Have a deep view into what people are curious about.

🔗 Classical Greece and Rome 🔗 Greece 🔗 Middle Ages 🔗 Middle Ages/History 🔗 Sociology 🔗 Sports 🔗 Greece/Byzantine world

The Nika riots (Greek: Στάσις τοῦ Νίκα, romanized: Stásis toû Níka), Nika revolt or Nika sedition took place against Byzantine emperor Justinian I in Constantinople over the course of a week in 532 C.E. They are often regarded as the most violent riots in the city's history, with nearly half of Constantinople being burned or destroyed and tens of thousands of people killed.

🔗 Plants

Cyclanthera brachystachya, the exploding cucumber (but not to be confused with Ecballium elaterium), in the cucurbit or gourd family (Cucurbitaceae), is a herbaceous vine usually grown for its curiosity value, but the fruit is also edible.

🔗 Lists

This is a list of countries and territories by home ownership rate, which is the ratio of owner-occupied units to total residential units in a specified area.

🔗 Computing 🔗 Computing/Software 🔗 Computing/Computer science 🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography and computer science, a hash tree or Merkle tree is a tree in which every leaf node is labelled with the cryptographic hash of a data block, and every non-leaf node is labelled with the cryptographic hash of the labels of its child nodes. Hash trees allow efficient and secure verification of the contents of large data structures. Hash trees are a generalization of hash lists and hash chains.

Demonstrating that a leaf node is a part of a given binary hash tree requires computing a number of hashes proportional to the logarithm of the number of leaf nodes of the tree; this contrasts with hash lists, where the number is proportional to the number of leaf nodes itself.

The concept of hash trees is named after Ralph Merkle, who patented it in 1979.

🔗 Architecture

A saw-tooth roof is a roof comprising a series of ridges with dual pitches either side. The steeper surfaces are glazed to admit daylight and face away from the equator to shield workers and machinery from direct sunlight. This kind of roof admits natural light into a deep plan building or factory. It was therefore most commonly built during the Machine Age from the mid-nineteenth century to the mid-twentieth, when electrification of factories was not yet common.

Many factories of the era had little or no electrical wiring; their main power sources for the machinery were often steam engines driving line shafting, and the lighting was chiefly via daylighting through the windows. Work done at night, when necessary, was typically lit by oil lamps and candles, but many factories closed for the night. Their norm of an early working day (for example, 6 a.m. to 4 p.m.) was not merely a tradition but a functional decision based on this reliance on daylighting. The same was true of the farmer's workday, for the same reason.

🔗 Physics 🔗 Systems 🔗 Systems/Chaos theory

In condensed matter physics, Hofstadter's butterfly describes the spectral properties of non-interacting two dimensional electrons in a magnetic field. The fractal, self-similar, nature of the spectrum was discovered in the 1976 Ph.D. work of Douglas Hofstadter and is one of the early examples of computer graphics. The name reflects the visual resemblance of the figure on the right to a swarm of butterflies flying to infinity.

The Hofstadter butterfly plays an important role in the theory of the integer quantum Hall effect, and D.J. Thouless has been awarded the Nobel prize in physics in 2016 for the discovery that the wings of the butterfly are characterized by Chern integers, the quantized Hall conductances discovered in 1980 by Klaus von Klitzing for which he has been awarded the Nobel prize in 1985. The colors in the diagram reflect the different Chern numbers.

🔗 Germany

The Bielefeld conspiracy (German: Bielefeldverschwörung or Bielefeld-Verschwörung, pronounced [ˈbiːləfɛltfɛɐ̯ˌʃvøːʁʊŋ]) is a satire of conspiracy theories that claims that the city of Bielefeld, Germany, does not exist, but is an illusion propagated by various forces. First posted on the German Usenet in 1994, the conspiracy has since been mentioned in the city's marketing, and referenced by Chancellor Angela Merkel.

🔗 Computing

Constraint programming (CP) is a paradigm for solving combinatorial problems that draws on a wide range of techniques from artificial intelligence, computer science, and operations research. In constraint programming, users declaratively state the constraints on the feasible solutions for a set of decision variables. Constraints differ from the common primitives of imperative programming languages in that they do not specify a step or sequence of steps to execute, but rather the properties of a solution to be found. In addition to constraints, users also need to specify a method to solve these constraints. This typically draws upon standard methods like chronological backtracking and constraint propagation, but may use customized code like a problem specific branching heuristic.

Constraint programming takes its root from and can be expressed in the form of constraint logic programming, which embeds constraints into a logic program. This variant of logic programming is due to Jaffar and Lassez, who extended in 1987 a specific class of constraints that were introduced in Prolog II. The first implementations of constraint logic programming were Prolog III, CLP(R), and CHIP.

Instead of logic programming, constraints can be mixed with functional programming, term rewriting, and imperative languages. Programming languages with built-in support for constraints include Oz (functional programming) and Kaleidoscope (imperative programming). Mostly, constraints are implemented in imperative languages via constraint solving toolkits, which are separate libraries for an existing imperative language.

🔗 Mathematics

The Banach–Tarski paradox is a theorem in set-theoretic geometry, which states the following: Given a solid ball in 3‑dimensional space, there exists a decomposition of the ball into a finite number of disjoint subsets, which can then be put back together in a different way to yield two identical copies of the original ball. Indeed, the reassembly process involves only moving the pieces around and rotating them without changing their shape. However, the pieces themselves are not "solids" in the usual sense, but infinite scatterings of points. The reconstruction can work with as few as five pieces.

A stronger form of the theorem implies that given any two "reasonable" solid objects (such as a small ball and a huge ball), the cut pieces of either one can be reassembled into the other. This is often stated informally as "a pea can be chopped up and reassembled into the Sun" and called the "pea and the Sun paradox".

The reason the Banach–Tarski theorem is called a paradox is that it contradicts basic geometric intuition. "Doubling the ball" by dividing it into parts and moving them around by rotations and translations, without any stretching, bending, or adding new points, seems to be impossible, since all these operations ought, intuitively speaking, to preserve the volume. The intuition that such operations preserve volumes is not mathematically absurd and it is even included in the formal definition of volumes. However, this is not applicable here because in this case it is impossible to define the volumes of the considered subsets. Reassembling them reproduces a volume, which happens to be different from the volume at the start.

Unlike most theorems in geometry, the proof of this result depends in a critical way on the choice of axioms for set theory. It can be proven using the axiom of choice, which allows for the construction of non-measurable sets, i.e., collections of points that do not have a volume in the ordinary sense, and whose construction requires an uncountable number of choices.

It was shown in 2005 that the pieces in the decomposition can be chosen in such a way that they can be moved continuously into place without running into one another.

🔗 Computing

PL/0 is a programming language, intended as an educational programming language, that is similar to but much simpler than Pascal, a general-purpose programming language. It serves as an example of how to construct a compiler. It was originally introduced in the book, Algorithms + Data Structures = Programs, by Niklaus Wirth in 1976. It features quite limited language constructs: there are no real numbers, very few basic arithmetic operations and no control-flow constructs other than "if" and "while" blocks. While these limitations make writing real applications in this language impractical, it helps the compiler remain compact and simple.