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🔗 United States 🔗 Biography 🔗 Aviation 🔗 Aviation/Aviation accident 🔗 Oregon 🔗 Aviation/aerospace biography 🔗 United States/FBI 🔗 Crime and Criminal Biography

D. B. Cooper is a media epithet used to refer to an unidentified man who hijacked a Boeing 727 aircraft in United States airspace between Portland, Oregon, and Seattle, Washington, on the afternoon of November 24, 1971. He extorted $200,000 in ransom (equivalent to $1,278,000 in 2020) and parachuted to an uncertain fate over southwestern Washington. The man purchased his airline ticket using the alias Dan Cooper but, because of a news miscommunication, became known in popular lore as D. B. Cooper.

The FBI maintained an active investigation for 45 years after the hijacking. Despite a case file that grew to over 60 volumes over that period, no definitive conclusions were reached regarding Cooper's true identity or fate. The crime remains the only unsolved air piracy in commercial aviation history.

Numerous theories of widely varying plausibility have been proposed over the years by investigators, reporters, and amateur enthusiasts. $5,880 of the ransom was found along the banks of the Columbia River in 1980, which triggered renewed interest but ultimately only deepened the mystery. The great majority of the ransom remains unrecovered.

The FBI officially suspended active investigation of the case in July 2016, but the agency continues to request that any physical evidence that might emerge related to the parachutes or the ransom money be submitted for analysis.

🔗 Germany 🔗 Time 🔗 Radio Stations

DCF77 is a German longwave time signal and standard-frequency radio station. It started service as a standard-frequency station on 1 January 1959. In June 1973 date and time information was added. Its primary and backup transmitter are located at 50°0′56″N 9°00′39″E in Mainflingen, about 25 km south-east of Frankfurt am Main, Germany. The transmitter generates a nominal power of 50 kW, of which about 30 to 35 kW can be radiated via a T-antenna.

DCF77 is controlled by the Physikalisch-Technische Bundesanstalt (PTB), Germany's national physics laboratory and transmits in continuous operation (24 hours). It is operated by Media Broadcast GmbH (previously a subsidiary of Deutsche Telekom AG), on behalf of the PTB. With Media Broadcast GmbH, a temporal transmission availability of at least 99.7% per year or under 26.28 hours of annual downtime has been agreed upon. Most service interruptions are short-term disconnections of under two minutes. Longer lasting transmission service interruptions are generally caused by strong winds, freezing rain or snow-induced T-antenna movement. This manifests itself in electrical detuning of the antenna resonance circuit and hence a measurable phase modulation of the received signal. When the maladjustment is too large, the transmitter is taken out of service temporarily. In the year 2002, almost 99.95% availability, or just over 4.38 hours of downtime, was realized. The timestamp sent is either in Coordinated Universal Time (UTC)+1 or UTC+2 depending on daylight saving time.

The highly accurate 77.5 kHz (approximately 3868.3 m wavelength) carrier signal is generated from local atomic clocks that are linked with the German master clocks at the PTB in Braunschweig. The DCF77 time signal is used for the dissemination of the German national legal time to the public.

Radio clocks and watches have been very popular in Europe since the late 1980s and, in mainland Europe, most of them use the DCF77 signal to set their time automatically. Further industrial time-keeping systems at railway stations, in the field of telecommunication and information technology, and at radio and TV stations are radio-controlled by DCF77 as well as tariff change-over clocks of energy supply companies and clocks in traffic-light facilities.

🔗 United States 🔗 Computing 🔗 Computing/Computer hardware 🔗 Computing/Early computers 🔗 United States/Iowa

The Atanasoff–Berry computer (ABC) was the first automatic electronic digital computer. Limited by the technology of the day, and execution, the device has remained somewhat obscure. The ABC's priority is debated among historians of computer technology, because it was neither programmable, nor Turing-complete. Conventionally, the ABC would be considered the first electronic ALU (arithmetic logic unit) – which is integrated into every modern processor's design.

Its unique contribution was to make computing faster by being the first to use vacuum tubes to do the arithmetic calculations. Prior to this, slower electro-mechanical methods were used by Konrad Zuse's Z1, and the simultaneously developed Harvard Mark I. The first electronic, programmable, digital machine, the Colossus computer from 1943 to 1945, used similar tube-based technology as ABC.

🔗 Songs

"Old Man Trump" is a song with lyrics written by American folk singer-songwriter Woody Guthrie in 1954. The song describes the racist housing practices and discriminatory rental policies of his landlord, Fred Trump (the father of the 45th president of the United States, Donald Trump). Although the lyrics were written in 1954, it was never recorded by Guthrie. In January 2016, Will Kaufman, a Guthrie scholar and professor of American literature and culture at the University of Central Lancashire, unearthed the handwritten lyrics while conducting research at the Woody Guthrie Archives in Tulsa, Oklahoma.

🔗 Palaeontology 🔗 Marine life 🔗 Indigenous peoples of the Americas 🔗 Bivalves

Spondylus is a genus of bivalve molluscs, the only genus in the family Spondylidae. They are known in English as spiny oysters or thorny oysters (though they are not, in fact, true oysters).

🔗 Mathematics

A prime number (or a prime) is a natural number greater than 1 that cannot be formed by multiplying two smaller natural numbers. A natural number greater than 1 that is not prime is called a composite number. For example, 5 is prime because the only ways of writing it as a product, 1 × 5 or 5 × 1, involve 5 itself. However, 6 is composite because it is the product of two numbers (2 × 3) that are both smaller than 6. Primes are central in number theory because of the fundamental theorem of arithmetic: every natural number greater than 1 is either a prime itself or can be factorized as a product of primes that is unique up to their order.

The property of being prime is called primality. A simple but slow method of checking the primality of a given number ${\displaystyle n}$, called trial division, tests whether ${\displaystyle n}$ is a multiple of any integer between 2 and ${\displaystyle {\sqrt {n}}}$. Faster algorithms include the Miller–Rabin primality test, which is fast but has a small chance of error, and the AKS primality test, which always produces the correct answer in polynomial time but is too slow to be practical. Particularly fast methods are available for numbers of special forms, such as Mersenne numbers. As of December 2018 the largest known prime number has 24,862,048 decimal digits.

There are infinitely many primes, as demonstrated by Euclid around 300 BC. No known simple formula separates prime numbers from composite numbers. However, the distribution of primes within the natural numbers in the large can be statistically modelled. The first result in that direction is the prime number theorem, proven at the end of the 19th century, which says that the probability of a randomly chosen number being prime is inversely proportional to its number of digits, that is, to its logarithm.

Several historical questions regarding prime numbers are still unsolved. These include Goldbach's conjecture, that every even integer greater than 2 can be expressed as the sum of two primes, and the twin prime conjecture, that there are infinitely many pairs of primes having just one even number between them. Such questions spurred the development of various branches of number theory, focusing on analytic or algebraic aspects of numbers. Primes are used in several routines in information technology, such as public-key cryptography, which relies on the difficulty of factoring large numbers into their prime factors. In abstract algebra, objects that behave in a generalized way like prime numbers include prime elements and prime ideals.

🔗 Computing 🔗 Computing/Computer Security

In computing, a fork bomb (also called rabbit virus or wabbit) is a denial-of-service attack wherein a process continually replicates itself to deplete available system resources, slowing down or crashing the system due to resource starvation.

🔗 Physics 🔗 History of Science

The ultraviolet catastrophe, also called the Rayleigh–Jeans catastrophe, was the prediction of late 19th century to early 20th century classical physics that an ideal black body at thermal equilibrium would emit an unbounded quantity of energy as wavelength decreased into the ultraviolet range.^: 6–7 The term "ultraviolet catastrophe" was first used in 1911 by Paul Ehrenfest, but the concept originated with the 1900 statistical derivation of the Rayleigh–Jeans law.

The phrase refers to the fact that the empirically derived Rayleigh–Jeans law, which accurately predicted experimental results at large wavelengths, failed to do so for short wavelengths. (See the image for further elaboration.) As the theory diverged from empirical observations when these frequencies reached the ultraviolet region of the electromagnetic spectrum, there was a problem. This problem was later found to be due to a property of quanta as proposed by Max Planck: There could be no fraction of a discrete energy package already carrying minimal energy.

Since the first use of this term, it has also been used for other predictions of a similar nature, as in quantum electrodynamics and such cases as ultraviolet divergence.

🔗 Video games

I Get This Call Every Day is a 2012 point-and-click video game developed and published by Toronto-based developer David S Gallant. It was released for Microsoft Windows and OS X on December 21, 2012. It focuses on a call received by an employee of a customer service call centre; the player must navigate through the call without irritating the caller or breaking confidentiality laws. Gallant was fired from his job at a call centre as a direct result of publishing the game.

🔗 India 🔗 Board and table games

Ganjifa, Ganjapa or Gânjaphâ, is a card game and type of playing cards that are most associated with Persia and India. After Ganjifa cards fell out of use in Iran before the twentieth century, India became the last country to produce them. The form prevalent in Odisha is Ganjapa.