Random Articles (Page 97)
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🔗 Polynesian Voyaging Society
The Polynesian Voyaging Society (PVS) is a non-profit research and educational corporation based in Honolulu, Hawaiʻi. PVS was established to research and perpetuate traditional Polynesian voyaging methods. Using replicas of traditional double-hulled canoes, PVS undertakes voyages throughout Polynesia navigating without modern instruments.
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- "Polynesian Voyaging Society" | 2019-06-07 | 38 Upvotes 6 Comments
🔗 Abductive Logic Programming
Abductive logic programming (ALP) is a high-level knowledge-representation framework that can be used to solve problems declaratively based on abductive reasoning. It extends normal logic programming by allowing some predicates to be incompletely defined, declared as abducible predicates. Problem solving is effected by deriving hypotheses on these abducible predicates (abductive hypotheses) as solutions of problems to be solved. These problems can be either observations that need to be explained (as in classical abduction) or goals to be achieved (as in normal logic programming). It can be used to solve problems in diagnosis, planning, natural language and machine learning. It has also been used to interpret negation as failure as a form of abductive reasoning.
🔗 Kardashev Scale
The Kardashev scale is a method of measuring a civilization's level of technological advancement based on the amount of energy they are able to use. The measure was proposed by Soviet astronomer Nikolai Kardashev in 1964. The scale has three designated categories:
- A Type I civilization, also called a planetary civilization—can use and store all of the energy available on its planet.
- A Type II civilization, also called a stellar civilization—can use and control energy at the scale of its stellar system.
- A Type III civilization, also called a galactic civilization—can control energy at the scale of its entire host galaxy.
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- "Kardashev Scale" | 2024-05-11 | 34 Upvotes 28 Comments
- "Kardashev Scale" | 2021-10-13 | 14 Upvotes 1 Comments
- "Kardashev Scale" | 2019-08-03 | 74 Upvotes 31 Comments
- "Kardashev scale" | 2011-02-05 | 72 Upvotes 15 Comments
🔗 Hypothetical types of biochemistry
Hypothetical types of biochemistry are forms of biochemistry speculated to be scientifically viable but not proven to exist at this time. The kinds of living organisms currently known on Earth all use carbon compounds for basic structural and metabolic functions, water as a solvent, and DNA or RNA to define and control their form. If life exists on other planets or moons, it may be chemically similar; it is also possible that there are organisms with quite different chemistries—for instance, involving other classes of carbon compounds, compounds of another element, or another solvent in place of water.
The possibility of life-forms being based on "alternative" biochemistries is the topic of an ongoing scientific discussion, informed by what is known about extraterrestrial environments and about the chemical behaviour of various elements and compounds. It is of interest in synthetic biology and is also a common subject in science fiction.
The element silicon has been much discussed as a hypothetical alternative to carbon. Silicon is in the same group as carbon on the periodic table and, like carbon, it is tetravalent. Hypothetical alternatives to water include ammonia, which, like water, is a polar molecule, and cosmically abundant; and non-polar hydrocarbon solvents such as methane and ethane, which are known to exist in liquid form on the surface of Titan.
Discussed on
- "Hypothetical Types of Biochemistry" | 2020-05-21 | 49 Upvotes 7 Comments
- "Hypothetical types of biochemistry" | 2015-03-25 | 42 Upvotes 2 Comments
🔗 Conjugate Acids and Bases
A conjugate acid, within the Brønsted–Lowry acid–base theory, is a chemical compound formed when an acid donates a proton (H+) to a base—in other words, it is a base with a hydrogen ion added to it, as in the reverse reaction it loses a hydrogen ion. On the other hand, a conjugate base is what is left over after an acid has donated a proton during a chemical reaction. Hence, a conjugate base is a species formed by the removal of a proton from an acid, as in the reverse reaction it is able to gain a hydrogen ion. Because some acids are capable of releasing multiple protons, the conjugate base of an acid may itself be acidic.
In summary, this can be represented as the following chemical reaction:
Johannes Nicolaus Brønsted and Martin Lowry introduced the Brønsted–Lowry theory, which proposed that any compound that can transfer a proton to any other compound is an acid, and the compound that accepts the proton is a base. A proton is a nuclear particle with a unit positive electrical charge; it is represented by the symbol H+ because it constitutes the nucleus of a hydrogen atom, that is, a hydrogen cation.
A cation can be a conjugate acid, and an anion can be a conjugate base, depending on which substance is involved and which acid–base theory is the viewpoint. The simplest anion which can be a conjugate base is the solvated electron whose conjugate acid is the atomic hydrogen.
Discussed on
- "Conjugate Acids and Bases" | 2023-06-13 | 24 Upvotes 17 Comments
🔗 Magdeburg Water Bridge
The Magdeburg Water Bridge (German: Kanalbrücke Magdeburg) is a large navigable aqueduct in central Germany, located near Magdeburg. The largest canal underbridge in Europe, it spans the river Elbe and directly connects the Mittellandkanal to the west and Elbe-Havel Canal to the east of the river, allowing large commercial ships to pass between the Rhineland and Berlin without having to descend into and then climb out of the Elbe itself.
Discussed on
- "Magdeburg Water Bridge" | 2019-11-21 | 52 Upvotes 41 Comments
🔗 Unique Games Conjecture
In computational complexity theory, the unique games conjecture (often referred to as UGC) is a conjecture made by Subhash Khot in 2002. The conjecture postulates that the problem of determining the approximate value of a certain type of game, known as a unique game, has NP-hard computational complexity. It has broad applications in the theory of hardness of approximation. If the unique games conjecture is true and P ≠ NP, then for many important problems it is not only impossible to get an exact solution in polynomial time (as postulated by the P versus NP problem), but also impossible to get a good polynomial-time approximation. The problems for which such an inapproximability result would hold include constraint satisfaction problems, which crop up in a wide variety of disciplines.
The conjecture is unusual in that the academic world seems about evenly divided on whether it is true or not.
Discussed on
- "Unique Games Conjecture" | 2025-05-10 | 26 Upvotes 2 Comments
🔗 Indian Ocean garbage patch
The Indian Ocean garbage patch, discovered in 2010, is a gyre of marine litter suspended in the upper water column of the central Indian Ocean, specifically the Indian Ocean Gyre, one of the five major oceanic gyres. The patch does not appear as a continuous debris field. As with other patches in each of the five oceanic gyres, the plastics in it break down to ever smaller particles, and to constituent polymers. As with the other patches, the field constitutes an elevated level of pelagic plastics, chemical sludge, and other debris; primarily particles that are invisible to the naked eye. The concentration of particle debris has been estimated to be approximately 10,000 particles per square kilometer.
A similar patch of floating plastic debris in the Pacific Ocean, the Great Pacific garbage patch, was predicted in 1985, and discovered in 1997 by Charles J. Moore as he passed through the North Pacific Gyre on his return from the Transpacific Yacht Race. The North Atlantic garbage patch was discovered in 2010.
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- "Indian Ocean garbage patch" | 2014-03-20 | 92 Upvotes 45 Comments
🔗 ReFS
Resilient File System (ReFS), codenamed "Protogon", is a Microsoft proprietary file system introduced with Windows Server 2012 with the intent of becoming the "next generation" file system after NTFS.
ReFS was designed to overcome problems that had become significant over the years since NTFS was conceived, which are related to how data storage requirements had changed. The key design advantages of ReFS include automatic integrity checking and data scrubbing, removal of the need for running chkdsk, protection against data degradation, built-in handling of hard disk drive failure and redundancy, integration of RAID functionality, a switch to copy/allocate on write for data and metadata updates, handling of very long paths and filenames, and storage virtualization and pooling, including almost arbitrarily sized logical volumes (unrelated to the physical sizes of the used drives).
These requirements arose from two major changes in storage systems and usage – the size of storage in use (large or massive arrays of multi-terabyte drives now being fairly common), and the need for continual reliability. As a result, the file system needs to be self-repairing (to prevent disk checking from being impractically slow or disruptive), along with abstraction or virtualization between physical disks and logical volumes.
ReFS was initially added to Windows Server 2012 only, with the aim of gradual migration to consumer systems in future versions; this was achieved as of Windows 8.1. The initial versions removed some NTFS features, such as disk quotas, alternate data streams, and extended attributes. Some of these were re-implemented in later versions of ReFS.
In early versions (2012–2013), ReFS was similar to or slightly faster than NTFS in most tests, but far slower when full integrity checking was enabled, a result attributed to the relative newness of ReFS. Pre-release concerns were also voiced by one blogger over Storage Spaces, the storage system designed to underpin ReFS, which reportedly could fail in a manner that prevented ReFS from recovering automatically.
The ability to create ReFS volumes was removed in Windows 10's 2017 Fall Creators Update for all editions except Enterprise and Pro for Workstations.
The cluster size of a ReFS volume is either 4 KiB or 64 KiB.
🔗 You Will
"You Will" was an AT&T marketing campaign that launched in 1993, consisting of commercials directed by David Fincher. Each ad presented a futuristic scenario beginning with "Have you ever…" and ending with "…you will. And the company that will bring it to you: AT&T."
The ads were narrated by Tom Selleck.
The creative team that created the ad campaign at N.W. Ayer & Partners were Copy Supervisor Gordon Hasse, Art Supervisor Nick Scordato and Producer Gaston Braun.
One of the first web banner ads ever sold was part of an AT&T campaign that ran on HotWired starting October 27, 1994, asking "Have you ever clicked your mouse right HERE? You Will".
In 2016, technology writer Timothy B. Lee commented that "overall, the ads were remarkably accurate in predicting the cutting-edge technologies of the coming decades. But the ads were mostly wrong about one thing: the company that brought these technologies to the world was not AT&T. At least not on its own. AT&T does provide some of the infrastructure on which the world's communications flow. But the gadgets and software that brought these futuristic capabilities to consumers were created by a new generation of Silicon Valley companies that mostly didn't exist when these ads were made."
The ads won a few different awards at the time, notably the first annual David Ogilvy Award for the most effective campaign supported by research, the 1994 PCIA (Personal Communications Industry Award), and two ADDY Awards.
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- "You Will" | 2025-06-04 | 20 Upvotes 6 Comments