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🔗 Ancient Egypt 🔗 Maps 🔗 Geology

The Turin Papyrus Map is an ancient Egyptian map, generally considered the oldest surviving map of topographical interest from the ancient world. It is drawn on a papyrus reportedly discovered at Deir el-Medina in Thebes, collected by Bernardino Drovetti (known as Napoleon's Proconsul) in Egypt sometime before 1824 AD and now preserved in Turin's Museo Egizio. The map was drawn about 1150 BC by the well-known Scribe-of-the-Tomb Amennakhte, son of Ipuy. It was prepared for Ramesses IV's quarrying expedition to the Wadi Hammamat in the Eastern Desert, which exposes Precambrian rocks of the Arabian-Nubian Shield. The purpose of the expedition was to obtain blocks of bekhen-stone (metagraywacke sandstone) to be used for statues of the king.

🔗 United States 🔗 Mathematics 🔗 Education 🔗 United States/Massachusetts 🔗 Higher Education

Math 55 is a two-semester long first-year undergraduate mathematics course at Harvard University, founded by Lynn Loomis and Shlomo Sternberg. The official titles of the course are Honors Abstract Algebra (Math 55a) and Honors Real and Complex Analysis (Math 55b). Previously, the official title was Honors Advanced Calculus and Linear Algebra.

🔗 Psychology

The narcissism of small differences (German: der Narzissmus der kleinen Differenzen) is the thesis that communities with adjoining territories and close relationships are especially likely to engage in feuds and mutual ridicule because of hypersensitivity to details of differentiation. The term was coined by Sigmund Freud in 1917, based on the earlier work of British anthropologist Ernest Crawley. In language differing only slightly from current psychoanalytic terminology, Crawley declared that each individual is separated from others by a taboo of personal isolation, a narcissism of minor differences.

🔗 Statistics

In mathematics, Buffon's needle problem is a question first posed in the 18th century by Georges-Louis Leclerc, Comte de Buffon:

Suppose we have a floor made of parallel strips of wood, each the same width, and we drop a needle onto the floor. What is the probability that the needle will lie across a line between two strips?

Buffon's needle was the earliest problem in geometric probability to be solved; it can be solved using integral geometry. The solution for the sought probability p, in the case where the needle length l is not greater than the width t of the strips, is

${\displaystyle p={\frac {2}{\pi }}{\frac {l}{t}}.}$

This can be used to design a Monte Carlo method for approximating the number π, although that was not the original motivation for de Buffon's question.

🔗 Cryptography 🔗 Cryptography/Computer science

In cryptography and steganography, plausibly deniable encryption describes encryption techniques where the existence of an encrypted file or message is deniable in the sense that an adversary cannot prove that the plaintext data exists.

The users may convincingly deny that a given piece of data is encrypted, or that they are able to decrypt a given piece of encrypted data, or that some specific encrypted data exists. Such denials may or may not be genuine. For example, it may be impossible to prove that the data is encrypted without the cooperation of the users. If the data is encrypted, the users genuinely may not be able to decrypt it. Deniable encryption serves to undermine an attacker's confidence either that data is encrypted, or that the person in possession of it can decrypt it and provide the associated plaintext.

In their pivotal 1996 paper, Ran Canetti, Cynthia Dwork, Moni Naor, and Rafail Ostrovsky introduced the concept of deniable encryption, a cryptographic breakthrough that ensures privacy even under coercion. This concept allows encrypted communication participants to plausibly deny the true content of their messages. Their work lays the foundational principles of deniable encryption, illustrating its critical role in protecting privacy against forced disclosures. This research has become a cornerstone for future advancements in cryptography, emphasizing the importance of deniable encryption in maintaining communication security. The notion of deniable encryption was used by Julian Assange and Ralf Weinmann in the Rubberhose filesystem.

🔗 Aviation 🔗 Aviation/aircraft

The Giffard dirigible or Giffard airship was an airship built in France in 1852 by Henri Giffard, the first powered and steerable (French: dirigeable – "directable") airship to fly. The craft featured an elongated hydrogen-filled envelope that tapered to a point at each end. From this was suspended a long beam with a triangular, sail-like rudder at its aft end, and beneath the beam a platform for the pilot and steam engine. Due to the highly flammable nature of the lift gas, special precautions were taken to minimise the potential for the envelope to be ignited by the engine beneath it. The engine's exhaust was diverted downwards to a long pipe projecting below the platform, and the area surrounding the boiler's stoke hole was surrounded by wire gauze. On 24 September 1852, Giffard flew the airship from the hippodrome at Place de l'Etoile to Élancourt, covering the 27 km (17 mi) in around 3 hours, demonstrating maneuvering along the way. The engine, however, was not sufficiently powerful to allow Giffard to fly against the wind to make a return journey.

🔗 Transport 🔗 Transport/Maritime 🔗 Lighthouses

A light characteristic is all of the properties that make a particular navigational light identifiable. Graphical and textual descriptions of navigational light sequences and colours are displayed on nautical charts and in Light Lists with the chart symbol for a lighthouse, lightvessel, buoy or sea mark with a light on it. Different lights use different colours, frequencies and light patterns, so mariners can identify which light they are seeing.

🔗 Technology 🔗 Architecture

A Matrioshka brain is a hypothetical megastructure of immense computational capacity powered by a Dyson sphere. It was proposed in 1997 by Robert J. Bradbury (1956–2011). It is an example of a Class B stellar engine, employing the entire energy output of a star to drive computer systems. This concept derives its name from the nesting Russian Matryoshka dolls. The concept was deployed by Bradbury in the anthology Year Million: Science at the Far Edge of Knowledge.