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🔗 Mathematics

Gödel's completeness theorem is a fundamental theorem in mathematical logic that establishes a correspondence between semantic truth and syntactic provability in first-order logic. It makes a close link between model theory that deals with what is true in different models, and proof theory that studies what can be formally proven in particular formal systems.

It was first proved by Kurt Gödel in 1929. It was then simplified in 1947, when Leon Henkin observed in his Ph.D. thesis that the hard part of the proof can be presented as the Model Existence Theorem (published in 1949). Henkin's proof was simplified by Gisbert Hasenjaeger in 1953.

🔗 Numbers 🔗 Canada 🔗 Arctic 🔗 Writing systems 🔗 Indigenous peoples of North America 🔗 Canada/Canadian Territories 🔗 Alaska

Kaktovik numerals are a featural positional numeral system created by Alaskan Iñupiat.

Arabic numeral notation, which was designed for a base-10 numeral system, is inadequate for the Inuit languages, which use a base-20 numeral system. Students in Kaktovik, Alaska, invented a base-20 numeral notation in 1994 to rectify this issue, and this system spread among the Alaskan Iñupiat and has been considered in other countries where Inuit languages are spoken.

The image at right shows the digits 0 to 19. Twenty is written as a one and a zero (\ɤ), forty as a two and a zero (Vɤ), four hundred as a one and two zeros (\ɤɤ), eight hundred as a two and two zeros (Vɤɤ), etc.

🔗 Computer science 🔗 Linguistics 🔗 Linguistics/Applied Linguistics

Soundex is a phonetic algorithm for indexing names by sound, as pronounced in English. The goal is for homophones to be encoded to the same representation so that they can be matched despite minor differences in spelling. The algorithm mainly encodes consonants; a vowel will not be encoded unless it is the first letter. Soundex is the most widely known of all phonetic algorithms (in part because it is a standard feature of popular database software such as DB2, PostgreSQL, MySQL, SQLite, Ingres, MS SQL Server and Oracle.) Improvements to Soundex are the basis for many modern phonetic algorithms.

🔗 Philosophy 🔗 Education 🔗 Philosophy/Analytic philosophy

In philosophy, Wittgenstein's ladder is a metaphor set out by Ludwig Wittgenstein about learning. In what may be a deliberate reference to Søren Kierkegaard's Concluding Unscientific Postscript to Philosophical Fragments, the penultimate proposition of the Tractatus Logico-Philosophicus (translated from the original German) reads:

6.54

   My propositions serve as elucidations in the following way: anyone who understands me eventually recognizes them as nonsensical, when he has used them—as steps—to climb beyond them. (He must, so to speak, throw away the ladder after he has climbed up it.)

   He must transcend these propositions, and then he will see the world aright.

Given the preceding problematic at work in his Tractatus, this passage suggests that, if a reader understands Wittgenstein's aims in the text, then those propositions the reader would have just read would be recognized as nonsense. From Propositions 6.4–6.54, the Tractatus shifts its focus from primarily logical considerations to what may be considered more traditionally philosophical topics (God, ethics, meta-ethics, death, the will) and, less traditionally along with these, the mystical. The philosophy presented in the Tractatus attempts to demonstrate just what the limits of language are—and what it is to run up against them. Among what can be said for Wittgenstein are the propositions of natural science, and to the nonsensical, or unsayable, those subjects associated with philosophy traditionally—ethics and metaphysics, for instance.

Curiously, the penultimate proposition of the Tractatus, proposition 6.54, states that once one understands the propositions of the Tractatus, one will recognize that they are nonsensical (unsinnig), and that they must be thrown away. Proposition 6.54, then, presents a difficult interpretative problem. If the so-called picture theory of language is correct, and it is impossible to represent logical form, then the theory, by trying to say something about how language and the world must be for there to be meaning, is self-undermining. This is to say that the picture theory of language itself requires that something be said about the logical form sentences must share with reality for meaning to be possible. This requires doing precisely what the picture theory of language precludes. It would appear, then, that the metaphysics and the philosophy of language endorsed by the Tractatus give rise to a paradox: for the Tractatus to be true, it will necessarily have to be nonsense by self-application; but for this self-application to render the propositions of the Tractatus nonsense (in the Tractarian sense), then the Tractatus must be true.

Other philosophers before Wittgenstein, including Zhuang Zhou, Schopenhauer and Fritz Mauthner, had used a similar metaphor.

In his notes of 1930 Wittgenstein returns to the image of a ladder with a different perspective:

I might say: if the place I want to get could only be reached by way of a ladder, I would give up trying to get there. For the place I really have to get to is a place I must already be at now.
Anything that I might reach by climbing a ladder does not interest me.

🔗 Economics

A job guarantee (JG) is an economic policy proposal aimed at providing a sustainable solution to the dual problems of inflation and unemployment. Its aim is to create full employment and price stability, by having the state promise to hire unemployed workers as an employer of last resort (ELR).

The economic policy stance currently dominant around the world uses unemployment as a policy tool to control inflation; when inflation rises, the government pursues contractionary fiscal or monetary policy, creating a buffer stock of unemployed people, reducing wage demands, and ultimately inflation. When inflationary expectations subside, expansionary policy aims to produce the opposite effect. In Marxian terms, the unemployed serve as a reserve army of labor. By contrast, in a job guarantee program, a buffer stock of employed people (employed in the job guarantee program) provides the same protection against inflation without the social costs of unemployment, hence potentially fulfilling the dual mandate of full employment and price stability.

🔗 Computer Security 🔗 Computer Security/Computing 🔗 Project-independent assessment

Slopsquatting is a type of cybersquatting. It is the practice of registering a non-existent software package name that a large language model (LLM) may hallucinate in its output, whereby someone unknowingly may copy-paste and install the software package without realizing it is fake. Attempting to install a non-existent package should result in an error, but some have exploited this for their gain in the form of typosquatting.

The name is a portmanteau of "slop" and "typosquatting".

🔗 Typography

Tiresias is a family of TrueType sans-serif typefaces that were designed with the aim of legibility by people with impaired vision at the Scientific Research Unit of Royal National Institute of Blind People in London. The font was originally designed for the RNIB by Chris Sharville of Laker Sharville Design Associates who was working with John Gill at the time.

The family includes

• Tiresias Infofont – for information labels, optimized for maximum legibility at a distance of 30–100 cm.
• Tiresias Keyfont – for labeling the tops of keys of keyboards, PIN pads, appliances, remote controls (features exaggerated punctuation marks, no descender on the J)
• Tiresias LPfont – for large-print publications. A wedge-serif design.
• Tiresias PCfont – for raster displays
• Tiresias Screenfont – for television subtitling and on-screen user interfaces
• Tiresias Signfont – a more open spacing for use on signs

In late 2007, all Tiresias fonts except Tiresias Screenfont were released under the GNU General Public License version 3 or any later version.

The Tiresias Screenfont was sold by Bitstream Inc., who in 2012 were acquired by Monotype Corporation. The acquiring company continues to market Tiresias on its websites.

🔗 Oregon

The Neskowin Ghost Forest is the remnants of a Sitka spruce forest on the Oregon Coast of the United States. The stumps were likely created when an earthquake of the Cascadia subduction zone abruptly lowered the trees, that were then covered by mud from landslides or debris from a tsunami. Many of the stumps are over 2,000 years old.

The stumps were unearthed when turbulent storms swept away sand during the winter of 1997–1998. It is one of over thirty ghost forests along the Oregon and Washington Coast, though many appear as flat roots and not stumps. Most notably, Washington's ghost forest of red cedars was integral to the discovery of the Cascadia fault line. These ghost forests are evidence of significant, rapid changes in coastline – often due to seismic events such as the 1700 Cascadia earthquake.

The stumps at Neskowin are 2,000 years old, according to carbon dating. While living, the trees that make up the Neskowin Ghost Forest were similar to present-day coastal rain forest. They stood 150–200 feet (46–61 m) high and were at least 200 years old when buried. However, it's difficult to determine when or how the trees died, because it occurred before written history in the region. It was originally believed that these trees died slowly, as the roots were gradually submerged in saltwater due to changes in the sea levels. Yet research by geologists revealed that the soil, still present at the roots of the stumps, was buried abruptly – indicating a more sudden and dramatic event, like an earthquake, as the cause.

The ghost forest is near Proposal Rock. It is part of the Neskowin Beach State Recreation Site. The best time to see the stumps is low tide, during winter (due to January, February and March bringing the lowest tides of the year.)

🔗 California 🔗 Skepticism 🔗 Geography 🔗 Alternative Views 🔗 Geology

Sailing stones (also known as sliding rocks, walking rocks, rolling stones, and moving rocks), are a geological phenomenon where rocks move and inscribe long tracks along a smooth valley floor without human or animal intervention. The movement of the rocks occurs when large ice sheets a few millimeters thick and floating in an ephemeral winter pond start to break up during sunny days. Frozen during cold winter nights, these thin floating ice panels are driven by wind and shove rocks at speeds up to 5 meters per minute.

Trails of sliding rocks have been observed and studied in various locations, including Little Bonnie Claire Playa in Nevada, and most famously at Racetrack Playa, Death Valley National Park, California, where the number and length of tracks are notable.

🔗 Spaceflight 🔗 Rocketry

Black Arrow, officially capitalised BLACK ARROW, was a British satellite carrier rocket. Developed during the 1960s, it was used for four launches between 1969 and 1971. Its final flight was the first and only successful orbital launch to be conducted by the United Kingdom, and placed the Prospero satellite into low Earth orbit.

Black Arrow originated from studies by the Royal Aircraft Establishment for carrier rockets based on the Black Knight rocket, with the project being authorised in 1964. It was initially developed by Saunders-Roe, and later Westland Aircraft as the result of a merger.

Black Arrow was a three-stage rocket, fuelled by RP-1 paraffin (kerosene) and high test peroxide, a concentrated form of hydrogen peroxide (85% hydrogen peroxide + 15% water). It was retired after only four launches in favour of using American Scout rockets, which the Ministry of Defence calculated to be cheaper than maintaining the Black Arrow programme.