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🔗 Biography 🔗 Chemistry 🔗 Florida

Marvin Pipkin (November 18, 1889 – January 7, 1977) was an American chemist. During his time in the United States Army he worked on gas masks. In his civilian life he invented a process for frosting the inside of incandescent light bulbs to cut down on the sharp glare and diffuse the light. He went on to make many other inventions and innovative improvements to the light bulb.

🔗 Biography 🔗 Systems 🔗 Biography/arts and entertainment

John Gall (September 18, 1925 – December 15, 2014) was an American author and retired pediatrician. Gall is known for his 1975 book General systemantics: an essay on how systems work, and especially how they fail..., a critique of systems theory. One of the statements from this book has become known as Gall's law.

🔗 Internet 🔗 Computing 🔗 Law 🔗 Computing/Software 🔗 Computing/Websites 🔗 Computing/Networking

In computer networking, HTTP 451 Unavailable For Legal Reasons is an error status code of the HTTP protocol to be displayed when the user requests a resource which cannot be served for legal reasons, such as a web page censored by a government. The number 451 is a reference to Ray Bradbury's 1953 dystopian novel Fahrenheit 451, in which books are outlawed. 451 intends to provide more information than 403 Forbidden, which is often used for the same purpose. This status code is standardized in RFC 7725.

Examples of situations where an HTTP 451 error code could be displayed include web pages deemed a danger to national security, or web pages deemed to violate copyright, privacy, blasphemy laws, or any other law or court order.

The RFC is specific that a 451 response does not indicate whether the resource exists but requests for it have been blocked, if the resource has been removed for legal reasons and no longer exists, or even if the resource has never existed, but any discussion of its topic has been legally forbidden (see superinjunction). Some sites have previously returned HTTP 404 (Not Found) or similar if they are not legally permitted to disclose that the resource has been removed. Such a tactic is used in the United Kingdom by some internet service providers utilising the Internet Watch Foundation blacklist, returning a 404 message or another error message instead of showing a message indicating the site is blocked.

The status code was formally proposed in 2013 by Tim Bray, following earlier informal proposals by Chris Applegate in 2008 and Terence Eden in 2012. It was approved by the IESG on December 18, 2015. It was published as RFC 7725 in February 2016.

HTTP 451 was mentioned by the BBC's From Our Own Correspondent program, as an indication of the effects of sanctions on Sudan and the inability to access Airbnb, iOS's App Store, or other Western web services.

After introduction of the GDPR in European Economic Area (EEA) many websites located outside EEA started to serve HTTP 451 instead of trying to comply with this new privacy law.

🔗 Spaceflight

A mass driver or electromagnetic catapult is a proposed method of non-rocket spacelaunch which would use a linear motor to accelerate and catapult payloads up to high speeds. All existing and contemplated mass drivers use coils of wire energized by electricity to make electromagnets. Sequential firing of a row of electromagnets accelerates the payload along a path. After leaving the path, the payload continues to move due to momentum.

Although any device used to propel a ballistic payload is technically a mass driver, in this context a mass driver is essentially a coilgun that magnetically accelerates a package consisting of a magnetizable holder containing a payload. Once the payload has been accelerated, the two separate, and the holder is slowed and recycled for another payload.

Mass drivers can be used to propel spacecraft in three different ways: A large, ground-based mass driver could be used to launch spacecraft away from Earth, the Moon, or another body. A small mass driver could be on board a spacecraft, flinging pieces of material into space to propel itself. Another variation would have a massive facility on a moon or asteroid send projectiles to assist a distant craft.

Miniaturized mass drivers can also be used as weapons in a similar manner as classic firearms or cannon using chemical combustion. Hybrids between coilguns and railguns such as helical railguns are also possible.

🔗 China/Chinese history 🔗 China

The south-pointing chariot (or carriage) was an ancient Chinese two-wheeled vehicle that carried a movable pointer to indicate the south, no matter how the chariot turned. Usually, the pointer took the form of a doll or figure with an outstretched arm. The chariot was supposedly used as a compass for navigation and may also have had other purposes.

The ancient Chinese invented a mobile-like armored cart in the 5th century BC called the Dongwu Che (Chinese: 洞屋车). It was used for the purpose of protecting warriors on the battlefield. The Chinese war wagon was designed as a kind of mobile protective cart with a shed-like roof. It would serve to be rolled up to city fortifications to provide protection for sappers digging underneath to weaken a wall's foundation. The early Chinese war wagon became the basis of technologies for the making of ancient Chinese south-pointing chariots.

There are legends of earlier south-pointing chariots, but the first reliably documented one was created by the Chinese mechanical engineer Ma Jun (c. 200–265 CE) of Cao Wei during the Three Kingdoms. No ancient chariots still exist, but many extant ancient Chinese texts mention them, saying they were used intermittently until about 1300 CE. Some include information about their inner components and workings.

There were probably several types of south-pointing chariot which worked differently. In most or all of them, the rotating road wheels mechanically operated a geared mechanism to keep the pointer aimed correctly. The mechanism had no magnets and did not automatically detect which direction was south. The pointer was aimed southward by hand at the start of a journey. Subsequently, whenever the chariot turned, the mechanism rotated the pointer relative to the body of the chariot to counteract the turn and keep the pointer aiming in a constant direction, to the south. Thus the mechanism did a kind of directional dead reckoning, which is inherently prone to cumulative errors and uncertainties. Some chariots' mechanisms may have had differential gears, technology unseen since the ancient Greek Antikythera mechanism.

🔗 Computing 🔗 Software 🔗 Software/Computing

In x86 computing, unreal mode, also big real mode, huge real mode, flat real mode, or voodoo mode is a variant of real mode, in which one or more segment descriptors has been loaded with non-standard values, like 32-bit limits allowing access to the entire memory. Contrary to its name, it is not a separate addressing mode that the x86 processors can operate in. It is used in the 80286 and later x86 processors.

🔗 United States 🔗 Skepticism 🔗 Alternative medicine 🔗 United States/Louisiana

Hadacol was a patent medicine marketed as a vitamin supplement. Its principal attraction, however, was that it contained 12 percent alcohol (listed on the tonic bottle's label as a "preservative"), which made it quite popular in the dry counties of the southern United States. It was the product of four-term Louisiana State Senator Dudley J. LeBlanc, a Democrat from Erath in Vermilion Parish in southwestern Louisiana. He was not a medical doctor, nor a registered pharmacist, but had a strong talent for self-promotion. Time magazine once described him as "a stem-winding salesman who knows every razzle-dazzle switch in the pitchman's trade".

🔗 Mathematics 🔗 Television 🔗 Statistics 🔗 Game theory 🔗 Television/Television game shows

The Monty Hall problem is a brain teaser, in the form of a probability puzzle, loosely based on the American television game show Let's Make a Deal and named after its original host, Monty Hall. The problem was originally posed (and solved) in a letter by Steve Selvin to the American Statistician in 1975 (Selvin 1975a), (Selvin 1975b). It became famous as a question from a reader's letter quoted in Marilyn vos Savant's "Ask Marilyn" column in Parade magazine in 1990 (vos Savant 1990a):

Suppose you're on a game show, and you're given the choice of three doors: Behind one door is a car; behind the others, goats. You pick a door, say No. 1, and the host, who knows what's behind the doors, opens another door, say No. 3, which has a goat. He then says to you, "Do you want to pick door No. 2?" Is it to your advantage to switch your choice?

Vos Savant's response was that the contestant should switch to the other door (vos Savant 1990a). Under the standard assumptions, contestants who switch have a 2/3 chance of winning the car, while contestants who stick to their initial choice have only a 1/3 chance.

The given probabilities depend on specific assumptions about how the host and contestant choose their doors. A key insight is that, under these standard conditions, there is more information about doors 2 and 3 than was available at the beginning of the game when door 1 was chosen by the player: the host's deliberate action adds value to the door he did not choose to eliminate, but not to the one chosen by the contestant originally. Another insight is that switching doors is a different action than choosing between the two remaining doors at random, as the first action uses the previous information and the latter does not. Other possible behaviors than the one described can reveal different additional information, or none at all, and yield different probabilities. Yet another insight is that your chance of winning by switching doors is directly related to your chance of choosing the winning door in the first place: if you choose the correct door on your first try, then switching loses; if you choose a wrong door on your first try, then switching wins; your chance of choosing the correct door on your first try is 1/3, and the chance of choosing a wrong door is 2/3.

Many readers of vos Savant's column refused to believe switching is beneficial despite her explanation. After the problem appeared in Parade, approximately 10,000 readers, including nearly 1,000 with PhDs, wrote to the magazine, most of them claiming vos Savant was wrong (Tierney 1991). Even when given explanations, simulations, and formal mathematical proofs, many people still do not accept that switching is the best strategy (vos Savant 1991a). Paul Erdős, one of the most prolific mathematicians in history, remained unconvinced until he was shown a computer simulation demonstrating vos Savant’s predicted result (Vazsonyi 1999).

The problem is a paradox of the veridical type, because the correct choice (that one should switch doors) is so counterintuitive it can seem absurd, but is nevertheless demonstrably true. The Monty Hall problem is mathematically closely related to the earlier Three Prisoners problem and to the much older Bertrand's box paradox.