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🔗 Computing 🔗 Computing/Early computers

Lehmer sieves are mechanical devices that implement sieves in number theory. Lehmer sieves are named for Derrick Norman Lehmer and his son Derrick Henry Lehmer. The father was a professor of mathematics at the University of California, Berkeley at the time, and his son followed in his footsteps as a number theorist and professor at Berkeley.

A sieve in general is intended to find the numbers which are remainders when a set of numbers are divided by a second set. Generally, they are used in finding solutions of Diophantine equations or to factor numbers. A Lehmer sieve will signal that such solutions are found in a variety of ways depending on the particular construction.

🔗 Computing 🔗 Computing/Computer hardware

The 6800 ("sixty-eight hundred") is an 8-bit microprocessor designed and first manufactured by Motorola in 1974. The MC6800 microprocessor was part of the M6800 Microcomputer System that also included serial and parallel interface ICs, RAM, ROM and other support chips. A significant design feature was that the M6800 family of ICs required only a single five-volt power supply at a time when most other microprocessors required three voltages. The M6800 Microcomputer System was announced in March 1974 and was in full production by the end of that year.

The 6800 has a 16-bit address bus that can directly access 64 KB of memory and an 8-bit bi-directional data bus. It has 72 instructions with seven addressing modes for a total of 197 opcodes. The original MC6800 could have a clock frequency of up to 1 MHz. Later versions had a maximum clock frequency of 2 MHz.

In addition to the ICs, Motorola also provided a complete assembly language development system. The customer could use the software on a remote timeshare computer or on an in-house minicomputer system. The Motorola EXORciser was a desktop computer built with the M6800 ICs that could be used for prototyping and debugging new designs. An expansive documentation package included datasheets on all ICs, two assembly language programming manuals, and a 700-page application manual that showed how to design a point-of-sale terminal (a computerized cash register) around the 6800.

The 6800 was popular in computer peripherals, test equipment applications and point-of-sale terminals. It also found use in arcade games and pinball machines. The MC6802, introduced in 1977, included 128 bytes of RAM and an internal clock oscillator on chip. The MC6801 and MC6805 included RAM, ROM and I/O on a single chip and were popular in automotive applications. The Motorola 6809 was an updated compatible design.

🔗 Climate change 🔗 Environment 🔗 Science Fiction 🔗 Literature 🔗 Politics 🔗 Visual arts 🔗 Ecology 🔗 Punk music

Solarpunk is a movement that encourages optimistic envisionings of the future in light of present environmental concerns, such as climate change and pollution, as well as social inequality. Solarpunk encompasses a multitude of media such as literature, art, architecture, fashion, music, and games. Solarpunk focuses on renewable energies, as well as technology as a whole, to envision a positive future for humanity; although, it also embraces less advanced ways to reduce carbon emissions, like gardening. Solarpunk is also a genre of speculative fiction; some of the most well-known examples are Solarpunk: Ecological and Fantastical Stories in a Sustainable World and Sunvault: Stories of Solarpunk and Eco-Speculation.

🔗 Mathematics 🔗 Systems 🔗 Systems/Chaos theory

In mathematics, the Weierstrass function is an example of a real-valued function that is continuous everywhere but differentiable nowhere. It is an example of a fractal curve. It is named after its discoverer Karl Weierstrass.

The Weierstrass function has historically served the role of a pathological function, being the first published example (1872) specifically concocted to challenge the notion that every continuous function is differentiable except on a set of isolated points. Weierstrass's demonstration that continuity did not imply almost-everywhere differentiability upended mathematics, overturning several proofs that relied on geometric intuition and vague definitions of smoothness. These types of functions were denounced by contemporaries: Henri Poincaré famously described them as "monsters" and called Weierstrass' work "an outrage against common sense", while Charles Hermite wrote that they were a "lamentable scourge". The functions were difficult to visualize until the arrival of computers in the next century, and the results did not gain wide acceptance until practical applications such as models of Brownian motion necessitated infinitely jagged functions (nowadays known as fractal curves).

🔗 Sociology 🔗 Finland

Wiio's laws are humoristically formulated observations about how humans communicate.

Wiio's laws are usually summarized with "Human communications usually fail except by accident", which is the main observation made by Professor Osmo Antero Wiio in 1978.

🔗 Video games 🔗 Computer science 🔗 Mathematics

Fast inverse square root, sometimes referred to as Fast InvSqrt() or by the hexadecimal constant 0x5F3759DF, is an algorithm that estimates ​¹⁄_√x, the reciprocal (or multiplicative inverse) of the square root of a 32-bit floating-point number x in IEEE 754 floating-point format. This operation is used in digital signal processing to normalize a vector, i.e., scale it to length 1. For example, computer graphics programs use inverse square roots to compute angles of incidence and reflection for lighting and shading. The algorithm is best known for its implementation in 1999 in the source code of Quake III Arena, a first-person shooter video game that made heavy use of 3D graphics. The algorithm only started appearing on public forums such as Usenet in 2002 or 2003. At the time, it was generally computationally expensive to compute the reciprocal of a floating-point number, especially on a large scale; the fast inverse square root bypassed this step.

The algorithm accepts a 32-bit floating-point number as the input and stores a halved value for later use. Then, treating the bits representing the floating-point number as a 32-bit integer, a logical shift right by one bit is performed and the result subtracted from the number 0x5F3759DF, which is a floating point representation of an approximation of √2¹²⁷. This results in the first approximation of the inverse square root of the input. Treating the bits again as a floating-point number, it runs one iteration of Newton's method, yielding a more precise approximation.

The algorithm was originally attributed to John Carmack, but an investigation showed that the code had deeper roots in both the hardware and software side of computer graphics. Adjustments and alterations passed through both Silicon Graphics and 3dfx Interactive, with Gary Tarolli's implementation for the SGI Indigo as the earliest known use. It is not known how the constant was originally derived, though investigation has shed some light on possible methods.

With subsequent hardware advancements, especially the x86 SSE instruction rsqrtss, this method is not generally applicable to modern computing, though it remains an interesting example both historically and for more limited machines.

🔗 Cryptography 🔗 Cryptography/Computer science 🔗 Virginia

The Beale ciphers (or Beale Papers) are a set of three ciphertexts, one of which allegedly states the location of a buried treasure of gold, silver and jewels estimated to be worth over US$43 million as of January 2018. Comprising three ciphertexts, the first (unsolved) text describes the location, the second (solved) ciphertext the content of the treasure, and the third (unsolved) lists the names of the treasure's owners and their next of kin.

The story of the three ciphertexts originates from an 1885 pamphlet detailing treasure being buried by a man named Thomas J. Beale in a secret location in Bedford County, Virginia, in the 1820s. Beale entrusted a box containing the encrypted messages to a local innkeeper named Robert Morriss and then disappeared, never to be seen again. According to the story, the innkeeper opened the box 23 years later, and then decades after that gave the three encrypted ciphertexts to a friend before he died. The friend then spent the next twenty years of his life trying to decode the messages, and was able to solve only one of them which gave details of the treasure buried and the general location of the treasure. The unnamed friend then published all three ciphertexts in a pamphlet which was advertised for sale in the 1880s.

Since the publication of the pamphlet, a number of attempts have been made to decode the two remaining ciphertexts and to locate the treasure, but all efforts have resulted in failure.

There are many arguments that the entire story is a hoax, including the 1980 article "A Dissenting Opinion" by cryptographer Jim Gillogly, and a 1982 scholarly analysis of the Beale Papers and their related story by Joe Nickell, using historical records that cast doubt on the existence of Thomas J. Beale. Nickell also presents linguistic evidence demonstrating that the documents could not have been written at the time alleged (words such as "stampeding", for instance, are of later vintage). His analysis of the writing style showed that Beale was almost certainly James B. Ward, whose 1885 pamphlet brought the Beale Papers to light. Nickell argues that the tale is thus a work of fiction; specifically, a "secret vault" allegory of the Freemasons; James B. Ward was a Mason himself.

🔗 Astronomy 🔗 Sweden 🔗 Solar System 🔗 Astronomy/Solar System

The Sweden Solar System is the world's largest permanent scale model of the Solar System. The Sun is represented by the Ericsson Globe in Stockholm, the largest hemispherical building in the world. The inner planets can also be found in Stockholm but the outer planets are situated northward in other cities along the Baltic Sea. The system was started by Nils Brenning and Gösta Gahm and is on the scale of 1:20 million.

🔗 Aviation 🔗 Disaster management 🔗 Aviation/Aviation accident 🔗 Syria

Syrian Air Flight 9218 was a cargo flight operated by Syrian Air that disappeared from flight tracking near Homs while flying out of Damascus International Airport on December 8, 2024.