To stay up to date you can also follow on Mastodon.

🔗 Cryptography 🔗 Cryptography/Computer science

BB84 is a quantum key distribution scheme developed by Charles Bennett and Gilles Brassard in 1984. It is the first quantum cryptography protocol. The protocol is provably secure, relying on the quantum property that information gain is only possible at the expense of disturbing the signal if the two states one is trying to distinguish are not orthogonal (see no-cloning theorem) and an authenticated public classical channel. It is usually explained as a method of securely communicating a private key from one party to another for use in one-time pad encryption.

🔗 Technology 🔗 Canada 🔗 Guild of Copy Editors 🔗 Engineering

A screw drive is a system used to turn a screw. At a minimum, it is a set of shaped cavities and protrusions on the screw head that allows torque to be applied to it. Usually, it also involves a mating tool, such as a screwdriver, that is used to turn it. The following heads are categorized based on commonality, with some of the less-common drives being classified as "tamper-resistant".

Most heads come in a range of sizes, typically distinguished by a number, such as "Phillips #00". These sizes do not necessarily describe a particular dimension of the drive shape, but rather are arbitrary designations.

🔗 Computer science 🔗 Mathematics

Tupper's self-referential formula is a formula that visually represents itself when graphed at a specific location in the (x, y) plane.

🔗 Companies 🔗 Aviation 🔗 Spaceflight 🔗 Aviation/aircraft 🔗 Rocketry

Rotary Rocket Company was a rocketry company that developed the Roton concept in the late 1990s as a fully reusable single-stage-to-orbit (SSTO) crewed spacecraft. The design was initially conceived by Bevin McKinney, who shared it with Gary Hudson. In 1996, Rotary Rocket Company was formed to commercialize the concept. The Roton was intended to reduce costs of launching payloads into low earth orbit by a factor of ten.

The company gathered considerable venture capital from angel investors and opened a factory headquartered in a 45,000-square-foot (4,200 m²) facility at Mojave Air and Space Port in Mojave, California. The fuselage for their vehicles was made by Scaled Composites, at the same airport, while the company developed the novel engine design and helicopter-like landing system. A full-scale test vehicle made three hover flights in 1999, but the company exhausted its funds and closed its doors in early 2001.

🔗 Physics 🔗 Firearms

A projectile is any object thrown into space (empty or not) by the exertion of a force. Although any object in motion through space (for example a thrown baseball) may be called a projectile, the term more commonly refers to a ranged weapon. Mathematical equations of motion are used to analyze projectile trajectory. An object projected at an angle to the horizontal has both the vertical and horizontal components of velocity. The vertical component of the velocity on the y-axis given as Vy=USin(teta) while the horizontal component of the velocity Vx=UCos(teta). There are various terms used in projectiles at specific angle teta 1. Time to reach maximum height. It is symbolized as (t), which is the time taken for the projectile to reach the maximum height from the plane of projection. Mathematically, it is given as t=USin(teta)/g Where g=acceleration due to gravity(app 9.81m/s²) U= initial velocity (m/s) teta= angle made by the projectile with the horizontal axis.

2. Time of flight (T): this is the total time taken for the projectile to fall back to the same plane from which it was projected. Mathematically it is given as T=2USin(teta)/g

3. Maximum Height (H): this is the maximum height attained by the projectile OR the maximum displacement on the vertical axis(y-axis) covered by the projectile. It is given as H= U²Sin²(teta)/2g

4. Range(R): The Range of a projectile is the horizontal distance covered (on the x-axis) by the projectile. Mathematically, R= U²Sin2(teta)/g. The Range is maximum when angle teta= 45° I.e Sin2(teta)=1.

🔗 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.

An auto-antonym or autantonym, also called a contronym, contranym or Janus word, is a word with multiple meanings (senses) of which one is the reverse of another. For example, the word cleave can mean "to cut apart" or "to bind together". This phenomenon is called enantiosemy, enantionymy (enantio- means "opposite"), antilogy or autantonymy. An enantiosemic term is necessarily polysemic.

🔗 Olympics 🔗 Classical Greece and Rome 🔗 Greece 🔗 Martial arts 🔗 Mixed martial arts

Pankration (; Greek: παγκράτιον) was a sporting event introduced into the Greek Olympic Games in 648 BC and was an empty-hand submission sport with scarcely any rules. The athletes used boxing and wrestling techniques, but also others, such as kicking and holds, locks and chokes on the ground. The term comes from the Greek παγκράτιον [paŋkrátion], literally meaning "all of power" from πᾶν (pan) "all" and κράτος (kratos) "strength, might, power".

It was known in ancient times for its ferocity and allowance of such tactics as knees to the head and eye gouging. One ancient account tells of a situation in which the judges were trying to determine the winner of a match. The difficulty lay in that fact that both men had died in the arena from their injuries, making it hard to determine a victor. Eventually, the judges decided the winner was the one who didn't have his eyes gouged out. Over time, however, maneuvers like eye gouging were discouraged to prevent such unpleasant incidents.

🔗 Biology 🔗 Genetics 🔗 Computational Biology 🔗 Evolutionary biology 🔗 Human Genetic History

The last universal common ancestor (LUCA), also called the last universal ancestor (LUA), or concestor, is the most recent population of organisms from which all organisms now living on Earth have a common descent, the most recent common ancestor of all current life on Earth. (A related concept is that of progenote.) LUCA is not thought to be the first life on Earth but only one of many early organisms, all the others becoming extinct.

While there is no specific fossil evidence of LUCA, it can be studied by comparing the genomes of all modern organisms, its descendants. By this means, a 2016 study identified a set of 355 genes most likely to have been present in LUCA. (However, some of those genes could have developed later, then spread universally by horizontal gene transfer between archaea and bacteria.) The genes describe a complex life form with many co-adapted features, including transcription and translation mechanisms to convert information from DNA to RNA to proteins. The study concluded that the LUCA probably lived in the high-temperature water of deep sea vents near ocean-floor magma flows.

Studies from 2000 to 2018 have suggested an increasingly ancient time for LUCA. In 2000, estimations suggested LUCA existed 3.5 to 3.8 billion years ago in the Paleoarchean era, a few hundred million years after the earliest fossil evidence of life, for which there are several candidates ranging in age from 3.48 to 4.28 billion years ago. A 2018 study from the University of Bristol, applying a molecular clock model, places the LUCA shortly after 4.5 billion years ago, within the Hadean.

Charles Darwin first proposed the theory of universal common descent through an evolutionary process in his book On the Origin of Species in 1859: "Therefore I should infer from analogy that probably all the organic beings which have ever lived on this earth have descended from some one primordial form, into which life was first breathed." Later biologists have separated the problem of the origin of life from that of the LUCA.

🔗 Philosophy 🔗 Philosophy/Logic

The raven paradox, also known as Hempel's paradox, Hempel's ravens, or rarely the paradox of indoor ornithology, is a paradox arising from the question of what constitutes evidence for a statement. Observing objects that are neither black nor ravens may formally increase the likelihood that all ravens are black even though, intuitively, these observations are unrelated.

This problem was proposed by the logician Carl Gustav Hempel in the 1940s to illustrate a contradiction between inductive logic and intuition.