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🔗 Engineering 🔗 Chicago

During the 1850s and 1860s, engineers carried out a piecemeal raising of the level of central Chicago. Streets, sidewalks, and buildings were physically raised on jackscrews. The work was funded by private property owners and public funds.

🔗 Physics

The one-electron universe postulate, proposed by John Wheeler in a telephone call to Richard Feynman in the spring of 1940, is the hypothesis that all electrons and positrons are actually manifestations of a single entity moving backwards and forwards in time. According to Feynman:

🔗 Linguistics 🔗 Linguistics/Applied Linguistics 🔗 Languages 🔗 Constructed languages 🔗 English Language

E-Prime (short for English-Prime or English Prime, sometimes denoted É or E′) is a version of the English language that excludes all forms of the verb to be, including all conjugations, contractions and archaic forms.

Some scholars advocate using E-Prime as a device to clarify thinking and strengthen writing. A number of other scholars have criticized E-Prime's utility.

🔗 Metalworking 🔗 Materials

Low-background steel is any steel produced prior to the detonation of the first nuclear bombs in the 1940s and 1950s. With the Trinity test and the nuclear bombings of Hiroshima and Nagasaki in 1945, and then subsequent nuclear weapons testing during the early years of the Cold War, background radiation levels increased across the world. Modern steel is contaminated with radionuclides because its production uses atmospheric air. Low-background steel is so-called because it does not suffer from such nuclear contamination. This steel is used in devices that require the highest sensitivity for detecting radionuclides.

The primary source of low-background steel is ships that were constructed before the Trinity test, most famously the scuttled German World War I warships in Scapa Flow.

🔗 Military history/Early Muslim military history 🔗 Games

The two envelopes problem, also known as the exchange paradox, is a brain teaser, puzzle, or paradox in logic, probability, and recreational mathematics. It is of special interest in decision theory, and for the Bayesian interpretation of probability theory. Historically, it arose as a variant of the necktie paradox. The problem typically is introduced by formulating a hypothetical challenge of the following type:

It seems obvious that there is no point in switching envelopes as the situation is symmetric. However, because you stand to gain twice as much money if you switch while risking only a loss of half of what you currently have, it is possible to argue that it is more beneficial to switch. The problem is to show what is wrong with this argument.

🔗 Aviation 🔗 Disaster management 🔗 Aviation/Aviation accident 🔗 Canada 🔗 Aviation/aircraft 🔗 Aviation/gliding 🔗 Canada/History of Canada 🔗 Canada/Manitoba

Air Canada Flight 143 was a Canadian scheduled domestic passenger flight between Montreal and Edmonton that ran out of fuel on July 23, 1983, at an altitude of 41,000 feet (12,000 m), midway through the flight. The crew was able to glide the Boeing 767 aircraft safely to an emergency landing at a former Royal Canadian Air Force base in Gimli, Manitoba, that had been turned into a motor racing track. This unusual aviation incident earned the aircraft the nickname "Gimli Glider".

The subsequent investigation revealed that a combination of company failures, human errors and confusion over unit measures had led to the aircraft being refuelled with insufficient fuel for the planned flight.

🔗 Mathematics

A galactic algorithm is one that runs faster than any other algorithm for problems that are sufficiently large, but where "sufficiently large" is so big that the algorithm is never used in practice. Galactic algorithms were so named by Richard Lipton and Ken Regan, as they will never be used on any of the merely terrestrial data sets we find here on Earth.

An example of a galactic algorithm is the fastest known way to multiply two numbers, which is based on a 1729-dimensional Fourier transform. This means it will not reach its stated efficiency until the numbers have at least 2¹⁷²⁹¹² bits (at least 10¹⁰³⁸ digits), which is vastly larger than the number of atoms in the known universe. So this algorithm is never used in practice.

Despite the fact that they will never be used, galactic algorithms may still contribute to computer science:

• An algorithm, even if impractical, may show new techniques that may eventually be used to create practical algorithms.
• Computer sizes may catch up to the crossover point, so that a previously impractical algorithm becomes practical.
• An impractical algorithm can still demonstrate that conjectured bounds can be achieved, or alternatively show that conjectured bounds are wrong. As Lipton says "This alone could be important and often is a great reason for finding such algorithms. For example, if tomorrow there were a discovery that showed there is a factoring algorithm with a huge but provably polynomial time bound, that would change our beliefs about factoring. The algorithm might never be used, but would certainly shape the future research into factoring." Similarly, a ${\displaystyle O\left(n^{2^{100}}\right)}$ algorithm for the Boolean satisfiability problem, although unusable in practice, would settle the P versus NP problem, the most important open problem in computer science and one of the Millennium Prize Problems.

🔗 Philosophy 🔗 Skepticism 🔗 Psychology

Brandolini's law, also known as the bullshit asymmetry principle, is an internet adage which emphasizes the difficulty of debunking bullshit: "The amount of energy needed to refute bullshit is an order of magnitude bigger than to produce it."

🔗 Palaeontology

The cat gap is a period in the fossil record of approximately 25 to 18.5 million years ago in which there are few fossils of cats or cat-like species found in North America. The cause of the "cat gap" is disputed, but may have been caused by changes in the climate (global cooling), changes in the habitat and environmental ecosystem, the increasingly hypercarnivorous trend of the cats (especially the nimravids), volcanic activity, evolutionary changes in dental morphology of the Canidae species present in North America, or a periodicity of extinctions called van der Hammen cycles.

🔗 Computing 🔗 Marketing & Advertising 🔗 Computing/Software 🔗 Computing/Free and open-source software 🔗 Open 🔗 Microsoft

"Embrace, extend, and extinguish" (EEE), also known as "embrace, extend, and exterminate", is a phrase that the U.S. Department of Justice found was used internally by Microsoft to describe its strategy for entering product categories involving widely used standards, extending those standards with proprietary capabilities, and then using those differences in order to strongly disadvantage its competitors.