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π Proving something exists nonconstructively using probability.
The probabilistic method is a nonconstructive method, primarily used in combinatorics and pioneered by Paul ErdΕs, for proving the existence of a prescribed kind of mathematical object. It works by showing that if one randomly chooses objects from a specified class, the probability that the result is of the prescribed kind is strictly greater than zero. Although the proof uses probability, the final conclusion is determined for certain, without any possible error.
This method has now been applied to other areas of mathematics such as number theory, linear algebra, and real analysis, as well as in computer science (e.g. randomized rounding), and information theory.
Discussed on
- "Proving something exists nonconstructively using probability." | 2009-05-27 | 26 Upvotes 8 Comments
π Cosmological Lithium Problem
In astronomy, the lithium problem or lithium discrepancy refers to the discrepancy between the primordial abundance of lithium as inferred from observations of metal-poor (Population II) halo stars in our galaxy and the amount that should theoretically exist due to Big Bang nucleosynthesis+WMAP cosmic baryon density predictions of the CMB. Namely, the most widely accepted models of the Big Bang suggest that three times as much primordial lithium, in particular lithium-7, should exist. This contrasts with the observed abundance of isotopes of hydrogen (1H and 2H) and helium (3He and 4He) that are consistent with predictions. The discrepancy is highlighted in a so-called "Schramm plot", named in honor of astrophysicist David Schramm, which depicts these primordial abundances as a function of cosmic baryon content from standard BBN predictions.
π The Buzzer
UVB-76, also known as "The Buzzer", is a nickname given by radio listeners to a shortwave radio station that broadcasts on the frequencies 4625 and 4810 kHz. It broadcasts a short, monotonous buzz toneΒ , repeating at a rate of approximately 25 tones per minute, 24 hours per day. Sometimes, the buzzer signal is interrupted and a voice transmission in Russian takes place. The first reports were made of a station on this frequency in 1973.
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- "UVB-76" | 2020-11-25 | 195 Upvotes 63 Comments
- "The Buzzer" | 2010-06-05 | 227 Upvotes 55 Comments
π List of Topics Categorized as Pseudoscience
This is a list of topics that have, at one point or another in their history, been characterized as pseudoscience by academics or researchers. Detailed discussion of these topics may be found on their main pages. These characterizations were made in the context of educating the public about questionable or potentially fraudulent or dangerous claims and practicesβefforts to define the nature of science, or humorous parodies of poor scientific reasoning.
Criticism of pseudoscience, generally by the scientific community or skeptical organizations, involves critiques of the logical, methodological, or rhetorical bases of the topic in question. Though some of the listed topics continue to be investigated scientifically, others were only subject to scientific research in the past, and today are considered refuted but resurrected in a pseudoscientific fashion. Other ideas presented here are entirely non-scientific, but have in one way or another impinged on scientific domains or practices.
Many adherents or practitioners of the topics listed here dispute their characterization as pseudoscience. Each section here summarizes the alleged pseudoscientific aspects of that topic.
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- "List of Topics Categorized as Pseudoscience" | 2019-07-12 | 14 Upvotes 8 Comments
- "List of topics characterized as pseudoscience" | 2019-01-24 | 11 Upvotes 2 Comments
π Potrzebie
Potrzebie (; Polish pronunciation:Β [pΙtΛΚΙbΚ²e] dative/locative of potrzeba, "a need") is a Polish word popularized by its non sequitur use as a running gag in the early issues of Mad not long after the comic book began in 1952.
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- "Potrzebie" | 2018-12-17 | 61 Upvotes 12 Comments
π Thermobaric Weapon
A thermobaric weapon, aerosol bomb, or vacuum bomb is a type of explosive that uses oxygen from the surrounding air to generate a high-temperature explosion. In practice, the blast wave typically produced by such a weapon is of a significantly longer duration than that of a conventional condensed explosive. The fuelβair explosive is one of the best-known types of thermobaric weapon.
Most conventional explosives consist of a fuelβoxidizer premix (black powder, for example, contains 25% fuel and 75% oxidizer), but thermobaric weapons are almost 100% fuel and so are significantly more energetic than conventional condensed explosives of equal weight. Their reliance on atmospheric oxygen makes them unsuitable for use under water, at high altitude, and in adverse weather. They are, however, considerably more destructive when used against field fortifications such as foxholes, tunnels, bunkers, and caves, partly because of the sustained blast wave and partly by the consumption of the oxygen inside it.
Many types of thermobaric weapons can be fitted to hand-held launchers.
Discussed on
- "Thermobaric Weapon" | 2022-02-28 | 20 Upvotes 9 Comments
π October Suprise
In American political jargon, an October surprise is a news event deliberately created or timed to influence the outcome of an election, particularly one for the U.S. presidency, or sometimes an event occurring spontaneously that has the same effect. Because the date for national elections (as well as many state and local elections) is in early November, events that take place in October have greater potential to influence the decisions of prospective voters. Thus these relatively last-minute news stories could either completely change the entire course of an election or strongly reinforce the inevitable.
The term "October surprise" was coined by William Casey when he served as campaign manager of Ronald Reagan's 1980 presidential campaign. However, there were October election-upending events that predated the coining of the term.
Discussed on
- "October Suprise" | 2020-10-02 | 17 Upvotes 5 Comments
π Nagle's Algorithm
Nagle's algorithm is a means of improving the efficiency of TCP/IP networks by reducing the number of packets that need to be sent over the network. It was defined by John Nagle while working for Ford Aerospace. It was published in 1984 as a Request for Comments (RFC) with title Congestion Control in IP/TCP Internetworks in RFCΒ 896.
The RFC describes what he called the "small-packet problem", where an application repeatedly emits data in small chunks, frequently only 1 byte in size. Since TCP packets have a 40-byte header (20 bytes for TCP, 20 bytes for IPv4), this results in a 41-byte packet for 1 byte of useful information, a huge overhead. This situation often occurs in Telnet sessions, where most keypresses generate a single byte of data that is transmitted immediately. Worse, over slow links, many such packets can be in transit at the same time, potentially leading to congestion collapse.
Nagle's algorithm works by combining a number of small outgoing messages and sending them all at once. Specifically, as long as there is a sent packet for which the sender has received no acknowledgment, the sender should keep buffering its output until it has a full packet's worth of output, thus allowing output to be sent all at once.
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- "Nagle's Algorithm" | 2026-03-12 | 10 Upvotes 1 Comments
- "Nagle's Algorithm" | 2022-12-30 | 25 Upvotes 2 Comments
π 8-Circuit Model of Consciousness
The eight-circuit model of consciousness is a hypothesis by Timothy Leary, and later expanded on by Robert Anton Wilson and Antero Alli, that "suggested eight periods [circuits] and twenty-four stages of neurological evolution". The eight circuits, or eight "brains" as referred by other authors, operate within the human nervous system, each corresponding to its own imprint and direct experience of reality. Leary and Alli include three stages for each circuit that details developmental points for each level of consciousness.
The first four circuits deal with life on Earth, and survival of the species. The last four circuits are post-terrestrial, and deal with the evolution of the species, altered states of consciousness, enlightenment, mystical experiences, psychedelic states of mind, and psychic abilities. The proposal suggests that these altered states of consciousness are recently realized, but not widely utilized. Leary describes the first four as "larval circuits", necessary for surviving and functioning in a terrestrial human society, and proposed that the post terrestrial circuits will be useful for future humans who, through a predetermined script, continue to act on their urge to migrate to outer space and live extra-terrestrially. Leary, Wilson, and Alli have written about the idea in depth, and have explored and attempted to define how each circuit operates, both in the lives of individual people and in societies and civilization.
The term "circuit" is equated to a metaphor of the brain being computer hardware, and the wiring of the brain as circuitry.
Leary uses the eight circuits along with recapitulation theory to explain the evolution of the human species, the personal development of an individual, and the biological evolution of all life.
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- "8-Circuit Model of Consciousness" | 2011-01-10 | 12 Upvotes 6 Comments
π Third Pole
The Third Pole, also known as the Hindu Kush-Karakoram-Himalayan system (HKKH), is a mountainous region located in the west and south of the Tibetan Plateau. Part of High-Mountain Asia, it spreads over an area of more than 4.2Β million square kilometres (1.6Β million square miles) across nine countries, i.e. Afghanistan, Bangladesh, Bhutan, China, India, Myanmar, Nepal, Pakistan and Tajikistan, bordering ten countries. The area is nicknamed the "Third Pole" because its mountain glaciers and snowfields store more frozen water than anywhere else in the world after the Arctic and Antarctic polar caps. With the world's loftiest mountains, comprising all 14 peaks above 8,000 metres (26,000Β ft), it is the source of 10 major rivers and forms a global ecological buffer.
The Third Pole area is rich with natural resources and consists of all or some of four global biodiversity hotspots. The mountain resources administer a wide range of ecosystem benefits and are the base for the drinking water, food production and livelihoods of the 220 million inhabitants of the region, as well as indirectly to the 1.5 billion people β one sixth of the world's population β living in the downstream river basins. Billions of people benefit from the food and energy produced in these river basins whose headwaters rely on meltwaters and precipitations that run off these mountains.