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🔗 Cognitive science

The Sussman anomaly is a problem in artificial intelligence, first described by Gerald Sussman, that illustrates a weakness of noninterleaved planning algorithms, which were prominent in the early 1970s. In the problem, three blocks (labeled A, B, and C) rest on a table. The agent must stack the blocks such that A is atop B, which in turn is atop C. However, it may only move one block at a time. The problem starts with B on the table, C atop A, and A on the table:

However, noninterleaved planners typically separate the goal (stack A atop B atop C) into subgoals, such as:

1. get A atop B
2. get B atop C

Suppose the planner starts by pursuing Goal 1. The straightforward solution is to move C out of the way, then move A atop B. But while this sequence accomplishes Goal 1, the agent cannot now pursue Goal 2 without undoing Goal 1, since both A and B must be moved atop C:

If instead the planner starts with Goal 2, the most efficient solution is to move B. But again, the planner cannot pursue Goal 1 without undoing Goal 2:

The problem was first identified by Sussman as a part of his PhD research. Sussman (and his supervisor, Marvin Minsky) believed that intelligence requires a list of exceptions or tricks, and developed a modular planning system for "debugging" plans. Most modern planning systems can handle this anomaly, but it is still useful for explaining why planning is non-trivial.

🔗 Systems 🔗 Systems/Chaos theory

The Burning Ship fractal, first described and created by Michael Michelitsch and Otto E. Rössler in 1992, is generated by iterating the function:

${\displaystyle z_{n+1}=(|\operatorname {Re} \left(z_{n}\right)|+i|\operatorname {Im} \left(z_{n}\right)|)^{2}+c,\quad z_{0}=0}$

in the complex plane ${\displaystyle \mathbb {C} }$ which will either escape or remain bounded. The difference between this calculation and that for the Mandelbrot set is that the real and imaginary components are set to their respective absolute values before squaring at each iteration. The mapping is non-analytic because its real and imaginary parts do not obey the Cauchy–Riemann equations.

🔗 Spaceflight 🔗 Europe

Cluster was a constellation of four European Space Agency spacecraft which were launched on the maiden flight of the Ariane 5 rocket, Flight 501, and subsequently lost when that rocket failed to achieve orbit. The launch, which took place on Tuesday, 4 June 1996, ended in failure due to multiple errors in the software design: Dead code (running, but purposeful so only for Ariane 4) with inadequate protection against integer overflow led to an exception handled inappropriately—halting the whole inertial navigation system that otherwise would have been unaffected. This resulted in the rocket veering off its flight path 37 seconds after launch, beginning to disintegrate under high aerodynamic forces, and finally self-destructing by its automated flight termination system. The failure has become known as one of the most infamous and expensive software bugs in history. The failure resulted in a loss of more than US$370 million.

🔗 Books

"Uncleftish Beholding" (1989) is a short text by Poul Anderson designed to illustrate what English might look like without its large number of loanwords from languages such as French, Greek, and Latin. Written in a form of "Anglish," the work explains atomic theory using Germanic words almost exclusively and coining new words when necessary; many of these new words have cognates in modern German, an important scientific language in its own right. The title phrase uncleftish beholding calques "atomic theory."

To illustrate, the text begins:

For most of its being, mankind did not know what things are made of, but could only guess. With the growth of worldken, we began to learn, and today we have a beholding of stuff and work that watching bears out, both in the workstead and in daily life.

It goes on to define firststuffs (chemical elements), such as waterstuff (hydrogen), sourstuff (oxygen), and ymirstuff (uranium), as well as bulkbits (molecules), bindings (compounds), and several other terms important to uncleftish worldken (atomic science). Wasserstoff and Sauerstoff are the modern German words for hydrogen and oxygen, and in Dutch the modern equivalents are waterstof and zuurstof. Sunstuff refers to helium, which derives from ἥλιος, the Ancient Greek word for "sun." Ymirstuff references Ymir, a giant in Norse mythology similar to Uranus in Greek mythology.

The vocabulary used in Uncleftish Beholding does not completely derive from Anglo-Saxon. Around, from Old French reond (Modern French rond), completely displaced Old English ymbe (cognate to German um) and left no "native" English word for this concept. The text also contains the French-derived words rest, ordinary and sort.

The text gained increased exposure and popularity after being circulated around the Internet, and has served as inspiration for some inventors of Germanic English conlangs. Douglas Hofstadter, in discussing the piece in his book Le Ton beau de Marot, jocularly refers to the use of only Germanic roots for scientific pieces as "Ander-Saxon."

🔗 Computer science 🔗 Philosophy 🔗 Philosophy/Logic 🔗 Philosophy/Philosophy of science 🔗 Philosophy/Philosophy of mind

Moravec's paradox is the observation by artificial intelligence and robotics researchers that, contrary to traditional assumptions, reasoning (which is high-level in humans) requires very little computation, but sensorimotor skills (comparatively low-level in humans) require enormous computational resources. The principle was articulated by Hans Moravec, Rodney Brooks, Marvin Minsky and others in the 1980s. As Moravec writes, "it is comparatively easy to make computers exhibit adult level performance on intelligence tests or playing checkers, and difficult or impossible to give them the skills of a one-year-old when it comes to perception and mobility".

Similarly, Minsky emphasized that the most difficult human skills to reverse engineer are those that are unconscious. "In general, we're least aware of what our minds do best", he wrote, and added "we're more aware of simple processes that don't work well than of complex ones that work flawlessly".

🔗 Board and table games

18XX is the generic term for a series of board games that, with a few exceptions, recreate the building of railroad corporations during the 19th century; individual games within the series use particular years in the 19th century as their title (usually the date of the start of railway development in the area of the world they cover), or "18" plus a two or more letter geographical designator (such as 18EU for a game set in the European Union). The games 2038, set in the future, and Poseidon and Ur, 1830 BC, both set in ancient history, are also regarded as 18XX titles as their game mechanics and titling nomenclature are similar despite variance from the common railroad/stock-market theme.

The 18XX series has its origins in the game 1829, first produced by Francis Tresham in the mid-1970s. 1829 was chosen as it was the year of the Rainhill Trials. 1830 was produced by Avalon Hill in 1986, and was the first game of the series widely available in the United States; it is seen as the basic 18XX game by the U.S. audience.

In addition to traditionally published games, the 18XX series has spawned self-published variants and games published by low-volume game companies.

With few exceptions (such as 2038), 18XX titles are multiplayer board games without random variables in their game mechanics.

🔗 Aviation

Balloonomania was a strong public interest or fad in balloons that originated in France in the late 18th century and continued into the 19th century, during the advent of balloon flights. The interest began with the first flights of the Montgolfier brothers in 1783 (in a balloon inflated with hot air). Soon afterwards Jacques Alexandre César Charles flew another type of balloon (inflated with hydrogen) and both types of balloon were in use from then on. The fad quickly spread in France and across the channel in England.

🔗 Organizations 🔗 Fashion

The Rational Dress Society was an organisation founded in 1881 in London, part of the movement for Victorian dress reform. It described its purpose thus:

The Rational Dress Society protests against the introduction of any fashion in dress that either deforms the figure, impedes the movements of the body, or in any way tends to injure the health. It protests against the wearing of tightly-fitting corsets; of high-heeled shoes; of heavily-weighted skirts, as rendering healthy exercise almost impossible; and of all tie down cloaks or other garments impeding on the movements of the arms. It protests against crinolines or crinolettes of any kind as ugly and deforming... [It] requires all to be dressed healthily, comfortably, and beautifully, to seek what conduces to birth, comfort and beauty in our dress as a duty to ourselves and each other.

In the catalogue of its inaugural exhibition, it listed the attributes of "perfect" dress as:

1. Freedom of Movement.
2. Absence of pressure over any part of the body.
3. Not more weight than is necessary for warmth, and both weight and warmth evenly distributed.
4. Grace and beauty combined with comfort and convenience.
5. Not departing too conspicuously from the ordinary dress of the time.

Leading members of the Society were Lady Harberton (who created the divided skirt), Mary Eliza Haweis and Constance Wilde (Irish author). Oscar Wilde helped spread the word by publishing the essay "The Philosophy of Dress" in which he stressed the important relationship between clothing and one’s soul. Woman cyclists, such as members of the Lady Cyclists' Association, were keen advocates of women's right to dress appropriately for the activity, as part of a belief that cycling offered women an opportunity to escape overly restrictive societal norms.

In 1889, a member of the Rational Dress Society, Charlotte Carmichael Stopes, staged a coup at a meeting of the British Association for the Advancement of Science in Newcastle upon Tyne, when she arranged an impromptu addition to the programme on the subject of rational dress. Her speech was reported by newspapers across Britain and the notion of rational dress was the biggest news from the meeting.

🔗 Computing 🔗 Computer science

In computer science, program synthesis is the task to construct a program that provably satisfies a given high-level formal specification. In contrast to program verification, the program is to be constructed rather than given; however, both fields make use of formal proof techniques, and both comprise approaches of different degrees of automation. In contrast to automatic programming techniques, specifications in program synthesis are usually non-algorithmic statements in an appropriate logical calculus.

The primary application of program synthesis is to relieve the programmer of the burden of writing correct, efficient code that satisfies a specification. However, program synthesis also has applications to superoptimization and inference of loop invariants.

🔗 Mathematics 🔗 Statistics

Local regression or local polynomial regression, also known as moving regression, is a generalization of the moving average and polynomial regression. Its most common methods, initially developed for scatterplot smoothing, are LOESS (locally estimated scatterplot smoothing) and LOWESS (locally weighted scatterplot smoothing), both pronounced . They are two strongly related non-parametric regression methods that combine multiple regression models in a k-nearest-neighbor-based meta-model. In some fields, LOESS is known and commonly referred to as Savitzky–Golay filter (proposed 15 years before LOESS).

LOESS and LOWESS thus build on "classical" methods, such as linear and nonlinear least squares regression. They address situations in which the classical procedures do not perform well or cannot be effectively applied without undue labor. LOESS combines much of the simplicity of linear least squares regression with the flexibility of nonlinear regression. It does this by fitting simple models to localized subsets of the data to build up a function that describes the deterministic part of the variation in the data, point by point. In fact, one of the chief attractions of this method is that the data analyst is not required to specify a global function of any form to fit a model to the data, only to fit segments of the data.

The trade-off for these features is increased computation. Because it is so computationally intensive, LOESS would have been practically impossible to use in the era when least squares regression was being developed. Most other modern methods for process modeling are similar to LOESS in this respect. These methods have been consciously designed to use our current computational ability to the fullest possible advantage to achieve goals not easily achieved by traditional approaches.

A smooth curve through a set of data points obtained with this statistical technique is called a loess curve, particularly when each smoothed value is given by a weighted quadratic least squares regression over the span of values of the y-axis scattergram criterion variable. When each smoothed value is given by a weighted linear least squares regression over the span, this is known as a lowess curve; however, some authorities treat lowess and loess as synonyms.