Have a deep view into what people are curious about.

🔗 Mathematics 🔗 Statistics

In statistics, the 68–95–99.7 rule, also known as the empirical rule, is a shorthand used to remember the percentage of values that lie within an interval estimate in a normal distribution: 68%, 95%, and 99.7% of the values lie within one, two, and three standard deviations of the mean, respectively.

In mathematical notation, these facts can be expressed as follows, where Pr() is the probability function, Χ is an observation from a normally distributed random variable, μ (mu) is the mean of the distribution, and σ (sigma) is its standard deviation:

${\displaystyle {\begin{aligned}\Pr(\mu -1\sigma \leq X\leq \mu +1\sigma )&\approx 68.27\%\\\Pr(\mu -2\sigma \leq X\leq \mu +2\sigma )&\approx 95.45\%\\\Pr(\mu -3\sigma \leq X\leq \mu +3\sigma )&\approx 99.73\%\end{aligned}}}$

The usefulness of this heuristic especially depends on the question under consideration.

In the empirical sciences, the so-called three-sigma rule of thumb (or 3σ rule) expresses a conventional heuristic that nearly all values are taken to lie within three standard deviations of the mean, and thus it is empirically useful to treat 99.7% probability as near certainty.

In the social sciences, a result may be considered "significant" if its confidence level is of the order of a two-sigma effect (95%), while in particle physics, there is a convention of a five-sigma effect (99.99994% confidence) being required to qualify as a discovery.

A weaker three-sigma rule can be derived from Chebyshev's inequality, stating that even for non-normally distributed variables, at least 88.8% of cases should fall within properly calculated three-sigma intervals. For unimodal distributions, the probability of being within the interval is at least 95% by the Vysochanskij–Petunin inequality. There may be certain assumptions for a distribution that force this probability to be at least 98%.

🔗 China 🔗 Spirits

Baijiu (Chinese: 白酒; pinyin: báijiǔ; literally: 'white (clear) liquor'), also known as shaojiu (烧酒/燒酒), is a clear Chinese distilled liquor of typically 40%-50%. Each type of baijiu uses a distinct type of Qū during the fermentation process in the distillery for the distinct and characteristic flavour profile.

Báijiǔ is a clear liquid usually distilled from fermented sorghum, although other grains may be used; some southeastern Chinese styles may employ rice or glutinous rice, while other Chinese varieties may use wheat, barley, millet, or even Job's tears (Chinese: 薏苡 yìyǐ) in their mash bills. The qū starter culture used in the production of baijiu is usually made from pulverized wheat grain or steamed rice.

Because of its clarity, baijiu can appear similar to several other East Asian liquors, but it often has a significantly higher alcohol content than, for example, Japanese shōchū (25%) or Korean soju (20–45%). Despite being a white spirit, its flavour more closely resembles a rich spirit like whisky in terms of complexity of flavour and sensation.

Baijiu is the world's bestselling spirit, with five billion litres sold in 2016. That number was up to 10.8 billion liters sold in 2018, more than whisky, vodka, gin, rum and tequila combined. Baijiu's popularity in China makes it the world's most consumed spirit, but outside of China it is not well known.

🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography, the socialist millionaire problem is one in which two millionaires want to determine if their wealth is equal without disclosing any information about their riches to each other. It is a variant of the Millionaire's Problem whereby two millionaires wish to compare their riches to determine who has the most wealth without disclosing any information about their riches to each other.

It is often used as a cryptographic protocol that allows two parties to verify the identity of the remote party through the use of a shared secret, avoiding a man-in-the-middle attack without the inconvenience of manually comparing public key fingerprints through an outside channel. In effect, a relatively weak password/passphrase in natural language can be used.

🔗 Physics

Flux pinning is the phenomenon where a superconductor is pinned in space above a magnet. The superconductor must be a type-II superconductor because type-I superconductors cannot be penetrated by magnetic fields. The act of magnetic penetration is what makes flux pinning possible. At higher magnetic fields (above Hc1 and below Hc2) the superconductor allows magnetic flux to enter in quantized packets surrounded by a superconducting current vortex (see Quantum vortex). These sites of penetration are known as flux tubes. The number of flux tubes per unit area is proportional to the magnetic field with a constant of proportionality equal to the magnetic flux quantum. On a simple 76 millimeter diameter, 1-micrometer thick disk, next to a magnetic field of 28 kA/m, there are approximately 100 billion flux tubes that hold 70,000 times the superconductor's weight. At lower temperatures the flux tubes are pinned in place and cannot move. This pinning is what holds the superconductor in place thereby allowing it to levitate. This phenomenon is closely related to the Meissner effect, though with one crucial difference — the Meissner effect shields the superconductor from all magnetic fields causing repulsion, unlike the pinned state of the superconductor disk which pins flux, and the superconductor in place.

🔗 Computing

A wetware computer is an organic computer (which can also be known as an artificial organic brain or a neurocomputer) composed of organic material such as living neurons. Wetware computers composed of neurons are different than conventional computers because they are thought to be capable in a way of "thinking for themselves", because of the dynamic nature of neurons. While wetware is still largely conceptual, there has been limited success with construction and prototyping, which has acted as a proof of the concept's realistic application to computing in the future. The most notable prototypes have stemmed from the research completed by biological engineer William Ditto during his time at the Georgia Institute of Technology. His work constructing a simple neurocomputer capable of basic addition from leech neurons in 1999 was a significant discovery for the concept. This research acted as a primary example driving interest in the creation of these artificially constructed, but still organic brains.

The Privilegium maius (German: Großer Freiheitsbrief 'greater privilege') was a medieval document forged in 1358 or 1359 at the behest of Duke Rudolf IV of Austria (1358–65) of the House of Habsburg, claiming the family has the right to rule Rome because of land rights granted to them by Nero and Julius Caesar. It was essentially a modified version of the Privilegium minus issued by Emperor Frederick I Barbarossa in 1156, which had elevated the former March of Austria into a duchy. In a similar way, the Privilegium maius elevated the duchy into an Archduchy of Austria.

The privileges described in the document had great influence on the Austrian political landscape, and created a unique connection between the House of Habsburg and Austria.

🔗 Video games 🔗 Lists

The following is a list of the most expensive video games ever developed, with a minimum total cost of US$50 million and sorted by the total cost adjusted for inflation. Most game budgets are not disclosed, so this list is not indicative of industry trends.

🔗 Military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Elements 🔗 Military history/Cold War

Red mercury is purportedly a substance of uncertain composition used in the creation of nuclear weapons, as well as other weapons systems. Because of the great secrecy surrounding the development and manufacture of nuclear weapons, there is no proof that red mercury exists. However, all samples of alleged "red mercury" analyzed in the public literature have proven to be well-known, common red substances of no interest to weapons makers.

Red mercury is therefore considered a hoax, perpetrated by con artists who sought to take advantage of gullible buyers on the black market for arms. There have been reports of "red mercury" on the international black markets since 1979, but the hoax seems to have been most common in the early 1990s, with very high asking prices.

🔗 Australia 🔗 Military history 🔗 Australia/Western Australia 🔗 Military history/Australia, New Zealand and South Pacific military history 🔗 Australia/Australian history

The Emu War, also known as the Great Emu War, was a nuisance wildlife management military operation undertaken in Australia over the latter part of 1932 to address public concern over the number of emus said to be running amok in the Campion district of Western Australia. The unsuccessful attempts to curb the population of emus, a large flightless bird indigenous to Australia, employed soldiers armed with Lewis guns—leading the media to adopt the name "Emu War" when referring to the incident. While a number of the birds were killed, the emu population persisted and continued to cause crop destruction.

🔗 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.