Have a deep view into what people are curious about.

🔗 Africa 🔗 Cats 🔗 Mammals 🔗 Africa/Western Sahara

The sand cat (Felis margarita), also known as the sand dune cat, is the only cat living chiefly in true deserts. This small cat is widely distributed in the deserts of North Africa, the Middle East and Central Asia. Starting in 2002, it was listed as near threatened on the IUCN Red List because the population was considered fragmented and small with a declining trend. It was downlisted to least concern in 2016.

Owing to long hairs covering the soles of its feet, the sand cat is well adapted to the extremes of a desert environment and tolerant of extremely hot and cold temperatures. It inhabits both sandy and stony deserts, in areas far from water sources.

🔗 Physics 🔗 Physics/relativity

The Gödel metric is an exact solution of the Einstein field equations in which the stress–energy tensor contains two terms, the first representing the matter density of a homogeneous distribution of swirling dust particles (dust solution), and the second associated with a negative cosmological constant (see lambdavacuum solution). It is also known as the Gödel solution or Gödel universe.

This solution has many unusual properties—in particular, the existence of closed timelike curves that would allow time travel in a universe described by the solution. Its definition is somewhat artificial in that the value of the cosmological constant must be carefully chosen to match the density of the dust grains, but this spacetime is an important pedagogical example.

This solution was found in 1949 by Kurt Gödel.

🔗 Video games 🔗 Computing

The VIC-20 (known as the VC-20 in Germany and the VIC-1001 in Japan) is an 8-bit entry level home computer that was sold by Commodore Business Machines. The VIC-20 was announced in 1980, roughly three years after Commodore's first personal computer, the PET. The VIC-20 was the first computer of any description to sell one million units, eventually reaching 2.5 million. It was described as "one of the first anti-spectatorial, non-esoteric computers by design...no longer relegated to hobbyist/enthusiasts or those with money, the computer Commodore developed was the computer of the future."

🔗 Education

Forest kindergarten is a type of preschool education for children between the ages of three and six that is held almost exclusively outdoors. Whatever the weather, children are encouraged to play, explore and learn in a forest environment. The adult supervision is meant to assist rather than lead. It is also known as Waldkindergarten (in German), outdoor nursery, or nature kindergarten.

🔗 Books 🔗 Anthropology 🔗 Mythology

An Instinct for Dragons is a book by University of Central Florida anthropologist, David E. Jones, in which he seeks to explain the universality of dragon images in the folklore of human societies. In the introduction, Jones conducts a survey of dragon myths from cultures around the world and argues that certain aspects of dragons or dragon-like mythical creatures are found very widely. He claims that even the Inuit have a reptilian dragon-like monster, even though (living in a frigid environment unsuited for cold-blooded animals) they had never seen an actual reptile.

Jones then argues against the common hypothesis that dragon myths might be motivated by primitive discoveries of dinosaur fossils (he argues that there are widespread traits of dragons in folklore which are not observable from fossils), and claims that the common traits of dragons seem to be an amalgam of the principal predators of our ancestral hominids, which he names as the raptors, great cats (especially leopards) and pythons.

The hypothesis to which Jones conforms is that over millions of years of evolution, members of a species will evolve an instinctive fear of their predators, and he proposes ways in which these fearful images may be merged in artistic or cultural expression to create the dragon image and, perhaps, other kinds of hybrid monster.

Finally he suggests sociological reasons for why such images may be perceived differently at different stages of a culture to try to explain why Chinese dragons are considered basically good and representative of government, but the great majority (although not all) European dragons are evil and often represent chaos.

🔗 Disability 🔗 Writing systems 🔗 Constructed languages

Blissymbols or Blissymbolics is a constructed language conceived as an ideographic writing system called Semantography consisting of several hundred basic symbols, each representing a concept, which can be composed together to generate new symbols that represent new concepts. Blissymbols differ from most of the world's major writing systems in that the characters do not correspond at all to the sounds of any spoken language.

Blissymbols was published by Charles K. Bliss in 1949 and found use in the education of people with communication difficulties.

🔗 United States 🔗 Law 🔗 Politics 🔗 National Archives 🔗 Politics/American politics

The Alien and Sedition Acts were a set of four laws enacted in 1798 that applied restrictions to immigration and speech in the United States. The Naturalization Act increased the requirements to seek citizenship, the Alien Friends Act allowed the president to imprison and deport non-citizens, the Alien Enemies Act gave the president additional powers to detain non-citizens during times of war, and the Sedition Act criminalized false and malicious statements about the federal government. The Alien Friends Act and the Sedition Act expired after a set number of years, and the Naturalization Act was repealed in 1802. The Alien Enemies Act is still in effect.

The Alien and Sedition Acts were controversial. They were supported by the Federalist Party, and supporters argued that the bills strengthened national security during the Quasi-War, an undeclared naval war with France from 1798 to 1800. The acts were denounced by Democratic-Republicans as suppression of voters and violation of free speech under the First Amendment. While they were in effect, the Alien and Sedition Acts, and the Sedition Act in particular, were used to suppress publishers affiliated with the Democratic-Republicans, and several publishers were arrested for criticism of the Adams administration. The Democratic-Republicans took power in 1800, in part because of backlash to the Alien and Sedition Acts, and all but the Alien Enemies Act were eliminated by the next Congress. The Alien Enemies Act has been invoked several times since, particularly during World War II. The Alien and Sedition Acts are generally received negatively by modern historians, and the Supreme Court has since indicated that aspects of the laws would be found unconstitutional if challenged.

🔗 Computing 🔗 Computer science 🔗 Mathematics 🔗 Physics 🔗 Statistics

Monte Carlo methods, or Monte Carlo experiments, are a broad class of computational algorithms that rely on repeated random sampling to obtain numerical results. The underlying concept is to use randomness to solve problems that might be deterministic in principle. They are often used in physical and mathematical problems and are most useful when it is difficult or impossible to use other approaches. Monte Carlo methods are mainly used in three problem classes: optimization, numerical integration, and generating draws from a probability distribution.

In physics-related problems, Monte Carlo methods are useful for simulating systems with many coupled degrees of freedom, such as fluids, disordered materials, strongly coupled solids, and cellular structures (see cellular Potts model, interacting particle systems, McKean–Vlasov processes, kinetic models of gases).

Other examples include modeling phenomena with significant uncertainty in inputs such as the calculation of risk in business and, in mathematics, evaluation of multidimensional definite integrals with complicated boundary conditions. In application to systems engineering problems (space, oil exploration, aircraft design, etc.), Monte Carlo–based predictions of failure, cost overruns and schedule overruns are routinely better than human intuition or alternative "soft" methods.

In principle, Monte Carlo methods can be used to solve any problem having a probabilistic interpretation. By the law of large numbers, integrals described by the expected value of some random variable can be approximated by taking the empirical mean (a.k.a. the sample mean) of independent samples of the variable. When the probability distribution of the variable is parameterized, mathematicians often use a Markov chain Monte Carlo (MCMC) sampler. The central idea is to design a judicious Markov chain model with a prescribed stationary probability distribution. That is, in the limit, the samples being generated by the MCMC method will be samples from the desired (target) distribution. By the ergodic theorem, the stationary distribution is approximated by the empirical measures of the random states of the MCMC sampler.

In other problems, the objective is generating draws from a sequence of probability distributions satisfying a nonlinear evolution equation. These flows of probability distributions can always be interpreted as the distributions of the random states of a Markov process whose transition probabilities depend on the distributions of the current random states (see McKean–Vlasov processes, nonlinear filtering equation). In other instances we are given a flow of probability distributions with an increasing level of sampling complexity (path spaces models with an increasing time horizon, Boltzmann–Gibbs measures associated with decreasing temperature parameters, and many others). These models can also be seen as the evolution of the law of the random states of a nonlinear Markov chain. A natural way to simulate these sophisticated nonlinear Markov processes is to sample multiple copies of the process, replacing in the evolution equation the unknown distributions of the random states by the sampled empirical measures. In contrast with traditional Monte Carlo and MCMC methodologies, these mean-field particle techniques rely on sequential interacting samples. The terminology mean field reflects the fact that each of the samples (a.k.a. particles, individuals, walkers, agents, creatures, or phenotypes) interacts with the empirical measures of the process. When the size of the system tends to infinity, these random empirical measures converge to the deterministic distribution of the random states of the nonlinear Markov chain, so that the statistical interaction between particles vanishes.

Despite its conceptual and algorithmic simplicity, the computational cost associated with a Monte Carlo simulation can be staggeringly high. In general the method requires many samples to get a good approximation, which may incur an arbitrarily large total runtime if the processing time of a single sample is high. Although this is a severe limitation in very complex problems, the embarrassingly parallel nature of the algorithm allows this large cost to be reduced (perhaps to a feasible level) through parallel computing strategies in local processors, clusters, cloud computing, GPU, FPGA, etc.

🔗 History 🔗 Economics 🔗 Politics 🔗 Trade 🔗 Politics/Libertarianism

Mercantilism is a nationalist economic policy that is designed to maximize the exports and minimize the imports of an economy. In other words, it seeks to maximize the accumulation of resources within the country and use those resources for one-sided trade.

The concept aims to reduce a possible current account deficit or reach a current account surplus, and it includes measures aimed at accumulating monetary reserves by a positive balance of trade, especially of finished goods. Historically, such policies may have contributed to war and motivated colonial expansion. Mercantilist theory varies in sophistication from one writer to another and has evolved over time.

Mercantilism promotes government regulation of a nation's economy for the purpose of augmenting and bolstering state power at the expense of rival national powers. High tariffs, especially on manufactured goods, were almost universally a feature of mercantilist policy. Before it fell into decline, mercantilism was dominant in modernized parts of Europe and some areas in Africa from the 16th to the 19th centuries, a period of proto-industrialization. Some commentators argue that it is still practised in the economies of industrializing countries in the form of economic interventionism.

With the efforts of supranational organizations such as the World Trade Organization to reduce tariffs globally, non-tariff barriers to trade have assumed a greater importance in neomercantilism.