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๐ Hessdalen Lights
The Hessdalen lights are unidentified lights which have been observed in a 12-kilometre-long (7.5ย mi) stretch of the Hessdalen valley in rural central Norway periodically since at least the 1930s.
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- "Hessdalen Lights" | 2024-10-30 | 23 Upvotes 6 Comments
๐ Regular Heptadecagon Inscribed in a Circle
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- "Regular Heptadecagon Inscribed in a Circle" | 2010-04-15 | 44 Upvotes 13 Comments
๐ List of unsolved problems in physics
Some of the major unsolved problems in physics are theoretical, meaning that existing theories seem incapable of explaining a certain observed phenomenon or experimental result. The others are experimental, meaning that there is a difficulty in creating an experiment to test a proposed theory or investigate a phenomenon in greater detail.
There are still some deficiencies in the Standard Model of physics, such as the origin of mass, the strong CP problem, neutrino mass, matterโantimatter asymmetry, and the nature of dark matter and dark energy. Another problem lies within the mathematical framework of the Standard Model itselfโthe Standard Model is inconsistent with that of general relativity, to the point that one or both theories break down under certain conditions (for example within known spacetime singularities like the Big Bang and the centers of black holes beyond the event horizon).
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- "List of unsolved problems in physics" | 2016-08-13 | 119 Upvotes 39 Comments
- "List of Unsolved Problems in Physics" | 2015-01-22 | 105 Upvotes 21 Comments
- "Unsolved problems in physics" | 2009-05-07 | 21 Upvotes 27 Comments
๐ Norden bombsight
The Norden Mk. XV, known as the Norden M series in U.S. Army service, is a bombsight that was used by the United States Army Air Forces (USAAF) and the United States Navy during World War II, and the United States Air Force in the Korean and the Vietnam Wars. It was an early tachometric design that directly measured the aircraft's ground speed and direction, which older bombsights could only estimate with lengthy manual procedures. The Norden improved on older designs by using an analog computer that continuously recalculated the bomb's impact point based on changing flight conditions, and an autopilot that reacted quickly and accurately to changes in the wind or other effects.
Together, these features promised unprecedented accuracy for daytime bombing from high altitudes. During prewar testing the Norden demonstrated a circular error probable (CEP) of 75 feet (23ย m), an astonishing performance for that period. This accuracy would enable direct attacks on ships, factories, and other point targets. Both the Navy and the USAAF saw it as a means to conduct successful high-altitude bombing. For example, an invasion fleet could be destroyed long before it could reach U.S. shores. To protect these advantages, the Norden was granted the utmost secrecy well into the war, and was part of a production effort on a similar scale as the Manhattan Project. Carl L. Norden, Inc. ranked 46th among United States corporations in the value of World War II military production contracts.
Under combat conditions the Norden did not achieve its expected accuracy, yielding an average CEP in 1943 of 1,200 feet (370ย m), similar to other Allied and German results. Both the Navy and Air Forces had to give up using pinpoint attacks. The Navy turned to dive bombing and skip bombing to attack ships, while the Air Forces developed the lead bomber procedure to improve accuracy, and adopted area bombing techniques for ever larger groups of aircraft. Nevertheless, the Norden's reputation as a pin-point device endured, due in no small part to Norden's own advertising of the device after secrecy was reduced late in the war.
The Norden's secrecy had already been compromised by espionage before the United States entered the war. As early as January 1941, the Germans introduced a lightened derivative of the Norden called the Carl Zeiss Lotfernrohr 7 as the primary bombsight for most Luftwaffe level bombers and the first of its bombsights to have gyroscopic stabilization.
The Norden saw reduced use in the post-World War II period after radar-based targeting was introduced, but the need for accurate daytime attacks kept it in service, especially during the Korean War. The last combat use of the Norden was in the U.S. Navy's VO-67 squadron, which used them to drop sensors onto the Ho Chi Minh Trail as late as 1967. The Norden remains one of the best-known bombsights ever invented.
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- "Norden bombsight" | 2017-03-28 | 77 Upvotes 36 Comments
๐ A True Story
A True Story (Ancient Greek: แผฮปฮทฮธแฟ ฮดฮนฮทฮณฮฎฮผฮฑฯฮฑ, Alฤthฤ diฤgฤmata; Latin: Vera Historia or Latin: Verae Historiae) is a novel written in the second century AD by Lucian of Samosata, a Greek-speaking author of Assyrian descent. The novel is a satire of outlandish tales which had been reported in ancient sources, particularly those which presented fantastic or mythical events as if they were true. It is Lucian's best-known work.
It is the earliest known work of fiction to include travel to outer space, alien lifeforms, and interplanetary warfare. As such, A True Story has been described as "the first known text that could be called science fiction". However the work does not fit into typical literary genres: its multilayered plot and characters have been interpreted as science fiction, fantasy, satire or parody, and have been the subject of much scholarly debate.
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- "A True Story" | 2018-10-15 | 525 Upvotes 72 Comments
๐ The Colditz Glider
The Colditz Cock was a glider built by British prisoners of war for an escape attempt from Oflag IV-C (Colditz Castle) in Germany.
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- "The Colditz Glider" | 2017-07-23 | 47 Upvotes 7 Comments
๐ Disneyland with Death Penalty
"Disneyland with the Death Penalty" is a 4,500-word article about Singapore written by William Gibson. His first major piece of non-fiction, it was first published as the cover story for Wired magazine's September/October 1993 issue (1.4).
The article follows Gibson's observations of the architecture, phenomenology and culture of Singapore, and the clean, bland and conformist impression the city-state conveys during his stay. Its title and central metaphorโSingapore as Disneyland with the death penaltyโis a reference to the authoritarian artifice the author perceives the city-state to be. Singapore, Gibson details, is lacking any sense of creativity or authenticity, absent of any indication of its history or underground culture. He finds the government to be pervasive, corporatist and technocratic, and the judicial system rigid and draconian. Singaporeans are characterized as consumerists of insipid taste. The article is accentuated by local news reports of criminal trials by which the author illustrates his observations, and bracketed by contrasting descriptions of the Southeast Asian airports he arrives and leaves by.
Though Gibson's first major piece of non-fiction, the article had an immediate and lasting impact. The Singaporean government banned Wired upon the publication of the issue. The phrase "Disneyland with the death penalty" came to stand internationally for an authoritarian and austere reputation that the city-state found difficult to shake off.
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- "Disneyland with Death Penalty" | 2022-08-01 | 230 Upvotes 222 Comments
๐ Boids
Boids is an artificial life program, developed by Craig Reynolds in 1986, which simulates the flocking behaviour of birds. His paper on this topic was published in 1987 in the proceedings of the ACM SIGGRAPH conference. The name "boid" corresponds to a shortened version of "bird-oid object", which refers to a bird-like object. Incidentally, "boid" is also a New York Metropolitan dialect pronunciation for "bird".
As with most artificial life simulations, Boids is an example of emergent behavior; that is, the complexity of Boids arises from the interaction of individual agents (the boids, in this case) adhering to a set of simple rules. The rules applied in the simplest Boids world are as follows:
- separation: steer to avoid crowding local flockmates
- alignment: steer towards the average heading of local flockmates
- cohesion: steer to move towards the average position (center of mass) of local flockmates
More complex rules can be added, such as obstacle avoidance and goal seeking.
The basic model has been extended in several different ways since Reynolds proposed it. For instance, Delgado-Mata etย al. extended the basic model to incorporate the effects of fear. Olfaction was used to transmit emotion between animals, through pheromones modelled as particles in a free expansion gas. Hartman and Benes introduced a complementary force to the alignment that they call the change of leadership. This steer defines the chance of the boid to become a leader and try to escape.
The movement of Boids can be characterized as either chaotic (splitting groups and wild behaviour) or orderly. Unexpected behaviours, such as splitting flocks and reuniting after avoiding obstacles, can be considered emergent.
The boids framework is often used in computer graphics, providing realistic-looking representations of flocks of birds and other creatures, such as schools of fish or herds of animals. It was for instance used in the 1998 video game Half-Life for the flying bird-like creatures seen at the end of the game on Xen, named "boid" in the game files.
The Boids model can be used for direct control and stabilization of teams of simple Unmanned Ground Vehicles (UGV) or Micro Aerial Vehicles (MAV) in swarm robotics. For stabilization of heterogeneous UAV-UGV teams, the model was adapted for using onboard relative localization by Saska etย al.
At the time of proposal, Reynolds' approach represented a giant step forward compared to the traditional techniques used in computer animation for motion pictures. The first animation created with the model was Stanley and Stella in: Breaking the Ice (1987), followed by a feature film debut in Tim Burton's film Batman Returns (1992) with computer generated bat swarms and armies of penguins marching through the streets of Gotham City.
The boids model has been used for other interesting applications. It has been applied to automatically program Internet multi-channel radio stations. It has also been used for visualizing information and for optimization tasks.
๐ Interactive EasyFlow
Interactive EasyFlow was one of the first diagramming and flow charting software packages available for personal computers. This product was the flagship software produced by HavenTree Software Limited, of Kingston, Ontario Canada. HavenTree software, formed in 1981, offered predecessor non-interactive products "EasyFlow" (1983) and "EasyFlow-Plus" (1984). Interactive EasyFlow - so named to distinguish it from the preceding products - was offered from 1985 until the early 1990s, when the company dropped the "Interactive" adjective in favour of simply "HavenTree EasyFlow". It offered the software for sale until it filed for protection under Canada's Bankruptcy and Insolvency Act in April 1996. The assets of the company were purchased by SPSS Inc. in 1998.
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- "Interactive EasyFlow" | 2016-08-24 | 34 Upvotes 6 Comments
๐ World on a Wire
World on a Wire (German: Welt am Draht) is a 1973 West German science fiction television serial, starring Klaus Lรถwitsch and directed by Rainer Werner Fassbinder. Shot in 16 mm, it was made for West German television and originally aired in 1973 in ARD as a two-part miniseries. It was based on the 1964 novel Simulacron-3 by Daniel F. Galouye. An adaptation of the Fassbinder version was presented as the play World of Wires, directed by Jay Scheib, in 2012.
Its focus is not on action, but on sophistic and philosophic aspects of the human mind, simulation, and the role of scientific research. A movie based on the same novel titled The Thirteenth Floor starring Craig Bierko was released in 1999.
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- "World on a Wire" | 2024-11-30 | 14 Upvotes 6 Comments