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🔗 Physics 🔗 Philosophy 🔗 Skepticism 🔗 History of Science 🔗 Science

Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.

There are still some deficiencies in the Standard Model of physics, such as the origin of mass, the strong CP problem, neutrino mass, matter–antimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the mathematical framework of the Standard Model itself—the Standard Model is inconsistent with that of general relativity, to the point that one or both theories break down under certain conditions (for example within known spacetime singularities like the Big Bang and the centers of black holes beyond the event horizon).

🔗 Philosophy 🔗 Philosophy/Philosophy of religion

The self-referencing doomsday argument rebuttal is an attempt to refute the doomsday argument (that there is a credible link between the brevity of the human race's existence and its expected extinction) by applying the same reasoning to the lifetime of the doomsday argument itself.

The first researchers to write about this were P. T. Landsberg and J. N. Dewynne in 1997; they applied belief in the doomsday argument to itself, and claimed that a paradox results.

🔗 Typography 🔗 Industrial design

The IBM Selectric typewriter was a highly successful line of electric typewriters introduced by IBM on 31 July 1961.

Instead of the "basket" of individual typebars that swung up to strike the ribbon and page in a typical typewriter of the period, the Selectric had an "element" (frequently called a "typeball", or less formally, a "golf ball") that rotated and pivoted to the correct position before striking. The element could be easily changed so as to use different fonts in the same document typed on the same typewriter, resurrecting a capability that had been pioneered by typewriters such as the Hammond and Blickensderfer in the late 19th century. The Selectric also replaced the traditional typewriter's horizontally moving carriage with a roller (platen) that turned to advance the paper but did not move horizontally, while the typeball and ribbon mechanism did.

The Selectric mechanism was notable for using internal mechanical binary coding and two mechanical digital-to-analog converters, called whiffletree linkages, to select the character to be typed.

Selectrics and their descendants eventually captured 75 percent of the United States market for electric typewriters used in business. IBM replaced the Selectric line with the IBM Wheelwriter in 1984 and transferred its typewriter business to the newly formed Lexmark in 1991. By its 25th anniversary, in 1986, a total of more than 13 million machines were made and sold.

🔗 British Museum 🔗 Visual arts

Dürer's Rhinoceros is the name commonly given to a woodcut executed by German painter and printmaker Albrecht Dürer in 1515. The image is based on a written description and brief sketch by an unknown artist of an Indian rhinoceros that had arrived in Lisbon in 1515. Dürer never saw the actual rhinoceros, which was the first living example seen in Europe since Roman times. In late 1515, the King of Portugal, Manuel I, sent the animal as a gift for Pope Leo X, but it died in a shipwreck off the coast of Italy in early 1516. A live rhinoceros was not seen again in Europe until a second specimen, named Abada, arrived from India at the court of Sebastian of Portugal in 1577, being later inherited by Philip II of Spain around 1580.

Dürer's woodcut is not an entirely accurate representation of a rhinoceros. He depicts an animal with hard plates that cover its body like sheets of armour, with a gorget at the throat, a solid-looking breastplate, and what appear to be rivets along the seams. He places a small twisted horn on its back and gives it scaly legs and saw-like rear quarters. None of these features is present in a real rhinoceros, although the Indian rhinoceros does have deep folds in its skin that can look like armor from a distance. Despite its anatomical inaccuracies, Dürer's woodcut became very popular in Europe and was copied many times in the following three centuries. It was regarded by Westerners as a true representation of a rhinoceros into the late 18th century. Eventually, it was supplanted by more realistic drawings and paintings, particularly those of Clara the rhinoceros, who toured Europe in the 1740s and 1750s. It has been said of Dürer's woodcut: "probably no animal picture has exerted such a profound influence on the arts".

🔗 Mathematics

The expression "casting out nines" may refer to any one of three arithmetical procedures:

• Adding the decimal digits of a positive whole number, while optionally ignoring any 9s or digits which sum to a multiple of 9. The result of this procedure is a number which is smaller than the original whenever the original has more than one digit, leaves the same remainder as the original after division by nine, and may be obtained from the original by subtracting a multiple of 9 from it. The name of the procedure derives from this latter property.
• Repeated application of this procedure to the results obtained from previous applications until a single-digit number is obtained. This single-digit number is called the "digital root" of the original. If a number is divisible by 9, its digital root is 9. Otherwise, its digital root is the remainder it leaves after being divided by 9.
• A sanity test in which the above-mentioned procedures are used to check for errors in arithmetical calculations. The test is carried out by applying the same sequence of arithmetical operations to the digital roots of the operands as are applied to the operands themselves. If no mistakes are made in the calculations, the digital roots of the two resultants should be the same. If they are different, therefore, one or more mistakes must have been made in the calculations.

🔗 Novels 🔗 Novels/Science fiction 🔗 LGBT studies 🔗 Novels/Short story

" '—All You Zombies—' " is a science fiction short story by American writer Robert A. Heinlein. It was written in one day, July 11, 1958, and first published in the March 1959 issue of Fantasy and Science Fiction magazine after being rejected by Playboy.

The story involves a number of paradoxes caused by time travel. In 1980, it was nominated for the Balrog Award for short fiction.

"'—All You Zombies—'" further develops themes explored by the author in a previous work: "By His Bootstraps", published some 18 years earlier. Some of the same elements also appear later in The Cat Who Walks Through Walls (1985), including the Circle of Ouroboros and the Temporal Corps.

The unusual title of the story, which includes both the quotation marks and dashes shown above, is a quotation from a sentence near the end of the story; the quotation is taken from the middle of the sentence, hence the dashes indicating edited text before and after the title.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Maritime warfare

Project Sanguine was a U.S. Navy project, proposed in 1968 for communication with submerged submarines using extremely low frequency (ELF) radio waves. The originally proposed system, hardened to survive a nuclear attack, would have required a giant antenna covering two fifths of the state of Wisconsin. Because of protests and potential environmental impact, the proposed system was never implemented. A smaller, less hardened system called Project ELF consisting of two linked ELF transmitters located at Clam Lake, Wisconsin and Republic, Michigan was built beginning in 1982 and operated from 1989 until 2004. The system transmitted at a frequency of 76 Hz. At ELF frequencies the bandwidth of the transmission is very small, so the system could only send short coded text messages at a very low data rate. These signals were used to summon specific vessels to the surface to receive longer operational orders by ordinary radio or satellite communication.

🔗 Spaceflight 🔗 Meteorology 🔗 Meteorology/weather data, products and instrumentation

GOES-3, known as GOES-C before becoming operational, is an American geostationary weather and communications satellite. It was originally built for the National Oceanic and Atmospheric Administration as part of the Geostationary Operational Environmental Satellite system, and was launched in June 1978. It is positioned in geostationary orbit, from where it was initially used for weather forecasting in the United States. Since ceasing to function as a weather satellite in 1989, it has been used as a communications satellite, and has spent over thirty-eight years in operation. GOES-3 was decommissioned 29 June 2016 at the CSTARS facility in Miami, Florida.

GOES-3 was built by Ford Aerospace, and is based on the satellite bus developed for the SMS programme. At launch it had a mass of 627 kilograms (1,382 lb).

🔗 History 🔗 Psychology

The method of loci (loci being Latin for "places") is a strategy of memory enhancement which uses visualizations of familiar spatial environments in order to enhance the recall of information. The method of loci is also known as the memory journey, memory palace, or mind palace technique. This method is a mnemonic device adopted in ancient Roman and Greek rhetorical treatises (in the anonymous Rhetorica ad Herennium, Cicero's De Oratore, and Quintilian's Institutio Oratoria). Many memory contest champions report using this technique to recall faces, digits, and lists of words.

The term is most often found in specialised works on psychology, neurobiology, and memory, though it was used in the same general way at least as early as the first half of the nineteenth century in works on rhetoric, logic, and philosophy. John O'Keefe and Lynn Nadel refer to:

'the method of loci', an imaginal technique known to the ancient Greeks and Romans and described by Yates (1966) in her book The Art of Memory as well as by Luria (1969). In this technique the subject memorizes the layout of some building, or the arrangement of shops on a street, or any geographical entity which is composed of a number of discrete loci. When desiring to remember a set of items the subject 'walks' through these loci in their imagination and commits an item to each one by forming an image between the item and any feature of that locus. Retrieval of items is achieved by 'walking' through the loci, allowing the latter to activate the desired items. The efficacy of this technique has been well established (Ross and Lawrence 1968, Crovitz 1969, 1971, Briggs, Hawkins and Crovitz 1970, Lea 1975), as is the minimal interference seen with its use.

The items to be remembered in this mnemonic system are mentally associated with specific physical locations. The method relies on memorized spatial relationships to establish order and recollect memorial content. It is also known as the "Journey Method", used for storing lists of related items, or the "Roman Room" technique, which is most effective for storing unrelated information.

🔗 Physics 🔗 Alternative Views

The Biefeld–Brown effect is an electrical phenomenon that produces an ionic wind that transfers its momentum to surrounding neutral particles. It describes a force observed on an asymmetric capacitor when high voltage is applied to the capacitor's electrodes. Once suitably charged up to high DC potentials, a thrust at the negative terminal, pushing it away from the positive terminal, is generated. The effect was named by inventor Thomas Townsend Brown who claimed that he did a series of experiments with professor of astronomy Paul Alfred Biefeld, a former teacher of Brown whom Brown claimed was his mentor and co-experimenter at Denison University in Ohio.

The use of an asymmetric capacitor, with the negative electrode being larger than the positive electrode, allowed for more thrust to be produced in the direction from the low-flux to the high-flux region compared to a conventional capacitor. These asymmetric capacitors became known as Asymmetrical Capacitor Thrusters (ACT). The Biefeld–Brown effect can be observed in ionocrafts and lifters, which utilize the effect to produce thrust in the air without requiring any combustion or moving parts.

In his 1960 patent titled "Electrokinetic Apparatus," Brown refers to electrokinesis to describe the Biefeld–Brown effect, linking the phenomenon to the field of electrohydrodynamics (EHD). Brown also believed the Biefeld–Brown effect could produce an anti-gravity force, referred to as "electrogravitics" based on it being an electricity/gravity phenomenon. However, there is little evidence that supports Brown's claim on the effect's anti-gravity properties.