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🔗 Mathematics 🔗 Books

Proofs from THE BOOK is a book of mathematical proofs by Martin Aigner and Günter M. Ziegler. The book is dedicated to the mathematician Paul Erdős, who often referred to "The Book" in which God keeps the most elegant proof of each mathematical theorem. During a lecture in 1985, Erdős said, "You don't have to believe in God, but you should believe in The Book."

🔗 United States 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Appalachia 🔗 Mining 🔗 Organized Labour 🔗 United States/West Virginia

The Battle of Blair Mountain was the largest labor uprising in United States history and the largest armed uprising since the American Civil War. The conflict occurred in Logan County, West Virginia, as part of the Coal Wars, a series of early-20th-century labor disputes in Appalachia. Up to 100 people were killed, and many more arrested. The United Mine Workers saw major declines in membership, but the long-term publicity led to some improvements in working conditions.

For five days from late August to early September 1921, some 10,000 armed coal miners confronted 3,000 lawmen and strikebreakers (called the Logan Defenders) who were backed by coal mine operators during the miners' attempt to unionize the southwestern West Virginia coalfields when tensions rose between workers and mine management. The battle ended after approximately one million rounds were fired and the United States Army, represented by the West Virginia Army National Guard led by McDowell County native William Eubanks, intervened by presidential order.

🔗 United States 🔗 Numismatics 🔗 Numismatics/American currency

The half cent was the smallest denomination of United States coin ever minted. It was first minted in 1793 and last minted in 1857. It was minted with five different designs.

🔗 Soviet Union 🔗 Russia 🔗 Russia/technology and engineering in Russia 🔗 Spaceflight 🔗 Russia/science and education in Russia 🔗 Russia/history of Russia

Sputnik 1 ( or ; "Satellite-1", or "PS-1", Простейший Спутник-1 or Prosteyshiy Sputnik-1, "Elementary Satellite 1") was the first artificial Earth satellite. The Soviet Union launched it into an elliptical low Earth orbit on 4 October 1957, orbiting for three weeks before its batteries died, then silently for two more months before falling back into the atmosphere. It was a 58 cm (23 in) diameter polished metal sphere, with four external radio antennas to broadcast radio pulses. Its radio signal was easily detectable by radio amateurs, and the 65° inclination and duration of its orbit made its flight path cover virtually the entire inhabited Earth. The satellite's unanticipated success precipitated the American Sputnik crisis and triggered the Space Race, a part of the Cold War. The launch was the beginning of a new era of political, military, technological, and scientific developments. The name "Sputnik" is Russian for spouse/traveling companion or satellite when interpreted in an astronomical context.

Tracking and studying Sputnik 1 from Earth provided scientists with valuable information. The density of the upper atmosphere could be deduced from its drag on the orbit, and the propagation of its radio signals gave data about the ionosphere.

Sputnik 1 was launched during the International Geophysical Year from Site No.1/5, at the 5th Tyuratam range, in Kazakh SSR (now known as the Baikonur Cosmodrome). The satellite travelled at about 29,000 kilometres per hour (18,000 mph; 8,100 m/s), taking 96.2 minutes to complete each orbit. It transmitted on 20.005 and 40.002 MHz, which were monitored by radio operators throughout the world. The signals continued for 21 days until the transmitter batteries ran out on 26 October 1957. Sputnik burned up on 4 January 1958 while reentering Earth's atmosphere, after three months, 1440 completed orbits of the Earth, and a distance travelled of about 70 million km (43 million mi).

🔗 Soviet Union 🔗 Russia 🔗 Russia/technology and engineering in Russia 🔗 Environment 🔗 Disaster management 🔗 Energy 🔗 Russia/history of Russia 🔗 Science Policy

The Kyshtym disaster, sometimes referred to as the Mayak disaster or Ozyorsk disaster in newer sources, was a radioactive contamination accident that occurred on 29 September 1957 at Mayak, a plutonium production site for nuclear weapons and nuclear fuel reprocessing plant located in the closed city of Chelyabinsk-40 (now Ozyorsk) in Chelyabinsk Oblast, Russian SFSR, Soviet Union.

The disaster was the second worst nuclear incident (by radioactivity released) after the Chernobyl disaster. It measured as a Level 6 disaster on the International Nuclear Event Scale (INES), making it the third highest on the INES (which ranks by population impact), behind Chernobyl (evacuated 335,000 people) and the Fukushima Daiichi nuclear disaster (evacuated 154,000 people) which are both Level 7 on the INES. At least twenty-two villages were exposed to radiation from the Kyshtym disaster, with a total population of around 10,000 people evacuated. Some were evacuated after a week, but it took almost two years for evacuations to occur at other sites.

The disaster spread hot particles over more than 52,000 square kilometres (20,000 sq mi), where at least 270,000 people lived. Since Chelyabinsk-40 (later renamed Chelyabinsk-65 until 1994) was not marked on maps, the disaster was named after Kyshtym, the nearest known town.

🔗 Japan

In Japanese culture, a hatsuyume (Japanese: 初夢) is the first dream one has in the new year. Traditionally, the contents of such a dream would foretell the luck of the dreamer in the ensuing year. In Japan, the night of December 31 was often passed without sleeping, so the hatsuyume is often experienced during the night of January 1; the day after the night of the "first dream" is also known as the hatsuyume. This day is January 2 in the Gregorian calendar, but was different in the traditional Japanese calendar.

It is considered to be particularly good luck to dream of Mount Fuji, a hawk, and an eggplant. This belief has been in place since the early Edo period but there are various theories regarding the origins as to why this particular combination was considered to be auspicious. One theory suggests that this combination is lucky because Mount Fuji is Japan's highest mountain, the hawk is a clever and strong bird, and the word for eggplant (茄子, nasu or nasubi) suggests achieving something great (成す nasu). Another theory suggests that this combination arose because Mount Fuji, falconry, and early eggplants were favorites of the shōgun Tokugawa Ieyasu.

Although this superstition is well known in Japan, often memorized in the form ichi-Fuji, ni-taka, san-nasubi (一富士、二鷹、三茄子; 1. Fuji, 2. Hawk, 3. Eggplant), the continuation of the list is not as well known. The continuation is yon-sen, go-tabako, roku-zatō (四扇、五煙草、六座頭; 4. Fan, 5. Tobacco, 6. Blind acupressurer). The origins of this trio are less well known, and it is unclear whether they were added after the original three or whether the list of six originated at the same time.

🔗 Judaism 🔗 Writing systems 🔗 Kabbalah

Gematria (; Hebrew: גמטריא or gimatria גימטריה, plural גמטראות or גימטריאות, gimatriot) is the practice of assigning a numerical value to a name, word or phrase by reading it as a number, or sometimes by using an alphanumerical cipher. The letters of the alphabets involved have standard numerical values, but a word can yield several values if a cipher is used.

According to Aristotle (384–322 BCE), isopsephy, based on the Milesian numbering of the Greek alphabet developed in the Greek city of Miletus, was part of the Pythagorean tradition, which originated in the 6th century BCE. The first evidence of use of Hebrew letters as numbers dates to 78 BCE; gematria is still used in Jewish culture. Similar systems have been used in other languages and cultures, derived from or inspired by either Greek isopsephy or Hebrew gematria, and include Arabic abjad numerals and English gematria.

The most common form of Hebrew gematria is used in the Talmud and Midrash, and elaborately by many post-Talmudic commentators. It involves reading words and sentences as numbers, assigning numerical instead of phonetic value to each letter of the Hebrew alphabet. When read as numbers, they can be compared and contrasted with other words or phrases – cf. the Hebrew proverb נכנס יין יצא סוד (nichnas yayin yatza sod, lit. 'wine entered, secret went out', i.e. "in vino veritas"). The gematric value of יין ('wine') is 70 (י=10; י=10; ן=50) and this is also the gematric value of סוד ('secret', ס=60; ו=6; ד=4)‎.

Although a type of gematria system ('Aru') was employed by the ancient Babylonian culture, their writing script was logographic, and the numerical assignments they made were to whole words. Aru was very different from the Milesian systems used by Greek and Hebrew cultures, which used alphabetic writing scripts. The value of words with Aru were assigned in an entirely arbitrary manner and correspondences were made through tables, and so cannot be considered a true form of gematria.

Gematria sums can involve single words, or a string of lengthy calculations. A short example of Hebrew numerology that uses gematria is the word חי (chai, lit. 'alive'), which is composed of two letters that (using the assignments in the mispar gadol table shown below) add up to 18. This has made 18 a "lucky number" among the Jewish people. Donations of money in multiples of 18 are very popular.

In early Jewish sources, the term can also refer to other forms of calculation or letter manipulation, for example atbash.

🔗 Internet 🔗 Computing 🔗 Computing/Software 🔗 Websites 🔗 Websites/Computing 🔗 Computing/Computer Security 🔗 Computing/Websites

Evercookie is a JavaScript-based application created by Samy Kamkar that produces zombie cookies in a web browser that are intentionally difficult to delete. In 2013, a top-secret NSA document was leaked by Edward Snowden, citing Evercookie as a method of tracking Tor users.

🔗 Mathematics

In the computer science subfield of algorithmic information theory, a Chaitin constant (Chaitin omega number) or halting probability is a real number that, informally speaking, represents the probability that a randomly constructed program will halt. These numbers are formed from a construction due to Gregory Chaitin.

Although there are infinitely many halting probabilities, one for each method of encoding programs, it is common to use the letter Ω to refer to them as if there were only one. Because Ω depends on the program encoding used, it is sometimes called Chaitin's construction instead of Chaitin's constant when not referring to any specific encoding.

Each halting probability is a normal and transcendental real number that is not computable, which means that there is no algorithm to compute its digits. Indeed, each halting probability is Martin-Löf random, meaning there is not even any algorithm which can reliably guess its digits.

🔗 Apple Inc./Macintosh 🔗 Apple Inc. 🔗 Human–Computer Interaction 🔗 Industrial design 🔗 Apple Inc./iOS

A skeuomorph () is a derivative object that retains nonfunctional ornamental design cues (attributes) from structures that were inherent to the original. Examples include pottery embellished with imitation rivets reminiscent of similar pots made of metal and a software calendar that imitates the appearance of binding on a paper desk calendar.