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🔗 Numismatics 🔗 Numismatics/Cryptocurrency 🔗 Cryptocurrency

Base58 is a group of binary-to-text encoding schemes used to represent large integers as alphanumeric text, introduced by Satoshi Nakamoto for use with Bitcoin. It has since been applied to other cryptocurrencies and applications. It is similar to Base64 but has been modified to avoid both non-alphanumeric characters and letters which might look ambiguous when printed. It is therefore designed for human users who manually enter the data, copying from some visual source, but also allows easy copy and paste because a double-click will usually select the whole string.

Compared with Base64, the following similar-looking letters are omitted: 0 (zero), O (capital o), I (capital i) and l (lower case L) as well as the non-alphanumeric characters + (plus) and / (slash). In contrast with Base64, the digits of the encoding do not line up well with byte boundaries of the original data. For this reason, the method is well-suited to encode large integers, but not designed to encode longer portions of binary data. The actual order of letters in the alphabet depends on the application, which is the reason why the term “Base58” alone is not enough to fully describe the format. A variant, Base56, excludes 1 (one) and o (lowercase o) compared with Base 58.

Base58Check is a Base58 encoding format that unambiguously encodes the type of data in the first few characters and includes an error detection code in the last few characters.

🔗 Mathematics

In a foundational controversy in twentieth-century mathematics, L. E. J. Brouwer, a supporter of intuitionism, opposed David Hilbert, the founder of formalism.

🔗 Physics

Barometric light is a name for the light that is emitted by a mercury-filled barometer tube when the tube is shaken. The discovery of this phenomenon in 1675 revealed the possibility of electric lighting.

🔗 Aviation 🔗 Aviation/aircraft engine

The Coffman engine starter (also known as a "shotgun starter") was a starting system used on many piston engines in aircraft and armored vehicles of the 1930s and 1940s. It used a cordite cartridge to move a piston, which cranked the engine. The Coffman system was one of the most common brands; another was the Breeze cartridge system, which was produced under Coffman patents. Most American military aircraft and tanks which used radial engines were equipped with this system. Some versions of the Rolls-Royce Merlin engine used in the British Supermarine Spitfire used the Coffman system as a starter. The Hawker Typhoon also used the Coffman system to start its Napier Sabre engine.

Cartridge starters used on a number of jet engines, including such engines as the Rolls-Royce Avon, which were used in the English Electric Canberra and Hawker Hunter, used a high gas volume cartridge driving a turbine instead of a piston.

Some Snowcat and similar vehicles used in extreme low temperatures were historically equipped with cartridge start.

🔗 Cognitive science 🔗 Neuroscience

Sparse distributed memory (SDM) is a mathematical model of human long-term memory introduced by Pentti Kanerva in 1988 while he was at NASA Ames Research Center. It is a generalized random-access memory (RAM) for long (e.g., 1,000 bit) binary words. These words serve as both addresses to and data for the memory. The main attribute of the memory is sensitivity to similarity, meaning that a word can be read back not only by giving the original write address but also by giving one close to it, as measured by the number of mismatched bits (i.e., the Hamming distance between memory addresses).

SDM implements transformation from logical space to physical space using distributed data representation and storage, similarly to encoding processes in human memory. A value corresponding to a logical address is stored into many physical addresses. This way of storing is robust and not deterministic. A memory cell is not addressed directly. If input data (logical addresses) are partially damaged at all, we can still get correct output data.

The theory of the memory is mathematically complete and has been verified by computer simulation. It arose from the observation that the distances between points of a high-dimensional space resemble the proximity relations between concepts in human memory. The theory is also practical in that memories based on it can be implemented with conventional RAM-memory elements.

🔗 Birds

Brood parasites are organisms that rely on others to raise their young. The strategy appears among birds, insects and fish. The brood parasite manipulates a host, either of the same or of another species, to raise its young as if it were its own, using brood mimicry, for example by having eggs that resemble the host's (egg mimicry).

Brood parasitism relieves the parasitic parents from the investment of rearing young or building nests for the young, enabling them to spend more time on other activities such as foraging and producing further offspring. Bird parasite species mitigate the risk of egg loss by distributing eggs amongst a number of different hosts. As this behaviour damages the host, it often results in an evolutionary arms race between parasite and host as the pair of species coevolve.

The strength of defenses and counter-adaptation rely on the host/parasitic species' ability to evolve; some host species have very strong rejection defenses resulting in the parasitic species evolving to have very close mimicry. In other species, hosts do not show rejection defenses and as a result, the parasitic species will show no evolved trait (example: egg mimicry).

🔗 Chess 🔗 Hungary 🔗 Turkey

The Turk, also known as the Mechanical Turk or Automaton Chess Player (German: Schachtürke, "chess Turk"; Hungarian: A Török), was a fake chess-playing machine constructed in the late 18th century. From 1770 until its destruction by fire in 1854 it was exhibited by various owners as an automaton, though it was eventually revealed to be an elaborate hoax. Constructed and unveiled in 1770 by Wolfgang von Kempelen (Hungarian: Kempelen Farkas; 1734–1804) to impress the Empress Maria Theresa of Austria, the mechanism appeared to be able to play a strong game of chess against a human opponent, as well as perform the knight's tour, a puzzle that requires the player to move a knight to occupy every square of a chessboard exactly once.

The Turk was in fact a mechanical illusion that allowed a human chess master hiding inside to operate the machine. With a skilled operator, the Turk won most of the games played during its demonstrations around Europe and the Americas for nearly 84 years, playing and defeating many challengers including statesmen such as Napoleon Bonaparte and Benjamin Franklin. The device was later purchased in 1804 and exhibited by Johann Nepomuk Mälzel. The chess masters who secretly operated it included Johann Allgaier, Boncourt, Aaron Alexandre, William Lewis, Jacques Mouret, and William Schlumberger, but the operators within the mechanism during Kempelen's original tour remain a mystery.

🔗 United States 🔗 Biography 🔗 Africa 🔗 Poetry 🔗 Women's History 🔗 Women writers 🔗 United States/Massachusetts 🔗 African diaspora 🔗 United States History 🔗 United States/Massachusetts - Boston 🔗 Africa/Gambia

Phillis Wheatley, also spelled Phyllis and Wheatly (c. 1753 – December 5, 1784) was the first African-American woman to publish a book of poetry. Born in West Africa, she was sold into slavery at the age of seven or eight and transported to North America. She was purchased by the Wheatley family of Boston, who taught her to read and write and encouraged her poetry when they saw her talent.

On a 1773 trip to London with her master's son, seeking publication of her work, she was aided in meeting prominent people who became patrons. The publication in London of her Poems on Various Subjects, Religious and Moral on September 1, 1773, brought her fame both in England and the American colonies. Figures such as George Washington praised her work. A few years later, African-American poet Jupiter Hammon praised her work in a poem of his own.

Wheatley was emancipated (set free) by the Wheatleys shortly after the publication of her book. She married in about 1778. Two of her children died as infants. After her husband was imprisoned for debt in 1784, Wheatley fell into working poverty and died of illness. Her last infant son died soon after.

🔗 Mathematics

The Basel problem is a problem in mathematical analysis with relevance to number theory, first posed by Pietro Mengoli in 1650 and solved by Leonhard Euler in 1734, and read on 5 December 1735 in The Saint Petersburg Academy of Sciences. Since the problem had withstood the attacks of the leading mathematicians of the day, Euler's solution brought him immediate fame when he was twenty-eight. Euler generalised the problem considerably, and his ideas were taken up years later by Bernhard Riemann in his seminal 1859 paper "On the Number of Primes Less Than a Given Magnitude", in which he defined his zeta function and proved its basic properties. The problem is named after Basel, hometown of Euler as well as of the Bernoulli family who unsuccessfully attacked the problem.

The Basel problem asks for the precise summation of the reciprocals of the squares of the natural numbers, i.e. the precise sum of the infinite series:

${\displaystyle \sum _{n=1}^{\infty }{\frac {1}{n^{2}}}={\frac {1}{1^{2}}}+{\frac {1}{2^{2}}}+{\frac {1}{3^{2}}}+\cdots .}$

The sum of the series is approximately equal to 1.644934. The Basel problem asks for the exact sum of this series (in closed form), as well as a proof that this sum is correct. Euler found the exact sum to be π²/6 and announced this discovery in 1735. His arguments were based on manipulations that were not justified at the time, although he was later proven correct, and it was not until 1741 that he was able to produce a truly rigorous proof.

🔗 Toys 🔗 Shipwrecks 🔗 Oceans

Friendly Floatees are plastic bath toys marketed by The First Years, and made famous by the work of Curtis Ebbesmeyer, an oceanographer who models ocean currents on the basis of flotsam movements. Ebbesmeyer studied the movements of a consignment of 29,000 Friendly Floatees—yellow ducks, red beavers, blue turtles and green frogs—which were washed into the Pacific Ocean in 1992. Some of the toys landed along Pacific Ocean shores, such as Hawaii. Others traveled over 17,000 miles, floating over the site where the Titanic sank, and spent years frozen in Arctic ice to reach the U.S. Eastern Seaboard, British and Irish shores 15 years later in 2007.