Have a deep view into what people are curious about.

🔗 Sanitation

A shit flow diagram (also called excreta flow diagram or SFD) is a high level technical drawing used to display how excreta moves through a location, and functions as a tool to identify where improvements are needed. The diagram has a particular focus on treatment of the waste, and its final disposal or use. SFDs are most often used in developing countries.

🔗 Mathematics

Hilbert's twenty-fourth problem is a mathematical problem that was not published as part of the list of 23 problems known as Hilbert's problems but was included in David Hilbert's original notes. The problem asks for a criterion of simplicity in mathematical proofs and the development of a proof theory with the power to prove that a given proof is the simplest possible.

The 24th problem was rediscovered by German historian Rüdiger Thiele in 2000, noting that Hilbert did not include the 24th problem in the lecture presenting Hilbert's problems or any published texts. Hilbert's friends and fellow mathematicians Adolf Hurwitz and Hermann Minkowski were closely involved in the project but did not have any knowledge of this problem.

This is the full text from Hilbert's notes given in Rüdiger Thiele's paper. The section was translated by Rüdiger Thiele.

The 24th problem in my Paris lecture was to be: Criteria of simplicity, or proof of the greatest simplicity of certain proofs. Develop a theory of the method of proof in mathematics in general. Under a given set of conditions there can be but one simplest proof. Quite generally, if there are two proofs for a theorem, you must keep going until you have derived each from the other, or until it becomes quite evident what variant conditions (and aids) have been used in the two proofs. Given two routes, it is not right to take either of these two or to look for a third; it is necessary to investigate the area lying between the two routes. Attempts at judging the simplicity of a proof are in my examination of syzygies and syzygies [Hilbert misspelled the word syzygies] between syzygies (see Hilbert 42, lectures XXXII–XXXIX). The use or the knowledge of a syzygy simplifies in an essential way a proof that a certain identity is true. Because any process of addition [is] an application of the commutative law of addition etc. [and because] this always corresponds to geometric theorems or logical conclusions, one can count these [processes], and, for instance, in proving certain theorems of elementary geometry (the Pythagoras theorem, [theorems] on remarkable points of triangles), one can very well decide which of the proofs is the simplest. [Author's note: Part of the last sentence is not only barely legible in Hilbert's notebook but also grammatically incorrect. Corrections and insertions that Hilbert made in this entry show that he wrote down the problem in haste.]

🔗 Spaceflight

Project Orion was a study of a spacecraft intended to be directly propelled by a series of explosions of atomic bombs behind the craft (nuclear pulse propulsion). Early versions of this vehicle were proposed to take off from the ground (with significant associated nuclear fallout); later versions were presented for use only in space. Six non-nuclear tests were conducted using models. The project was eventually abandoned for multiple reasons such as the Partial Test Ban Treaty which banned nuclear explosions in space as well as concerns over nuclear fallout.

The idea of rocket propulsion by combustion of explosive substance was first proposed by Russian explosives expert Nikolai Kibalchich in 1881, and in 1891 similar ideas were developed independently by German engineer Hermann Ganswindt. Robert A. Heinlein mentions powering spaceships with nuclear bombs in his 1940 short story "Blowups Happen." Real life proposals of nuclear propulsion were first made by Stanislaw Ulam in 1946, and preliminary calculations were made by F. Reines and Ulam in a Los Alamos memorandum dated 1947. The actual project, initiated in 1958, was led by Ted Taylor at General Atomics and physicist Freeman Dyson, who at Taylor's request took a year away from the Institute for Advanced Study in Princeton to work on the project.

The Orion concept offered high thrust and high specific impulse, or propellant efficiency, at the same time. The unprecedented extreme power requirements for doing so would be met by nuclear explosions, of such power relative to the vehicle's mass as to be survived only by using external detonations without attempting to contain them in internal structures. As a qualitative comparison, traditional chemical rockets—such as the Saturn V that took the Apollo program to the Moon—produce high thrust with low specific impulse, whereas electric ion engines produce a small amount of thrust very efficiently. Orion would have offered performance greater than the most advanced conventional or nuclear rocket engines then under consideration. Supporters of Project Orion felt that it had potential for cheap interplanetary travel, but it lost political approval over concerns with fallout from its propulsion.

The Partial Test Ban Treaty of 1963 is generally acknowledged to have ended the project. However, from Project Longshot to Project Daedalus, Mini-Mag Orion, and other proposals which reach engineering analysis at the level of considering thermal power dissipation, the principle of external nuclear pulse propulsion to maximize survivable power has remained common among serious concepts for interstellar flight without external power beaming and for very high-performance interplanetary flight. Such later proposals have tended to modify the basic principle by envisioning equipment driving detonation of much smaller fission or fusion pellets, in contrast to Project Orion's larger nuclear pulse units (full nuclear bombs) based on less speculative technology.

To Mars by A-Bomb: The Secret History of Project Orion was a 2003 BBC documentary film about the project.

🔗 United States 🔗 Environment 🔗 Mammals 🔗 United States/Idaho

The beaver drop was a 1948 Idaho Department of Fish and Game program to relocate beavers (Castor canadensis). The program involved moving 76 beavers by airplane and parachuting them to new areas in Central Idaho. The program was initiated to both reduce cost and decrease mortality rates during the relocation. Alleviating complaints about "nuisance beavers" and their activities were an underlying reason for it.

🔗 Mathematics

A hinged dissection, also known as a swing-hinged dissection or Dudeney dissection, is a kind of geometric dissection in which all of the pieces are connected into a chain by "hinged" points, such that the rearrangement from one figure to another can be carried out by swinging the chain continuously, without severing any of the connections. Typically, it is assumed that the pieces are allowed to overlap in the folding and unfolding process; this is sometimes called the "wobbly-hinged" model of hinged dissection.

🔗 Ancient Near East 🔗 Meteorology 🔗 Meteorology/droughts and fire events 🔗 Ancient Egypt

The 4.2-kiloyear BP aridification event was one of the most severe climatic events of the Holocene epoch. It defines the beginning of the current Meghalayan age in the Holocene epoch. Starting in about 2200 BC, it probably lasted the entire 22nd century BC. It has been hypothesised to have caused the collapse of the Old Kingdom in Egypt as well as the Akkadian Empire in Mesopotamia, and the Liangzhu culture in the lower Yangtze River area. The drought may also have initiated the collapse of the Indus Valley Civilisation, with some of its population moving southeastward to follow the movement of their desired habitat, as well as the migration of Indo-European-speaking people into India.

Some scientists disagree with this conclusion and point out that the event was neither a global drought nor did it happen in a clear timeline.

🔗 Biology 🔗 Politics 🔗 Psychology 🔗 Neuroscience 🔗 Genetics 🔗 Physiology 🔗 Physiology/neuro 🔗 Evolutionary biology 🔗 Conservatism

A number of studies have found that biology can be linked with political orientation. This means that biology is a possible factor in political orientation but may also mean that the ideology a person identifies with changes a person's ability to perform certain tasks. Many of the studies linking biology to politics remain controversial and unreplicated, although the overall body of evidence is growing.

🔗 Typography

The Paige Compositor was an invention developed by James W. Paige (1842–1917) between 1872 and 1888. It was designed to replace the human typesetter of a lead type-composed printing form with a mechanical arm. In the early 1890s, a group of inventors signed a contract with Towner K. Webster in Chicago to produce 3000 compositors. However, the machine was not nearly as precise as it should have been and never turned a profit because of its complexity and continual need for adjustment based upon trial and error. As a result, it was the Linotype typesetting machine, which composed in a hot metal typesetting process, that became the new popular typesetting machine.

The Paige typesetting machine is notable for substantial investment that the prominent writer Mark Twain made into the failed endeavor: $300,000 ($6,000,000 today). Twain, a former printer, invested not only the bulk of his book profits but also a large portion of the inheritance of Olivia Clemens, his wife. Many point to his over-investment in the Paige typesetting machine and other inventions as the cause of not only his family's financial decline but also the decline of his wit and humor.

Webster Manufacturing made fewer than six machines costing $15,000 apiece, over three times as much as the initial production estimates. One was donated by Cornell University for a scrap metal drive during World War II. The only surviving machine is displayed at the Mark Twain House in Hartford, Connecticut.

🔗 United States 🔗 Politics 🔗 Food and drink 🔗 Health and fitness

The ketchup as a vegetable controversy stemmed from proposed regulations of school lunches by the USDA's Food and Nutrition Service (FNS) in 1981, early in the presidency of Ronald Reagan. The regulations were intended to provide meal planning flexibility to local school lunch administrators coping with cuts to the National School Lunch Program enacted by the Omnibus Reconciliation Acts of 1980 and 1981. The proposed changes allowed administrators to meet nutritional requirements by crediting food items not explicitly listed. While ketchup was not mentioned in the original regulations, pickle relish was used as an example of an item that could count as a vegetable.

A similar controversy arose in 2011, when Congress passed a bill prohibiting the USDA from increasing the amount of tomato paste required to constitute a vegetable; the bill allowed pizza with two tablespoons (30 mL) of tomato paste to qualify as a vegetable.