generic man. Similarly, girl was the generic term for children, with knave girl and gay girl denoting male and female children, respectively. Over time, girl came to refer to female children only.

The Pereiaslav Agreement of 1654 between Cossacks and the Tsar politically unified Ukraine with Russia, a unification which effectively lasted until the breakup of the Soviet Union

Boxing Day is believed to be named from the tradition of distributing the contents of the alms boxes in the narthex of Christian churches. The holiday is coincident with the Feast of Saint Stephen, one of the earliest deacons charged with caring for the poor.

Even more important to the functioning of the French government than the provincial estates were the sovereign courts, of which the most significant were the thirteen parlements that met in Paris and the main provincial capitals. Tracing their origins to the thirteenth century-the Parlement of Paris had been established in 1278-these courts heard appeals from lower courts throughout the realm. More importantly, they insisted that it was their duty to verify that royal laws and edicts did not violate the fundamental rights of the king’s subjects, which each French monarch solemnly swore to uphold when he was crowned. The parlements asserted the right to send the king remontrances (remonstrances) containing their criticisms and objections to new laws, and the right to delay registering laws until their complaints had been dealt with.

The ancient kingdom of Makuria was a Nubian Christian kingdom that extended from North of Thebes in Egypt to Northern Sudan. After repulsing a Muslim invasion in 651, they coexisted with Islamic neighbors until they were conquered in the 14th century by the Mamluks

Ships of the line were >= 60 guns and 400 men, frigates were 20 to 44 guns and <300 men

Galileo was allowed to speculate that the earth revolves around the sun, but was forbidden from describing this as settled, since he could not prove it. He was placed under house arrest after he published a fictional dialog in which a simpleton echoes the words of Urban VIII.

Blackletter was one of the three major typefaces in early Western typography, along with Italic and Roman types. Most of Western Europe shifted to Roman types by the 16th century, but Blackletter stayed prominent in German printing until Hitler (who considered it Jewish-influenced) mandated a shift to Antiqua, a Roman font.

The term white noise is used to describe noise with equal intensity at different frequencies, analogous to white light, which was thought to have a similarly flat power spectrum. Different colors of noise represent different distributions of frequencies.

The word barrel refers generally to casks of all sizes, but was originally used for a specific size of cask (32 gallons)

Police power refers to the generalized power to regulate, as distinct from enumerated powers

Jerusalem’s status as a Muslim holy site was greatly enhanced after the conflict with Christian crusaders. Multiple Muslim rulers in the __ th century offered up control of Jerusalem in negotiations with Christians.

Christians and Muslims were not monolithically aligned against each other throughout the crusades. At various times, factions within each group allied with “infidels”, sometimes against their co-religionists

The Roman province of Lusitania consisted mainly of present-day Portugal plus parts of Western Spain.

At the time of the First Crusade, the Fatimid fleet was overseen by the emir of the sea, or emir al-bahr (the source of the English word admiral).

The naming convention for Soviet small arms consisted of the weapon class/description followed by the weapon designer’s name and year of introduction. For instance, the AK-47 was the Avtomat Kalashnikova 47 (automatic rifle designed by Kalashnikov in 1947), and the PPS-43 was the Pistolet-pulemyot Sudayeva 43 (the submachine-gun designed by Sudayev in 1943)

Sprezzatura is a studied carelessness, especially as a style of art, fashion, or literature.

Corbettian and Mahanian are used as shorthand terms for the core principles of two masters of naval strategic thought. Mahanian (after Alfred Thayer Mahan) refers to the massing of capital ships (battleships or carriers) for a decisive fleet-on-fleet battle in order to achieve near-total command of the sea. Corbettian (after Sir Julian Stafford Corbett) is shorthand for a strategy of cumulative effects, in which capital ships are deployed in an elastic configuration across a broader but still mutually supporting front and in which naval actions are integrated with amphibious landings. -Masters of War: History’s Greatest Strategic Thinkers, by Andrew R. Wilson, US Naval War College

In ancient times, the cup bearer would taste the king’s drink before the king did, but not as a mere human shield - he was an important executive and the shared drink was a way of guarding against any plotting on his part

Due to fire code restrictions, most households in Dickensian London did not have an oven, so they would send their food off to the baker. The children’s patty cake rhyme describes marking one’s food with an initial so that it can be identified after baking in communal ovens

Puyi was the last emperor of China and final Qing dynasty ruler, becoming emperor at age two in 1908 but dethroned in 1912 in the Xinhai Revolution. In 1924, he was expelled from the palace and began to court the various factions fighting for control over China, including the Japanese, who installed him as the puppet ruler of Manchukuo during World War II.

With the fall of Japan, he was imprisoned as a war criminal by Stalin, who refused extradition to the Republic of China (likely saving his life) before handing him over to Mao, who realized the propaganda value of a reeducated emperor and allowed him to live. After his time in prison, Puyi expressed deep regret for his actions while emperor.

The founding fathers were influenced by theories of anacyclosis, specifically Polybius’ sequence of monarchy > kingship > tyranny > aristocracy > oligarchy > democracy > ochlocracy. In the early 1800s, the Federalists were called Anti-Republicans by the Republicans, who were called Democrats (initially as an insult) in turn.

In the 19th century stockholders of a bankrupt company could be dunned for the company’s outstanding debts. When companies went bankrupt, there was usually a rush to sell shares of that company to a banker who could absorb that debt. JP Morgan acquired a lot of money this way.

Pharma Decile = 10 - FLOOR(10* (sum() over (order by DESC ROWS BETWEEN UNBOUNDED PRECEDING AND CURRENT ROW) / sum() over ()) )

In a rocket engine, fuel and oxidizer must be forced into the engine at very high pressures, so a pre-burner engine is used to push them in (somewhat like a turbocharger in a car). An open-cycle pre-burner exhausts out into the air, while a closed cycle pre-burner sends the exhaust into the main engine. A full flow closed cycle pre burner send all of the fuel through a pre-burner (but only part of the oxidizer)

The Glass-Steagall act of 1933 separated commercial (deposits and loans) from investment (stocks and bonds) banking. Morgan Stanley was spun off from JP Morgan as a result.

On a submarine, oxygen is produced by A) electrolysis and B) oxygen candles, which create heat from burning small amounts of iron to release oxygen from sodium chlorate (NaClO3), resulting in a net production of oxygen. Carbon dioxide is scrubbed from the air using A) a monoethanolamine (MEA) cycle, which involves spraying lean MEA onto a flow of air, where it becomes rich by absorbing CO2, then boiling the solution in another chamber to release the CO2, and B) lithium hydroxide (LiOH), which passively absorbs CO2

The Levantine port of Byblos (about 15 miles north of Beirut) was a major trading destination for Egypt and an important source of papyrus for the Greeks, so much so that it gave its name to the Greek word for book, and in turn, the Bible.

The prevailing wind in Egypt blows boats upriver, making it an ideal conduit for trade in both directions, while the winds on the Tigris and Euphrates blow downriver, making it much more difficult to go upstream.

Trade winds are so called not because of their utility for trade, but because they are steady and regular

Bayes Factor for positive test = (true positive rate)/(false positive rate) = (sensitivity)/(1-specificity). For prevalence << 1, posterior ≈ (prior)x(Bayes Factor)

SONAR = SOund NAvigation and Ranging

The initial use of the term capitalism in its modern sense is attributed to French socialist Louis Blanc in 1850: “What I call ‘capitalism’ that is to say the appropriation of capital by some to the exclusion of others.”

Christmas is dated on Dec 25th because of a traditional belief that Jesus died on the same date that he was conceived. In the West, Good Friday was set as March 25th (equivalent to 14th day of Nisan), while in the East, the 14th day of the first spring month of the Greek calendar was chosen (equivalent to April 6th). From these dates, the West fixed Jesus’s birthday as March 25th + 9 months (Dec 25th), while the East fixed it as April 6th + 9 months (Jan 6th).

Traditional vaccines work by introducing the actual virus, or part of it, into the body to induce an immune response. To avoid actually causing disease, the virus is weakened or inactivated, or only a piece (subunit) of the virus is used. Manufacturing these vaccines requires growing the virus in large quantities (in chicken eggs for flu vaccines, for example), which takes months. Messenger RNA (mRNA) vaccines don’t use an actual virus – just instructions for cells to assemble proteins – and these can be synthesized in about a week. For the COVID-19 vaccine, the mRNA used contains assembly instructions for the “spike” protein that the virus uses to bind to and invade cells. Those antibodies should then work to fend off infection if the patient is exposed to the actual virus. Since only a piece the virus is replicated, mRNA vaccines eliminate the risk of a “bad batch” actually causing disease, as occurred during the early rollout of polio vaccine. -Akino Yamashita, 11/19, The Dispatch

The name coronavirus is derived from Latin corona, meaning “crown” or “wreath”, and refers to the characteristic appearance created by the viral spike proteins on the surface of the virus.

teleological ethical theories locate moral goodness in the consequences of our actions… There are many philosophers who reject the entire teleological agenda by arguing that moral goodness has nothing to do with the pleasure, happiness, and or consequences. Deontological theories are by definition duty-based. That is to say, that morality, according to deontology, consists in the fulfillment of moral obligations, or duties. Duties, in the deontological tradition, are most often associated with obeying absolute moral rules. TELEOLOGICAL AND DEONTOLOGICAL THEORIES By: Ronald F. White, Ph.D.

Penicillin was initially so costly to manufacture that it was recycled. Between 40 and 99% of penicillin is excreted intact within 4 hours of treatment, and it can be extracted from the crystalized urine of treated patients.

The Norse “vic” and the English “wic” both can mean bay or inlet, surviving in English in placenames such as Greenwich — linguistically if not socioeconomically equivalent to Green Bay — and in the name of the Icelandic capital, Reykjavik, the “smoking bay.”

— Kevin D Williamson, ‘Print the Legend’, NR Online, August 24, 2021

Marx and Ricardo both had a heterodox view of real wages such that Marx would say workers real wages fell if they got a smaller proportion of profit from their labor, even if they were much better off in absolute terms… Sowell, chapter 7

Marxism-Leninism branched off from classical Marxism in the early twentieth-century as a way to explain why the working class, instead of descending into grinding poverty and developing a revolutionary consciousness as predicted by Marx and Engels, was growing increasingly wealthy and adopting bourgeois values. Lenin theorized that the imperialist powers had temporarily circumvented Marx’s Laws of Economic Movement by claiming the wealth and raw materials of their colonies, and providing their workers with just enough benefits to keep them docile. To counter this, a vanguard of highly-trained revolutionaries was needed, rather than relying on a broad uprising of revolutionary consciousness to overthrow the capitalists. (New World Encyclopedia)… This changed the ideal of Communism from an uprising of the will of the people into something that needed to be imposed on the masses - by brutal oppression if necessary.

chuño, made by spreading potatoes outside to freeze on cold nights. As it expands, the ice inside potato cells ruptures cell walls. The potatoes are thawed by morning sun, then frozen again the next night. Repeated freeze thaw cycles transform the spuds into soft, juicy blobs. Farmers squeeze out the water to produce chuño: stiff, Styrofoam-like nodules about two-thirds smaller and lighter than the original tubers. Long exposure to the sun turns them gray-black; cooked into a spicy Andean stew, they resemble gnocchi, the potato-flour dumplings favored in central Italy. Chuño can be kept for years without refrigeration, meaning that it can be stored as insurance against bad harvests. It was the food that sustained the conquering Inka armies.

— Charles Mann, “1493”

In the altiplano, guanacos and vicuñas (wild relatives of the llama) lick clay before eating poisonous plants. The toxins in the foliage stick - more technically, “adsorb” - to the fine clay particles. Bound to dirt, the harmful substances pass through the animals’ digestive system without affecting it.

— Charles Mann, “1493”

Native Americans north of roughly the Chesapeake Bay did not practice slavery as extensively as the Mississippi civilizations to the south, and at the beginning of the 18th century, most of the slaves in Carolina were natives.

Earthworms are not native to North America, and were brought over by colonists. They transform forest floors by more rapidly decomposing the organic layer.

In the Roman era, copper was mined principally on Cyprus, the origin of the name of the metal, from aes сyprium (metal of Cyprus), later corrupted to сuprum

Asphalt is recyclable, and can be removed, heated, mixed, and replaced in a single ”pass”, eliminating the need for major transportation costs

Pressure drag is induced from airflow separation - a low-pressure zone is created behind a wing, and the pressure differential between the front and back of the wing pushes the plane backwards.

Wend and go were interchangeable in Old English, with past tenses went and gaed, respectively. Ultimately, went survived as the irregular past tense of go, while wend and gaed fell by the wayside.

The Ottoman Empire banned printing for nearly three hundred years (until 1726) and then only lifted the ban for non-religious works

To reclaim land from the sea, the Dutch had to build a dyke, pump out the sea water, then “rinse” the alluvial soil left behind by pumping in fresh water and draining repeatedly to get rid of the excess salt. This constant pumping was aided greatly by windmills, particularly after the advent of rotating windmills that could pump regardless of wind direction

After Britain announced that it would stop supporting the Greek government against Communists, Truman developed the Truman Doctrine (“The policy of the United States to support free peoples who are resisting attempted subjugation by armed minorities or by outside pressures”).

supine means face up and prone is face down

The H#N# designation of flu viruses denotes the combination of surface proteins Hemagglutinin and Neuraminidase, each of which have several sub-types

Russia

Russian rulers traditionally had two aspects of leadership that were expected from a Czar: their grozny (power and might) and tshishie (caring and nurturing)

Traditional Marxist dogma held that capitalism was a necessary historical step before communism and would eventually collapse, but some revolutionaries believed they could “skip past” capitalism straight to communism

The Russian Social Democratic Labour Party (RSDLP) splintered at its 2nd Congress in 1903 following a dispute between Julius Martov and Vladimir Lenin. Martov and his supporters viewed freedom and democracy as internally good natural rights, and favored educating the populace to foment change. Lenin, on the other hand, saw no value in freedom or rights beyond their immediate utilitarian value, and believed that a revolutionary vanguard of hardcore believers was necessary. Accordingly, Martov’s faction favored a more expansive definition of party membership, while Lenin wanted to restrict it to a dedicated few. Lenin won a crucial vote on the question of party membership, leading to his faction taking the name Bolsheviks, from большинство (majority) and Martov’s faction being called Mensheviks, from меньшинство (minority).

Israel

In the late 19th and early 20th centuries, Jewish immigration into Palestine was opposed by the Arab inhabitants, who were mostly not landowners. The Ottoman rulers, though ostensibly sympathetic to their co-religionists, could be bribed and mostly looked the other way. When the British took over the Palestine Mandate, they encouraged Jewish immigration (under the Balfour Declaration), resulting in a sharp increase in the Jewish population. Tensions quickly escalated as Arab nationalism emerged, and increasingly violent Arab revolts and riots broke out in the 1920s and 1930s

In 1937, the Peel Commission recommended a 2-state solution, with a Jewish state containing Galilee and much of the Mediterranean coast, and with Britain retaining a strip of land encompassing Jerusalem and Bethlehem and extending to Jaffa. The commission proposed resettling hundreds of thousands of Arabs from the proposed Jewish state and a few hundred Jews from the proposed Arab state

In 1939, after stamping out a major Arab revolt and facing the prospect of war in Europe, Britain reversed course and issued a white paper stating its intentions for drastically reduced Jewish immigration and Palestinian statehood within 10 years. The aftermath of the crushed revolt weakened Arab military capability, while Jewish volunteers serving with the British army gained valuable experience

In 1946, against the backdrop of terrorist activities by hardline Jewish paramilitary groups (e.g., the Irgun / IZL and Lehi / Stern Gang), the 12-person Anglo-American Committee recommended placing Palestine under UN trusteeship (with an eventual goal of either a 1- or 2-state solution) and increasing Jewish immigration. This recommendation was vehemently rejected by the Arab community, leading Britain to ask the UN for help in April 1947

The UN set up a special committee on Palestine (UNSCOP) that toured the region, met with Zionist representatives (Arabs boycotted) and recommended a partition plan. This resolution was supported by the Soviet Union, actively lobbied for by the USA, and quietly opposed by the UK. It passed by a narrow vote in the UN General Assembly on November 27, 1947.

Edith Roosevelt (Teddy’s 2nd wife) was a childhood friend and reunited with him a couple years after his first wife Alice died

William Taft was appointed governor general of the Philippines shortly after they were annexed, missing an appointment to the US Supreme Court

When navigating channels, returning refers to moving from a larger body of water to a smaller (going upstream). Red lights are placed near the shore such that they will be on a boater’s right side when heading upstream, leading to the mnemonic red right returning.

The Greek word metis meant a quality that combined wisdom and cunning, considered to be highly admirable, and embodied by the hero Odysseus. This quality was opposed to Βία (meaning “power, force, might”), embodied by Achilles.

British presence in India was confined to trading posts until the mid 1770s, when adventurers in the employ of the East India Company (notably Robert Clive) exploited European military supremacy to play kingmakers in various territories of the crumbling Mogul empire. Each successive client granted lucrative concessions (monetary and territorial) to the EIC upon taking power. Warren Hastings (Governor-General of Bengal from 1772–1785) was opposed to alliances and conquests in India but prosecuted a successful war on the French and their Marathi and Mysorean allies, the financing of which played a major role in his impeachment trial.

In the 19th century, natural gas was obtained as a by-product of producing oil, since the small, light gas carbon chains came out of solution as the extracted fluids underwent pressure reduction on the way to the surface, similar to uncapping a soft drink bottle where the carbon dioxide effervesces (the escape of gas from an aqueous solution and the resulting foaming or fizzing). Natural gas is comprised of a mixture of gasses, including methane and propane. Refined propane has a higher energy density

Blood types are determined by the presence or absence of two antigens (A and B) and a protein called the Rh factor (+ and -) on the surface of red blood cells. Each person can have either (A / B), neither (O), or both (AB) antigens, and the Rh factor can be either present (+) or absent (–), creating the 8 most common blood types (A+, A-, B+, B-, O+, O-, AB+, AB-). Blood transfusions will be accepted only if the donor blood does not contain antigens or Rh factor foreign to the recipient. O- blood, having neither antigen and no Rh factor, is the universal donor. AB+ blood, having both antigens and an Rh factor, is the universal recipient.

John D Rockefeller

John D Rockefeller’s father (Big Bill) was a traveling snake oil salesmen and bigamist who abandoned his first family

Rockefeller set up his first refinery near Cleveland so he could play railroads off of lake/canal shipping and lower his transportation costs. After gaining a dominant position in oil refining, he maintained it through what he called “cooperation”, often overpaying to buy out his rivals. Those who took payment in standard oil stock often went on to become fabulously wealthy as a result.

Edith Rockefeller went to Switzerland and became a benefactor and devotee of Carl Jung and Jungian analysis

The Islamic, or Hijri calendar is a lunar calendar consisting of 12 lunar months in a year of 354 or 355 days. The Hebrew lunar year is about eleven days shorter than the solar year, so the Hebrew calendar is lunisolar and uses the 19-year Metonic cycle to bring it into line with the solar year, with the addition of an intercalary month every two or three years, for a total of seven times per 19 years.

The Metonic cycle is a period of very close to 19 years that is nearly a common multiple of the solar year and the synodic (lunar) month. The Greek astronomer Meton of Athens (fifth century BC) observed that a period of 19 years is almost exactly equal to 235 synodic months and, rounded to full days, counts 6,940 days. The difference between the two periods (of 19 solar years and 235 synodic months) is only a few hours, depending on the definition of the year.

The human airway is coated in a mucus that traps foreign particles before they reach the delicate membranes of the lungs. This mucus is constantly being replenished, and the old mucus is pushed up into the throat by cilia. Nicotine paralyzes the cilia, causing the mucus to become saturated and less effective. Immediately after smokers quit, their newly-active cilia begin pushing up the saturated mucus.

Heading into the 1860 Republican National Convention, Lincoln was not considered a likely candidate. Chicago was selected as the convention site in part because it was considered neutral ground between the likely candidates: William Seward (later Secretary of State), Salmon Chase (later Treasury secretary), and Edwin Bates (later Attorney General). Lincoln was chosen largely as the consensus second choice of multiple competing factions.

Electrum is a naturally occurring gold/silver alloy

Before Pope Gregory VII’s ”Gregorian Reforms” Catholic priests could buy clerical appointments (known as “simony”) and many had wives and/or concubines (“nicolaitism”). Clerical appointments could also be bequeathed to sons, which led to corruption of the church. Gregory VII was also a key player in the “Investiture Controversy” over the ability to choose and install clergy. It began as a power struggle between Gregory VII and Henry IV (then King, later Holy Roman Emperor) and ended nearly 50 years later when Pope Callixtus II and Emperor Henry V agreed on the Concordat of Worms, which required bishops to swear an oath of fealty to the secular monarch but left selection to the church.

The most energy efficient method to stop an orbit and crash a satellite into a larger body is to thrust “forwards” to speed up the satellite to nearly escape velocity, wait until it is far from the body, then thrust “backwards” to zero the orbital velocity. Eventually the satellite will accelerate towards and then crash into the larger body. This method requires a large Delta-V to accelerate the satellite to escape velocity - then a minimal burn to cancel out the orbital velocity when far away.

Quarks: two kinds in everyday nature: Up and Down; other kinds decay quickly. There are also Anti-up and Anti-down quarks sometimes.

Protons and neutrons are each made of three quarks. Proton = 2Up + 1Down, Neutron = 1Up+2Down

Up quarks have +2/3 electric charge, Down quarks have -1/3 charge; this is why protons have +1 charge and neutrons have 0

Quarks have color charge (nothing to do with visual color or light), which is like electric charge, but not intrinsic (it can be traded around) and there are three different “axes” of charge (red, green, blue), each of which can be positive or negative, and also red+green+blue = 0. Within a proton or neutron, there is one each of red, green, and blue, and they’re all positive or all negative, so that total charge = 0. The assignment color charge to quarks randomly changes as it is passed back and forth with smaller particles called gluons.

Quantum color confinement: the color force (gluon field) between two quarks has a weird property: as two quarks are separated, the color force, unlike electric charge, increases linearly (like a spring) rather than falling off. At small distances (atomic scale), the force becomes great enough that the potential energy of the bond spontaneously converts into a new quark-antiquark pair. So if you pulled an Up quark out of a proton, very soon it would “pop out” an additional Up/Anti-up pair, the new Up would go back into the proton, and the new Anti-up would spin off with the old Up to form a new kind of particle called a meson. Bottom line: it’s impossible to observe an individual quark except at ridiculous energies (cosmic rays, particle collider), and then only very briefly.

Rubisco is a plant enzyme that grabs either CO2 or O2 indisciminately, leading to either carboxylation or oxygenation, respectively of RuBP. If carboxylation happens, then the Calvin cycle proceeds, but if oxygenation happens, photorespiration occurs, and is much less efficient as the plant needs to detox the resulting ammonia. Researchers have engineered a new, more efficient pathway for photorespiration, boosting plant growth. Corn, sugar cane, and a few other plants are called C4 plants - they shield the Rubisco enzyme from the open air and a secondary enzyme pumps CO2 to it, massively reducing the “error rate” of the Rubisco enzyme. Thus corn and sugar cane grow very efficiently.

Quantum computing uses particles entangled together in discrete ways. E.g., if two particles are linked, their individual spins may be unknown, but they are known to be opposite of each other. If you carefully build a chain out of these interactions (with each known link serving as a logical operator of sorts), you can then measure the value of one particle and know the value of all the other particles, similar to how differential equations can be modeled using electrical circuits of known resistance: set up the problem using a physical analogue, then measure the answer.

Molten salt reactors (MSRs) fall into two classes: salt-cooled reactors, in which the core contains a solid fuel and liquid salt coolant, and salt-fueled reactors, in which the fuel is dissolved within the salt. The term fluoride salt-cooled high-temperature reactor (FHR) is used to distinguish fluoride salt-cooled MSRs from other MSRs.

Uranium 235 is the fissile isotope, 238 is the non fissile isotope. The natural state is 0.7% 235U. To achieve fission, uranium must be enriched to about 4% for nuclear power plants, and to about 90% for bombs.

Overwatering causes oxygen loss in the soil as the plant and bacteria consume it with no way for gases to penetrate the water logged soil. Lack of oxygen causes bad bacteria to start forming that will often eat plant roots and/or emit toxins that kill the plant roots so they can eat the decaying organic matter.

— r/askscience

Anadromous fish migrate from the sea up (Greek: ἀνά ana, “up” and δρόμος dromos, “course”) into fresh water to spawn, such as salmon, striped bass, and the sea lamprey…Catadromous fish migrate from fresh water down into the sea to spawn, such as eels

The Meredith effect is a phenomenon whereby the heat of an engine can be used to produce thrust by expanding and accelerating the air flowing into the radiator. In the P51 Mustang, up to 90% of the aerodynamic drag produced by the radiator was offset by the design of the cooling duct.

Seven Years’ War

Before the Seven Years’ War, Britain wanted to protect the Netherlands (strategic ally) and Hanover (George II’s homeland). Austria was more focused on Prussia than France, so Britain had trouble getting them to commit resources to Dutch defense, and British public opinion was far more worried about Dutch defense than Hanoverian.

At the outset of the Seven Years’ War, Britain sent three expeditions: Braddock, a naval expedition to intercept French reinforcements, and a New England militia expedition to Nova Scotia. The naval expedition was partially successful and the militia took Nova Scotia, but Braddock was utterly defeated. The upshot was that Britain appeared to be the aggressor in the Seven Years War but had not achieved a decisive victory. Thus France was not discouraged from entering the war.

At the outset of the Seven Years’ War, France and Austria signed a treaty of mutual defense whereby France also agreed not to invade the Netherlands, which was very strategically limiting in a war with Britain

Leading up to the Seven Years’ War, the French were responding to English trading (not settlement) in the Ohio river valley. Superior shipping and industry allowed English traders to offer better deals to native fur traders.

When the French and English were setting the new world, the French would claim entire river valleys /drainage basins at a time (e.g., the Ohio River valley), while the English preferred drawing lines on the map

Churchill’s parents were quite famous and frequently absent

Under Jimmy Carter, the USA ended its support for the Shah of Iran, and he was overthrown soon after

Nuclear missiles were pointed at cities rather than silos as a gesture of defensive intent. striking silos only made sense if there were missiles in them - i.e., as a pre-emptive, aggressive attack

Reconstruction died quickly - almost as soon as Grant left office

Northern Democrats opposed the Dred Scott decision because it undermined popular sovereignty

The us started the war of 1812

South Vietnam was not overrun immediately after US ground troops withdrew. North Vietnam launched the Easter Offensive in 1972 (a conventional attack w/ armor) and was beaten back by Operation Linebacker. It took another 2 years or so for Saigon to be overrun.

Wristwatches did not become popular with men until WW1, when they were necessary for coordinating artillery barrages

An azeotrope is a mixture ratio of two or more chemicals such that the mixture cannot be refined by distillation - that is, the vapor produced from boiling the mixture has a composition ratio equal to the mixture itself, and does not change the ratio. Thus alcohol (ethanol : water) has a limit of ~190 proof (95.63% ethanol)

Domesticable animals tend to have a strong herd instinct and a strict hierarchy that lets humans “skip to the front of the line” when domesticating them

Dutch philosopher/lawyer Hugo Grotius helped lay the foundations for international free trade and laissez faire legal and economic theory

A panegyric is a self-serving historical account

Hungary has a tradition of semi-democratic government going all the way back to the Golden Bull of 1222

Melanin concentrates near the nucleus of cells to protect the DNA from UV light

Baryonic matter is regular (non-dark) matter. Dark matter interacts via gravity but not much else. When 2 galaxy clusters collide, the Stars mostly miss each other, the gas clouds (representing most of the baryonic matter) collide a lot and end up smashing into one big cloud, and the dark matter collides very little. By examining gravitational lensing, we can see that most of the dark matter is in or near the galaxies rather than the gas cloud (which is where the baryonic mass center is)

Plans are worthless, but planning is everything.

— Eisenhower, quoting an Army aphorism

Fed bailed out institutions and got mortgage-backed securities as collateral. It ended up working out ok, but using securities as collateral is not at all prudent EconTalk with George Selgin, 2015-12-14

RSA Cryptography uses large prime numbers multiplied together, which are hard to back-calculate