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🔗 California 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/World War II 🔗 Paranormal 🔗 California/Southern California

The Battle of Los Angeles, also known as the Great Los Angeles Air Raid, is the name given by contemporary sources to a rumored attack on the mainland United States by Imperial Japan and the subsequent anti-aircraft artillery barrage which took place from late 24 February to early 25 February 1942, over Los Angeles, California. The incident occurred less than three months after the U.S. entered World War II in response to the Imperial Japanese Navy's surprise attack on Pearl Harbor, and one day after the bombardment of Ellwood near Santa Barbara on 23 February. Initially, the target of the aerial barrage was thought to be an attacking force from Japan, but speaking at a press conference shortly afterward, Secretary of the Navy Frank Knox called the purported attack a "false alarm". Newspapers of the time published a number of reports and speculations of a cover-up.

When documenting the incident in 1949, the United States Coast Artillery Association identified a meteorological balloon sent aloft at 1:00 am as having "started all the shooting" and concluded that "once the firing started, imagination created all kinds of targets in the sky and everyone joined in". In 1983, the U.S. Office of Air Force History attributed the event to a case of "war nerves" triggered by a lost weather balloon and exacerbated by stray flares and shell bursts from adjoining batteries.

🔗 Mathematics

The number e is a mathematical constant approximately equal to 2.71828 and is the base of the natural logarithm: the unique number whose natural logarithm is equal to one. It is the limit of (1 + 1/n)ⁿ as n approaches infinity, an expression that arises in the study of compound interest. It can also be calculated as the sum of the infinite series

${\displaystyle e=\sum \limits _{n=0}^{\infty }{\frac {1}{n!}}={\frac {1}{1}}+{\frac {1}{1}}+{\frac {1}{1\cdot 2}}+{\frac {1}{1\cdot 2\cdot 3}}+\cdots }$

The constant can be characterized in many different ways. For example, it can be defined as the unique positive number a such that the graph of the function y = a^x has unit slope at x = 0. The function f(x) = e^x is called the (natural) exponential function, and is the unique exponential function equal to its own derivative. The natural logarithm, or logarithm to base e, is the inverse function to the natural exponential function. The natural logarithm of a number k > 1 can be defined directly as the area under the curve y = 1/x between x = 1 and x = k, in which case e is the value of k for which this area equals one (see image). There are alternative characterizations.

e is sometimes called Euler's number after the Swiss mathematician Leonhard Euler (not to be confused with γ, the Euler–Mascheroni constant, sometimes called simply Euler's constant), or as Napier's constant. However, Euler's choice of the symbol e is said to have been retained in his honor. The constant was discovered by the Swiss mathematician Jacob Bernoulli while studying compound interest.

The number e has eminent importance in mathematics, alongside 0, 1, π, and i. All five of these numbers play important and recurring roles across mathematics, and these five constants appear in one formulation of Euler's identity. Like the constant π, e is also irrational (i.e. it cannot be represented as ratio of integers) and transcendental (i.e. it is not a root of any non-zero polynomial with rational coefficients). The numerical value of e truncated to 50 decimal places is

🔗 Military history 🔗 Military history/Early Modern warfare 🔗 Military history/American Revolutionary War 🔗 Military history/Maritime warfare 🔗 Ships 🔗 Connecticut

Turtle (also called American Turtle) was the world's first submersible vessel with a documented record of use in combat. It was built in 1775 by American David Bushnell as a means of attaching explosive charges to ships in a harbor, for use against Royal Navy vessels occupying North American harbors during the American Revolutionary War. Connecticut Governor Jonathan Trumbull recommended the invention to George Washington, who provided funds and support for the development and testing of the machine.

Several attempts were made using Turtle to affix explosives to the undersides of British warships in New York Harbor in 1776. All failed, and her transport ship was sunk later that year by the British with the submarine aboard. Bushnell claimed eventually to have recovered the machine, but its final fate is unknown. Modern replicas of Turtle have been constructed and are on display in the Connecticut River Museum, the U.S. Navy's Submarine Force Library and Museum, the Royal Navy Submarine Museum, and the Oceanographic Museum (Monaco).

🔗 Ancient Near East 🔗 Turkey 🔗 Archaeology

Göbekli Tepe (Turkish: [ɟœbecˈli teˈpe], "Potbelly Hill") is an archaeological site in the Southeastern Anatolia Region of Turkey approximately 12 km (7 mi) northeast of the city of Şanlıurfa. The tell (artificial mound) has a height of 15 m (49 ft) and is about 300 m (980 ft) in diameter. It is approximately 760 m (2,490 ft) above sea level.

The tell includes two phases of use, believed to be of a social or ritual nature by site discoverer and excavator Klaus Schmidt, dating back to the 10th–8th millennium BCE. During the first phase, belonging to the Pre-Pottery Neolithic A (PPNA), circles of massive "T-shaped" stone pillars were erected – the world's oldest known megaliths.

More than 200 pillars in about 20 circles are currently known through geophysical surveys. Each pillar has a height of up to 6 m (20 ft) and weighs up to 10 tons. They are fitted into sockets that were hewn out of the bedrock. In the second phase, belonging to the Pre-Pottery Neolithic B (PPNB), the erected pillars are smaller and stood in rectangular rooms with floors of polished lime. The site was abandoned after the Pre-Pottery Neolithic B (PPNB). Younger structures date to classical times.

The details of the structure's function remain a mystery. The excavations have been ongoing since 1996 by the German Archaeological Institute, but large parts still remain unexcavated. In 2018, the site was designated a UNESCO World Heritage Site.

🔗 Biography 🔗 California 🔗 California/San Francisco Bay Area 🔗 Finance & Investment 🔗 Business

Ronald Crawford Conway (born March 9, 1951) is an American angel investor and philanthropist, often described as one of Silicon Valley's "super angels". Conway is recognized as a strong networker.

🔗 Biography 🔗 Aviation 🔗 France 🔗 France/Paris 🔗 Iran 🔗 Aviation/airport

Mehran Karimi Nasseri (Persian: مهران کریمی ناصری‎ pronounced [mehˈrɒn kæriˈmi nɒseˈri]; born 1946), also known as Sir Alfred Mehran, is an Iranian refugee who lived in the departure lounge of Terminal One in Charles de Gaulle Airport from 26 August 1988 until July 2006, when he was hospitalized. His autobiography was published as a book, The Terminal Man, in 2004. His story was the inspiration for the 2004 Steven Spielberg film The Terminal.

🔗 Mathematics 🔗 Statistics

In the design of experiments in statistics, the lady tasting tea is a randomized experiment devised by Ronald Fisher and reported in his book The Design of Experiments (1935). The experiment is the original exposition of Fisher's notion of a null hypothesis, which is "never proved or established, but is possibly disproved, in the course of experimentation".

The example is loosely based on an event in Fisher's life. The woman in question, phycologist Muriel Bristol, claimed to be able to tell whether the tea or the milk was added first to a cup. Her future husband, William Roach, suggested that Fisher give her eight cups, four of each variety, in random order. One could then ask what the probability was for her getting the specific number of cups she identified correct (in fact all eight), but just by chance.

Fisher's description is less than 10 pages in length and is notable for its simplicity and completeness regarding terminology, calculations and design of the experiment. The test used was Fisher's exact test.

🔗 United States 🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Military history/Military science, technology, and theory 🔗 Military history/Weaponry 🔗 Military history/World War II 🔗 Mammals/Bats

Bat bombs were an experimental World War II weapon developed by the United States. The bomb consisted of a bomb-shaped casing with over a thousand compartments, each containing a hibernating Mexican free-tailed bat with a small, timed incendiary bomb attached. Dropped from a bomber at dawn, the casings would deploy a parachute in mid-flight and open to release the bats, which would then disperse and roost in eaves and attics in a 20–40-mile radius (32–64 km). The incendiaries, which were set on timers, would then ignite and start fires in inaccessible places in the largely wood and paper constructions of the Japanese cities that were the weapon's intended target.

🔗 Computing

The IBM 5100 Portable Computer is a portable computer (one of the first) introduced in September 1975, six years before the IBM Personal Computer. It was the evolution of a prototype called the SCAMP (Special Computer APL Machine Portable) that was developed at the IBM Palo Alto Scientific Center in 1973. In January 1978, IBM announced the IBM 5110, its larger cousin, and in February 1980 IBM announced the IBM 5120. The 5100 was withdrawn in March 1982.

When the IBM PC was introduced in 1981, it was originally designated as the IBM 5150, putting it in the "5100" series, though its architecture was unrelated to the IBM 5100's.

🔗 Mathematics

The shoelace formula or shoelace algorithm (also known as Gauss's area formula and the surveyor's formula) is a mathematical algorithm to determine the area of a simple polygon whose vertices are described by their Cartesian coordinates in the plane. The user cross-multiplies corresponding coordinates to find the area encompassing the polygon, and subtracts it from the surrounding polygon to find the area of the polygon within. It is called the shoelace formula because of the constant cross-multiplying for the coordinates making up the polygon, like tying shoelaces. It is also sometimes called the shoelace method. It has applications in surveying and forestry, among other areas.

The formula was described by Meister (1724–1788) in 1769 and by Gauss in 1795. It can be verified by dividing the polygon into triangles, and can be considered to be a special case of Green's theorem.

The area formula is derived by taking each edge AB, and calculating the area of triangle ABO with a vertex at the origin O, by taking the cross-product (which gives the area of a parallelogram) and dividing by 2. As one wraps around the polygon, these triangles with positive and negative area will overlap, and the areas between the origin and the polygon will be cancelled out and sum to 0, while only the area inside the reference triangle remains. This is why the formula is called the surveyor's formula, since the "surveyor" is at the origin; if going counterclockwise, positive area is added when going from left to right and negative area is added when going from right to left, from the perspective of the origin.

The area formula can also be applied to self-overlapping polygons since the meaning of area is still clear even though self-overlapping polygons are not generally simple. Furthermore, a self-overlapping polygon can have multiple "interpretations" but the Shoelace formula can be used to show that the polygon's area is the same regardless of the interpretation.