To stay up to date you can also follow on Mastodon.

This article is a list of notable unsolved problems in computer science. A problem in computer science is considered unsolved when no solution is known, or when experts in the field disagree about proposed solutions.

The Nebra sky disk is a bronze disk of around 30 centimeters (11 ³⁄₄ in) diameter and a weight of 2.2 kilograms (4.9 lb), having a blue-green patina and inlaid with gold symbols. These symbols are interpreted generally as the Sun or full moon, a lunar crescent, and stars (including a cluster of seven interpreted as the Pleiades). Two golden arcs along the sides, interpreted to mark the angle between the solstices, were added later. A final addition was another arc at the bottom surrounded with multiple strokes (of uncertain meaning, variously interpreted as a Solar Barge with numerous oars, the Milky Way, or a rainbow).

The disk is attributed to a site in present-day Germany near Nebra, Saxony-Anhalt, and dated by Archaeological association to c. 1600 BC. Researchers suggest the disk is an artifact of the Bronze Age Unetice culture.

The style in which the disk is executed was unlike any artistic style then known from the period, with the result that the object was initially suspected of being a forgery, but is now widely accepted as authentic.

The Nebra sky disk features the oldest concrete depiction of the cosmos yet known from anywhere in the world. In June 2013 it was included in the UNESCO Memory of the World Register and termed "one of the most important archaeological finds of the twentieth century."

Salter's duck, also known as the nodding duck or by its official name the Edinburgh duck, is a device that converts wave power into electricity. The wave impact induces rotation of gyroscopes located inside a pear-shaped "duck", and an electrical generator converts this rotation into electricity with an overall efficiency of up to 90%. The Salter's duck was invented by Stephen Salter in response to the oil shortage in the 1970s and was one of the earliest generator designs proposed to the Wave Energy programme in the United Kingdom. The funding for the project was cut off in the early 1980s after oil prices rebounded and the UK government moved away from alternative energy sources. As of May 2018 no wave-power devices have ever gone into large-scale production.

The Expert at the Card Table, originally titled Artifice, Ruse and Subterfuge at the Card Table: A Treatise on the Science and Art of Manipulating Cards, often referred to simply as Erdnase, is an extensive book on the art of sleight of hand published in 1902 by S. W. Erdnase, a pseudonymous author whose identity has remained a mystery for over a century. As a detailed manual of card sharps, the book is considered to be one of the most influential works on magic or conjuring with cards.

The Expert at the Card Table is the most famous, the most carefully studied book ever published on the art of manipulating cards at gaming tables."

The Dolgopolsky list is a word list compiled by Aharon Dolgopolsky in 1964. It lists the 15 lexical items that have the most semantic stability, i.e. they are the 15 words least likely to be replaced by other words as a language evolves. It was based on a study of 140 languages from across Eurasia.

The words, with the first being the most stable, are:

1. I/me
2. two/pair
3. you (singular, informal)
4. who/what
5. tongue
6. name
7. eye
8. heart
9. tooth
10. no/not
11. nail (finger-nail)
12. louse/nit
13. tear/teardrop
14. water
15. dead

The first item in the list, I/me, has been replaced in none of the 140 languages during their recorded history; the fifteenth, dead, has been replaced in 25% of the languages.

The twelfth item, louse/nit, is well kept in the North Caucasian languages, Dravidian and Turkic, but not in other proto-languages.

Shatranj (Arabic: شطرنج‎; Persian: شترنگ‎; from Middle Persian chatrang) is an old form of chess, as played in the Sasanian Empire. Its origins are in the Indian game of chaturaṅga. Modern chess gradually developed from this game, as it was introduced to the western world via contacts in Muslim Andalusia (modern Spain) and in Sicily in the 10th century.

Implicate order and explicate order are ontological concepts for quantum theory coined by theoretical physicist David Bohm during the early 1980s. They are used to describe two different frameworks for understanding the same phenomenon or aspect of reality. In particular, the concepts were developed in order to explain the bizarre behavior of subatomic particles which quantum physics struggles to explain.

In Bohm's Wholeness and the Implicate Order, he used these notions to describe how the appearance of such phenomena might appear differently, or might be characterized by, varying principal factors, depending on contexts such as scales. The implicate (also referred to as the "enfolded") order is seen as a deeper and more fundamental order of reality. In contrast, the explicate or "unfolded" order include the abstractions that humans normally perceive. As he wrote,

In the enfolded [or implicate] order, space and time are no longer the dominant factors determining the relationships of dependence or independence of different elements. Rather, an entirely different sort of basic connection of elements is possible, from which our ordinary notions of space and time, along with those of separately existent material particles, are abstracted as forms derived from the deeper order. These ordinary notions in fact appear in what is called the "explicate" or "unfolded" order, which is a special and distinguished form contained within the general totality of all the implicate orders (Bohm 1980, p. xv).

Padonkaffsky jargon (Russian: язык падонкафф, yazyk padonkaff) or Olbanian (олбанский, olbanskiy) is a cant language developed by a subculture of Runet called padonki (Russian: падонки). It started as an Internet slang language originally used in the Russian Internet community. It is comparable to the English-based Leet. Padonkaffsky jargon became so popular that the former President of Russia Dmitry Medvedev jokingly suggested that Olbanian be taught in schools.

The magic SysRq key is a key combination understood by the Linux kernel, which allows the user to perform various low-level commands regardless of the system's state. It is often used to recover from freezes, or to reboot a computer without corrupting the filesystem. Its effect is similar to the computer's hardware reset button (or power switch) but with many more options and much more control.

This key combination provides access to powerful features for software development and disaster recovery. In this sense, it can be considered a form of escape sequence. Principal among the offered commands are means to forcibly unmount file systems, kill processes, recover keyboard state, and write unwritten data to disk. With respect to these tasks, this feature serves as a tool of last resort.

The magic SysRq key cannot work under certain conditions, such as a kernel panic or a hardware failure preventing the kernel from running properly.

Below is a mostly comprehensive gallery of all images — illustrations, diagrams and animations — that I have created for Wikipedia over the years, some of which have been selected as featured pictures, or even picture of the day. As you'll probably notice, they're mostly related to physics and mathematics, which are my main areas of interest.

If you have any comments, requests, suggestions or corrections, feel free to drop me a message on my talk page. But please, before making a suggestion, first take a look and see what sort of stuff I can do. Due to time, knowledge and complexity constraints, I cannot guarantee I'll be able to make a good illustration of any topic.

You can also follow me on tumblr for WIPs, current and failed projects and other creations.

If you appreciate my work, consider making a donation.