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🔗 Biography 🔗 Biography/sports and games 🔗 Cycling

Thomas Stevens (24 December 1854 – 24 January 1935) was the first person to circle the globe by bicycle. He rode a large-wheeled Ordinary, also known as a penny-farthing, from April 1884 to December 1886. He later searched for Henry Morton Stanley in Africa, investigated the claims of Indian ascetics and became manager of the Garrick Theatre in London.

🔗 Religion 🔗 Classical Greece and Rome 🔗 Middle Ages 🔗 Middle Ages/History 🔗 Cryptography 🔗 Cryptography/Computer science 🔗 Latin 🔗 Christianity 🔗 Jewish history 🔗 Occult 🔗 Mysticism

The Sator Square (or Rotas Square) is a word square containing a five-word Latin palindrome. The earliest form has ROTAS as the top line, but in time the version with SATOR on the top line became dominant. It is a 5X5 square made up of five 5-letter words, thus consisting of 25 letters in total. These 25 letters are all derived from 8 Latin letters: 5 consonants (S, T, R, P, N) and 3 vowels (A, E, O).

In particular, this is a square 2D palindrome, which is when a square text admits four symmetries: identity, two diagonal reflections, and 180 degree rotation. As can be seen, the text may be read top-to-bottom, bottom-to-top, left-to-right, or right-to-left; and it may be rotated 180 degrees and still be read in all those ways.

The Sator Square is the earliest dateable 2D palindrome. It was found in the ruins of Pompeii, at Herculaneum, a city buried in the ash of Mount Vesuvius in 79 AD. It consists of a sentence written in Latin: "Sator Arepo Tenet Opera Rotas." Its translation has been the subject of speculation with no clear consensus; see below for details.

Other 2D Palindrome examples may be found carved on stone tablets or pressed into clay before being fired.

🔗 Philosophy 🔗 Philosophy/Logic 🔗 Business 🔗 Politics 🔗 Psychology 🔗 Marketing & Advertising

Serial-position effect is the tendency of a person to recall the first and last items in a series best, and the middle items worst. The term was coined by Hermann Ebbinghaus through studies he performed on himself, and refers to the finding that recall accuracy varies as a function of an item's position within a study list. When asked to recall a list of items in any order (free recall), people tend to begin recall with the end of the list, recalling those items best (the recency effect). Among earlier list items, the first few items are recalled more frequently than the middle items (the primacy effect).

One suggested reason for the primacy effect is that the initial items presented are most effectively stored in long-term memory because of the greater amount of processing devoted to them. (The first list item can be rehearsed by itself; the second must be rehearsed along with the first, the third along with the first and second, and so on.) The primacy effect is reduced when items are presented quickly and is enhanced when presented slowly (factors that reduce and enhance processing of each item and thus permanent storage). Longer presentation lists have been found to reduce the primacy effect.

One theorised reason for the recency effect is that these items are still present in working memory when recall is solicited. Items that benefit from neither (the middle items) are recalled most poorly. An additional explanation for the recency effect is related to temporal context: if tested immediately after rehearsal, the current temporal context can serve as a retrieval cue, which would predict more recent items to have a higher likelihood of recall than items that were studied in a different temporal context (earlier in the list). The recency effect is reduced when an interfering task is given. Intervening tasks involve working memory, as the distractor activity, if exceeding 15 to 30 seconds in duration, can cancel out the recency effect. Additionally, if recall comes immediately after the test, the recency effect is consistent regardless of the length of the studied list, or presentation rate.

Amnesiacs with poor ability to form permanent long-term memories do not show a primacy effect, but do show a recency effect if recall comes immediately after study. People with Alzheimer's disease exhibit a reduced primacy effect but do not produce a recency effect in recall.

🔗 United States 🔗 Military history 🔗 Philosophy 🔗 Philosophy/Logic 🔗 Military history/Military biography

The McNamara fallacy (also known as the quantitative fallacy), named for Robert McNamara, the US Secretary of Defense from 1961 to 1968, involves making a decision based solely on quantitative observations (or metrics) and ignoring all others. The reason given is often that these other observations cannot be proven.

The first step is to measure whatever can be easily measured. This is OK as far as it goes. The second step is to disregard that which can't be easily measured or to give it an arbitrary quantitative value. This is artificial and misleading. The third step is to presume that what can't be measured easily really isn't important. This is blindness. The fourth step is to say that what can't be easily measured really doesn't exist. This is suicide.

The fallacy refers to McNamara's belief as to what led the United States to defeat in the Vietnam War—specifically, his quantification of success in the war (e.g., in terms of enemy body count), ignoring other variables.

🔗 Aviation 🔗 Aviation/aircraft

A propfan, also called an open rotor engine, or unducted fan, is a type of aircraft engine related in concept to both the turboprop and turbofan, but distinct from both. The design is intended to offer the speed and performance of a turbofan, with the fuel economy of a turboprop. A propfan is typically designed with a large number of short, highly twisted blades, similar to a turbofan's bypass compressor (the fan itself). For this reason, the propfan has been variously described as an "unducted fan" or an "ultra-high-bypass (UHB) turbofan."

🔗 History 🔗 Mathematics 🔗 Books 🔗 Greece 🔗 History of Science

The Archimedes Palimpsest is a parchment codex palimpsest, originally a Byzantine Greek copy of a compilation of Archimedes and other authors. It contains two works of Archimedes that were thought to have been lost (the Ostomachion and the Method of Mechanical Theorems) and the only surviving original Greek edition of his work On Floating Bodies. The first version of the compilation is believed to have been produced by Isidorus of Miletus, the architect of the geometrically complex Hagia Sophia cathedral in Constantinople, sometime around AD 530. The copy found in the palimpsest was created from this original, also in Constantinople, during the Macedonian Renaissance (c. AD 950), a time when mathematics in the capital was being revived by the former Greek Orthodox bishop of Thessaloniki Leo the Geometer, a cousin of the Patriarch.

Following the sack of Constantinople by Western crusaders in 1204, the manuscript was taken to an isolated Greek monastery in Palestine, possibly to protect it from occupying crusaders, who often equated Greek script with heresy against their Latin church and either burned or looted many such texts (including at least two other copies of Archimedes). The complex manuscript was not appreciated at this remote monastery and was soon overwritten (1229) with a religious text. In 1899, nine hundred years after it was written, the manuscript was still in the possession of the Greek church, and back in Istanbul, where it was catalogued by the Greek scholar Papadopoulos-Kerameus, attracting the attention of Johan Heiberg. Heiberg visited the church library and was allowed to make detailed photographs in 1906. Most of the original text was still visible, and Heiberg published it in 1915. In 1922 the manuscript went missing in the midst of the evacuation of the Greek Orthodox library in Istanbul, during a tumultuous period following the World War I. Concealed for over 70 years by a Western businessman, forged pictures were painted on top of some text to increase resale value. Unable to sell the book privately, in 1998 the businessman's daughter risked a public auction in New York contested by the Greek church; the U.S. court ruled for the auction, and the manuscript was purchased by an anonymous buyer (rumored to be Jeff Bezos). The texts under the forged pictures, and previously unreadable texts, were revealed by analyzing images produced by ultraviolet, infrared, visible and raking light, and X-ray.

All images and transcriptions are now freely available on the web at the Archimedes Digital Palimpsest under the Creative Commons License CC BY.

🔗 England 🔗 English Royalty

The Groom of the Stool (formally styled: "Groom of the King's Close Stool") was the most intimate of an English monarch's courtiers, responsible for assisting the king in excretion and ablution.

The physical intimacy of the role naturally led to his becoming a man in whom much confidence was placed by his royal master and with whom many royal secrets were shared as a matter of course. This secret information—while it would never have been revealed, for it would have led to the discredit of his honour—in turn led to his becoming feared and respected and therefore powerful within the royal court in his own right. The office developed gradually over decades and centuries into one of administration of the royal finances, and under Henry VII, the Groom of the Stool became a powerful official involved in setting national fiscal policy, under the "chamber system".

Later, the office was renamed Groom of the Stole. The Tudor historian David Starkey classes this change as classic Victorianism: "When the Victorians came to look at this office, they spelt it s-t-o-l-e, and imagined all kinds of fictions about elaborate robes draped around the neck of the monarch at the coronation;" however, the change is in fact seen as early as the 17th century.

🔗 Electronics

The two capacitor paradox or capacitor paradox is a paradox, or counterintuitive thought experiment, in electric circuit theory. The thought experiment is usually described as follows: Two identical capacitors are connected in parallel with an open switch between them. One of the capacitors is charged with a voltage of ${\displaystyle V_{i}}$, the other is uncharged. When the switch is closed, some of the charge ${\displaystyle Q=CV_{i}}$ on the first capacitor flows into the second, reducing the voltage on the first and increasing the voltage on the second. When a steady state is reached and the current goes to zero, the voltage on the two capacitors must be equal since they are connected together. Since they both have the same capacitance ${\displaystyle C}$ the charge will be divided equally between the capacitors so each capacitor will have a charge of ${\displaystyle {Q \over 2}}$ and a voltage of ${\displaystyle V_{f}={Q \over 2C}={V_{i} \over 2}}$. At the beginning of the experiment the total initial energy ${\displaystyle W_{i}}$ in the circuit is the energy stored in the charged capacitor:

${\displaystyle W_{i}={1 \over 2}CV_{i}^{2}}$.

At the end of the experiment the final energy ${\displaystyle W_{f}}$ is equal to the sum of the energy in the two capacitors

${\displaystyle W_{f}={1 \over 2}CV_{f}^{2}+{1 \over 2}CV_{f}^{2}=CV_{f}^{2}=C({V_{i} \over 2})^{2}={1 \over 4}CV_{i}^{2}={1 \over 2}W_{i}}$

Thus the final energy ${\displaystyle W_{f}}$ is equal to half of the initial energy ${\displaystyle W_{i}}$. Where did the other half of the initial energy go?

🔗 Military history 🔗 Comedy 🔗 Military history/Maritime warfare 🔗 Military history/European military history 🔗 Military history/British military history

The Dreadnought hoax was a practical joke pulled by Horace de Vere Cole in 1910. Cole tricked the Royal Navy into showing their flagship, the battleship HMS Dreadnought, to a fake delegation of Abyssinian royals. The hoax drew attention in Britain to the emergence of the Bloomsbury Group, among whom some of Cole's collaborators numbered. The hoax was a repeat of a similar impersonation which Cole and Adrian Stephen had organised while they were students at Cambridge in 1905.

🔗 Typography 🔗 Primates