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🔗 Military history 🔗 Military history/North American military history 🔗 Military history/United States military history 🔗 Cold War 🔗 Military history/Asian military history 🔗 Military history/Southeast Asian military history 🔗 Vietnam

The Fall of Saigon, also known as the Liberation of Saigon by North Vietnamese, was the capture of Saigon, the capital of South Vietnam, by the People's Army of Vietnam (PAVN) and the Viet Cong on 30 April 1975. The event marked the end of the Vietnam War and the start of a transition period to the formal reunification of Vietnam into the Socialist Republic of Vietnam.

The PAVN, under the command of General Văn Tiến Dũng, began their final attack on Saigon on 29 April 1975, with the Army of the Republic of Vietnam (ARVN) forces commanded by General Nguyễn Văn Toàn suffering a heavy artillery bombardment. By the afternoon of the next day, the PAVN had occupied the important points of the city and raised their flag over the South Vietnamese presidential palace. The city was renamed Hồ Chí Minh City, after the late North Vietnamese President Hồ Chí Minh.

The capture of the city was preceded by Operation Frequent Wind, the evacuation of almost all American civilian and military personnel in Saigon, along with tens of thousands of South Vietnamese civilians who had been associated with the Republic of Vietnam. A few Americans chose not to be evacuated. United States ground combat units had left South Vietnam more than two years prior to the fall of Saigon and were not available to assist with either the defense of Saigon or the evacuation. The evacuation was the largest helicopter evacuation in history. In addition to the flight of refugees, the end of the war and the institution of new rules by the communists contributed to a decline in the city's population.

🔗 Cryptography 🔗 Cryptography/Computer science

The known-plaintext attack (KPA) is an attack model for cryptanalysis where the attacker has access to both the plaintext (called a crib), and its encrypted version (ciphertext). These can be used to reveal further secret information such as secret keys and code books. The term "crib" originated at Bletchley Park, the British World War II decryption operation, where it was defined as:

A plain language (or code) passage of any length, usually obtained by solving one or more cipher or code messages, and occurring or believed likely to occur in a different cipher or code message, which it may provide a means of solving.

🔗 Physics 🔗 Physics/relativity 🔗 Chemistry

Relativistic quantum chemistry combines relativistic mechanics with quantum chemistry to explain elemental properties and structure, especially for the heavier elements of the periodic table. A prominent example of such an explanation is the color of gold: due to relativistic effects, it is not silvery like most other metals.

The term relativistic effects was developed in light of the history of quantum mechanics. Initially quantum mechanics was developed without considering the theory of relativity. Relativistic effects are those discrepancies between values calculated by models that consider and that do not consider relativity. Relativistic effects are important for the heavier elements with high atomic numbers. In the most common layout of the periodic table, these elements are shown in the lower area. Examples are the lanthanides and actinides.

Relativistic effects in chemistry can be considered to be perturbations, or small corrections, to the non-relativistic theory of chemistry, which is developed from the solutions of the Schrödinger equation. These corrections affect the electrons differently depending on the electron speed relative to the speed of light. Relativistic effects are more prominent in heavy elements because only in these elements do electrons attain sufficient speeds for the elements to have properties that differ from what non-relativistic chemistry predicts.

🔗 Film 🔗 Lists 🔗 European Microstates 🔗 European Microstates/Vatican City

In 1995, on the occasion of the 100th anniversary of cinema, the Vatican compiled a list of 45 "great films". The 45 movies are divided into three categories: religion, values, and art.

🔗 Economics 🔗 Taxation

A land value tax (LVT) is a levy on the value of land without regard to buildings, personal property and other improvements. It is also known as a location value tax, a site valuation tax, split rate tax, or a site-value rating,

Land value taxes are generally favored by economists as they do not cause economic inefficiency, and reduce inequality. A land value tax is a progressive tax, in that the tax burden falls on land owners, because land ownership is correlated with wealth and income. The land value tax has been referred to as "the perfect tax" and the economic efficiency of a land value tax has been accepted since the eighteenth century. Economists since Adam Smith and David Ricardo have advocated this tax because it does not hurt economic activity or discourage or subsidize development.

LVT is associated with Henry George, whose ideology became known as Georgism. George argued that taxing the land value is most logical source of public revenue because the supply of land is fixed and because public infrastructure improvements would be reflected in (and thus paid for) by increased land values.

Land value taxation is currently implemented throughout Denmark, Estonia, Lithuania, Russia, Singapore, and Taiwan; it has also been applied to lesser extents in parts of Australia, Mexico (Mexicali), and the United States (e.g., Pennsylvania).

🔗 Judaism

Tza'ar ba'alei chayim (Hebrew: צער בעלי חיים‎), literally "suffering of living creatures", is a Jewish commandment which bans causing animals unnecessary suffering. This concept is not clearly enunciated in the written Torah, but was accepted by the Talmud as being a biblical mandate. It is linked in the Talmud from the biblical law requiring people to assist in unloading burdens from animals (Exodus 23:5).

🔗 Companies 🔗 Internet 🔗 Crime 🔗 Finance & Investment 🔗 Numismatics 🔗 Websites 🔗 Websites/Computing 🔗 Numismatics/Cryptocurrency 🔗 Cryptocurrency

Mt. Gox was a bitcoin exchange based in Shibuya, Tokyo, Japan. Launched in July 2010, by 2013 and into 2014 it was handling over 70% of all bitcoin (BTC) transactions worldwide, as the largest bitcoin intermediary and the world's leading bitcoin exchange.

In February 2014, Mt. Gox suspended trading, closed its website and exchange service, and filed for bankruptcy protection from creditors. In April 2014, the company began liquidation proceedings.

Mt. Gox announced that approximately 850,000 bitcoins belonging to customers and the company were missing and likely stolen, an amount valued at more than $450 million at the time. Although 200,000 bitcoins have since been "found", the reasons for the disappearance—theft, fraud, mismanagement, or a combination of these—were initially unclear. New evidence presented in April 2015 by Tokyo security company WizSec led them to conclude that "most or all of the missing bitcoins were stolen straight out of the Mt. Gox hot wallet over time, beginning in late 2011."

🔗 Time 🔗 University of Cambridge

The Corpus Clock, also known as the Grasshopper clock, is a large sculptural clock at street level on the outside of the Taylor Library at Corpus Christi College, Cambridge University, in the United Kingdom, at the junction of Bene't Street and Trumpington Street, looking out over King's Parade. It was conceived and funded by John C. Taylor, an old member of the college.

It was officially unveiled to the public on 19 September 2008 by Cambridge physicist Stephen Hawking. The clock was named one of Time's Best Inventions of 2008.

🔗 Physics 🔗 Meteorology 🔗 Radio

A whistler is a very low frequency or VLF electromagnetic (radio) wave generated by lightning. Frequencies of terrestrial whistlers are 1 kHz to 30 kHz, with a maximum amplitude usually at 3 kHz to 5 kHz. Although they are electromagnetic waves, they occur at audio frequencies, and can be converted to audio using a suitable receiver. They are produced by lightning strikes (mostly intracloud and return-path) where the impulse travels along the Earth's magnetic field lines from one hemisphere to the other. They undergo dispersion of several kHz due to the slower velocity of the lower frequencies through the plasma environments of the ionosphere and magnetosphere. Thus they are perceived as a descending tone which can last for a few seconds. The study of whistlers categorizes them into Pure Note, Diffuse, 2-Hop, and Echo Train types.

Voyager 1 and 2 spacecraft detected whistler-like activity in the vicinity of Jupiter known as "Jovian Whistlers", implying the presence of lightning there.

🔗 Astronomy

A Messier marathon is an attempt, usually organized by amateur astronomers, to find as many Messier objects as possible during one night. The Messier catalogue was compiled by French astronomer Charles Messier during the late 18th century and consists of 110 relatively bright deep-sky objects (galaxies, nebulae, and star clusters).