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Painters and Dockers are a rock band formed in Melbourne, Australia in 1982.
Paul Stewart, singer-songwriter and trumpet player,Dave Pace (vocals and trumpet) and Mick Morris (vocals and sax) are all original members in the band which was named for the Federated Ship Painters and Dockers Union when they performed an early gig at a pub rock venue in Port Melbourne frequented by the union's members.[1] Some members of the band went on to form the Dili Allstars.
Their best-performing album Kiss My Art, peaked in the top 30 of the Australian Recording Industry Association (ARIA) albums charts in 1988.[3] The album included two top 50 singles, "Nude School" and "Die Yuppie Die". In 2009, the band was inducted into the Music Victoria Hall of Fame.[6]
1982−1987: Beginnings, Love Planet and Bucket
Painters and Dockers formed in Melbourne, Australia in 1982 with five members, Vladimir Juric on guitars and backing vocals, Andy Marron on drums, Phil Nelson on bass guitar, Chris O'Connor on guitars and backing vocals, and mainstay Paul Stewart on lead vocals and trumpet.[1] One of the earliest gigs for the unnamed group was at a pub rock venue in Port Melbourne frequented by members of the Federated Ship Painters and Dockers Union so they chose Painters and Dockers for the event and retained the name thereafter.[1][7] In their earlier years, they were the headline act at the Port Melbourne Community Festival, and in a government initiative called Rockin' the Rails, where they played songs from the back of a train, as it stopped at various Melbourne stations, including Ringwood, Camberwell and Flinders Street.
Painters and Dockers' first recording, "Mohawk Baby", was released on independent label, Au Go Go records' compilation album, Asleep at the Wheel early in 1984.[1] Soon after, Marron was replaced by Colin Buckler on drums, and they released their debut album, Love Planet, which was produced by veteran hard rocker, Lobby Loyde and released on Big Time Records in 1984 and contained the tracks, "Basia!", also released as a single in March 1985, and "The Boy Who Lost His Jocks on Flinders Street Station". Joining after the album's release were Mick Morris on tenor saxophone and Dave Pace on trumpet / backing vocals, and with Stewart the horn section was called the Brassholes.[1] Music historian, Ian McFarlane, describes their sound as "adding an earthy R&B edge to the band's raucous, punk-infused power pop".[1]
A four-track EP, Kill Kill Kill was released in 1985 containing cover versions of "Kill Kill Kill" originally by The Sacred Cows on "The Groovy Guru" episode of US comedy TV series, Get Smart; Australian group Supernaut's "I Like it Both Ways"; The Ramones' "Do You Remember Rock'n'Roll Radio?" and The Saints' "Know Your Product".[1] Their first single, "Basia!", released in March 1985 on Big Time Records, was a paean to Basia Bonkowski—lyrics include "B she's so beautiful, A articulate too, S sensual, I international, Ay Ay" and "She's sitting there with her multi-coloured hair / She's sitting there with that multi-cultured stare"—who was presenter of SBS' music television show, Rock Around the World from 1982 to late 1984.
A live album, Bucket, released in October 1986 on the band's own label Dock Records (distributed by Shock Records) and Big Time Records, featured one of their live pub rock performances.
1988–1997: Kiss My Art, Touch One, Touch All and The Things that Matter
The band's second studio album, Kiss My Art, was released in August 1988 on White Label Records (a subsidiary of Mushroom Records) and peaked at No. 23 on the Australian Recording Industry Association (ARIA) albums charts in September 1988.[3] The album spawned four singles, "Nude School", "Die Yuppie Die", "Love on Your Breath" and "Safe Sex", and the first two achieved top 50 chart success.[4][5] and were accompanied with video clips directed by ex Hunters & Collectors Geoff Crosby.[9] The album was again produced by Lobby Loyde,[2] except for "Nude School" which was produced by Francois Taviaux aka Franswah.
Their third studio album, Touch One, Touch All, was released in December 1989 spawning the related singles, "Dirty Filthy Rock'n'Roll" in November, and "Eat Shit Die" in May 1990.[1] Neither album nor singles peaked into the top 50.[5] Morris left in 1989 and Darren Garth had replaced Juric on guitar by early 1990; the band undertook a Canadian tour promoting the album.
In December 1991 they released the mini-album, Hickory Dickory Dock with its track "Merry Christmas, Carol" and the single, "New World Order".[1] Nervous '90s appeared in June 1992 and contained six studio tracks and three live tracks recorded with the Salvation Army Brass Band.[1] During 1992 they became involved in Performers Releasing Information about Clean Syringes (PRICS), which included running workshops and gigs on safe sex and drug use.[1] In 1993, Garth left and Colin Badger joined on guitar and backing vocals, Painters and Dockers undertook the Australia-wide Return to the Love Planet tour and released a pro gay single, "I Know Better Queens than That".[1] The EP, Hickory Dickory Dock, and the album The Things that Matter were released in 1994.
1998–present: The Things that Matter
A mini-album, Advance Australia Where?, was released in August 1998 with the single "You're Going Home in the Back of a Divi Van".[1] By that stage, original members, Nelson and O'Connor had left, mainstay Stewart now with Badger and Buckler were joined by Paul Calvert on bass guitar, Sonja Parkinson on trombone and backing vocals, and Jenny Pineapple on saxophone and backing vocals.[1] This line-up appeared at Mushroom 25 Live concert in November to celebrate the record label's anniversary, their track "Divi Van" appeared on the related VHS release, Mushroom 25 Live: The Concert of the Century.[1]
In 2009 Stewart featured on the ABC Compass religious program following a liver transplant with the episode featuring Painters And Dockers songs Nude School and Die Yuppie Die. Stewart is actively involved in fundraising for the Alma Nuns, a Timorese-based Catholic order who care for disabled children and orphans.[
On 20 November 2009, early members, Paul Stewart, Chris O'Connor, Colin Buckler, Vladimir Juric, David Pace and Mick Morris, with Michael Badger (not an original member) reformed for a one-off show at the Prince Bandroom in St Kilda, Melbourne, where the band was inducted into Music Victoria's Hall of Fame.
In 2017, Painters and Dockers undertook their 30th Anniversary, Kiss My Art tour.
This sculpture is a reproduction of English artist Henry Moore’s mother and child abstract piece.
In my sculpture there are three recurring themes: mother with child; the reclining figure; large form protecting small form. In this sculpture I have united all three motifs. I draw on human feelings, on the primary feelings of man. The need of protection is one of these feelings or primary instincts.
~ Henry Moore quoted from an interview with Constanzo Costantini in Il Messagero, Rome, 10th April 1974
Reclining Connected Forms sculpture by Henry Moore is made of Roman travertine marble. It is located in The Park between ARIA Resort & Casino and Crystals retail and entertainment district. Henry Moore won the International Prize for Sculpture at the Venice Biennial in 1948. His signature form is a reclining figure of which he is said to have been influenced by the ancient cultures of Egypt and pre-Colombian Mexico.
Las Vegas: Aria - Henry Moore Sculpture
December 27, 2013, Aria Casino & Hotel, Las Vegas, Nevada.
The limestone forming Batu Caves is said to be around 400 million years old. Some of the cave entrances were used as shelters by the indigenous Temuan people (a tribe of Orang Asli).
As early as 1860, Chinese settlers began excavating guano for fertilising their vegetable patches. However, they became famous only after the limestone hills were recorded by colonial authorities including Daly and Syers as well as American Naturalist, William Hornaday in 1878.
Batu Caves was promoted as a place of worship by K. Thamboosamy Pillai, an Indian trader. He was inspired by the 'vel'-shaped entrance of the main cave and was inspired to dedicate a temple to Lord Murugan within the caves. In 1890, Pillai, who also founded the Sri Mahamariamman Temple, Kuala Lumpur, installed the murti (consecrated statue) of Sri Murugan Swami in what is today known as the Temple Cave. Since 1892, the Thaipusam festival in the Tamil month of Thai (which falls in late January/early February) has been celebrated there.
Wooden steps up to the Temple Cave were built in 1920 and have since been replaced by 272 concrete steps. Of the various cave temples that comprise the site, the largest and best known is the Temple Cave, so named because it houses several Hindu shrines beneath its high vaulted ceiling.
Curso de “Corte e Costura” ABECAO
As beneficiárias da Oficina de Corte e Costura da ABECAO estão colocando em prática as técnicas adquiridas nas aulas, confeccionando vários modelos de vestuários. O objetivo do curso visa resgatar este projeto de qualificação tradicional, ensinando as técnicas para confecção de vestuários de maneira clara, objetiva e completa de como cortar e costurar, promovendo a profissionalização da mão de obra prioritariamente às pessoas em risco social, formando profissionais atendendo a necessidade do mercado de trabalho, estimulando o desenvolvimento da criatividade com qualidade as alunas, Natalia Aparecida Silva Santos, Alessandra Carla da Silva, Aparecida Castanha Vieira, Elaine Pereira Gomes, Graziela Pereira Celestino, Lindalva Leite Melo Barboza, Maria Aparecida Olmedo, Rose Mara Domelas de Castro,Tassiana de Menezes da Silva, demonstra grande aptidão profissional como mostra as fotos, parabéns as alunas e a monitora Marlene Canhada.
4/9/2017 - Curso “A Importância da Formação Humanística do Magistrado – Uma comparação filosófica Europa/América Latina” - Emagis TRF4 - Foto: Sylvio Sirangelo/TRF4
Formado em 2000, o JAM Project é um grupo de cantores japoneses especializados em temas de animês (desenhos animados), tokusatsus (séries live-action) e jogos de videogames japoneses. É o principal expoente do gênero.
O objetivo do grupo é preservar as características originais do gênero musical, que desde a década de 90 tem a interferência do marketing da indústria fonográfica, envolvendo artistas do pop-rock japonês.
A formação atual é composta por Hironobu Kageyama, Masaaki Endoh, Masami Okui, Yoshiki Fukuyama, Hiroski Kitadani e Ricardo Cruz.
Apollo Bay formed its own Town Band towards the end of the First World War but it only lasted a few years.
Many of the members of the band were descendants of the original pioneers.
Back Row: Percival Thomas (Pos) CAWOOD, Edward Alfred (Eddie) NOSEDA, Roy Edgar CAWOOD, Alexander (Alec) CURRIE, Harold George MARTIN, Malcolm McPHEE
Sitting: Norman Noble TELFORD, Wilfred (Bill) MITCHELL, Jack DWYER, Lionel HALL, Jack HARRISON, George BROWN (Bandmaster), George HARRISON, Neil McPHEE, Malcolm THOMSON, Walter (Wattie) TELFORD
Standing Left Front:
Right Front: Stanley (Stan WRIGHT
Drummers: Bill SMITH, George EDWARDS
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Page d’aide sur l’homonymie
Pour les articles homonymes, voir Trou et Ver (homonymie).
Page d’aide sur les redirections
« Pont d'Einstein-Rosen » redirige ici. Pour les autres significations, voir Pont (homonymie).
Page d’aide sur l’homonymie
Ne doit pas être confondu avec un trou noir ni un trou blanc (fontaine blanche) ni le paradoxe d'Einstein-Podolsky-Rosen (EPR).
Exemple de trou de ver dans une métrique de Schwarzschild, tel qu'il serait vu par un observateur ayant franchi l'horizon du trou noir. La région d'où vient l'observateur est située à droite de l'image. Mise à part la région située près de l'ombre du trou noir, les effets de décalage vers le rouge gravitationnel rendent le fond du ciel très sombre. Celui-ci est en revanche très lumineux dans la seconde région, visible une fois l'horizon passé. Cette région ne sera cependant pas accessible, quelle que soit la trajectoire de l'observateur, car celui-ci est condamné à finir sur la singularité gravitationnelle en un temps relativement bref.
Schéma du principe du trou de ver.
Un trou de ver (en anglais : wormhole) est, en astrophysique, un objet hypothétique qui relierait deux feuillets distincts ou deux régions distinctes de l'espace-temps et se manifesterait, d'un côté, comme un trou noir et, de l'autre côté, comme un trou blanc1.
Un trou de ver formerait un raccourci à travers l'espace-temps. Pour le représenter plus simplement, on peut figurer l'espace-temps non en quatre dimensions mais en deux, à la manière d'un tapis ou d'une feuille de papier, dont la surface serait pliée sur elle-même dans un espace à trois dimensions. L'utilisation du raccourci « trou de ver » permettrait un voyage du point A directement au point B en un temps considérablement réduit par rapport au temps qu'il faudrait pour parcourir la distance séparant ces deux points de manière linéaire, à la surface de la feuille. Visuellement, il faut s'imaginer voyager non pas à la surface de la feuille de papier, mais à travers le trou de ver ; la feuille, étant repliée sur elle-même, permet au point A de toucher directement le point B, la rencontre des deux points correspondant au trou de ver.
L'utilisation d'un trou de ver permettrait théoriquement le voyage d'un point de l'espace à un autre (déplacement dans l'espace), le voyage d'un point à l'autre du temps (déplacement dans le temps), et le voyage d'un point de l'espace-temps à un autre (déplacement à travers l'espace et, simultanément, à travers le temps).
Les trous de ver sont des concepts purement théoriques : l'existence et la formation physique de tels objets dans l'Univers n'ont pas été vérifiées. Ils ne doivent pas être confondus avec les trous noirs, dont l'existence a été vérifiée en 2019 et dont le champ gravitationnel est si intense qu’il empêche toute forme de matière de s'en échapper.
Historique
Le physicien autrichien Ludwig Flamm (1885-1964) est parfois présenté comme étant le premier à avoir suggéré, dès 19162, l'existence des trous de ver. Mais la communauté scientifique s'accorde3 pour considérer que leur existence n'a été suggérée qu'en 1935, par Albert Einstein et Nathan Rosen4.
Les trous de ver (wormholes) doivent leur nom à Charles W. Misner et John A. Wheeler qui désignèrent ainsi en 1957 les propriétés de connexions des différents points de l'espace5. Le nom vient de l'analogie de l'asticot et de la pomme, symbole de la gravité depuis Isaac Newton : comme le ver, en rongeant la pomme, peut se rendre directement à un point diamétralement opposé, un vaisseau spatial pourrait utiliser le trou de ver, à la façon d'un raccourci, pour ressortir ailleurs dans l'espace et dans le temps6.
Quelques années plus tard à l’université Harvard, Stephen Hawking et Richard Coleman reprirent le concept de Wheeler et suggérèrent que l'espace-temps pouvait être soumis à l'effet tunnel précité, reprenant l'idée avancée par Hugh Everett. À l'instar des électrons qui peuvent sauter d'un point à l'autre de l'espace, l'Univers ferait de même. L'effet tunnel créerait des ouvertures dans l'espace-temps qui conduiraient à d'autres univers, des univers cul-de-sac ou tout aussi vastes que le nôtre.
En 2013, Juan Maldacena et Leonard Susskind ont proposé une conjecture qui établit un lien entre l'intrication quantique et le trou de ver7 : la conjecture ER=EPR8.
Présentation générale
Cette section ne cite pas suffisamment ses sources (octobre 2019).
Simulation d'un trou de ver permanent.
À l'heure actuelle, différents types de trous de ver ont été décrits de façon théorique :
le trou de ver de Schwarzschild, infranchissable ;
le trou de ver de Reissner-Nordstrøm ou de Kerr-Newman, franchissable mais dans un seul sens, pouvant contenir un trou de ver de Schwarzschild ;
le trou de ver de Lorentz à masse négative, franchissable dans les deux sens.
Tous sont des solutions mathématiques plutôt que des objets concrets.
Ont également été distingués des trous de ver à symétrie sphérique, tels ceux de Schwarzschild et de Reissner-Nordstrøm, qui ne sont pas en rotation, et des trous de ver tels ceux de Kerr-Newmann qui tournent sur eux-mêmes.
Si on essaie de fabriquer un trou de ver à partir de matière à masse positive, il explose et se désintègre. Si une matière à masse négative existe (matière exotique), on peut en principe élaborer un trou de ver statique en accumulant des masses négatives.[réf. souhaitée]
La théorie d'Einstein précise qu'on peut fabriquer n'importe quel type de géométrie spatio-temporelle, statique ou dynamique. Toutefois, une fois la géométrie définie, ce sont les équations d'Einstein qui diront quel devra être le tenseur énergie-impulsion de la matière pour obtenir cette géométrie spatiale. En général, les solutions de trous de ver statiques requièrent une masse négative.
Einstein et Rosen ont sérieusement suggéré que les singularités pouvaient mener à d'autres endroits de l'Univers, d'autres régions de l'espace et du temps. Ces connexions spatio-temporelles sont connues sous le nom de « ponts d'Einstein-Rosen ». Mais ni l'un ni l'autre n'entrevoyaient une possibilité d'entretenir ces connexions en raison du caractère instable des fluctuations quantiques. Selon la formule de John L. Friedman[Qui ?] de l'université de Californie à Santa Barbara, il s'agit d'une « censure topologique »[réf. nécessaire].
Ces trous de vers dits de Lorentz requièrent de la matière exotique pour rester ouverts car celle-ci demande moins d'énergie que le vide quantique, qui subit des fluctuations d'amplitude variables. Il peut s'agir d'énergie négative qui maintiendrait l'ouverture du trou de ver loin de l'horizon. L'ouverture elle-même présente une pression de surface positive [Négative?] qui la maintient ouverte durant les transferts et évite qu'elle ne s'effondre. Seulement, on ne sait comment stocker autant d'antimatière et suffisamment longtemps au même endroit pour entretenir ce tunnel dans l'espace-temps.[réf. nécessaire]
Vaisseau interstellaire empruntant un trou de ver (Vision d'artiste pour la NASA, 1998).
Pour approfondir les conséquences de la relativité générale, Kip Thorne et Richard Morris du Caltech ont tenté de découvrir par le biais de la physique quantique de nouvelles particules capables d'entretenir les trous de ver de Wheeler. Celles-ci ont fait apparaître d'hypothétiques « sas de liaisons » parcourus par des « voyageurs de Langevin ». La littérature de science-fiction s'en est grandement inspirée9.
Selon John Wheeler, deux singularités pourraient être reliées par un trou de ver, sorte de sas entre deux régions éloignées de l’univers. Entretenir un tel passage et lui donner une taille macroscopique reste un défi théorique. En effet ce « pont » est à l’échelle de Planck : il mesure 10−33 cm et est instable ; il se referme sur lui-même en l’espace de 10−43 s. Si on essaye de l’agrandir, il s'autodétruit. Le trou de ver appartient à la mousse quantique et obéit aux lois probabilistes.
Au contraire d’une singularité, un trou de ver est « nu », il demeure visible et, plus extraordinaire encore, il permet de voyager dans le temps en fonction du sens emprunté.
Exemple : le trou de ver de Morris-Thorne
Le trou de ver de Morris-Thorne (en anglais : Morris-Thorne wormhole)10 est un trou de ver traversable, décrit par la métrique du même nom.
Ses éponymes sont Michael S. Morris et Kip S. Thorne, qui ont publié leur solution en 198811,12 dans l'American Journal of Physics. Elle consiste en une adaptation du sujet de l'examen final d'un cours d'introduction à la relativité générale, donné au California Institute of Technology en 198513.
La métrique de Morris-Thorne s'écrit14,15 :
{\displaystyle \mathrm {d} s^{2}=-c^{2}\mathrm {d} t^{2}+\mathrm {d} l^{2}+\left(b_{0}^{2}+l^{2}\right)\left(\mathrm {d} \theta ^{2}+\sin ^{2}\theta \,\mathrm {d} \phi ^{2}\right)}{\displaystyle \mathrm {d} s^{2}=-c^{2}\mathrm {d} t^{2}+\mathrm {d} l^{2}+\left(b_{0}^{2}+l^{2}\right)\left(\mathrm {d} \theta ^{2}+\sin ^{2}\theta \,\mathrm {d} \phi ^{2}\right)},
où :
{\displaystyle \left(x^{\mu }\right)=\left(ct,l,\theta ,\phi \right)}{\displaystyle \left(x^{\mu }\right)=\left(ct,l,\theta ,\phi \right)} sont les coordonnées d'espace-temps :
{\displaystyle t}t est la coordonnée temporelle,
{\displaystyle l}l est la coordonnée radiale,
{\displaystyle \theta }\theta est la colatitude,
{\displaystyle \phi }\phi est la longitude,
{\displaystyle b_{0}^{2}}{\displaystyle b_{0}^{2}} est une constante,
{\displaystyle c}c est la vitesse de la lumière dans le vide.
En coordonnées de Schwarzschild, elle s'écrit16 :
{\displaystyle \mathrm {d} s^{2}=-c^{2}\mathrm {d} t^{2}+{\frac {\mathrm {d} r^{2}}{1-{\frac {b_{0}^{2}}{r^{2}}}}}+r^{2}\left(\mathrm {d} \theta ^{2}+\sin ^{2}\theta \,\mathrm {d} \phi ^{2}\right)}{\displaystyle \mathrm {d} s^{2}=-c^{2}\mathrm {d} t^{2}+{\frac {\mathrm {d} r^{2}}{1-{\frac {b_{0}^{2}}{r^{2}}}}}+r^{2}\left(\mathrm {d} \theta ^{2}+\sin ^{2}\theta \,\mathrm {d} \phi ^{2}\right)},
avec {\displaystyle r^{2}=b_{0}^{2}+l^{2}}{\displaystyle r^{2}=b_{0}^{2}+l^{2}}.
La « bouche » du trou de ver est une hypersurface ayant la topologie d'une sphère d'aire {\displaystyle A=4\pi \left(b_{0}^{2}+l^{2}\right)}{\displaystyle A=4\pi \left(b_{0}^{2}+l^{2}\right)}17.
La « gorge » du trou de ver est localisée en {\displaystyle l=0}{\displaystyle l=0}17.
Dans la fiction
Article détaillé : trou de ver dans la fiction.
Le concept des trous de ver est très utilisé dans la science-fiction pour autoriser le voyage dans l'espace, voire dans le temps. Il est souvent utilisé comme prétexte à la découverte de lieux inaccessibles par des moyens conventionnels, et donc à des rencontres avec diverses civilisations ou espèces inconnues. Voici des exemples d'œuvres traitant des trous de vers et de leur utilisation.
Littérature et bande dessinée
Dans la série des romans autour de Honor Harrington se passant dans l'Honorverse créé par David Weber, les trous de ver sont utilisés pour les trajets spatiaux et jouent un rôle important dans l'économie du royaume de Manticore.
Dans Lumière des jours enfuis, publié en 2000, Arthur C. Clarke et Stephen Baxter racontent qu'en 2033, une équipe de chercheurs parvient à transmettre des images par un trou de ver.
Dans la série de bande dessinée de science-fiction Universal War One, l’auteur, Denis Bajram, place la notion de trou de ver au centre de l’intrigue de son œuvre.
Dans la série La Saga du Commonwealth de Peter F. Hamilton, les trous de ver sont devenus, dans le futur, un moyen de transport courant pour se déplacer de planète en planète. Ils sont décrits comme étant très fins, composés d'énergie exotique et modulables en fonction de la quantité d'énergie utilisée pour les créer.
Cette notion est de plus en plus fréquente dans la littérature « Hard science-fiction » : on peut citer Stephen Baxter (Les Vaisseaux du temps, Retour sur Titan, Singularité) ou John Clute (Appleseed), qui offrent une approche romancée de la théorie. Ce concept se retrouve en particulier dans les romans de type néo space opéra. Dans la série de romans The Expanse écrite par Corey James S.A., un trou de ver fabriqué par une ancienne puissance extra-terrestre permet d'accéder à un espace vide entouré de trous de ver ouvrant sur des systèmes planétaires lointains.
Cinéma et séries télévisées
Dans la série Sliders, un tel passage est appelé par erreur « pont Einstein-Rosen-Podolski » au lieu de « ponts d’Einstein-Rosen », par confusion avec le paradoxe Einstein-Podolsky-Rosen, lequel n’a rien à voir avec les trous de ver. Curieusement, le nom est resté chez quelques vulgarisateurs. Podolsky a donc vu son nom associé à un objet particulier de la relativité générale sans avoir travaillé dans ce domaine.
Dans le film Contact est mentionnée une série de vortex appelée « pont d'Einstein-Rosen ».
Toute la série Farscape repose sur la découverte et la compréhension des trous de ver (wormholes en VO, vortex en VF), ceux-ci permettant de parcourir de très grandes distances, de voyager dans le temps et dans d’autres dimensions.
Dans Star Trek: Deep Space Nine, la traduction française utilise vortex pour le terme anglais wormhole, mais il s’agit bien d’un trou de ver utilisé pour voyager de et vers le Quadrant Gamma à 70 000 années-lumière de l'autre côté de la galaxie. La particularité de la station Deep Space Nine est d'être stratégiquement placée à proximité de ce trou de ver, d'où la grande importance de celui-ci dans la série.
Une porte des étoiles à Japan Expo 2009.
Une réplique de porte des étoiles à Japan Expo 2009.
Le film de science-fiction Stargate, la porte des étoiles et les séries Stargate SG-1, Stargate Atlantis et Stargate Universe font appel au concept de trou de ver. Un engin appelé porte des étoiles (en anglais stargate) y relie différentes planètes de l’univers en créant un trou de ver de Reissner-Nordstrøm (ou de Kerr-Newman) artificiel. Cependant un corps entier comme celui d'un homme ne survivrait pas au voyage dans le vortex, il est donc démolécularisé par la porte de départ et remolécularisé par la porte d'arrivée. En temps normal, la porte des étoiles ne permet pas de voyager dans le temps, sauf s'il y a un dysfonctionnement (dans un épisode, le vortex passe près d'une éruption solaire et est renvoyé vers la porte de départ mais dans une autre époque). De même, les trous de ver sont utilisés dans les séries Stargate pour faire traverser aux vaisseaux spatiaux de grandes distances en peu de temps en entrant en hyperespace, c'est-à-dire en créant un trou de ver de Reissner-Nordstrøm afin de voyager plus vite que la lumière.
Dans le film Donnie Darko, sorti en 2001, le trou de ver est un élément central permettant un voyage vers le passé.
Dans la série Fringe, l'un des personnages principaux crée un « pont d'Einstein-Rosen » pour voyager dans un univers alternatif. Cet acte sera cause de plusieurs autres trous de vers intempestifs dans les deux univers.
Dans le film Thor, le personnage de Jane Foster parle du Bifröst comme d'un Pont Einstein-Rosen.
Dans l'épisode Le Fantôme de Caliburn de la série Doctor Who, la femme disparue est en fait enfermée dans un univers en perdition, et le seul moyen d'y parvenir est d'utiliser un de ces trous de ver. Ces trous de ver sont aussi cités dans un autre épisode de cette série, L'Invasion des cubes : sept sont éparpillés sur Terre pour mener vers un vaisseau spatial en orbite autour de la planète, alors que des cubes sont envoyés pour arrêter les cœurs humains.
Dans le film Interstellar réalisé par Christopher Nolan et sorti en 2014, un des thèmes principaux est la théorie des trous de ver et son utilisation pour atteindre des planètes potentiellement colonisables situées à des années-lumière de la Terre. Le thème de la distorsion temporelle due à un trou noir y est également important.
Dans le film d'horreur Event Horizon de Paul W.S Anderson sorti en 1997, le système de propulsion du vaisseau est un prototype utilisant une singularité à l'aide d'un trou noir artificiel qui lui permet de créer son propre trou de ver. Ce concept est vulgarisé par le personnage incarné par Sam Neill à l'aide d'un poster érotique emprunté à un des membres de l'équipage.
Dans la série animée Voltron, le défenseur légendaire, les trous de vers sont associés à la magie altéenne[Quoi ?] et ne semblent pas obéir aux lois de la physique.
Dans la série Dark, le destin des protagonistes est influencé par l'existence d'un trou de ver permettant de voyager dans le temps, car le passé, le présent et le futur sont liés formant une boucle temporelle.
Dans la deuxième saison de Star Trek: Discovery, la combinaison temporelle du Dr Burnham permet de voyager dans l'espace-temps au moyen de trous de ver générés par un cristal temporel embarqué.
Dans la saison 6 de the 100 apparaît « l’anomalie » dont on apprend dans la saison 7 qu’il s’agit de trous de ver permettant de se déplacer entre différentes planètes où le temps ne s’écoule pas à la même vitesse (sanctum, Bardo, la terre, etc.) ces trous de ver sont générés par un dispositif appelé la pierre, couverte de symboles et inventée par une civilisation disparue après leur ascension. parfois critiquée, l’influence évidente de stargate marque le scénario de la saison 7 de the 100.
Dans le jeu vidéo Chernobylite, le trou de ver permet au personnage principal de voyager d'un endroit à un autre de la région de Tchernobyl.
Les voyages dans le temps
Article connexe : Voyage dans le temps.
Notes et références
Entrée « trou de ver », dans Richard Taillet, Loïc Villain et Pascal Febvre, Dictionnaire de physique, Bruxelles, De Boeck Université, 2008, XI-672 p. (ISBN 978-2-8041-5688-6, BNF 41256105, lire en ligne [archive]), p. 507.
(de) Ludwig Flamm, « Beiträge zur Einsteinschen Gravitationstheorie », Physikalische Zeitschrift, vol. 17, 1916, p. 448-454
(en) David Lindley, « Focus: The Birth of Wormholes », Physical Review, vol. 15, 2005 (DOI 10.1103/PhysRevFocus.15.11)
(en) Albert Einstein et Nathan Rosen, « The Particle Problem in the General Theory of Relativity », Physical Review, vol. 48, no 1, 1er juillet 1935, p. 73-77 (DOI 10.1103/PhysRev.48.73, Bibcode 1935PhRv...48...73E, lire en ligne [archive], consulté le 26 juillet 2014)
(en) Charles W. Misner et John A. Wheeler, « Classical physics as geometry », Annals of Physics, vol. 2, no 6, 1957, p. 525-603 (DOI 10.1016/0003-4916(57)90049-0).
Jean-Pierre Luminet, « Trou noir : la porte des étoiles ? » [archive], sur France Inter.fr, 21 août 2019 (consulté le 19 septembre 2020).
(en) Juan Martín Maldacena et Leonard Susskind, « Cool horizons for entangled black holes », Fortschritte der Physik (de), vol. 61, no 9, septembre 2013, p. 781-811 (DOI 10.1002/prop.201300020, Bibcode 2013ForPh..61..781M, arXiv 1306.0533, lire en ligne [archive] [PDF], consulté le 28 août 2014).
(en) Hrant Gharibyan et Robert F. Penna, « Are entangled particles connected by wormholes? Support for the ER=EPR conjecture from entropy inequalities », Physical Review D, vol. 89, no 6, mars 2014, p. 066001 (DOI 10.1103/PhysRevD.89.066001, Bibcode 2014PhRvD..89f6001G, arXiv 1308.0289, lire en ligne [archive] [PDF], consulté le 28 août 2014).
« Voyage au centre d'un trou de ver » [archive], sur Astrosurf (consulté le 26 octobre 2019).
Müller 2008, résumé, p. 1.
Müller 2008, I, p. 1, col. 1.
Morris et Thorne 1988.
Morris et Thorne 1988, I, C, p. 398, col. 1.
Müller 2008, II, p. 2, col. 1 (1).
Morris et Thorne 1988, p. 398 (B2a).
Müller 2008, II, p. 2, col. 1 (2).
Müller 2008, II, p. 2, col. 1.
Annexes
Sur les autres projets Wikimedia :
Trou de ver, sur Wikimedia Commons
trou de ver, sur le Wiktionnaire
Bibliographie
(en) Andrew DeBenedictis et A. Das, « On a General Class of Wormhole Geometries », Classical and Quantum Gravity, vol. 18, no 7, 2001, p. 1187-1204 (DOI 10.1088/0264-9381/18/7/304, Bibcode 2001CQGra..18.1187D, arXiv 0009072).
Stephen Hawking, Une brève histoire du temps. Du Big Bang aux trous noirs, Flammarion, 2005.
Stephen Hawking et Roger Penrose, La nature de l'espace et du temps, Gallimard, 2003.
Stephen Hawking, Trous noirs et bébés univers et autres essais, Odile Jacob, 2000.
Kip S. Thorne, Trous noirs et distorsions du temps : l'héritage sulfureux d'Einstein, trad. Alain Bouquet et Jean Kaplan, Flammarion, 2009. Avec une préface de Stephen Hawking. (ISBN 978-2081224964)
M. Begelmen et M. Rees, Gravity’s Fatal Attraction : Black Holes in the Universe, W.H.Freeman, 1996.
(en) Stuart L. Shapiro et Saul A. Teukolsky, « Formation of naked singularities: The violation of cosmic censorship », Physical Review Letters, vol. 66, no 8, 25 février 1991, p. 994–997 (DOI 10.1103/PhysRevLett.66.994, lire en ligne [archive], consulté le 26 octobre 2019).
(en) Stuart L. Shapiro et Saul A. Teukolsky, « Building Black Holes: Supercomputer Cinema », Science, vol. 241, no 4864, 22 juillet 1988, p. 421–425 (ISSN 0036-8075 et 1095-9203, PMID 17792605, DOI 10.1126/science.241.4864.421, lire en ligne [archive], consulté le 26 octobre 2019).
(en) Michael S. Morris, Kip Thorne et Ulvi Yurtsever, « Wormholes, Time Machines, and the Weak Energy Condition », Physical Review Letters, vol. 61, no 13, 26 septembre 1988, p. 1446-1449 (DOI 10.1103/PhysRevLett.61.1446, Bibcode 1988PhRvL..61.1446M, lire en ligne [archive] [PDF], consulté le 29 août 2014)
H. Everett III, Reviews of Modern Physics, 29, 1958, p. 454[réf. incomplète].
Mika - "Akimmik" 1992 - p. 415-712[réf. incomplète].
(en) Thomas A. Roman, « Some thoughts on energy conditions and wormholes », The Tenth Marcel Grossmann Meeting, février 2006 (DOI 10.1142/9789812704030_0236, Bibcode 2006tmgm.meet.1909R, arXiv gr-qc/0409090, lire en ligne [archive] [PDF], consulté le 29 août 2014)
(en) Edward Teo, « Rotating traversable wormholes », Physical Review D, vol. 58, no 2, 15 juillet 1998 (DOI 10.1103/PhysRevD.58.024014, Bibcode 1998PhRvD..58b4014T, arXiv gr-qc/9803098, lire en ligne [archive] [PDF], consulté le 29 août 2014)
(en) Matt Visser, « Traversable wormholes: Some simple examples », Physical Review D, vol. 39, no 10, 15 mai 1989, p. 3182-3184 (DOI 10.1103/PhysRevD.39.3182, Bibcode 1989PhRvD..39.3182V, arXiv 0809.0907, lire en ligne [archive] [PDF], consulté le 29 août 2014)
(en) Léo-Paul Euvé et Germain Rousseaux, « Classical analogue of an interstellar travel through a hydrodynamic wormhole », Physical Review D, vol. 96, no 6, 25 septembre 2017 (DOI 10.1103/PhysRevD.96.064042)
[Taillet, Villain et Febvre 2013] R. Taillet, L. Villain et P. Febvre, Dictionnaire de physique, Louvain-la-Neuve, De Boeck Sup., hors coll., février 2013 (réimpr. 2015), 3e éd. (1re éd. mai 2008), X-899 p., ill. et fig., 17 × 24 cm (ISBN 978-2-8041-7554-2, EAN 9782804175542, OCLC 842156166, BNF 43541671, SUDOC 167932349, présentation en ligne [archive], lire en ligne [archive]), s.v.trou de ver, p. 701, col. 1.
Sur le trou de ver de Morris-Thorne
[Ellis 1973] (en) H. G. Ellis, « Ether flow through a drainhole : a particle model in general relativity », J. Math. Phys., vol. 14, no 1, janvier 1973, p. 104-118, article no 16 (OCLC 5542485827, DOI 10.1063/1.1666161, Bibcode 1973JMP....14..104E, résumé [archive], lire en ligne [archive]).
[Bronnikov 1973] (en) K. A. Bronnikov, « Scalar-tensor theory and scalar charge », Acta Phys. Pol. B (en), vol. 4, nos 3-4, mars-avril 1973, p. 251-266, article no 10 (OCLC 4434848908, lire en ligne [archive]).
[Morris et Thorne 1988] (en) M. S. Morris et K. S Thorne, « Wormholes in spacetime and their use for interstellar travel : A tool for teaching general relativity » [« Les trous de ver dans l'espace-temps et leur utilisation pour les voyages interstellaires : un outil d'enseignement de la relativité générale »], American Journal of Physics, vol. 56, no 5, mai 1988, p. 395-412, article no 1 (OCLC 4660684580, DOI 10.1119/1.15620, Bibcode 1988AmJPh..56..395M, résumé [archive], lire en ligne [archive] [PDF]).
[Müller 2008] (en) Th. Müller, « Exact geometric optics in a Morris-Thorne wormhole spacetime », Physical Review D, vol. 77, no 4, février 2008, p. 2e part. (OCLC 4631578262, DOI 10.1103/PhysRevD.77.044043, Bibcode 2008PhRvD..77d4043M, résumé [archive], lire en ligne [archive] [PDF]).
[James, Tunzelmann, Franklin et Thorne 2015] (en) O. James, E. v. Tunzelmann, P. Franklin et K. S Thorne, « Visualizing Interstellar's wormhole » [« Visualiser le trou de ver d'Interstellar »], American Journal of Physics, vol. 83, no 6, juin 2015, article no 1 pages= (OCLC 5856563581, DOI 10.1119/1.4916949, Bibcode 2015AmJPh..83..486J, arXiv 1502.03809, résumé [archive], lire en ligne [archive] [PDF]).
[Deza et Deza 2014] (en) M. M. Deza et E. Deza, Encyclopedia of distances [« Encyclopédie des distances »], Heidelberg, Springer, octobre 2014, 3e éd. (1re éd. mai 2009), XX-733 p., ill. et portr., 25 cm (ISBN 978-3-662-44341-5, EAN 9783662443415, OCLC 898123993, DOI 10.1007/978-3-662-44342-2, SUDOC 182433501, présentation en ligne [archive], lire en ligne [archive]), VIe part., chap. 26, § 26.2, s.v.Morris–Thorne metric [« Métrique de Morris-Thorne »], p. 580.
Articles connexes
Trou noir
Espace-temps
Voyage dans le temps
Liens externes
Notices d'autorité : Bibliothèque nationale de France (données)Système universitaire de documentationBibliothèque du CongrèsGemeinsame NormdateiBibliothèque nationale d’Israël
Notices dans des dictionnaires ou encyclopédies généralistes : Encyclopædia Britannica [archive]Store norske leksikon [archive]
Ressource relative à la littérature : (en) The Encyclopedia of Science Fiction [archive]
(fr) Un lien possible entre les trous de ver et l'intrication quantique [archive] a été découvert en 2013.
(en) White holes and Wormholes [archive], Andrew Hamilton, Université du Colorado
(en) Des méta matériaux permettent d'émuler un trou de ver, selon la théorie d'alcubierre jusqu'à 25 % de la vitesse de la lumière [archive]
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v · m
Trou noir
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Colonisation de l'espace Bon article
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Science-fiction
icône décorative Portail de la cosmologie icône décorative Portail de la physique icône décorative Portail de l’astronomie icône décorative Portail de la science-fiction
Catégories : Relativité généraleConcept de la science-fictionVitesse supraluminiqueMatière exotiqueVer dans la culture[+]
Molecule formed by an open back triangle twist, with the three arms pleated in 3D shape.
EH paper and 32 division grid.
Molécula formada por un giro triangular abierto, con sus tres brazos plegados en forma tridimensional.
Papel EH y trama de 32 divisiones.
This is inside one of the casting forms for a pontoons that will support a new floating bridge across Lake Washington. Showing the scale of this project in a photo is challenging, but there's room to play football inside these walls:
Fish, any of approximately 34,000 species of vertebrate animals (phylum Chordata) found in the fresh and salt waters of the world. Living species range from the primitive jawless lampreys and hagfishes through the cartilaginous sharks, skates, and rays to the abundant and diverse bony fishes. Most fish species are cold-blooded; however, one species, the opah (Lampris guttatus), is warm-blooded.
The term fish is applied to a variety of vertebrates of several evolutionary lines. It describes a life-form rather than a taxonomic group. As members of the phylum Chordata, fish share certain features with other vertebrates. These features are gill slits at some point in the life cycle, a notochord, or skeletal supporting rod, a dorsal hollow nerve cord, and a tail. Living fishes represent some five classes, which are as distinct from one another as are the four classes of familiar air-breathing animals—amphibians, reptiles, birds, and mammals. For example, the jawless fishes (Agnatha) have gills in pouches and lack limb girdles. Extant agnathans are the lampreys and the hagfishes. As the name implies, the skeletons of fishes of the class Chondrichthyes (from chondr, “cartilage,” and ichthyes, “fish”) are made entirely of cartilage. Modern fish of this class lack a swim bladder, and their scales and teeth are made up of the same placoid material. Sharks, skates, and rays are examples of cartilaginous fishes. The bony fishes are by far the largest class. Examples range from the tiny seahorse to the 450-kg (1,000-pound) blue marlin, from the flattened soles and flounders to the boxy puffers and ocean sunfishes. Unlike the scales of the cartilaginous fishes, those of bony fishes, when present, grow throughout life and are made up of thin overlapping plates of bone. Bony fishes also have an operculum that covers the gill slits.
The study of fishes, the science of ichthyology, is of broad importance. Fishes are of interest to humans for many reasons, the most important being their relationship with and dependence on the environment. A more obvious reason for interest in fishes is their role as a moderate but important part of the world’s food supply. This resource, once thought unlimited, is now realized to be finite and in delicate balance with the biological, chemical, and physical factors of the aquatic environment. Overfishing, pollution, and alteration of the environment are the chief enemies of proper fisheries management, both in fresh waters and in the ocean. (For a detailed discussion of the technology and economics of fisheries, see commercial fishing.) Another practical reason for studying fishes is their use in disease control. As predators on mosquito larvae, they help curb malaria and other mosquito-borne diseases.
Fishes are valuable laboratory animals in many aspects of medical and biological research. For example, the readiness of many fishes to acclimate to captivity has allowed biologists to study behaviour, physiology, and even ecology under relatively natural conditions. Fishes have been especially important in the study of animal behaviour, where research on fishes has provided a broad base for the understanding of the more flexible behaviour of the higher vertebrates. The zebra fish is used as a model in studies of gene expression.
There are aesthetic and recreational reasons for an interest in fishes. Millions of people keep live fishes in home aquariums for the simple pleasure of observing the beauty and behaviour of animals otherwise unfamiliar to them. Aquarium fishes provide a personal challenge to many aquarists, allowing them to test their ability to keep a small section of the natural environment in their homes. Sportfishing is another way of enjoying the natural environment, also indulged in by millions of people every year. Interest in aquarium fishes and sportfishing supports multimillion-dollar industries throughout the world.
Fishes have been in existence for more than 450 million years, during which time they have evolved repeatedly to fit into almost every conceivable type of aquatic habitat. In a sense, land vertebrates are simply highly modified fishes: when fishes colonized the land habitat, they became tetrapod (four-legged) land vertebrates. The popular conception of a fish as a slippery, streamlined aquatic animal that possesses fins and breathes by gills applies to many fishes, but far more fishes deviate from that conception than conform to it. For example, the body is elongate in many forms and greatly shortened in others; the body is flattened in some (principally in bottom-dwelling fishes) and laterally compressed in many others; the fins may be elaborately extended, forming intricate shapes, or they may be reduced or even lost; and the positions of the mouth, eyes, nostrils, and gill openings vary widely. Air breathers have appeared in several evolutionary lines.
Many fishes are cryptically coloured and shaped, closely matching their respective environments; others are among the most brilliantly coloured of all organisms, with a wide range of hues, often of striking intensity, on a single individual. The brilliance of pigments may be enhanced by the surface structure of the fish, so that it almost seems to glow. A number of unrelated fishes have actual light-producing organs. Many fishes are able to alter their coloration—some for the purpose of camouflage, others for the enhancement of behavioral signals.
Fishes range in adult length from less than 10 mm (0.4 inch) to more than 20 metres (60 feet) and in weight from about 1.5 grams (less than 0.06 ounce) to many thousands of kilograms. Some live in shallow thermal springs at temperatures slightly above 42 °C (100 °F), others in cold Arctic seas a few degrees below 0 °C (32 °F) or in cold deep waters more than 4,000 metres (13,100 feet) beneath the ocean surface. The structural and, especially, the physiological adaptations for life at such extremes are relatively poorly known and provide the scientifically curious with great incentive for study.
Almost all natural bodies of water bear fish life, the exceptions being very hot thermal ponds and extremely salt-alkaline lakes, such as the Dead Sea in Asia and the Great Salt Lake in North America. The present distribution of fishes is a result of the geological history and development of Earth as well as the ability of fishes to undergo evolutionary change and to adapt to the available habitats. Fishes may be seen to be distributed according to habitat and according to geographical area. Major habitat differences are marine and freshwater. For the most part, the fishes in a marine habitat differ from those in a freshwater habitat, even in adjacent areas, but some, such as the salmon, migrate from one to the other. The freshwater habitats may be seen to be of many kinds. Fishes found in mountain torrents, Arctic lakes, tropical lakes, temperate streams, and tropical rivers will all differ from each other, both in obvious gross structure and in physiological attributes. Even in closely adjacent habitats where, for example, a tropical mountain torrent enters a lowland stream, the fish fauna will differ. The marine habitats can be divided into deep ocean floors (benthic), mid-water oceanic (bathypelagic), surface oceanic (pelagic), rocky coast, sandy coast, muddy shores, bays, estuaries, and others. Also, for example, rocky coastal shores in tropical and temperate regions will have different fish faunas, even when such habitats occur along the same coastline.
Although much is known about the present geographical distribution of fishes, far less is known about how that distribution came about. Many parts of the fish fauna of the fresh waters of North America and Eurasia are related and undoubtedly have a common origin. The faunas of Africa and South America are related, extremely old, and probably an expression of the drifting apart of the two continents. The fauna of southern Asia is related to that of Central Asia, and some of it appears to have entered Africa. The extremely large shore-fish faunas of the Indian and tropical Pacific oceans comprise a related complex, but the tropical shore fauna of the Atlantic, although containing Indo-Pacific components, is relatively limited and probably younger. The Arctic and Antarctic marine faunas are quite different from each other. The shore fauna of the North Pacific is quite distinct, and that of the North Atlantic more limited and probably younger. Pelagic oceanic fishes, especially those in deep waters, are similar the world over, showing little geographical isolation in terms of family groups. The deep oceanic habitat is very much the same throughout the world, but species differences do exist, showing geographical areas determined by oceanic currents and water masses.
All aspects of the life of a fish are closely correlated with adaptation to the total environment, physical, chemical, and biological. In studies, all the interdependent aspects of fish, such as behaviour, locomotion, reproduction, and physical and physiological characteristics, must be taken into account.
Correlated with their adaptation to an extremely wide variety of habitats is the extremely wide variety of life cycles that fishes display. The great majority hatch from relatively small eggs a few days to several weeks or more after the eggs are scattered in the water. Newly hatched young are still partially undeveloped and are called larvae until body structures such as fins, skeleton, and some organs are fully formed. Larval life is often very short, usually less than a few weeks, but it can be very long, some lampreys continuing as larvae for at least five years. Young and larval fishes, before reaching sexual maturity, must grow considerably, and their small size and other factors often dictate that they live in a habitat different than that of the adults. For example, most tropical marine shore fishes have pelagic larvae. Larval food also is different, and larval fishes often live in shallow waters, where they may be less exposed to predators.
After a fish reaches adult size, the length of its life is subject to many factors, such as innate rates of aging, predation pressure, and the nature of the local climate. The longevity of a species in the protected environment of an aquarium may have nothing to do with how long members of that species live in the wild. Many small fishes live only one to three years at the most. In some species, however, individuals may live as long as 10 or 20 or even 100 years.
Fish behaviour is a complicated and varied subject. As in almost all animals with a central nervous system, the nature of a response of an individual fish to stimuli from its environment depends upon the inherited characteristics of its nervous system, on what it has learned from past experience, and on the nature of the stimuli. Compared with the variety of human responses, however, that of a fish is stereotyped, not subject to much modification by “thought” or learning, and investigators must guard against anthropomorphic interpretations of fish behaviour.
Fishes perceive the world around them by the usual senses of sight, smell, hearing, touch, and taste and by special lateral line water-current detectors. In the few fishes that generate electric fields, a process that might best be called electrolocation aids in perception. One or another of these senses often is emphasized at the expense of others, depending upon the fish’s other adaptations. In fishes with large eyes, the sense of smell may be reduced; others, with small eyes, hunt and feed primarily by smell (such as some eels).
Specialized behaviour is primarily concerned with the three most important activities in the fish’s life: feeding, reproduction, and escape from enemies. Schooling behaviour of sardines on the high seas, for instance, is largely a protective device to avoid enemies, but it is also associated with and modified by their breeding and feeding requirements. Predatory fishes are often solitary, lying in wait to dart suddenly after their prey, a kind of locomotion impossible for beaked parrot fishes, which feed on coral, swimming in small groups from one coral head to the next. In addition, some predatory fishes that inhabit pelagic environments, such as tunas, often school.
Sleep in fishes, all of which lack true eyelids, consists of a seemingly listless state in which the fish maintains its balance but moves slowly. If attacked or disturbed, most can dart away. A few kinds of fishes lie on the bottom to sleep. Most catfishes, some loaches, and some eels and electric fishes are strictly nocturnal, being active and hunting for food during the night and retiring during the day to holes, thick vegetation, or other protective parts of the environment.
Communication between members of a species or between members of two or more species often is extremely important, especially in breeding behaviour (see below Reproduction). The mode of communication may be visual, as between the small so-called cleaner fish and a large fish of a very different species. The larger fish often allows the cleaner to enter its mouth to remove gill parasites. The cleaner is recognized by its distinctive colour and actions and therefore is not eaten, even if the larger fish is normally a predator. Communication is often chemical, signals being sent by specific chemicals called pheromones.
Many fishes have a streamlined body and swim freely in open water. Fish locomotion is closely correlated with habitat and ecological niche (the general position of the animal to its environment).
Many fishes in both marine and fresh waters swim at the surface and have mouths adapted to feed best (and sometimes only) at the surface. Often such fishes are long and slender, able to dart at surface insects or at other surface fishes and in turn to dart away from predators; needlefishes, halfbeaks, and topminnows (such as killifish and mosquito fish) are good examples. Oceanic flying fishes escape their predators by gathering speed above the water surface, with the lower lobe of the tail providing thrust in the water. They then glide hundreds of yards on enlarged, winglike pectoral and pelvic fins. South American freshwater flying fishes escape their enemies by jumping and propelling their strongly keeled bodies out of the water.
So-called mid-water swimmers, the most common type of fish, are of many kinds and live in many habitats. The powerful fusiform tunas and the trouts, for example, are adapted for strong, fast swimming, the tunas to capture prey speedily in the open ocean and the trouts to cope with the swift currents of streams and rivers. The trout body form is well adapted to many habitats. Fishes that live in relatively quiet waters such as bays or lake shores or slow rivers usually are not strong, fast swimmers but are capable of short, quick bursts of speed to escape a predator. Many of these fishes have their sides flattened, examples being the sunfish and the freshwater angelfish of aquarists. Fish associated with the bottom or substrate usually are slow swimmers. Open-water plankton-feeding fishes almost always remain fusiform and are capable of rapid, strong movement (for example, sardines and herrings of the open ocean and also many small minnows of streams and lakes).
Bottom-living fishes are of many kinds and have undergone many types of modification of their body shape and swimming habits. Rays, which evolved from strong-swimming mid-water sharks, usually stay close to the bottom and move by undulating their large pectoral fins. Flounders live in a similar habitat and move over the bottom by undulating the entire body. Many bottom fishes dart from place to place, resting on the bottom between movements, a motion common in gobies. One goby relative, the mudskipper, has taken to living at the edge of pools along the shore of muddy mangrove swamps. It escapes its enemies by flipping rapidly over the mud, out of the water. Some catfishes, synbranchid eels, the so-called climbing perch, and a few other fishes venture out over damp ground to find more promising waters than those that they left. They move by wriggling their bodies, sometimes using strong pectoral fins; most have accessory air-breathing organs. Many bottom-dwelling fishes live in mud holes or rocky crevices. Marine eels and gobies commonly are found in such habitats and for the most part venture far beyond their cavelike homes. Some bottom dwellers, such as the clingfishes (Gobiesocidae), have developed powerful adhesive disks that enable them to remain in place on the substrate in areas such as rocky coasts, where the action of the waves is great.
The methods of reproduction in fishes are varied, but most fishes lay a large number of small eggs, fertilized and scattered outside of the body. The eggs of pelagic fishes usually remain suspended in the open water. Many shore and freshwater fishes lay eggs on the bottom or among plants. Some have adhesive eggs. The mortality of the young and especially of the eggs is very high, and often only a few individuals grow to maturity out of hundreds, thousands, and in some cases millions of eggs laid.
Males produce sperm, usually as a milky white substance called milt, in two (sometimes one) testes within the body cavity. In bony fishes a sperm duct leads from each testis to a urogenital opening behind the vent or anus. In sharks and rays and in cyclostomes the duct leads to a cloaca. Sometimes the pelvic fins are modified to help transmit the milt to the eggs at the female’s vent or on the substrate where the female has placed them. Sometimes accessory organs are used to fertilize females internally—for example, the claspers of many sharks and rays.
In the females the eggs are formed in two ovaries (sometimes only one) and pass through the ovaries to the urogenital opening and to the outside. In some fishes the eggs are fertilized internally but are shed before development takes place. Members of about a dozen families each of bony fishes (teleosts) and sharks bear live young. Many skates and rays also bear live young. In some bony fishes the eggs simply develop within the female, the young emerging when the eggs hatch (ovoviviparous). Others develop within the ovary and are nourished by ovarian tissues after hatching (viviparous). There are also other methods utilized by fishes to nourish young within the female. In all live-bearers the young are born at a relatively large size and are few in number. In one family of primarily marine fishes, the surfperches from the Pacific coast of North America, Japan, and Korea, the males of at least one species are born sexually mature, although they are not fully grown.
Some fishes are hermaphroditic—an individual producing both sperm and eggs, usually at different stages of its life. Self-fertilization, however, is probably rare.
Successful reproduction and, in many cases, defense of the eggs and the young are assured by rather stereotypical but often elaborate courtship and parental behaviour, either by the male or the female or both. Some fishes prepare nests by hollowing out depressions in the sand bottom (cichlids, for example), build nests with plant materials and sticky threads excreted by the kidneys (sticklebacks), or blow a cluster of mucus-covered bubbles at the water surface (gouramis). The eggs are laid in these structures. Some varieties of cichlids and catfishes incubate eggs in their mouths.
Some fishes, such as salmon, undergo long migrations from the ocean and up large rivers to spawn in the gravel beds where they themselves hatched (anadromous fishes). Some, such as the freshwater eels (family Anguillidae), live and grow to maturity in fresh water and migrate to the sea to spawn (catadromous fishes). Other fishes undertake shorter migrations from lakes into streams, within the ocean, or enter spawning habitats that they do not ordinarily occupy in other ways.
The basic structure and function of the fish body are similar to those of all other vertebrates. The usual four types of tissues are present: surface or epithelial, connective (bone, cartilage, and fibrous tissues, as well as their derivative, blood), nerve, and muscle tissues. In addition, the fish’s organs and organ systems parallel those of other vertebrates.
The typical fish body is streamlined and spindle-shaped, with an anterior head, a gill apparatus, and a heart, the latter lying in the midline just below the gill chamber. The body cavity, containing the vital organs, is situated behind the head in the lower anterior part of the body. The anus usually marks the posterior termination of the body cavity and most often occurs just in front of the base of the anal fin. The spinal cord and vertebral column continue from the posterior part of the head to the base of the tail fin, passing dorsal to the body cavity and through the caudal (tail) region behind the body cavity. Most of the body is of muscular tissue, a high proportion of which is necessitated by swimming. In the course of evolution this basic body plan has been modified repeatedly into the many varieties of fish shapes that exist today.
The skeleton forms an integral part of the fish’s locomotion system, as well as serving to protect vital parts. The internal skeleton consists of the skull bones (except for the roofing bones of the head, which are really part of the external skeleton), the vertebral column, and the fin supports (fin rays). The fin supports are derived from the external skeleton but will be treated here because of their close functional relationship to the internal skeleton. The internal skeleton of cyclostomes, sharks, and rays is of cartilage; that of many fossil groups and some primitive living fishes is mostly of cartilage but may include some bone. In place of the vertebral column, the earliest vertebrates had a fully developed notochord, a flexible stiff rod of viscous cells surrounded by a strong fibrous sheath. During the evolution of modern fishes the rod was replaced in part by cartilage and then by ossified cartilage. Sharks and rays retain a cartilaginous vertebral column; bony fishes have spool-shaped vertebrae that in the more primitive living forms only partially replace the notochord. The skull, including the gill arches and jaws of bony fishes, is fully, or at least partially, ossified. That of sharks and rays remains cartilaginous, at times partially replaced by calcium deposits but never by true bone.
The supportive elements of the fins (basal or radial bones or both) have changed greatly during fish evolution. Some of these changes are described in the section below (Evolution and paleontology). Most fishes possess a single dorsal fin on the midline of the back. Many have two and a few have three dorsal fins. The other fins are the single tail and anal fins and paired pelvic and pectoral fins. A small fin, the adipose fin, with hairlike fin rays, occurs in many of the relatively primitive teleosts (such as trout) on the back near the base of the caudal fin.
The skin of a fish must serve many functions. It aids in maintaining the osmotic balance, provides physical protection for the body, is the site of coloration, contains sensory receptors, and, in some fishes, functions in respiration. Mucous glands, which aid in maintaining the water balance and offer protection from bacteria, are extremely numerous in fish skin, especially in cyclostomes and teleosts. Since mucous glands are present in the modern lampreys, it is reasonable to assume that they were present in primitive fishes, such as the ancient Silurian and Devonian agnathans. Protection from abrasion and predation is another function of the fish skin, and dermal (skin) bone arose early in fish evolution in response to this need. It is thought that bone first evolved in skin and only later invaded the cartilaginous areas of the fish’s body, to provide additional support and protection. There is some argument as to which came first, cartilage or bone, and fossil evidence does not settle the question. In any event, dermal bone has played an important part in fish evolution and has different characteristics in different groups of fishes. Several groups are characterized at least in part by the kind of bony scales they possess.
Scales have played an important part in the evolution of fishes. Primitive fishes usually had thick bony plates or thick scales in several layers of bone, enamel, and related substances. Modern teleost fishes have scales of bone, which, while still protective, allow much more freedom of motion in the body. A few modern teleosts (some catfishes, sticklebacks, and others) have secondarily acquired bony plates in the skin. Modern and early sharks possessed placoid scales, a relatively primitive type of scale with a toothlike structure, consisting of an outside layer of enamel-like substance (vitrodentine), an inner layer of dentine, and a pulp cavity containing nerves and blood vessels. Primitive bony fishes had thick scales of either the ganoid or the cosmoid type. Cosmoid scales have a hard, enamel-like outer layer, an inner layer of cosmine (a form of dentine), and then a layer of vascular bone (isopedine). In ganoid scales the hard outer layer is different chemically and is called ganoin. Under this is a cosminelike layer and then a vascular bony layer. The thin, translucent bony scales of modern fishes, called cycloid and ctenoid (the latter distinguished by serrations at the edges), lack enameloid and dentine layers.
Skin has several other functions in fishes. It is well supplied with nerve endings and presumably receives tactile, thermal, and pain stimuli. Skin is also well supplied with blood vessels. Some fishes breathe in part through the skin, by the exchange of oxygen and carbon dioxide between the surrounding water and numerous small blood vessels near the skin surface.
Skin serves as protection through the control of coloration. Fishes exhibit an almost limitless range of colours. The colours often blend closely with the surroundings, effectively hiding the animal. Many fishes use bright colours for territorial advertisement or as recognition marks for other members of their own species, or sometimes for members of other species. Many fishes can change their colour to a greater or lesser degree, by movement of pigment within the pigment cells (chromatophores). Black pigment cells (melanophores), of almost universal occurrence in fishes, are often juxtaposed with other pigment cells. When placed beneath iridocytes or leucophores (bearing the silvery or white pigment guanine), melanophores produce structural colours of blue and green. These colours are often extremely intense, because they are formed by refraction of light through the needlelike crystals of guanine. The blue and green refracted colours are often relatively pure, lacking the red and yellow rays, which have been absorbed by the black pigment (melanin) of the melanophores. Yellow, orange, and red colours are produced by erythrophores, cells containing the appropriate carotenoid pigments. Other colours are produced by combinations of melanophores, erythrophores, and iridocytes.
The major portion of the body of most fishes consists of muscles. Most of the mass is trunk musculature, the fin muscles usually being relatively small. The caudal fin is usually the most powerful fin, being moved by the trunk musculature. The body musculature is usually arranged in rows of chevron-shaped segments on each side. Contractions of these segments, each attached to adjacent vertebrae and vertebral processes, bends the body on the vertebral joint, producing successive undulations of the body, passing from the head to the tail, and producing driving strokes of the tail. It is the latter that provides the strong forward movement for most fishes.
The digestive system, in a functional sense, starts at the mouth, with the teeth used to capture prey or collect plant foods. Mouth shape and tooth structure vary greatly in fishes, depending on the kind of food normally eaten. Most fishes are predacious, feeding on small invertebrates or other fishes and have simple conical teeth on the jaws, on at least some of the bones of the roof of the mouth, and on special gill arch structures just in front of the esophagus. The latter are throat teeth. Most predacious fishes swallow their prey whole, and the teeth are used for grasping and holding prey, for orienting prey to be swallowed (head first) and for working the prey toward the esophagus. There are a variety of tooth types in fishes. Some fishes, such as sharks and piranhas, have cutting teeth for biting chunks out of their victims. A shark’s tooth, although superficially like that of a piranha, appears in many respects to be a modified scale, while that of the piranha is like that of other bony fishes, consisting of dentine and enamel. Parrot fishes have beaklike mouths with short incisor-like teeth for breaking off coral and have heavy pavementlike throat teeth for crushing the coral. Some catfishes have small brushlike teeth, arranged in rows on the jaws, for scraping plant and animal growth from rocks. Many fishes (such as the Cyprinidae or minnows) have no jaw teeth at all but have very strong throat teeth.
Some fishes gather planktonic food by straining it from their gill cavities with numerous elongate stiff rods (gill rakers) anchored by one end to the gill bars. The food collected on these rods is passed to the throat, where it is swallowed. Most fishes have only short gill rakers that help keep food particles from escaping out the mouth cavity into the gill chamber.
Once reaching the throat, food enters a short, often greatly distensible esophagus, a simple tube with a muscular wall leading into a stomach. The stomach varies greatly in fishes, depending upon the diet. In most predacious fishes it is a simple straight or curved tube or pouch with a muscular wall and a glandular lining. Food is largely digested there and leaves the stomach in liquid form.
Between the stomach and the intestine, ducts enter the digestive tube from the liver and pancreas. The liver is a large, clearly defined organ. The pancreas may be embedded in it, diffused through it, or broken into small parts spread along some of the intestine. The junction between the stomach and the intestine is marked by a muscular valve. Pyloric ceca (blind sacs) occur in some fishes at this junction and have a digestive or absorptive function or both.
The intestine itself is quite variable in length, depending upon the fish’s diet. It is short in predacious forms, sometimes no longer than the body cavity, but long in herbivorous forms, being coiled and several times longer than the entire length of the fish in some species of South American catfishes. The intestine is primarily an organ for absorbing nutrients into the bloodstream. The larger its internal surface, the greater its absorptive efficiency, and a spiral valve is one method of increasing its absorption surface.
Sharks, rays, chimaeras, lungfishes, surviving chondrosteans, holosteans, and even a few of the more primitive teleosts have a spiral valve or at least traces of it in the intestine. Most modern teleosts have increased the area of the intestinal walls by having numerous folds and villi (fingerlike projections) somewhat like those in humans. Undigested substances are passed to the exterior through the anus in most teleost fishes. In lungfishes, sharks, and rays, it is first passed through the cloaca, a common cavity receiving the intestinal opening and the ducts from the urogenital system.
Oxygen and carbon dioxide dissolve in water, and most fishes exchange dissolved oxygen and carbon dioxide in water by means of the gills. The gills lie behind and to the side of the mouth cavity and consist of fleshy filaments supported by the gill arches and filled with blood vessels, which give gills a bright red colour. Water taken in continuously through the mouth passes backward between the gill bars and over the gill filaments, where the exchange of gases takes place. The gills are protected by a gill cover in teleosts and many other fishes but by flaps of skin in sharks, rays, and some of the older fossil fish groups. The blood capillaries in the gill filaments are close to the gill surface to take up oxygen from the water and to give up excess carbon dioxide to the water.
Most modern fishes have a hydrostatic (ballast) organ, called the swim bladder, that lies in the body cavity just below the kidney and above the stomach and intestine. It originated as a diverticulum of the digestive canal. In advanced teleosts, especially the acanthopterygians, the bladder has lost its connection with the digestive tract, a condition called physoclistic. The connection has been retained (physostomous) by many relatively primitive teleosts. In several unrelated lines of fishes, the bladder has become specialized as a lung or, at least, as a highly vascularized accessory breathing organ. Some fishes with such accessory organs are obligate air breathers and will drown if denied access to the surface, even in well-oxygenated water. Fishes with a hydrostatic form of swim bladder can control their depth by regulating the amount of gas in the bladder. The gas, mostly oxygen, is secreted into the bladder by special glands, rendering the fish more buoyant; the gas is absorbed into the bloodstream by another special organ, reducing the overall buoyancy and allowing the fish to sink. Some deep-sea fishes may have oils, rather than gas, in the bladder. Other deep-sea and some bottom-living forms have much-reduced swim bladders or have lost the organ entirely.
The swim bladder of fishes follows the same developmental pattern as the lungs of land vertebrates. There is no doubt that the two structures have the same historical origin in primitive fishes. More or less intermediate forms still survive among the more primitive types of fishes, such as the lungfishes Lepidosiren and Protopterus.
The circulatory, or blood vascular, system consists of the heart, the arteries, the capillaries, and the veins. It is in the capillaries that the interchange of oxygen, carbon dioxide, nutrients, and other substances such as hormones and waste products takes place. The capillaries lead to the veins, which return the venous blood with its waste products to the heart, kidneys, and gills. There are two kinds of capillary beds: those in the gills and those in the rest of the body. The heart, a folded continuous muscular tube with three or four saclike enlargements, undergoes rhythmic contractions and receives venous blood in a sinus venosus. It passes the blood to an auricle and then into a thick muscular pump, the ventricle. From the ventricle the blood goes to a bulbous structure at the base of a ventral aorta just below the gills. The blood passes to the afferent (receiving) arteries of the gill arches and then to the gill capillaries. There waste gases are given off to the environment, and oxygen is absorbed. The oxygenated blood enters efferent (exuant) arteries of the gill arches and then flows into the dorsal aorta. From there blood is distributed to the tissues and organs of the body. One-way valves prevent backflow. The circulation of fishes thus differs from that of the reptiles, birds, and mammals in that oxygenated blood is not returned to the heart prior to distribution to the other parts of the body.
The primary excretory organ in fishes, as in other vertebrates, is the kidney. In fishes some excretion also takes place in the digestive tract, skin, and especially the gills (where ammonia is given off). Compared with land vertebrates, fishes have a special problem in maintaining their internal environment at a constant concentration of water and dissolved substances, such as salts. Proper balance of the internal environment (homeostasis) of a fish is in a great part maintained by the excretory system, especially the kidney.
The kidney, gills, and skin play an important role in maintaining a fish’s internal environment and checking the effects of osmosis. Marine fishes live in an environment in which the water around them has a greater concentration of salts than they can have inside their body and still maintain life. Freshwater fishes, on the other hand, live in water with a much lower concentration of salts than they require inside their bodies. Osmosis tends to promote the loss of water from the body of a marine fish and absorption of water by that of a freshwater fish. Mucus in the skin tends to slow the process but is not a sufficient barrier to prevent the movement of fluids through the permeable skin. When solutions on two sides of a permeable membrane have different concentrations of dissolved substances, water will pass through the membrane into the more concentrated solution, while the dissolved chemicals move into the area of lower concentration (diffusion).
The kidney of freshwater fishes is often larger in relation to body weight than that of marine fishes. In both groups the kidney excretes wastes from the body, but the kidney of freshwater fishes also excretes large amounts of water, counteracting the water absorbed through the skin. Freshwater fishes tend to lose salt to the environment and must replace it. They get some salt from their food, but the gills and skin inside the mouth actively absorb salt from water passed through the mouth. This absorption is performed by special cells capable of moving salts against the diffusion gradient. Freshwater fishes drink very little water and take in little water with their food.
Marine fishes must conserve water, and therefore their kidneys excrete little water. To maintain their water balance, marine fishes drink large quantities of seawater, retaining most of the water and excreting the salt. Most nitrogenous waste in marine fishes appears to be secreted by the gills as ammonia. Marine fishes can excrete salt by clusters of special cells (chloride cells) in the gills.
There are several teleosts—for example, the salmon—that travel between fresh water and seawater and must adjust to the reversal of osmotic gradients. They adjust their physiological processes by spending time (often surprisingly little time) in the intermediate brackish environment.
Marine hagfishes, sharks, and rays have osmotic concentrations in their blood about equal to that of seawater and so do not have to drink water nor perform much physiological work to maintain their osmotic balance. In sharks and rays the osmotic concentration is kept high by retention of urea in the blood. Freshwater sharks have a lowered concentration of urea in the blood.
Endocrine glands secrete their products into the bloodstream and body tissues and, along with the central nervous system, control and regulate many kinds of body functions. Cyclostomes have a well-developed endocrine system, and presumably it was well developed in the early Agnatha, ancestral to modern fishes. Although the endocrine system in fishes is similar to that of higher vertebrates, there are numerous differences in detail. The pituitary, the thyroid, the suprarenals, the adrenals, the pancreatic islets, the sex glands (ovaries and testes), the inner wall of the intestine, and the bodies of the ultimobranchial gland make up the endocrine system in fishes. There are some others whose function is not well understood. These organs regulate sexual activity and reproduction, growth, osmotic pressure, general metabolic activities such as the storage of fat and the utilization of foodstuffs, blood pressure, and certain aspects of skin colour. Many of these activities are also controlled in part by the central nervous system, which works with the endocrine system in maintaining the life of a fish. Some parts of the endocrine system are developmentally, and undoubtedly evolutionarily, derived from the nervous system.
As in all vertebrates, the nervous system of fishes is the primary mechanism coordinating body activities, as well as integrating these activities in the appropriate manner with stimuli from the environment. The central nervous system, consisting of the brain and spinal cord, is the primary integrating mechanism. The peripheral nervous system, consisting of nerves that connect the brain and spinal cord to various body organs, carries sensory information from special receptor organs such as the eyes, internal ears, nares (sense of smell), taste glands, and others to the integrating centres of the brain and spinal cord. The peripheral nervous system also carries information via different nerve cells from the integrating centres of the brain and spinal cord. This coded information is carried to the various organs and body systems, such as the skeletal muscular system, for appropriate action in response to the original external or internal stimulus. Another branch of the nervous system, the autonomic nervous system, helps to coordinate the activities of many glands and organs and is itself closely connected to the integrating centres of the brain.
The brain of the fish is divided into several anatomical and functional parts, all closely interconnected but each serving as the primary centre of integrating particular kinds of responses and activities. Several of these centres or parts are primarily associated with one type of sensory perception, such as sight, hearing, or smell (olfaction).
The sense of smell is important in almost all fishes. Certain eels with tiny eyes depend mostly on smell for location of food. The olfactory, or nasal, organ of fishes is located on the dorsal surface of the snout. The lining of the nasal organ has special sensory cells that perceive chemicals dissolved in the water, such as substances from food material, and send sensory information to the brain by way of the first cranial nerve. Odour also serves as an alarm system. Many fishes, especially various species of freshwater minnows, react with alarm to a chemical released from the skin of an injured member of their own species.
Many fishes have a well-developed sense of taste, and tiny pitlike taste buds or organs are located not only within their mouth cavities but also over their heads and parts of their body. Catfishes, which often have poor vision, have barbels (“whiskers”) that serve as supplementary taste organs, those around the mouth being actively used to search out food on the bottom. Some species of naturally blind cave fishes are especially well supplied with taste buds, which often cover most of their body surface.
Sight is extremely important in most fishes. The eye of a fish is basically like that of all other vertebrates, but the eyes of fishes are extremely varied in structure and adaptation. In general, fishes living in dark and dim water habitats have large eyes, unless they have specialized in some compensatory way so that another sense (such as smell) is dominant, in which case the eyes will often be reduced. Fishes living in brightly lighted shallow waters often will have relatively small but efficient eyes. Cyclostomes have somewhat less elaborate eyes than other fishes, with skin stretched over the eyeball perhaps making their vision somewhat less effective. Most fishes have a spherical lens and accommodate their vision to far or near subjects by moving the lens within the eyeball. A few sharks accommodate by changing the shape of the lens, as in land vertebrates. Those fishes that are heavily dependent upon the eyes have especially strong muscles for accommodation. Most fishes see well, despite the restrictions imposed by frequent turbidity of the water and by light refraction.
Fossil evidence suggests that colour vision evolved in fishes more than 300 million years ago, but not all living fishes have retained this ability. Experimental evidence indicates that many shallow-water fishes, if not all, have colour vision and see some colours especially well, but some bottom-dwelling shore fishes live in areas where the water is sufficiently deep to filter out most if not all colours, and these fishes apparently never see colours. When tested in shallow water, they apparently are unable to respond to colour differences.
Sound perception and balance are intimately associated senses in a fish. The organs of hearing are entirely internal, located within the skull, on each side of the brain and somewhat behind the eyes. Sound waves, especially those of low frequencies, travel readily through water and impinge directly upon the bones and fluids of the head and body, to be transmitted to the hearing organs. Fishes readily respond to sound; for example, a trout conditioned to escape by the approach of fishermen will take flight upon perceiving footsteps on a stream bank even if it cannot see a fisherman. Compared with humans, however, the range of sound frequencies heard by fishes is greatly restricted. Many fishes communicate with each other by producing sounds in their swim bladders, in their throats by rasping their teeth, and in other ways.
A fish or other vertebrate seldom has to rely on a single type of sensory information to determine the nature of the environment around it. A catfish uses taste and touch when examining a food object with its oral barbels. Like most other animals, fishes have many touch receptors over their body surface. Pain and temperature receptors also are present in fishes and presumably produce the same kind of information to a fish as to humans. Fishes react in a negative fashion to stimuli that would be painful to human beings, suggesting that they feel a sensation of pain.
An important sensory system in fishes that is absent in other vertebrates (except some amphibians) is the lateral line system. This consists of a series of heavily innervated small canals located in the skin and bone around the eyes, along the lower jaw, over the head, and down the mid-side of the body, where it is associated with the scales. Intermittently along these canals are located tiny sensory organs (pit organs) that apparently detect changes in pressure. The system allows a fish to sense changes in water currents and pressure, thereby helping the fish to orient itself to the various changes that occur in the physical environment.
This is an early example of pure "abstract" art (abstract expressionism). These paintings are fun to look at because the longer you look the more you see.
With the vacuum cleaner running, push the frame and the hot plastic down onto the mould until the frame seals against the weather stripping -- and BAM, the plastic slams down onto the mould.
Turn off the vacuum and give the plastic a minute to cool.
Hey, this thing works pretty good. I got a couple ideas of stuff to make with it now, like custom model boat hulls, or maybe a storm trooper costume...