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🔗 Mathematics

Von Neumann's elephant is a problem in recreational mathematics, consisting of constructing a planar curve in the shape of an elephant from only four fixed parameters. It originated from a discussion between physicists John von Neumann and Enrico Fermi.

🔗 Aviation 🔗 France 🔗 Germany 🔗 Disaster management 🔗 Aviation/Aviation accident 🔗 Spain 🔗 Crime and Criminal Biography

Germanwings Flight 9525 was a scheduled international passenger flight from Barcelona–El Prat Airport in Spain to Düsseldorf Airport in Germany. The flight was operated by Germanwings, a low-cost carrier owned by the German airline Lufthansa. On 24 March 2015, the aircraft, an Airbus A320-211, crashed 100 km (62 mi; 54 nmi) north-west of Nice in the French Alps. All 144 passengers and six crew members were killed.

The crash was deliberately caused by the co-pilot, Andreas Lubitz, who had previously been treated for suicidal tendencies and declared unfit to work by his doctor. Lubitz kept this information from his employer and instead reported for duty. Shortly after reaching cruise altitude and while the captain was out of the cockpit, Lubitz locked the cockpit door and initiated a controlled descent that continued until the aircraft hit a mountainside.

Aviation authorities swiftly implemented new recommendations from the European Union Aviation Safety Agency that required two authorised personnel in the cockpit at all times but, by 2017, Germanwings and other German airlines had dropped the rule.

The Lubitz family held a press conference in March 2017 during which Lubitz's father said that they did not accept the official investigative findings that his son deliberately caused the crash. By 2017, Lufthansa had paid €75,000 to the family of every victim, as well as €10,000 in pain and suffering compensation to every close relative of a victim.

🔗 Computing 🔗 Computer science

In computer science, program synthesis is the task to construct a program that provably satisfies a given high-level formal specification. In contrast to program verification, the program is to be constructed rather than given; however, both fields make use of formal proof techniques, and both comprise approaches of different degrees of automation. In contrast to automatic programming techniques, specifications in program synthesis are usually non-algorithmic statements in an appropriate logical calculus.

The primary application of program synthesis is to relieve the programmer of the burden of writing correct, efficient code that satisfies a specification. However, program synthesis also has applications to superoptimization and inference of loop invariants.

🔗 Environment 🔗 Agriculture 🔗 Soil 🔗 Horticulture and Gardening

Hügelkultur (German pronunciation: [ˈhyːɡl̩kʊlˌtuːɐ̯]), literally mound bed or mound culture, is a horticultural technique where a mound constructed from decaying wood debris and other compostable biomass plant materials is later (or immediately) planted as a raised bed. Considered a permaculture practice, advocates claim that the technique helps to improve soil fertility, water retention, and soil warming, thus benefitting plants grown on or near such mounds.

🔗 Cycling 🔗 Motorcycling

Countersteering is used by single-track vehicle operators, such as cyclists and motorcyclists, to initiate a turn toward a given direction by momentarily steering counter to the desired direction ("steer left to turn right"). To negotiate a turn successfully, the combined center of mass of the rider and the single-track vehicle must first be leaned in the direction of the turn, and steering briefly in the opposite direction causes that lean. The rider's action of countersteering is sometimes referred to as "giving a steering command".^: 15

The scientific literature does not provide a clear and comprehensive definition of countersteering. In fact, "a proper distinction between steer torque and steer angle ... is not always made."

🔗 Mathematics 🔗 Statistics

The secretary problem is a problem that demonstrates a scenario involving optimal stopping theory. The problem has been studied extensively in the fields of applied probability, statistics, and decision theory. It is also known as the marriage problem, the sultan's dowry problem, the fussy suitor problem, the googol game, and the best choice problem.

The basic form of the problem is the following: imagine an administrator who wants to hire the best secretary out of ${\displaystyle n}$ rankable applicants for a position. The applicants are interviewed one by one in random order. A decision about each particular applicant is to be made immediately after the interview. Once rejected, an applicant cannot be recalled. During the interview, the administrator gains information sufficient to rank the applicant among all applicants interviewed so far, but is unaware of the quality of yet unseen applicants. The question is about the optimal strategy (stopping rule) to maximize the probability of selecting the best applicant. If the decision can be deferred to the end, this can be solved by the simple maximum selection algorithm of tracking the running maximum (and who achieved it), and selecting the overall maximum at the end. The difficulty is that the decision must be made immediately.

The shortest rigorous proof known so far is provided by the odds algorithm (Bruss 2000). It implies that the optimal win probability is always at least ${\displaystyle 1/e}$ (where e is the base of the natural logarithm), and that the latter holds even in a much greater generality (2003). The optimal stopping rule prescribes always rejecting the first ${\displaystyle \sim n/e}$ applicants that are interviewed and then stopping at the first applicant who is better than every applicant interviewed so far (or continuing to the last applicant if this never occurs). Sometimes this strategy is called the ${\displaystyle 1/e}$ stopping rule, because the probability of stopping at the best applicant with this strategy is about ${\displaystyle 1/e}$ already for moderate values of ${\displaystyle n}$. One reason why the secretary problem has received so much attention is that the optimal policy for the problem (the stopping rule) is simple and selects the single best candidate about 37% of the time, irrespective of whether there are 100 or 100 million applicants.

🔗 Spaceflight 🔗 Rocketry 🔗 Science 🔗 Photography

The V-2 No. 13 was a modified V-2 rocket that became the first object to take a photograph of the Earth from outer space. Launched on 24 October 1946, at the White Sands Missile Range in White Sands, New Mexico, the rocket reached a maximum altitude of 65 mi (105 km).

🔗 Internet culture 🔗 Climate change 🔗 Environment 🔗 United Kingdom 🔗 Antarctica 🔗 Arctic 🔗 Oceans 🔗 Antarctica/British Antarctic Territory

Boaty McBoatface (also known as Boaty) is the British lead boat in a fleet of three robotic lithium battery–powered autonomous underwater vehicles (AUVs) of the Autosub Long Range (ALR) class. Launched in 2017 and carried on board the polar scientific research vessel RRS Sir David Attenborough, she is a focal point of the Polar Explorer Programme of the UK Government.

Boaty and her two fleet-mates are part of the UK National Marine Equipment Pool and owned by the National Oceanography Centre in Southampton. She is classified as an "autosub long range (ALR) autonomous underwater vehicle", and will use her onboard sensors to map the movement of deep waters that play a vital role in regulating the Earth's climate.

🔗 Sports

Naismith's rule helps with the planning of a walking or hiking expedition by calculating how long it will take to travel the intended route, including any extra time taken when walking uphill. This rule of thumb was devised by William W. Naismith, a Scottish mountaineer, in 1892. A modern version can be formulated as follows:

Allow one hour for every 3 miles (5 km) forward, plus an additional hour for every 2,000 feet (600 m) of ascent.