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🔗 Galilean Moons and Determination of Longitude
The Galilean moons (), or Galilean satellites, are the four largest moons of Jupiter: Io, Europa, Ganymede, and Callisto. They are the most readily visible Solar System objects after Saturn, the dimmest of the classical planets; though their closeness to bright Jupiter makes naked-eye observation very difficult, they are readily seen with common binoculars, even under night sky conditions of high light pollution. The invention of the telescope enabled the discovery of the moons in 1610. Through this, they became the first Solar System objects discovered since humans have started tracking the classical planets, and the first objects to be found to orbit any planet beyond Earth.
They are planetary-mass moons and among the largest objects in the Solar System. All four, along with Titan, Triton, and Earth's Moon, are larger than any of the Solar System's dwarf planets. The largest, Ganymede, is the largest moon in the Solar System and surpasses the planet Mercury in size (though not mass). Callisto is only slightly smaller than Mercury in size; the smaller ones, Io and Europa, are about the size of the Moon. The three inner moons — Io, Europa, and Ganymede — are in a 4:2:1 orbital resonance with each other. While the Galilean moons are spherical, all of Jupiter's remaining moons have irregular forms because they are too small for their self-gravitation to pull them into spheres.
The Galilean moons are named after Galileo Galilei, who observed them in either December 1609 or January 1610, and recognized them as satellites of Jupiter in March 1610; they remained the only known moons of Jupiter until the discovery of the fifth largest moon of Jupiter Amalthea in 1892. Galileo initially named his discovery the Cosmica Sidera ("Cosimo's stars") or Medicean Stars, but the names that eventually prevailed were chosen by Simon Marius. Marius discovered the moons independently at nearly the same time as Galileo, 8 January 1610, and gave them their present individual names, after mythological characters that Zeus seduced or abducted, which were suggested by Johannes Kepler in his Mundus Jovialis, published in 1614. Their discovery showed the importance of the telescope as a tool for astronomers by proving that there were objects in space that cannot be seen by the naked eye. The discovery of celestial bodies orbiting something other than Earth dealt a serious blow to the then-accepted (among educated Europeans) Ptolemaic world system, a geocentric theory in which everything orbits around Earth.
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- "Galilean Moons and Determination of Longitude" | 2024-09-24 | 17 Upvotes 2 Comments
🔗 Dry Cask Storage
Dry cask storage is a method of storing high-level radioactive waste, such as spent nuclear fuel that has already been cooled in a spent fuel pool for at least one year and often as much as ten years. Casks are typically steel cylinders that are either welded or bolted closed. The fuel rods inside are surrounded by inert gas. Ideally, the steel cylinder provides leak-tight containment of the spent fuel. Each cylinder is surrounded by additional steel, concrete, or other material to provide radiation shielding to workers and members of the public.
There are various dry storage cask system designs. With some designs, the steel cylinders containing the fuel are placed vertically in a concrete vault; other designs orient the cylinders horizontally. The concrete vaults provide the radiation shielding. Other cask designs orient the steel cylinder vertically on a concrete pad at a dry cask storage site and use both metal and concrete outer cylinders for radiation shielding. Until 2024/25, there was no long term permanent storage facility anywhere in the world, and most countries still don't have a facility; dry cask storage is designed as an interim safer solution than spent fuel pool storage.
Some of the cask designs can be used for both storage and transportation. Three companies – Holtec International, NAC International and Areva-Transnuclear NUHOMS – are marketing Independent Spent Fuel Storage Installations (ISFSI) based upon an unshielded multi-purpose canister which is transported and stored in on-site vertical or horizontal shielded storage modules constructed of steel and concrete.
Discussed on
- "Dry Cask Storage" | 2024-09-20 | 11 Upvotes 21 Comments
🔗 M-DISC: The storage medium that lasts 1000 years
M-DISC (Millennial Disc) is a write-once optical disc technology introduced in 2009 by Millenniata, Inc. and available as DVD and Blu-ray discs.
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- "M-DISC: The storage medium that lasts 1000 years" | 2024-09-18 | 11 Upvotes 2 Comments
🔗 2024 Lebanon Pager Explosions
On 17 September 2024, communication pagers simultaneously exploded across Lebanon and Syria in an apparent coordinated attack. Many of the pagers were owned by members of the Hezbollah militant group. Eighteen people were confirmed killed: eleven in Lebanon (including a child and at least two Hezbollah members) and seven in Syria. Around 4,000 people were reportedly injured, including Hezbollah members and civilians.
The blasts affected several Hezbollah strongholds, including Beirut's Dahieh suburb, southern Lebanon, and in the Beqaa Valley. Over 500 of the group's militants lost their eyesight. They called the incident the organization's "biggest security breach yet" and accused Israel of responsibility.
A day after Hamas launched its October 7 attacks on Israel in 2023, the Iranian-backed organization Hezbollah joined the conflict in support of Hamas by firing on Israel. This led to a series of cross-border military exchanges between Hezbollah and Israel. In February 2024, the secretary-general of Hezbollah, Hassan Nasrallah, told the group's members to use pagers instead of cell phones, claiming that Israel had infiltrated their cell phone network. Hezbollah then bought a new brand of pagers that were recently imported to Lebanon.
Earlier on the day of the explosion, Israel's domestic security agency, the Shin Bet, announced it had thwarted a Hezbollah plot to assassinate a former senior defense official using an explosive device.
Around 150 hospitals across Lebanon received victims of the attack, which saw chaotic scenes.
Discussed on
- "2024 Lebanon Pager Explosions" | 2024-09-17 | 14 Upvotes 2 Comments
🔗 XJACK PC Card Ethernet Connector
In laptop computing, the XJACK is a type of extendable connector or antenna for a type II PC card, designed by the Megahertz subsidiary of 3Com. When not in use, the XJACK retracts into the PC card for storage.
The XJACK was originally used in modem and network cards, to attach a standard RJ11 or 8P8C plug directly to the PC card. They do not require a separate dongle, which could be lost or misplaced, and do not need to be removed from the laptop when travelling. An alternative approach is to use larger type III cards with a regular modular connector socket, but this approach requires more space.
Wi-Fi PC cards for accessing wireless networks have an external portion containing the antenna for improved reception (as compared with inside the laptop), but this portion of the card may be accidentally damaged while moving the laptop. 3Com manufactured wireless cards with retractable antenna portions, also under the XJACK name. Other companies have since manufactured wireless cards with retractable antennas.
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- "XJACK PC Card Ethernet Connector" | 2024-09-15 | 13 Upvotes 6 Comments
🔗 Iron Gall Ink
Iron gall ink (also known as common ink, standard ink, oak gall ink or iron gall nut ink) is a purple-black or brown-black ink made from iron salts and tannic acids from vegetable sources. It was the standard ink formulation used in Europe for the 1400-year period between the 5th and 19th centuries, remained in widespread use well into the 20th century, and is still sold today.
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- "Iron Gall Ink" | 2024-09-09 | 67 Upvotes 27 Comments
🔗 Floral formula
A floral formula is a notation for representing the structure of particular types of flowers. Such notations use numbers, letters and various symbols to convey significant information in a compact form. They may represent the floral form of a particular species, or may be generalized to characterize higher taxa, usually giving ranges of numbers of organs. Floral formulae are one of the two ways of describing flower structure developed during the 19th century, the other being floral diagrams. The format of floral formulae differs according to the tastes of particular authors and periods, yet they tend to convey the same information.
A floral formula is often used along with a floral diagram.
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- "Floral formula" | 2024-09-08 | 142 Upvotes 19 Comments
🔗 A game theory behind the dark forest strategy?
The Dark Forest (Chinese: 黑暗森林) is a 2008 science fiction novel by the Chinese writer Liu Cixin. It is the sequel to the Hugo Award-winning novel The Three-Body Problem in the trilogy titled Remembrance of Earth's Past, but Chinese readers generally refer to the series by the title of the first novel. The English version, translated by Joel Martinsen, was published in 2015. The novel is about the dark forest hypothesis (which was named after the novel), a possible solution to the Fermi paradox, though similar theories have been described as early as 1983.
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- "A game theory behind the dark forest strategy?" | 2024-09-08 | 9 Upvotes 13 Comments
🔗 Pizza in North Korea
North Korea has several restaurants serving pizza. Most people in the country cannot afford pizza, and it is mostly available for the elite. Pyongyang has five restaurants that serve pizza, including Pizza Restaurant on Kwangbok Street and Italy Pizza on Mirae Scientists Street. Kim Jong Il hired Italian chefs to train North Koreans in pizza making and introduced it to the country.
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- "Pizza in North Korea" | 2024-09-09 | 42 Upvotes 3 Comments
🔗 Hofstede's Cultural Dimensions Theory
Hofstede's cultural dimensions theory is a framework for cross-cultural psychology, developed by Geert Hofstede. It shows the effects of a society's culture on the values of its members, and how these values relate to behavior, using a structure derived from factor analysis.
Hofstede developed his original model as a result of using factor analysis to examine the results of a worldwide survey of employee values by IBM between 1967 and 1973. It has been refined since. The original theory proposed four dimensions along which cultural values could be analyzed: individualism-collectivism; uncertainty avoidance; power distance (strength of social hierarchy) and masculinity-femininity (task-orientation versus person-orientation). The Hofstede Cultural Dimensions factor analysis is based on extensive cultural preferences research conducted by Gert Jan Hofstede and his research teams. Hofstede based his research on national cultural preferences rather than individual cultural preferences. Hofstede included six key aspects of national culture country comparison scales, including: the power distance index (PDI), individualism vs. collectivism (IDV), motivation towards achievement and success (MAS, formerly masculinity versus femininity), uncertainty avoidance index (UAI), long term orientation versus short term normative orientation (LTO), and indulgence versus restraint (IVR). The PDI describes the degree to which authority is accepted and followed. The IDV measures the extent to which people look out for each other as a team or look out for themselves as an individual. MAS represents specific values that a society values. The UAI describes to what extent nations avoid the unknown. LTO expresses how societies either prioritize traditions or seek for the modern in their dealings with the present and the future. The IVR index is a comparison between a country's willingness to wait for long-term benefits by holding off on instant gratification, or preferences to no restraints on enjoying life at the present.
Independent research in Hong Kong led Hofstede to add a fifth dimension, long-term orientation, to cover aspects of values not discussed in the original paradigm. In 2010, Hofstede added a sixth dimension, indulgence versus self-restraint. Hofstede's work established a major research tradition in cross-cultural psychology and has also been drawn upon by researchers and consultants in many fields relating to international business and communication. The theory has been widely used in several fields as a paradigm for research, particularly in cross-cultural psychology, international management, and cross-cultural communication. It continues to be a major resource in cross-cultural fields.