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🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Geology 🔗 Explosives

Tired mountain syndrome is a condition in which underground nuclear testing fractures and weakens rock, increasing permeability and the risk of release of radionuclides and radioactive contamination of the environment. Locations said to have undergone the syndrome include the French Polynesian island of Moruroa, Rainier Mesa in the United States, the Dnepr 1 nuclear test site on the Kola Peninsula in Russia, possibly Mount Lazarev in the Novaya Zemlya Test Site in Russia, and Mount Mantap in North Korea.

🔗 United States 🔗 Biography 🔗 Mathematics 🔗 United States/Vermont

Zerah Colburn (September 1, 1804 – March 2, 1840) was a child prodigy of the 19th century who gained fame as a mental calculator.

🔗 Biography 🔗 Physics 🔗 Biography/science and academia 🔗 Physics/Biographies

Sir James Dewar (20 September 1842 – 27 March 1923) was a Scottish chemist and physicist. He is best known for his invention of the vacuum flask, which he used in conjunction with research into the liquefaction of gases. He also studied atomic and molecular spectroscopy, working in these fields for more than 25 years.

🔗 Books

The Opium of the Intellectuals (French: L'Opium des intellectuels) is a book written by Raymond Aron and published in 1955. It was first published in an English translation in 1957.

🔗 Popular Culture 🔗 Star Trek

The Vulcan salutation is a hand gesture popularized by the 1960s television series Star Trek. It consists of a raised hand with the palm forward and the thumb extended, while the fingers are parted between the middle and ring finger.

🔗 United States 🔗 International relations 🔗 Soviet Union 🔗 Russia 🔗 Politics 🔗 Media 🔗 Journalism

Whataboutism, also known as whataboutery, is a variant of the tu quoque logical fallacy that attempts to discredit an opponent's position by charging them with hypocrisy without directly refuting or disproving their argument. It is particularly associated with Soviet and Russian propaganda. When criticisms were leveled at the Soviet Union during the Cold War, the Soviet response would often be "What about..." followed by an event in the Western world. As Garry Kasparov noted, it is a word that was coined to describe the frequent use of a rhetorical diversion by Soviet apologists and dictators, who would counter charges of their oppression, "massacres, gulags, and forced deportations" by invoking American slavery, racism, lynchings, etc. It has been adopted by other politicians and countries.

🔗 Mathematics

John von Neumann's universal constructor is a self-replicating machine in a cellular automata (CA) environment. It was designed in the 1940s, without the use of a computer. The fundamental details of the machine were published in von Neumann's book Theory of Self-Reproducing Automata, completed in 1966 by Arthur W. Burks after von Neumann's death.

Von Neumann's goal was to specify an abstract machine which, when run, would replicate itself. In his design, the machine consists of three parts: a 'blueprint' for itself, a mechanism that can read any blueprint and construct the machine (sans blueprint) specified by that blueprint, and a 'copy machine' that can make copies of any blueprint. After the mechanism has been used to construct the machine specified by the blueprint, the copy machine is used to create a copy of that blueprint, and this copy is placed into the new machine, resulting in a working replication of the original machine. Some machines will do this backwards, copying the blueprint and then building a machine.

To define his machine in more detail, von Neumann invented the concept of a cellular automaton. The one he used consists of a two-dimensional grid of cells, each of which can be in one of 29 states at any point in time. At each timestep, each cell updates its state depending on the states of the surrounding cells at the prior timestep. The rules governing these updates are identical for all cells.

The universal constructor is a certain pattern of cell states in this cellular automaton. It contains one line of cells that serve as a 'tape', encoding a sequence of instructions that serve as a 'blueprint' for the machine. The machine reads these instructions one by one and performs the corresponding actions. The instructions direct the machine to use its 'construction arm' to build a copy of the machine, without tape, at some other location in the cell grid. The tape can't contain instructions to build an equally long tape, just as a container can't contain a container of the same size. Therefore, the machine contains a separate 'copy machine' which reads the tape and places a copy into the newly constructed machine. The resulting new machine and tape is identical to the old one, and it proceeds to replicate again.

🔗 Computing 🔗 Mathematics 🔗 Computing/Networking

In mathematics, the Cheeger constant (also Cheeger number or isoperimetric number) of a graph is a numerical measure of whether or not a graph has a "bottleneck". The Cheeger constant as a measure of "bottleneckedness" is of great interest in many areas: for example, constructing well-connected networks of computers, card shuffling. The graph theoretical notion originated after the Cheeger isoperimetric constant of a compact Riemannian manifold.

The Cheeger constant is named after the mathematician Jeff Cheeger.

🔗 Biology 🔗 Evolutionary biology 🔗 Tree of Life

The three-domain system is a biological classification introduced by Carl Woese et al. in 1990 that divides cellular life forms into archaea, bacteria, and eukaryote domains. In particular, it emphasizes the separation of prokaryotes into two groups, originally called Eubacteria (now Bacteria) and Archaebacteria (now Archaea). Woese argued that, on the basis of differences in 16S rRNA genes, these two groups and the eukaryotes each arose separately from an ancestor with poorly developed genetic machinery, often called a progenote. To reflect these primary lines of descent, he treated each as a domain, divided into several different kingdoms. Woese initially used the term "kingdom" to refer to the three primary phylogenic groupings, and this nomenclature was widely used until the term "domain" was adopted in 1990.

Parts of the three-domain theory have been fiercly challenged by scientists such as Radhey S. Gupta, who argues that the primary division within prokaryotes should be between those surrounded by a single membrane, and those with two membranes.

🔗 Extinction

An endling is the last known individual of a species or subspecies. Once the endling dies, the species becomes extinct. The word was coined in correspondence in the scientific journal Nature. Alternative names put forth for the last individual of its kind include ender and terminarch.

The word relict may also be used, but usually refers to a population, rather than an individual, that is the last of a species.