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Molar concentration

Molar concentration (also called molarity, amount concentration or substance concentration) is a measure of the concentration of a chemical species, in particular, of a solute in a solution, in terms of amount of substance per unit volume of solution. In chemistry, the most commonly used unit for molarity is the number of moles per liter, having the unit symbol mol/L or mol/dm3 in SI units. A solution with a concentration of 1 mol/L is said to be 1 molar, commonly designated as 1 M or 1 M. Molarity is often depicted with square brackets around the substance of interest; for example, the molarity of the hydrogen ion is depicted as [H+].

Definition
Molar concentration or molarity is most commonly expressed in units of moles of solute per litre of solution. For use in broader applications, it is defined as amount of substance of solute per unit volume of solution, or per unit volume available to the species, represented by lowercase $$c$$:

 * $$c = \frac{n}{V} = \frac{N}{N_\text{A}\,V} = \frac{C}{N_\text{A}}.$$

Here, $$n$$ is the amount of the solute in moles, $$N$$ is the number of constituent particles present in volume $$V$$ (in litres) of the solution, and $$N_\text{A}$$ is the Avogadro constant, since 2019 defined as exactly. The ratio $$\frac{N}{V}$$ is the number density $$C$$.

In thermodynamics the use of molar concentration is often not convenient because the volume of most solutions slightly depends on temperature due to thermal expansion. This problem is usually resolved by introducing temperature correction factors, or by using a temperature-independent measure of concentration such as molality.

The reciprocal quantity represents the dilution (volume) which can appear in Ostwald's law of dilution.

If a molecular entity dissociates in solution, the concentration refers to the original chemical formula in solution, the molar concentration is sometimes called formal concentration or formality (FA) or analytical concentration (cA). For example, if a sodium carbonate solution (Na2CO3) has a formal concentration of c(Na2CO3) = 1 mol/L, the molar concentrations are c(Na+) = 2 mol/L and c(CO3(2−)) = 1 mol/L because the salt dissociates into these ions.
 * Formality or analytical concentration

Units
In the International System of Units (SI), the coherent unit for molar concentration is mol/m3. However, most chemical literature traditionally uses mol/dm3, which is the same as mol/L. This traditional unit is often called a molar and denoted by the letter M, for example:
 * 1 mol/m3 = 10−3 mol/dm3 = 10−3 mol/L = 10−3 M = 1 mM = 1 mmol/L.

The SI prefix "mega" (symbol M) has the same symbol. However, the prefix is never used alone, so "M" unambiguously denotes molar. Sub-multiples, such as "millimolar" (mM) and "nanomolar" (nM), consist of the unit preceded by an SI prefix:

Number concentration
The conversion to number concentration $$C_i$$ is given by

 * $$C_i = c_i N_\text{A},$$

where $$N_\text{A}$$ is the Avogadro constant.

Mass concentration
The conversion to mass concentration $$\rho_i$$ is given by

 * $$\rho_i = c_i M_i,$$

where $$M_i$$ is the molar mass of constituent $$i$$.

Mole fraction
The conversion to mole fraction $$x_i$$ is given by

 * $$x_i = c_i \frac{\overline{M}}{\rho},$$

where $$\overline{M}$$ is the average molar mass of the solution, $$\rho$$ is the density of the solution.

A simpler relation can be obtained by considering the total molar concentration, namely, the sum of molar concentrations of all the components of the mixture:

 * $$x_i = \frac{c_i}{c} = \frac{c_i}{\sum_j c_j}.$$

Mass fraction
The conversion to mass fraction $$w_i$$ is given by

 * $$w_i = c_i \frac{M_i}{\rho}.$$

Molality
For binary mixtures, the conversion to molality $$b_2$$ is

 * $$b_2 = \frac{c_2}{\rho - c_1 M_1},$$

where the solvent is substance 1, and the solute is substance 2.

For solutions with more than one solute, the conversion is

 * $$b_i = \frac{c_i}{\rho - \sum_{j\neq i} c_j M_j}.$$

Sum of molar concentrations – normalizing relations
The sum of molar concentrations gives the total molar concentration, namely the density of the mixture divided by the molar mass of the mixture or by another name the reciprocal of the molar volume of the mixture. In an ionic solution, ionic strength is proportional to the sum of the molar concentration of salts.

Sum of products of molar concentrations and partial molar volumes
The sum of products between these quantities equals one:
 * $$\sum_i c_i \overline{V_i} = 1.$$

Dependence on volume
The molar concentration depends on the variation of the volume of the solution due mainly to thermal expansion. On small intervals of temperature, the dependence is

 * $$c_i = \frac {c_{i,T_0}}{1 + \alpha\Delta T},$$

where $$c_{i,T_0}$$ is the molar concentration at a reference temperature, $$\alpha$$ is the thermal expansion coefficient of the mixture.

license: Creative Commons - Attribution Share-Alike - https://creativecommons.org/licenses/by-sa/4.0/

title: Molar concentration


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User:Doradus

This is my page. I am Doradus. I use He/Him.

I wrote the Jupiter JVM and once worked on the MOST telescope.

Articles
Recently I have contributed to Roche Limit, Memory address, and Astrodynamics (which is still in fairly poor shape).

I also added yet another version of hyperlinked footnotes. They are at Template:Ref and Template:Endnote, with some discussion in Wikipedia Talk:Footnote3.

TODO

 * Space Shuttle Solid Rocket Booster - Clean up a bit and nominate for featured status. Probably needs more history and perspective on other similar technologies.
 * Astrodynamics - I really should try to find the time this article needs.
 * Napier's bones - copyedit from Spanish translation
 * Gravity drag - needs a coherent example, and some equations
 * Giant impact theory - wow. Can this become a featured article?
 * Spaghettification - copyedit
 * CPU cache - talk about working sets

Bookmarks

 * Count of my edits
 * Guide_to_writing_better_articles - a link I can use to defend simplifying links. Edit summary can looks like this:
 * Simplified some links as per the Principle of Least Astonishment

 * Template:Fair use reduced can be used if the resolution is too high to qualify as fair use.
 * Math markup documentation

Licencing of my contributions
I agree to multi-license all my contributions, with the exception of my user pages, as described below:

title: User:Doradus


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Talk:Specific impulse

Effective exhaust velocity
Farohki's "Aircraft Propulsion" https://archive.org/details/aircraftpropulsion2ed_201907 calculates values for effective exhaust velocities for rocket and air-breathing engines. However, his air-breathing example, similar to a CF-6 at cruise, has a value around 400 m/s which is nowhere near the 58,000 m/s shown in the Examples table in this article. Why is this? Thanks.Pieter1963 (talk) 16:44, 24 February 2021 (UTC)
 * For rocket engines, carrying the oxidizer, the result is related to the exhaust velocity. For air breathing engines, it is not. You should not try to compare the values between the two cases, just like you don't compare apples and oranges. Gah4 (talk) 08:26, 2 May 2022 (UTC)
 * For rocket engines, carrying the oxidizer, the result is related to the exhaust velocity. For air breathing engines, it is not. You should not try to compare the values between the two cases, just like you don't compare apples and oranges. Gah4 (talk) 08:26, 2 May 2022 (UTC)

"Specific impulse" of engines with no propellant
Nasa is working on an impulse engine based on the Mach effect (which has no Wikipedia page; the Mach effect page is about something else). This engine is driven by gravity, so it doesn't need to expel propellant. Yet it's still described as having a "specific impulse", which makes no sense if specific impulse is something that specifically applies to propellant, as the Wikipedia entry seems to imply. The article needs to explain specific impulse in a way that can be understood as it applies to engines like the one NASA is working on.
 * Seems to me that you have to see what WP:RS say, but I suspect you could do it based on energy instead of mass or weight. Gah4 (talk) 19:56, 22 December 2021 (UTC)
 * Seems to me that you have to see what WP:RS say, but I suspect you could do it based on energy instead of mass or weight. Gah4 (talk) 19:56, 22 December 2021 (UTC)

Definition of specific impulse in scientific terms
Impulse is, by definition, change in momentum. Anything specific in this type of context - such as specific heat capacity - refers to "amount per unit quantity" again by definition; in this case, it means mass (it can't possibly mean weight since - for example - propellant weights virtually nothing when floating around in free-fall).

Therefore a test of whether or not a source is reliable on the subject of specific impulse is to see if it uses that definition. This is applying editorial judgement, not doing original research: the point being that sources which are very obviously incorrect shouldn't be used.

The confused and confusing source at https://www.grc.nasa.gov/www/k-12/airplane/specimp.html fails this test - therefore, it is not a reliable source and should not be cited.

Think about it: that source states that the quantity of fuel for specific impulse calculations is specified in terms of the weight of propellant - calling it a force, which it is. Common sense will tell you that this varies with the acceleration of the rocket - does the amount of propellant being used by the rocket engine really increase hugely due to the acceleration of the rocket? Of course not, and the mathematical treatment on that page does not say that it does. The mathematical treatment actually uses what works out to be pounds-mass for the supposed "weight" of fuel. Editorial judgement, having spotted that obvious mismatch between the words and the maths, should treat this particular source as unreliable.

This source https://www.scienceabc.com/pure-sciences/specific-impulse-definition-formula-and-units.html contains a correct statement of specific impulse:

"it is the change in momentum per unit of mass for rocket fuels"

Very obviously, the old short description recently reverted to: "Change in velocity per amount of fuel" is completely wrong and must be replaced. Editorial judgement based on a quick reality check should make this obvious. Also, "fuel" tends to mean "not the oxidiser propellant" in the case of bipropellant engines, so it's clearer to replace the word "fuel" with "propellant". Again, editorial judgement rather than original research.

(Change in velocity of what, exactly? And how can "change in velocity" be a measure of rocket engine efficiency when the mass of a rocket is constantly changing?  In any case, "velocity" is not "impulse" - they are entirely different parameters)

The fundamental error which leads to "seconds" being mistakenly used as the conventional unit for specific impulse is confusing pounds-mass (amount of fuel) with pounds-force (thrust of the engine): see here Pound_(mass) for more on the subject. This usage must be covered in this article because it's so common, but it's not the true definition of specific impulse in scientific terms.

The pound-mass has been defined in terms of the kilogram since 1959. Correspondingly, the Pound_(force) has long been defined in terms of the kilogram and a standardized value for acceleration due to gravity - or, to put it another way, in terms of the SI unit of force, the newton.

Both are necessary since the only current internationally recognised measurement standards are SI standards: the old US and imperial measurement references have long been abandoned.

Thus, specific impulse when calculated in US customary units works out as being defined, ultimately, as impulse measured in newton-seconds divided by mass measured in kilograms multiplied by a constant to convert the units from SI to US customary units.

The main point is that pounds-force and pounds-mass by definition cannot cancel each other out: they are dimensionally different, so common sense editorial judgement says any source which fails to address this important point must be treated as unreliable - although as I pointed out above, since the mistaken understanding which causes specific impulse to be cited in seconds is so widespread, this issue must be covered in this article. But it needs to be covered using reliable sources which seem to be hard to find.

I suggest that my changes stand until better sources to explain specific impulse are found. I've failed so far.

Please discuss the matter here and please do not revert the article to obviously incorrect information based on what common sense editorial judgement readily identifies as unreliable sources.

Michael F 1967 (talk) 19:46, 18 October 2021 (UTC)

- I have at least found a reliable source which specifies rocket motor specific impulse in SI units: "a specific impulse of 1780 N s kg -1 (sea level)" https://www2.le.ac.uk/departments/physics/research/xroa/astronomical-facilities-1/rocket-science-at-leicester/the-skylark-rocket

Michael F 1967 (talk) 20:26, 18 October 2021 (UTC)

 * "Anything specific in this type of context - such as specific heat capacity - refers to "amount per unit quantity" again by definition; in this case, it means mass (it can't possibly mean weight since - for example - propellant weights virtually nothing when floating around in free-fall)."

 * This bit is wrong and you've based your edits on it. That's a problem. GliderMaven (talk) 01:10, 19 October 2021 (UTC)

 * "The fundamental error which leads to "seconds" being mistakenly used as the conventional unit for specific impulse"

 * Not our problem, Wikipedia has to reflect the real world, and the real world does this. GliderMaven (talk) 01:15, 19 October 2021 (UTC)

 * Please stop using the edit button in an attempt to WP:RIGHTGREATWRONGS. GliderMaven (talk) 01:13, 19 October 2021 (UTC)
 * Yes, don't think of it in terms of weight. Think of it as a convenient unit system, and little g as the convenient unit normalizing factor. We could take the heights of people in the US and Europe, divide them by the appropriate little g, and end up with a value in square seconds. It would be convenient unit, independent of the local length unit. How convenient. Gah4 (talk) 08:38, 2 May 2022 (UTC)
 * Yes, don't think of it in terms of weight. Think of it as a convenient unit system, and little g as the convenient unit normalizing factor. We could take the heights of people in the US and Europe, divide them by the appropriate little g, and end up with a value in square seconds. It would be convenient unit, independent of the local length unit. How convenient. Gah4 (talk) 08:38, 2 May 2022 (UTC)

General critique:
I really hate this page. 1. Using weight measures is archaic. Maybe some fields still do that, but this article ought to make sense to rational outsiders who know a little physics. The concept has nothing at all to do with g. The entire discussion should be in mass units, except with a section explaining how to convert to weight units. 2. I have tried to read it several times, and I still do not know an agreed perfectly general definition of specific impulse in mass units that is valid for jets, ordinary rockets, photon thrusters, and atomic rockets that heat up nonfuel to create exhaust. In fact, I'm left with the possibility that different fields might even use different fundamental definitions. If that is so, please label alternate definitions by fields. If not, please rewrite to make that clear. 3. Please rewrite to start out with a perfectly general definitions before mentioning any special cases. Burressd (talk) 06:13, 2 May 2022 (UTC)
 * Yes it is strange in weight units, but it seems to be the WP:COMMONNAME. It actually doesn't have anything to do with weight units or g, but is a convenient way to get a value independent of the system length unit. If you divide a velocity (in length units per second) by little g (in length units per second squared) you get a value in seconds, independent of length unit. In the case of rocket engines, that velocity has some physical meaning. In the case of jet engines, not much at all. (Only fuel, not oxidizer, goes into the calculation.) Since it is what people actually do, it is hard to complain about it. Gah4 (talk) 08:19, 2 May 2022 (UTC)
 * Yes it is strange in weight units, but it seems to be the WP:COMMONNAME. It actually doesn't have anything to do with weight units or g, but is a convenient way to get a value independent of the system length unit. If you divide a velocity (in length units per second) by little g (in length units per second squared) you get a value in seconds, independent of length unit. In the case of rocket engines, that velocity has some physical meaning. In the case of jet engines, not much at all. (Only fuel, not oxidizer, goes into the calculation.) Since it is what people actually do, it is hard to complain about it. Gah4 (talk) 08:19, 2 May 2022 (UTC)

Move airbreathing engine tables
I think the 3 tabulations for jet engines would be more at home in a more aircraft-oriented article such as Airbreathing jet engine since the only numbers recognised by wikipedia, ie sourced, are aircraft specific, ie in the TSFC columns. Any comments? Thanks Pieter1963 (talk) 00:05, 5 June 2022 (UTC)
 * It looks like air breathing engine tables are much more than rocket tables. Seems to make more sense to move the non-air breathing tables. We could have two articles: Specific impulse of jet engines and Specific impulse of rocket engines. Seems to me, though, that one article is fine. It allows one to compare and contrast the two. Gah4 (talk) 02:13, 5 June 2022 (UTC)
 * It looks like air breathing engine tables are much more than rocket tables. Seems to make more sense to move the non-air breathing tables. We could have two articles: Specific impulse of jet engines and Specific impulse of rocket engines. Seems to me, though, that one article is fine. It allows one to compare and contrast the two. Gah4 (talk) 02:13, 5 June 2022 (UTC)

Examples Tables and "SI" abbr.
In the head of the tables there is the "SI" column (s) als unit - this is extremely confusing, since the proper SI-unit is m/s which is stated als EEV in the next colum; both colums should get proper header cell (colspan 2) with Isp, the left colum gets labeld with "weight (s)" and the right "mass (m/s)"

this should avoid confusion if sombody is searching for values and looking for the SI units and looking at the "SI" but not finding the proper SI unit there, since the specific impulse is the ratio between the impulse (Force * Time) and the ejected mass (N*s/kg which is effectively m/s)

i'll change that in a moment, since similar critique was added in Talk:Specific_impulse about the units Suit (talk) 17:49, 29 November 2022 (UTC)
 * Note that the article is Specific impulse, not effective exhaust velocity. It happens that, at least for rockets, they are related. Otherwise, it is a simple constant to get between them. As I said a few times, don't think of it as mass vs. weight, but just a unit conversion constant. Gah4 (talk) 21:11, 30 November 2022 (UTC)
 * Note that the article is Specific impulse, not effective exhaust velocity. It happens that, at least for rockets, they are related. Otherwise, it is a simple constant to get between them. As I said a few times, don't think of it as mass vs. weight, but just a unit conversion constant. Gah4 (talk) 21:11, 30 November 2022 (UTC)

title: Talk:Specific impulse


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Piping plover

The piping plover (Charadrius melodus) is a small sand-colored, sparrow-sized shorebird that nests and feeds along coastal sand and gravel beaches in North America. The adult has yellow-orange-red legs, a black band across the forehead from eye to eye, and a black stripe running along the breast line. This chest band is usually thicker in males during the breeding season, and it is the only reliable way to tell the sexes apart. The bird is difficult to see when it is standing still, as it blends well with open, sandy beach habitats. It typically runs in short, quick spurts and then stops.

There are two subspecies of piping plovers: the eastern population is known as Charadrius melodus melodus and the mid-west population is known as C. m. circumcinctus. The bird's name is derived from its plaintive bell-like whistles which are often heard before the bird is visible.

In 1986, the U.S. Fish & Wildlife Service listed the Great Lakes population as endangered and the Northern Great Plains and Atlantic populations as threatened. Intensive conservation efforts have yielded slow population growth, but only some populations have met the recovery goals set for them. The growth trend is expected to reverse if conservation efforts were stopped. Total population was estimated to be between 7600 and 8400 individuals in 2020.

Their breeding habitat includes beaches and sand flats on the Atlantic coast, the shores of the Great Lakes, and in the mid-west of Canada and the United States. They nest on sandy or gravel beaches or shoals. These shorebirds forage for food on beaches, usually by sight, moving across the beaches in short bursts. Generally, piping plovers will forage for food around the high tide wrack zone and along the water's edge. They eat mainly insects, marine worms, and crustaceans.

Taxonomy
American naturalist George Ord described the piping plover in 1824. Two subspecies are recognized, including nominate C. m. melodus of the Atlantic Coast and C. m. circumcinctus of the Great Plains. On average, circumcinctus is darker overall with more contrastingly dark cheeks and lores. Breeding circumcinctus males show more extensive black on forehead and bill-base and more often shows complete breast-bands. Some overlap exists.

Description
The piping plover is a stout bird with a large rounded head, a short thick neck, and a stubby bill. It is a sand-colored, dull gray/khaki, sparrow-sized shorebird. The adult has yellow-orange legs, the male has a prominent black band across the forehead from eye to eye, and a black ring around the neck during the breeding season. The band on the female's brow is much fainter. During nonbreeding season, the black bands become less pronounced. Its bill is orange with a black tip. It ranges from 15 – in length, with a wingspan of 35 – and a mass of 42 –.

Vocalizations
The piping plover's light call is a soft, whistled peep peep given by standing and flying birds. Its frequently heard alarm call is a soft pee-werp, which the second syllable lower pitched.

Distribution and habitat
The piping plover lives the majority of its life on open sandy beaches or rocky shores, often in high, dry sections away from water. They can be found on the Atlantic Coast of the U.S. and Canada on the ocean or bay beaches and on the Great Lakes shores. It builds its nests higher on the shore near beach grass and other objects. It is very rare to see a piping plover anywhere outside of sand or rocky beaches/shores while not migrating. Notably, they are considered a disturbance-dependent species due to their habitat's relationship with severe flooding. They need their nesting sites to be far away from the water to be dry for their entire nesting period – yet, they also need to nest in open sand. Often, this combination only occurs in sites which are thoroughly flooded once every few years, which brings in fresh sand and clears away vegetation. As human coastal management strategies worked to minimize unpredictable flooding, their old habitats often became overgrown, and their populations declined. Nowadays, U.S. Army Corps of Engineers is forced to artificially clear shoals on the Platte and Missouri River to maintain some of the plovers' remaining habitat in the Great Plains. However, while these efforts are important, they remain inferior to natural periodically flooded habitats.

Alongside least terns, piping plovers also have an unusual relationship with mining. Whereas most species predictably suffer habitat loss from mining activities in their area, these birds are known to nest in waste sand piles generated by nearby mines, as the replacement for sand bars. Those sand piles remain topped-up and hostile to vegetation overgrowth as long as the mining activity continues. Often, mining sites end up reclaimed for housing development at the end of their lifespan, which means more construction work, and an extended persistence of waste sand piles. However, modern mining practices typically transport much of this waste sand to more remote areas, often to reuse it commercially, which limits colonization opportunities for these birds.

Piping plovers migrate from their northern range in the summer to the south in the winter months, migrating to the Gulf of Mexico, the southern Atlantic coast of the United States and the Caribbean, including The Bahamas. They have also been recorded across Cuba, with rarer occurrences elsewhere throughout the West Indies, and even Ecuador and Venezuela. They begin migrating north in mid-March. Their breeding grounds extend from southern Newfoundland south to the northern parts of South Carolina. Migration south begins in August for some adults and fledglings, and by mid-September most piping plovers have headed south for winter.

Breeding
The piping plover usually arrives at sandy beaches to breed in mid-March.

Males will begin claiming territories and pairing up in late March. When pairs are formed, the male begins digging out several scrapes (nests) along the high shore near the beach-grass line. The males also perform elaborate courtship ceremonies, including stone tossing and courtship flights featuring repeated dives. Scrapes, small depressions in the sand dug by kicking the sand, are often in the same area that least terns choose to colonize. Females will sit and evaluate the scrapes, then choose a good scrape and decorate the nest with shells and debris to camouflage it. Once a scrape is seen as sufficient, the female will allow the male to copulate with her. The male begins a mating ritual of standing upright and "marching" towards the female, puffing himself up and quickly stomping his legs. If the female had seen the scrape as adequate, she will allow the male to stand on her back and copulation occurs within a few minutes.

Most first-time nest attempts in each breeding season are four-egg nests which appear as early as mid-to-late April. Females lay one egg every other day. Second, third and sometimes fourth nesting attempts may have only three or two eggs. Incubation of the nest is shared by both the male and the female. Incubation is generally 27 days and eggs usually all hatch on the same day.

After chicks hatch, they are able to walk within hours, and must have access to feeding areas to feed on marine macro invertebrates. The adults' role is to protect them from the elements by brooding them. They also alert them to any danger. Like many other species of plovers, adult piping plovers will often feign a "broken wing display", drawing attention to themselves and away from the chicks when a predator may be threatening the chicks' safety. The broken wing display is also used during the nesting period to distract predators from the nest. A major defense mechanism of the chicks is their ability to blend in with the sand. It takes about 30 days before chicks achieve flight capability. They must be able to fly at least 50 yards before they can be considered fledglings.

To protect the nests from predators during incubation, many conservationists use exclosures, such as round turkey-wire cages with screened tops. These allow the adults to move in and out but stop predators from getting to the eggs. After the chicks hatch, many areas will put up snow fencing to restrict driving and pets for the safety of the chicks. Threats to nests include crows, cats, raccoons, and foxes, among others. Exclosures are not always used, as they occasionally draw more attention to the nest than would occur without the exclosure. Natural hazards to eggs or chicks include storms, high winds, and abnormal high tides; human disturbances can cause the abandonment of nests and chicks as well. It is best to stay away from any bird that appears distressed to prevent any unintended consequences.

Status and conservation
The piping plover is globally threatened and endangered; it is uncommon and local within its range, and has been listed by the United States as "endangered" in the Great Lakes region and "threatened" in the remainder of its range. While it is federally threatened, the piping plover has been listed as state endangered in Illinois, Indiana, Iowa, Maine, Michigan, Minnesota, Nebraska, New Hampshire, New York, New Jersey, Ohio, Pennsylvania, and Wisconsin. The Parker River Refuge on Plum Island, Massachusetts is a national network of lands and rivers dedicated to the safety of its native wildlife and specifically the piping plover. Protecting the Piper with full beach closures, the Refuge now "has the second largest plover population on the [Massachusetts] North Shore".

In eastern Canada, the piping plover is found only on coastal beaches. In 1985, it was declared an endangered species by the Committee on the Status of Endangered Wildlife in Canada. A large population in Ontario has disappeared entirely. In 2008, however, piping plover nests were found at Wasaga Beach and near Sauble Beach, Ontario, along the Ontario Great Lakes shores. There is also some evidence of nesting at other sites in Ontario, including Port Elgin, Ontario in 2014. In the 19th century and early 20th century, the piping plover was used for its feathers, as were many other birds at the time, as decorations for women's hats. These decorations, called plumes, became a symbol of high society, especially those from larger rare birds. This practice led to its initial population decline. The Migratory Bird Treaty Act of 1918 helped the population recover through the 1930s. The second decline in the piping plover's population and range has been attributed to increased development, shoreline stabilization efforts, habitat loss and human activity near nesting sites in the decades following World War II. The Great Lakes populations eventually shrank to only around two dozen. On the Missouri River sandbars, the number of breeding individuals varied, with the population increasing from 2012 to 2017 following a major habitat creation event.

Critical nesting habitats are now being protected to help the population during its breeding season. Populations have seen significant increases since the protection programs began, but the species remains in serious danger. Some USGS research suggests that in the northern Great Plains, low connectivity between scattered habitats mean that even maintaining the current population sizes will be a great challenge, and there's an 8–37% risk of those subpopulations disappearing near the end of the century. Current conservation strategies include identification and preservation of known nesting sites; public education; limiting or preventing pedestrian and/or off-road vehicle (ORV) traffic near nests and hatched chicks; limiting predation of free-ranging cats, dogs and other pets on breeding pairs, eggs and chicks; and removal of foxes, raccoons, skunks, and other predators.

In coastal areas such as Plymouth, Cape Cod, Long Island, Sandy Hook, Cape Henlopen State Park in Delaware, North Manitou Island in Lake Michigan, and most recently, Cape Hatteras National Seashore on the Outer Banks of North Carolina, beach access to pedestrians and off-road vehicles has been limited to protect piping plovers and their chicks at critical times of the breeding season.

Many studies have documented piping plovers' successes and struggles with human recreation or other predatory concerns. For example, piping plovers are much less likely to successfully fledge in heavily trafficked, popular recreational areas. Additionally, those that do fledge in active recreational areas tend to take longer to fledge. Most interestingly, chicks will spend less time foraging on weekends, since this tends to be when beaches are most active and disturbance will be at its highest. Despite the multitude of anthropogenic conservation concerns regarding the piping plover, a study on plovers on Long Island, New York found that the most significant cause of nest failure in the species was not humans, but depredation by the Red fox. Birds either lost their nests due to depredation of the nest, or significant predator presence and subsequent abandonment of the nest by adults. Birds rarely abandoned nests due to human presence.

Various environmental organizations are involved in aiding restoration efforts. The Goldenrod Foundation unsuccessfully filed suit against the Town of Plymouth in 2010 and 2015 to restrict offroad vehicle access to breeding habitat.

In 2019, the first documented pair of piping plovers in Chicago nested at Montrose Beach. The pair, named Monty and Rose by locals, hatched three chicks in July, becoming the first within Cook County in 60 years. Threats to the nest and chicks included a planned music festival that was canceled to ensure the birds were protected. Monty and Rose returned to the area in 2020 and 2021, again laying eggs and hatching chicks, although some eggs and chicks were lost to natural predators. In May 2022, the male shorebird, Monty, died after returning to Montrose Beach. Rose did not return in 2022. In late April 2023, Monty and Rose's offspring Imani was spotted at Montrose Beach along with an unbanded male and an unbanded female. In 2024, Imani returned to Montrose Beach again, this time joined by another banded male and a female named Searocket, who had been released at the beach as a captive-reared chick the previous summer; Imani and Searocket produced their first egg in late May.

Climate change
As shorebirds, piping plovers may be highly impacted by climate change, as it affects their aquatic and their terrestrial habitats. At the same time, the disturbance-dependent nature of their habitat makes their relationship to climate change more complex than of most other bird species.

Increasing sand temperatures
Higher sand temperatures directly and negatively affect piping plovers. Piping plovers nest on the ground in open areas, which regularly subjects them to high temperatures. Because of these high temperatures, piping plovers (along with other ground-nesting bird species) have specific strategies and behaviors for thermal regulation of their nests and themselves. Research has been conducted to evaluate how sand temperature affects piping plover nesting behaviors in a population of piping plovers in North Dakota during the 2014-2015 breeding seasons. As sand temperatures increased, piping plover nest attendance decreased and the frequency and duration of daily shading behaviors increased. Rising ground temperatures will likely have significant effects on piping plovers' ground-nesting behavior.

Inland habitat water level rise
A main part of the piping plover's range is in the Prairie Pothole Region of South Dakota, North Dakota, and Canada. The shallow wetlands of this region fluctuate water surface area in response to wet-dry periods. Piping plovers who breed in this region depend on the decreased water levels to reveal shorelines that they use for nesting. Climate change, along with consolidation drainage, drainage of smaller wetlands into another wetland to create fewer, larger wetlands, has begun to create fuller wetlands, reducing shoreline nesting habitat. Research of 32 piping plover wetland habitats in this region found that wetlands with risen water levels had lower chances of piping plover presence. This suggests that the warming climate and increased water levels and precipitation will degrade piping plover breeding habitats in the Prairie Pothole Region. On the other hand, research suggests that piping plover's habitat in Nebraska, on the shoals of Platte and Missouri River and around Lewis and Clark Lake would benefit from climate change, as it would make extensive flooding (so called "high-flow events") which keeps the shoals from getting overgrown occur more often than it does now, yet closer to the historical, pre-European colonization of the Americas patterns. The ideal frequency of high-flow events for piping plover population abundance in this river system is once in four years. Shoreline stabilization efforts reduced such high-flow events to once per twenty years, which is not enough to maintain piping plover populations outside of artificially cleared shoals, which become their only refuge in the long term. Climate change would only be harmful to these populations overall if it either makes high-flow events occur more often than once every four years, or if it ends making the basin drier and ultimately reduces their frequency even further, and both are considered unlikely. However, it is more plausible that in at least the near term, climate change adaptation efforts to protect human property in the area would continue to suppress high-flow events and negate this benefit to piping plover populations, while also making them more vulnerable to a potential, unprecedented catastrophic flooding event which could overwhelm those efforts and also submerge piping plover subpopulations across the entire area.

Coastal habitat sea level rise
Climate change is also causing sea level rise, which may affect the piping plover's other main habitat, the Atlantic Coast of the U.S. and Canada. Research has assessed sea level rise's threat to the piping plover habitat on barrier islands in Long Island, New York, finding that sea level rise will reduce piping plover breeding areas. Breeding habitats have the potential to migrate inland, but would still be reduced as a result of human development, which would reduce the migrated habitat 5-12%. This may lead to conflict between piping plover habitat conservation and human recreation because sea level rise will make the habitats take up a larger proportion of the islands. Research also shows that a large hurricane with the risen sea levels could flood up to 95% of piping plover habitat, so increased coastal storms induced by climate change, combined with rising sea level, could be very damaging.

Similar research has been conducted on the Florida coastline, part of the piping plovers's Atlantic coast habitat, to evaluate the habitat's sensitivity to sea level rise caused by climate change. Florida coastline species are at particular risk to climate change because of not just sea level rise, but also increased tropical storms. The piping plover depends on this habitat because it migrates south from its breeding habitats to winter in Florida for about three months. It is predicted that there will be a 16% loss of coastal landforms from inundation by the year 2100. Further, the sea level rise may make the coastline more complex, which may produce more habitat fragmentation. Thus, the changing landforms of the Florida coastline will likely affect piping plover ecology. Research also shows that of the shorebird species affected by the Florida coastline transformation, piping plovers are at high risk of decline.

In popular culture
In May 2023, the United States Postal Service released a piping plover Forever stamp as part of the Endangered Species set, based on a photograph from Joel Sartore's Photo Ark. The stamp was dedicated at a ceremony at the Jamaica Bay Wildlife Refuge, one of the biggest nesting sites for piping plovers.

title: Piping plover


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Jumping spider

Jumping spiders are a group of spiders that constitute the family Salticidae. As of 2019, this family contained over 600 described genera and over 6,000 described species, making it the largest family of spiders at 13% of all species. Jumping spiders have some of the best vision among arthropods and use it in courtship, hunting, and navigation. Although they normally move unobtrusively and fairly slowly, most species are capable of very agile jumps, notably when hunting, but sometimes in response to sudden threats or crossing long gaps. Both their book lungs and tracheal system are well-developed, and they use both systems (bimodal breathing). Jumping spiders are generally recognized by their eye pattern. All jumping spiders have four pairs of eyes, with the anterior median pair being particularly large.

Description

Jumping spiders are among the easiest to distinguish from similar spider families because of the shape of the cephalothorax and their eye patterns. The families closest to Salticidae in general appearance are the Corinnidae (distinguished also by prominent spines on the back four legs), the Oxyopidae (the lynx spiders, distinguished by very prominent spines on all legs), and the Thomisidae (the crab spiders, distinguished by their front four legs, which are very long and powerful). None of these families, however, have eyes that resemble those of the Salticidae. Conversely, the legs of jumping spiders are not covered with any very prominent spines. Their front four legs generally are larger than the hind four, but not as dramatically so as those of the crab spiders, nor are they held in the outstretched-arms attitude characteristic of the Thomisidae. In spite of the length of their front legs, Salticidae depend on their rear legs for jumping. The generally larger front legs are used partly to assist in grasping prey, and in some species, the front legs and pedipalps are used in species-recognition signaling.

The jumping spiders, unlike the other families, have faces that are roughly rectangular surfaces perpendicular to their direction of motion. In effect this means that their forward-looking, anterior eyes are on "flat faces", as shown in the photographs. Their eye pattern is the clearest single identifying characteristic. They have eight eyes, as illustrated. Most diagnostic are the front row of four eyes, in which the anterior median pair are more dramatically prominent than any other spider eyes apart from the posterior median eyes of the Deinopidae. There is, however, a radical functional difference between the major (anterior median) eyes of Salticidae and the major (posterior median) eyes of the Deinopidae; the large posterior eyes of Deinopidae are adapted mainly to vision in dim light, whereas the large anterior eyes of Salticidae are adapted to detailed, three-dimensional vision for purposes of estimating the range, direction, and nature of potential prey, permitting the spider to direct its attacking leaps with great precision. The anterior lateral eyes, though large, are smaller than the anterior median eyes and provide a wider forward field of vision.

The rear row of four eyes may be described as strongly bent, or as being rearranged into two rows, with two large posterior lateral eyes being the furthest back. They serve for lateral vision. The posterior median eyes also have been shifted out laterally, almost as far as the posterior lateral eyes. They are usually much smaller than the posterior lateral eyes and there is doubt about whether they are at all functional in many species.

The body length of jumping spiders generally ranges from 1 to(-). The largest is Hyllus giganteus, while other genera with relatively large species include Phidippus, Philaeus and Plexippus.

In addition to using their silk for safety lines while jumping, they also build silken "pup tents", where they take shelter from bad weather and sleep at night. They molt in these shelters, build and store egg cases in them, and also spend the winter in them.

Their body's sensory hairs are able to detect airborne acoustic stimuli up to 3 m away.

Vision
Jumping spiders have four pairs of eyes; three secondary pairs that are fixed and a principal pair that is movable.

The posterior median eyes are vestigial in many species, but in some primitive subfamilies, they are comparable in size with the other secondary eyes and help to detect motion. While unable to form images, the reduced pair of eyes is thought to have a role similar to that of insect ocelli by receiving light from the sky. The photoreceptors in the other secondary pairs are almost exclusively green-sensitive, but the posterior median eyes have two visual opsins different from those in all the other eyes, sensitive to blue and UV light.

The posterior lateral eyes (PLEs) are wide-angle motion detectors that sense motions from the side and behind. Combined with the other eyes, PLEs give the spider a near 360° view of the world.

The anterior lateral eyes (ALEs) have the best visual acuity of the secondary eyes. They are able to distinguish some details, as well, and without them, no "looming response" can be triggered by motion. Even with all the other pairs covered, jumping spiders in a study could still detect, stalk, and attack flies, using their ALEs only, which are also sufficiently widely spaced to provide stereoscopic vision.

The anterior median eyes have very good vision. This pair of eyes is built like a telescopic tube with a corneal lens in the front and a second lens in the back that focus images onto a four-layered retina, a narrow, boomerang-shaped strip oriented vertically. Physiological experiments have shown they may have up to four different kinds of receptor cells, with different absorption spectra, giving them the possibility of tetrachromatic color vision, with sensitivity extending into the ultraviolet (UV) range. As the eyes are too close together to allow depth perception, and the animals do not make use of motion parallax, they have instead evolved a method called image defocus. Of the four photoreceptor layers in the retina, the two closest to the surface contain a UV-sensitive opsin (visual pigment), while the two deepest contain a green-sensitive opsin. The incoming green light is only focused on the deepest layer, while the other one receives defocused or fuzzy images. By measuring the amount of defocus from the fuzzy layer, calculating the distance to the objects in front of them is possible. In addition to receptor cells, red filters also have been detected, located in front of the cells that normally register green light. All salticids, regardless of whether they have two, three, or four kinds of color receptors, seemingly are highly sensitive to UV light. Some species (such as Cosmophasis umbratica) are highly dimorphic in the UV spectrum, suggesting a role in sexual signaling. Color discrimination has been demonstrated in behavioral experiments.

The anterior median eyes have high resolution (11 min visual angle), but the field of vision is narrow, from 2 to 5°. The central region of the retina, where acuity is highest, is no more than six or seven receptor rows wide. However, the eye can scan objects off the direct axis of vision. As the lens is attached to the carapace, the eye's scanning movements are restricted to its retina through a complicated pattern of translations and rotations. This dynamic adjustment is a means of compensation for the narrowness of the static field of vision. Movement of the retina in jumping spiders is analogous to the way many vertebrates, such as primates, move their entire eyes to focus images of interest onto their fovea centralis. In jumping spiders with a translucent carapace, such movements within the jumping spider's eyes are visible from outside when the attention of the spider is directed to various targets.

Jumping
Many other arthropods are known to jump, including grasshoppers, fleas, leafhoppers, and sand fleas. Jumping spiders are different from these animals because they are able to make accurate, targeted jumps. Jumps are used for navigation, to escape danger, and to catch prey. When jumping, they use mainly their third or fourth pair of legs, or both pairs, depending on species. Jumping spiders' well-developed internal hydraulic system extends their limbs by altering the pressure of their body fluid (hemolymph) within them. This enables the spiders to jump without having large muscular legs like a grasshopper. The maximum horizontal jump distance varies greatly between species, with some capable of jumping two or three body lengths, while the jump of an individual Colonus puerperus was measured at 38 times the body length. The accuracy of their jumps is mediated by their well-developed visual system and the ability to quickly process visual information to tailor each jump. When a jumping spider moves from place to place, and especially just before it jumps, it tethers a filament of silk (or 'dragline') to whatever it is standing on. This dragline provides a mechanical aid to jumping, including braking and stabilization and if the jump should fail, the spider climbs back up the dragline.

Hunting
The hunting behaviour of the Salticidae is confusingly varied compared to that of most spiders in other families. Salticids hunt diurnally as a rule, which is consistent with their highly developed visual system. When it detects potential prey, a jumping spider typically begins orienting itself by swiveling its cephalothorax to bring the anterior median eyes to bear. It then moves its abdomen into line with its cephalothorax. After that, it might spend some time inspecting the object of its attention and determining whether a camouflaged or doubtful item of prey is promising, before it starts to stalk slowly forward. When close enough, the spider pauses to attach a dragline, then springs onto the prey.

Many variations on the theme and many surprising aspects exist. For one, salticids do not necessarily follow a straight path in approaching prey. They may follow a circuitous course, sometimes even a course that takes the hunter through regions from which the prey is not visible. Such complex adaptive behaviour is hard to reconcile with an organism that has such a tiny brain, but some jumping spiders, in particular some species of Portia, can negotiate long detours from one bush down to the ground, then up the stem of another bush to capture a prey item on a particular leaf. Such behaviour still is the subject of research.

Some salticid species are continually on the move, stopping periodically to look around for prey, which they then stalk immediately. Others spend more time scanning their surroundings from one position, actively stalking any prey they detect. Members of the genus Phaeacius take that strategy to extremes; they sit on a tree trunk, facing downwards and rarely do any stalking, but simply lunge down on any prey items that pass close before them.

Some Salticidae specialise in particular classes of prey, such as ants. Most spiders, including most salticids, avoid worker ants, but several species not only eat them as a primary item in their diets, but also employ specialised attack techniques; Anasaitis canosa, for example, circles around to the front of the ant and grabs it over the back of its head. Such myrmecophagous species, however, do not necessarily refuse other prey items, and routinely catch flies and similar prey in the usual salticid fashion, without the special precautions they apply in hunting dangerous prey such as ants. Ants offer the advantages of being plentiful prey items for which little competition from other predators occurs, but catching less hazardous prey when it presents itself remains profitable.

Some of the most surprising hunting behaviours occur among the araneophagous Salticidae, and vary greatly in method. Many of the spider-hunting species quite commonly attack other spiders, whether fellow salticids or not, in the same way as any other prey, but some kinds resort to web invasion; nonspecialists such as Phidippus audax sometimes attack prey ensnared in webs, basically in acts of kleptoparasitism; sometimes they leap onto and eat the web occupant itself, or simply walk over the web for that purpose.

Salticidae in the genera Brettus, Cyrba, Gelotia, and Portia display more advanced web-invasion behavior. They slowly advance onto the web and vibrate the silk with their pedipalps and legs. In this respect, their behaviour resembles that of the Mimetidae, probably the most specialised of the araneophagous spider families. If the web occupant approaches in the manner appropriate to dealing with ensnared prey, the predator attacks.

The foregoing examples present the Salticidae as textbook examples of active hunters; they would hardly seem likely to build webs other than those used in reproductive activities, and in fact, most species really do not build webs to catch prey. However, exceptions occur, though even those that do build capture webs generally also go hunting like other salticids. Some Portia species, for example, spin capture webs that are functional, though not as impressive as some orb webs of the Araneidae; Portia webs are of an unusual funnel shape and apparently adapted to the capture of other spiders. Spartaeus species, though, largely capture moths in their webs. In their review of the ethology of the Salticidae, Richman and Jackson speculate on whether such web building is a relic of the evolution of this family from web-building ancestors.

In hunting, the Salticidae also use their silk as a tether to enable them to reach prey that otherwise would be inaccessible. For example, by advancing towards the prey to less than the jumping distance, then retreating and leaping in an arc at the end of the tether line, many species can leap onto prey on vertical or even on inverted surfaces, which of course would not be possible without such a tether.

Having made contact with the prey, hunting Salticidae administer a bite to inject rapid-acting venom that gives the victim little time to react. In this respect, they resemble the Mimetidae and Thomisidae, families that ambush prey that often are larger than the predator, and they do so without securing the victim with silk; they accordingly must immobilise it immediately and their venom is adapted accordingly.

Diet
Although jumping spiders are generally carnivorous, many species have been known to include nectar in their diets, and one species, Bagheera kiplingi, feeds primarily on plant matter. None are known to feed on seeds or fruit. Extrafloral nectaries on plants, such as Chamaecrista fasciculata (partridge pea), provide jumping spiders with nectar; the plant benefits accordingly when the spiders prey on whatever pests they find.

The female of the Southeast Asian species Toxeus magnus feeds its offspring with a milky, nutritious fluid for the first 40 days of their lives.

Courtship and mating behavior
Jumping spiders conduct complex, visual courtship displays using movements and physical bodily attributes. A form of sexual dimorphism, the males possess plumose hairs, colored or iridescent hairs (particularly pronounced in the peacock spiders), front leg fringes, structures on other legs, and other, often bizarre, modifications. These characteristics are used in a courtship "dance" in which the colored or iridescent parts of the body are displayed. In addition to displaying colors, jumping spiders perform complex sliding, vibrational, or zigzag movements to attract females. Many males have auditory signals, as well. These amplified sounds presented to the females resemble buzzes or drum rolls. Species vary significantly in visual and vibratory components of courtship. The ability to sense UV light (see Vision section) is used by at least one species, Cosmophasis umbratica, in courtship behavior, though it is reasonable to assume that many other species exhibit this characteristic. Cosmophasis umbratica males have markings that are only visible in UV and the females use the markings for mate choice.

If receptive to the male, the female assumes a passive, crouching position. In some species, the female may vibrate her palps or abdomen. The male then extends his front legs towards the female to touch her. If the female remains receptive, the male climbs on her back and inseminates her with his palps.

Consequences of sexual dimorphism
Maintaining colorful ornamentation may seem strictly beneficial to sexual selection, yet costs to maintain such distinguishing characteristics occur. While colorful or UV-reflecting individuals may attract more female spiders, it can also increase the risk of predation.

Taxonomy
The monophyly of the family Salticidae is well established through both phylogenetic and morphological analyses. The sister group to Salticidae is the family Philodromidae. Synapomorphies of the two families include loss of cylindrical gland spigots and loss of tapeta in the indirect eyes.

A 2015 revision of the Salticidae family divided it into seven subfamilies:
 * Onomastinae Maddison, 2015 – 1 extant genus
 * Asemoneinae Maddison, 2015 – 4 extant genera (Hindumanes, originally placed here, was moved to Lyssomaninae )
 * Lyssomaninae Blackwall, 1877 – 4 extant genera (including Hindumanes)
 * Spartaeinae Wanless, 1984 – 29 extant genera in 3 tribes
 * Eupoinae Maddison, 2015 – 3 extant genera
 * Hisponinae Simon, 1901 – 6 extant genera
 * Salticinae Blackwall, 1841 – about 540 extant genera in 27 tribes

The Salticinae subfamily is the most diverse, comprising over 90% of the known species of jumping spiders.

Habitat
Jumping spiders live in a variety of habitats. Tropical forests harbor the most species, but they are also found in temperate forests, scrubland, deserts, intertidal zones, and mountainous regions. Euophrys omnisuperstes is the species reported to have been collected at the highest elevation, on the slopes of Mount Everest.

Models for mimicry
Some small insects are thought to have evolved an appearance or behavioural traits that resemble those of jumping spiders and this is suspected to prevent their predation, specifically from jumping spiders. Some examples appear to be provided by patterns on the wings of some tephritid flies, the nymph of a fulgorid and possibly some moths.

Fossils
Very few jumping spider fossils have been found. Of those known, all are from Cenozoic era amber. The oldest fossils are from Baltic amber dating to the Eocene epoch, specifically, 54 to 42 million years ago. Other fossil jumping spiders have been preserved within Chiapas amber and Dominican amber.

title: Jumping spider


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Talk:Prime meridian

Azores
The "List of historic prime meridians on Earth" gives the "Fortunate Isles / Azores" as 25° 40' 32″ W, but the map accompanying it shows the 32nd meridian west. This started with Revision as of 03:10, 23 February 2021. Should the map be brought into line with the text? Alekksandr (talk) 20:54, 16 May 2022 (UTC)
 * It looks to me like it was a mistake. Feel free to correct it. --Lasunncty (talk) 22:50, 16 May 2022 (UTC)

title: Talk:Prime meridian


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Wikipedia talk:Links to minor subjects

I'm not annoyed with this, not in the least. Ok, if Oola would be linked to from a zillion pages as a "See also" link, yes, that would be annoying. But if you wanted to say something like

 * Jerry Seinfeld could've played parts as important as Oola (you know, the Star Wars main character), were he not discovered by Margaret Thatcher.

then you can bet your life I would crave for that Oola link! :-D --Gutza 01:27 24 Jul 2003 (UTC)

 * It sounds like you're agreeing with me - links should only be made where they're highly relevant. :-) Evercat 01:29 24 Jul 2003 (UTC)

Shouldn't this be merged with make only links where relevant (?) and Build the web (?) and moved somewhere more memorable like link? We seem to be duplicating effort here... Martin 13:10 24 Jul 2003 (UTC)

 * make links only where relevant appears not to exist yet. It should.  I am going to remove the Idealist Press International link from List of American companies in accordance with the evolving standard, as it's an American company, just not important enough to be included in this list.  --Daniel C. Boyer 19:32 24 Jul 2003 (UTC)

 * I see this has already been done. Apologies.  --Daniel C. Boyer 19:33 24 Jul 2003 (UTC)

 * It does, I just got the name wrong. Martin

Hmm, possibly these 2 pages could be merged. But what I'm really complaining about is stuff like "See also: Yoism" in an article where such a link is really not useful but rather a sort of internal spamming. Whereas the page above is complaining about "unnecessary links like this" - not the same thing. Evercat 01:47 26 Jul 2003 (UTC)

Links to minor pages
Moved from Village pump on Saturday, August 2nd, 02003.

I was thinking, in regard to pages like Yoism, Idealist Press International, Ltd., and so on, that in cases of pages on (really) minor subjects, the pages themselves can be perfectly fine but links to them from major articles are what's really irritating.

I was wondering if this was enshrined in policy somewhere - by all means, create pages on minor subjects (though really, really minor ones may be deleted anyway) but avoid the temptation to link to them in such a way that they seem very important.

If it's not an official policy, it should be. :-) How about Links to minor subjects? Evercat 01:01 24 Jul 2003 (UTC)

 * This was kind of implied by the extended discussion of the neutral point of view policy that we nailed down (so long ago, it seems). However, making the point explicit can't hurt.

 * On this topic, there's been some mention of the "1000-person" or "5000-person" guideline for article inclusion (on the idea that if it's of relevance to less than that many people, we can't really write an article about it). Is this mentioned anywhere on the Wikipedia yet?  It's an interesting idea, and it would be nice to have guidelines  for "too obscure to be on Wikipedia.".  Some refinement would obviously be in order though... --Robert Merkel 04:46 24 Jul 2003 (UTC)

 * I threw out the idea a while back to see if it would stick, apparently it has. :-) I think I've pondered enough to write up a page now, I just hate to use up my precious article-writing time on meta-pages, and been putting it off. Stan 14:55 24 Jul 2003 (UTC)

 * I'm not sure I like this idea -- I think there are plenty of encyclopedic things known by fewer than 1000 people. For example, a lot of historical information in relatively obscure fields might fall into this category, or even some of the math pages on more specialized topics of which perhaps only 500 or so researchers in that particular field would be aware.  I don't see any reason these sorts of things shouldn't go in an encyclopedia though. --Delirium 00:48 25 Jul 2003 (UTC)

 * Wasn't it 1000 people affected rather than know about it? That would cover the obscure historical facts, most of which (I assume) affected at least that number. Where it leaves pure maths though is a problem. :-) Evercat 00:52 25 Jul 2003 (UTC)

Oola no longer a relevant example
Oola is no longer a relevant example for this page - it's now a redirect that points to Minor characters in Star Wars. Kevyn 06:45, 30 Aug 2004 (UTC)

 * Actually, it's now a page on a town in Ireland, with a dab link to the minor Star Wars page. zoney ♣ talk 19:23, 26 Sep 2004 (UTC)

Removed from page, another similar example may be needed:

 * For example, take the page Oola, which describes a fictional character from Star Wars so minor it is unlikely even devoted fans know her name. However, it is linked to from only one page, which gives a list of characters, even minor ones. As such, the link is perfectly appropriate. What would not be appropriate would be gratuitously linking to the page from articles where it would be by far the least important link.

 * To clarify, it is not the act of linking itself that is questionable, but rather the inclusion of relatively trivial information. If there was a page where mention of the character of Oola was relevant, then of course a link should exist (rather than an unlinked mention of her).

title: Wikipedia talk:Links to minor subjects


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Avant-garde music

Avant-garde music is music that is considered to be at the forefront of innovation in its field, with the term "avant-garde" implying a critique of existing aesthetic conventions, rejection of the status quo in favor of unique or original elements, and the idea of deliberately challenging or alienating audiences. Avant-garde music may be distinguished from experimental music by the way it adopts an extreme position within a certain tradition, whereas experimental music lies outside tradition.

Distinctions
Avant-garde music may be distinguished from experimental music by the way it adopts an extreme position within a certain tradition, whereas experimental music lies outside tradition. In a historical sense, some musicologists use the term "avant-garde music" for the radical compositions that succeeded the death of Anton Webern in 1945, but others disagree. For example, Ryan Minor writes that this period began with the work of Richard Wagner, whereas Edward Lowinsky cites Josquin des Prez. The term may also be used to refer to any post-1945 tendency of modernist music not definable as experimental music, though sometimes including a type of experimental music characterized by the rejection of tonality. A commonly cited example of avant-garde music is John Cage's 4'33" (1952), a piece which instructs the performer(s) not to play their instrument(s) during its entire duration. The piece has been described as "not a musical 'work' in the normal sense, only an occasion for a Zen-like meditation".

Although some modernist music is also avant-garde, a distinction can be made between the two categories. According to scholar Larry Sitsky, because the purpose of avant-garde music is necessarily political, social, and cultural critique, so that it challenges social and artistic values by provoking or goading audiences, composers such as Igor Stravinsky, Richard Strauss, Arnold Schoenberg, Anton Webern, George Antheil, and Claude Debussy may reasonably be considered to have been avant-gardists in their early works (which were understood as provocative, whether or not the composers intended them that way), but Sitsky does not consider the label appropriate for their later music. For example, modernists of the post–World War II period, such as Milton Babbitt, Luciano Berio, Elliott Carter, György Ligeti, and Witold Lutosławski, never conceived their music for the purpose of goading an audience and cannot, therefore, be classified as avant-garde. Composers such as John Cage and Harry Partch, on the contrary, remained avant-gardists throughout their creative careers.

A prominent feature of avant-garde music is to break through various rules and regulations of traditional culture, in order to transcend established creative principles and appreciation habits. Avant-garde music pursues novelty in musical form and style, insisting that art is above everything else; thus, it creates a transcendental and mysterious sound world. Hint, metaphor, symbol, association, imagery, synesthesia and perception are widely used in avant-garde music techniques to excavate the mystery of human heart and the flow of consciousness, so that many seemingly unrelated but essentially very important events interweave into multi-level structures and forms.

Popular music
Popular music, by definition, is designed for mass appeal. The 1960s saw a wave of avant-garde experimentation in jazz, represented by artists such as Ornette Coleman, Sun Ra, Albert Ayler, Archie Shepp, John Coltrane and Miles Davis. In the rock music of the 1970s, the "art" descriptor was generally understood to mean "aggressively avant-garde" or "pretentiously progressive". Post-punk artists from the late 1970s rejected traditional rock sensibilities in favor of an avant-garde aesthetic. In 1988 the writer Greg Tate described hip hop music as "the only avant-garde around, still delivering the shock of the new." The Beatles  song, Revolution 9, is one of the most popular examples of avant-garde music inspired pieces in popular music records. The song is the penultimate track to their 1968 album The Beatles (aka The White Album)

title: Avant-garde music