Have a deep view into what people are curious about.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Military history/African military history

The Vela incident, also known as the South Atlantic Flash, was an unidentified double flash of light detected by an American Vela Hotel satellite on 22 September 1979 near the Prince Edward Islands in the Indian Ocean.

The cause of the flash remains officially unknown, and some information about the event remains classified. While it has been suggested that the signal could have been caused by a meteoroid hitting the satellite, the previous 41 double flashes detected by the Vela satellites were caused by nuclear weapons tests. Today, most independent researchers believe that the 1979 flash was caused by a nuclear explosion — perhaps an undeclared nuclear test carried out by South Africa and Israel.

🔗 Physics 🔗 Philosophy 🔗 Philosophy/Philosophy of science 🔗 Philosophy/Metaphysics

In physics and cosmology, the mathematical universe hypothesis (MUH), also known as the ultimate ensemble theory, is a speculative "theory of everything" (TOE) proposed by cosmologist Max Tegmark.

🔗 Computer science

Boids is an artificial life program, developed by Craig Reynolds in 1986, which simulates the flocking behaviour of birds. His paper on this topic was published in 1987 in the proceedings of the ACM SIGGRAPH conference. The name "boid" corresponds to a shortened version of "bird-oid object", which refers to a bird-like object. Incidentally, "boid" is also a New York Metropolitan dialect pronunciation for "bird".

As with most artificial life simulations, Boids is an example of emergent behavior; that is, the complexity of Boids arises from the interaction of individual agents (the boids, in this case) adhering to a set of simple rules. The rules applied in the simplest Boids world are as follows:

• separation: steer to avoid crowding local flockmates
• alignment: steer towards the average heading of local flockmates
• cohesion: steer to move towards the average position (center of mass) of local flockmates

More complex rules can be added, such as obstacle avoidance and goal seeking.

The basic model has been extended in several different ways since Reynolds proposed it. For instance, Delgado-Mata et al. extended the basic model to incorporate the effects of fear. Olfaction was used to transmit emotion between animals, through pheromones modelled as particles in a free expansion gas. Hartman and Benes introduced a complementary force to the alignment that they call the change of leadership. This steer defines the chance of the boid to become a leader and try to escape.

The movement of Boids can be characterized as either chaotic (splitting groups and wild behaviour) or orderly. Unexpected behaviours, such as splitting flocks and reuniting after avoiding obstacles, can be considered emergent.

The boids framework is often used in computer graphics, providing realistic-looking representations of flocks of birds and other creatures, such as schools of fish or herds of animals. It was for instance used in the 1998 video game Half-Life for the flying bird-like creatures seen at the end of the game on Xen, named "boid" in the game files.

The Boids model can be used for direct control and stabilization of teams of simple Unmanned Ground Vehicles (UGV) or Micro Aerial Vehicles (MAV) in swarm robotics. For stabilization of heterogeneous UAV-UGV teams, the model was adapted for using onboard relative localization by Saska et al.

At the time of proposal, Reynolds' approach represented a giant step forward compared to the traditional techniques used in computer animation for motion pictures. The first animation created with the model was Stanley and Stella in: Breaking the Ice (1987), followed by a feature film debut in Tim Burton's film Batman Returns (1992) with computer generated bat swarms and armies of penguins marching through the streets of Gotham City.

The boids model has been used for other interesting applications. It has been applied to automatically program Internet multi-channel radio stations. It has also been used for visualizing information and for optimization tasks.

🔗 Cryptography 🔗 Cryptography/Computer science 🔗 Judaism

Atbash (Hebrew: אתבש‎; also transliterated Atbaš) is a monoalphabetic substitution cipher originally used to encrypt the Hebrew alphabet. It can be modified for use with any known writing system with a standard collating order.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Military history/French military history 🔗 Military history/Cold War 🔗 Rocketry 🔗 Military history/European military history

The S3 was a French land-based Intermediate Range Ballistic Missile, equipped with a single 1.2-megatonne thermonuclear warhead. In France it is called an SSBS, for Sol-Sol Balistique Stratégique, or Ground-Ground Strategic Ballistic Missile.

🔗 Mathematics 🔗 Statistics 🔗 Psychology

Accuracy and precision are two measures of observational error. Accuracy is how close a given set of measurements (observations or readings) are to their true value. Precision is how close the measurements are to each other.

The International Organization for Standardization (ISO) defines a related measure: trueness, "the closeness of agreement between the arithmetic mean of a large number of test results and the true or accepted reference value."

While precision is a description of random errors (a measure of statistical variability), accuracy has two different definitions:

1. More commonly, a description of systematic errors (a measure of statistical bias of a given measure of central tendency, such as the mean). In this definition of "accuracy", the concept is independent of "precision", so a particular set of data can be said to be accurate, precise, both, or neither. This concept corresponds to ISO's trueness.
2. A combination of both precision and trueness, accounting for the two types of observational error (random and systematic), so that high accuracy requires both high precision and high trueness. This usage corresponds to ISO's definition of accuracy (trueness and precision).

🔗 Philosophy 🔗 Politics 🔗 Psychology 🔗 Philosophy/Social and political philosophy 🔗 Sociology

A purity spiral is a theory which argues for the existence of a form of groupthink in which it becomes more beneficial to hold certain views than to not hold them, and more extreme views are rewarded while expressing doubt, nuance, or moderation is punished (a process sometimes called "moral outbidding"). It is argued that this feedback loop leads to members competing to demonstrate the zealotry or purity of their views.

A purity spiral is argued to occur when a community's primary focus becomes implementing a single value that has no upper limit, and where that value does not have an agreed interpretation.

🔗 Religion 🔗 Classical Greece and Rome 🔗 Greece

The agōgē (Greek: ἀγωγή in Attic Greek, or ἀγωγά, agōgā in Doric Greek) was the rigorous education and training program mandated for all male Spartan citizens, except for the firstborn son in the ruling houses, Eurypontid and Agiad. The training involved cultivating loyalty to the Spartan group, military training (e.g., pain tolerance), hunting, dancing, singing, and social (communicating) preparation. The word agōgē had various meaning in ancient Greek, but in this context it generally meant leading, guidance, or training.

According to folklore, agōgē was introduced by the semi-mythical Spartan law-giver Lycurgus but its origins are thought to be between the 7th and 6th centuries BC when the state trained male citizens from the ages of seven to twenty-one.

The aim of the system was to produce strong and capable warriors to serve the Spartan army. It encouraged conformity and the importance of the Spartan state over one's personal interest and generated the future elites of Sparta. The men would become the "walls of Sparta" because Sparta was the only Greek city with no defensive walls after they had been demolished at the order of Lycurgus. Discipline was strict and the males were encouraged to fight amongst themselves to determine the strongest member of the group.

The agōgē was prestigious throughout the Greek world, and many aristocratic families from other cities vied to send their sons to Sparta to participate in the agōgē for varying periods of time. The Spartans were very selective in which young men they would permit to enroll. Such honors were usually awarded to the próxenoi (πρόξενοι) of Sparta in other cities and to a few other families of supreme ancestry and importance.

🔗 Lists 🔗 Statistics

Many probability distributions that are important in theory or applications have been given specific names.