Have a deep view into what people are curious about.

🔗 Biography 🔗 Mathematics 🔗 Biography/science and academia 🔗 History of Science 🔗 India 🔗 India/Indian history workgroup 🔗 India/Tamil Nadu

Srinivasa Ramanujan FRS (; listen ; 22 December 1887 – 26 April 1920) was an Indian mathematician who lived during the British Rule in India. Though he had almost no formal training in pure mathematics, he made substantial contributions to mathematical analysis, number theory, infinite series, and continued fractions, including solutions to mathematical problems then considered unsolvable. Ramanujan initially developed his own mathematical research in isolation: "He tried to interest the leading professional mathematicians in his work, but failed for the most part. What he had to show them was too novel, too unfamiliar, and additionally presented in unusual ways; they could not be bothered". Seeking mathematicians who could better understand his work, in 1913 he began a postal partnership with the English mathematician G. H. Hardy at the University of Cambridge, England. Recognizing Ramanujan's work as extraordinary, Hardy arranged for him to travel to Cambridge. In his notes, Ramanujan had produced groundbreaking new theorems, including some that Hardy said had "defeated him and his colleagues completely", in addition to rediscovering recently proven but highly advanced results.

During his short life, Ramanujan independently compiled nearly 3,900 results (mostly identities and equations). Many were completely novel; his original and highly unconventional results, such as the Ramanujan prime, the Ramanujan theta function, partition formulae and mock theta functions, have opened entire new areas of work and inspired a vast amount of further research. Nearly all his claims have now been proven correct. The Ramanujan Journal, a scientific journal, was established to publish work in all areas of mathematics influenced by Ramanujan, and his notebooks—containing summaries of his published and unpublished results—have been analyzed and studied for decades since his death as a source of new mathematical ideas. As late as 2011 and again in 2012, researchers continued to discover that mere comments in his writings about "simple properties" and "similar outputs" for certain findings were themselves profound and subtle number theory results that remained unsuspected until nearly a century after his death. He became one of the youngest Fellows of the Royal Society and only the second Indian member, and the first Indian to be elected a Fellow of Trinity College, Cambridge. Of his original letters, Hardy stated that a single look was enough to show they could only have been written by a mathematician of the highest calibre, comparing Ramanujan to mathematical geniuses such as Euler and Jacobi.

In 1919, ill health—now believed to have been hepatic amoebiasis (a complication from episodes of dysentery many years previously)—compelled Ramanujan's return to India, where he died in 1920 at the age of 32. His last letters to Hardy, written in January 1920, show that he was still continuing to produce new mathematical ideas and theorems. His "lost notebook", containing discoveries from the last year of his life, caused great excitement among mathematicians when it was rediscovered in 1976.

A deeply religious Hindu, Ramanujan credited his substantial mathematical capacities to divinity, and said the mathematical knowledge he displayed was revealed to him by his family goddess. "An equation for me has no meaning," he once said, "unless it expresses a thought of God."

🔗 Economics 🔗 Sociology

The Lindy effect is a theory that the future life expectancy of some non-perishable things like a technology or an idea is proportional to their current age, so that every additional period of survival implies a longer remaining life expectancy. Where the Lindy effect applies, mortality rate decreases with time.

🔗 Physics 🔗 Geology 🔗 Physics/Acoustics

Singing sand, also called whistling sand, barking sand or singing dune, is sand that produces sound. The sound emission may be caused by wind passing over dunes or by walking on the sand.

Certain conditions have to come together to create singing sand:

1. The sand grains have to be round and between 0.1 and 0.5 mm in diameter.
2. The sand has to contain silica.
3. The sand needs to be at a certain humidity.

The most common frequency emitted seems to be close to 450 Hz.

There are various theories about the singing sand mechanism. It has been proposed that the sound frequency is controlled by the shear rate. Others have suggested that the frequency of vibration is related to the thickness of the dry surface layer of sand. The sound waves bounce back and forth between the surface of the dune and the surface of the moist layer, creating a resonance that increases the sound's volume. The noise may be generated by friction between the grains or by the compression of air between them.

Other sounds that can be emitted by sand have been described as "roaring" or "booming".

🔗 Computing 🔗 Time

The Day of the Programmer is an international professional day that is celebrated on the 256th (hexadecimal 100th, or the 2⁸th) day of each year (September 13 during common years and on September 12 in leap years). It is officially recognized in Russia.

The number 256 (2⁸) was chosen because it is the number of distinct values that can be represented with a byte, a value well known to programmers. 256 is also the highest power of two that is less than 365, the number of days in a common year.

🔗 Computing 🔗 Robotics

The Viterbi algorithm is a dynamic programming algorithm for obtaining the maximum a posteriori probability estimate of the most likely sequence of hidden states—called the Viterbi path—that results in a sequence of observed events, especially in the context of Markov information sources and hidden Markov models (HMM).

The algorithm has found universal application in decoding the convolutional codes used in both CDMA and GSM digital cellular, dial-up modems, satellite, deep-space communications, and 802.11 wireless LANs. It is now also commonly used in speech recognition, speech synthesis, diarization, keyword spotting, computational linguistics, and bioinformatics. For example, in speech-to-text (speech recognition), the acoustic signal is treated as the observed sequence of events, and a string of text is considered to be the "hidden cause" of the acoustic signal. The Viterbi algorithm finds the most likely string of text given the acoustic signal.

🔗 Skepticism 🔗 Paranormal

Jimmy Carter, United States president from 1977 until 1981, reported seeing an unidentified flying object while at Leary, Georgia, in 1969. While serving as governor of Georgia, Carter was asked (on September 14, 1973) by the International UFO Bureau in Oklahoma City to file a report of the sighting, and he filed a statement on September 18, mailed September 20. Since its writing, the report has been discussed several times by both ufologists and by members of the mainstream media.

🔗 Automobiles 🔗 Engineering

The Sinclair C5 is a small one-person battery electric velomobile, technically an "electrically assisted pedal cycle". It was the culmination of Sir Clive Sinclair's long-running interest in electric vehicles. Although widely described as an "electric car", Sinclair characterised it as a "vehicle, not a car".

Sinclair had become one of the UK's best-known millionaires, and earned a knighthood, on the back of the highly successful Sinclair Research range of home computers in the early 1980s. He hoped to repeat his success in the electric vehicle market, which he saw as ripe for a new approach. The C5 emerged from an earlier project to produce a small electric car called the C1. After a change in the law, prompted by lobbying from bicycle manufacturers, Sinclair developed the C5 as an electrically powered tricycle with a polypropylene body and a chassis designed by Lotus Cars. It was intended to be the first in a series of increasingly ambitious electric vehicles, but the development of the follow-up C10 and C15 models never got further than the drawing board.

On 10 January 1985, the C5 was unveiled at a glitzy launch event but it received a less than enthusiastic reception from the British media. Its sales prospects were blighted by poor reviews and safety concerns expressed by consumer and motoring organisations. The vehicle's limitations – a short range, a maximum speed of only 15 miles per hour (24 km/h), a battery that ran down quickly and a lack of weatherproofing – made it impractical for most people's needs. It was marketed as an alternative to cars and bicycles, but ended up appealing to neither group of owners, and it was not available in shops until several months after its launch. Within three months of the launch, production had been slashed by 90%. Sales never picked up despite Sinclair's optimistic forecasts and production ceased entirely by August 1985. Out of 14,000 C5s made, only 5,000 were sold before its manufacturer, Sinclair Vehicles, went into receivership.

The C5 became known as "one of the great marketing bombs of postwar British industry" and a "notorious ... example of failure". Despite its commercial failure, the C5 went on to become a cult item for collectors. Thousands of unsold C5s were purchased by investors and sold for hugely inflated prices – as much as £5,000, compared to the original retail value of £399. Enthusiasts have established owners' clubs and some have modified their vehicles substantially, adding monster wheels, jet engines, and high-powered electric motors to propel their C5s at speeds of up to 150 miles per hour (240 km/h).

🔗 Australia 🔗 United States History 🔗 Australia/Australian history 🔗 Australia/South Australia

Rain follows the plow is the conventional name for a now-discredited theory of climatology that was popular throughout the American West and Australia during the late 19th century. The phrase was employed as a summation of the theory by Charles Dana Wilber:

God speed the plow. ... By this wonderful provision, which is only man's mastery over nature, the clouds are dispensing copious rains ... [the plow] is the instrument which separates civilization from savagery; and converts a desert into a farm or garden. ... To be more concise, Rain follows the plow.

The basic premise of the theory was that human habitation and agriculture through homesteading effected a permanent change in the climate of arid and semi-arid regions, making these regions more humid. The theory was widely promoted in the 1870s as a justification for the settlement of the Great Plains, a region previously known as the "Great American Desert". It was also used to justify the expansion of wheat growing on marginal land in South Australia during the same period.

According to the theory, increased human settlement in the region and cultivation of soil would result in an increased rainfall over time, rendering the land more fertile and lush as the population increased. As later historical records of rainfall indicated, the theory was based on faulty evidence arising from brief climatological fluctuations that happened to coincide with settlement, an example of the logical fallacy that correlation means causation. The theory was later refuted by climatologists and is now definitively regarded as pure superstition.

🔗 Systems 🔗 Systems/Chaos theory

The Burning Ship fractal, first described and created by Michael Michelitsch and Otto E. Rössler in 1992, is generated by iterating the function:

${\displaystyle z_{n+1}=(|\operatorname {Re} \left(z_{n}\right)|+i|\operatorname {Im} \left(z_{n}\right)|)^{2}+c,\quad z_{0}=0}$

in the complex plane ${\displaystyle \mathbb {C} }$ which will either escape or remain bounded. The difference between this calculation and that for the Mandelbrot set is that the real and imaginary components are set to their respective absolute values before squaring at each iteration. The mapping is non-analytic because its real and imaginary parts do not obey the Cauchy–Riemann equations.