title: The Wrestler (2008 film)

text: Todd McCarthy, of "Variety", said, "Rourke creates a galvanizing, humorous, deeply moving portrait that instantly takes its place among the great, iconic screen performances." Ben Mankiewicz, from "At the Movies", said, "To put it simply, this is the best film I've seen this year." "Le Monde" praised the film for melding European film style with an American plot, and stated that "Mickey Rourke's performance in 'The Wrestler' is a continuous celebration of the burdens and splendors of the profession of performance." One other French film critic, Philippe Azoury, praised its portrayal of "the American heartland" as what he viewed as a bleak wasteland. Although "The Wrestler" was not technically in Roger Ebert's "Best Films" list, he includes a note at the bottom of his review: "'The Wrestler' is one of the year's best films. It wasn't on my 'best films' list for complicated and boring reasons."


title: The Wrestler (2008 film)

text: Prominent wrestling figures have commented on the film. During an NPR interview, Aronofsky remarked on WWE chairman Vince McMahon's feelings on "The Wrestler":


title: The Wrestler (2008 film)

text: WWE Hall of Famer Bret "The Hitman" Hart, who was a multi-time world champion in both WWE and WCW, enjoyed "The Wrestler" and applauded Rourke's "clairvoyant" performance, but called the film a "dark misinterpretation" of the business. He asserted: "Randy "The Ram" Robinson was a main-eventer who sold out Madison Square Garden. So was I ... Although the film speaks superbly to the speed bumps all pro wrestlers navigate, I'm happy to report most of us don't swerve off the road quite so severely." WWE play-by-play commentator Jim Ross called it a "really strong, dramatic film that depicts how people who are obsessed with their own lives and their careers can self-destruct".


title: The Wrestler (2008 film)

text: Former WWE and TNA world champion Mick Foley enjoyed the film, saying: "Within five [minutes], I had completely forgotten I was looking at Mickey Rourke. That guy on the screen simply "was" Randy 'the Ram' Robinson." WWE Hall of Famer "Rowdy" Roddy Piper was said to have been highly emotional after watching a screening of the film. Aronofsky said of Piper: "He loved it. He broke down and cried in Mickey's arms, so he was psyched that this story was finally told." Insights on the film from Roddy Piper and other former pro wrestlers can be seen in Fox Searchlight Pictures's "Wrestler Round Table", which was included on the Blu-ray release of the film.


title: The Wrestler (2008 film)

text: Professional wrestling manager, color commentator and former promoter Jim Cornette criticized the film for being an unrelentingly depressing view of the professional wrestling world, saying it was neither realistic nor accurate of the profession for most wrestlers involved in it.


title: The Wrestler (2008 film)

text: In March 2009, Javad Shamaqdari, cultural adviser to the-then Iranian President Mahmoud Ahmadinejad, demanded an apology from a delegation of Academy of Motion Picture Arts and Sciences actors and producers visiting Iran for what he characterized as negative and unfair portrayals of Iran in "The Wrestler" and other Hollywood films.


title: Ceramic

text: A ceramic is any of the various hard, brittle, heat-resistant and corrosion-resistant materials made by shaping and then firing an inorganic, nonmetallic material, such as clay, at a high temperature. Common examples are earthenware, porcelain, and brick.


title: Ceramic

text: The earliest ceramics made by humans were pottery objects ("pots," "vessels or vases") or figurines made from clay, either by itself or mixed with other materials like silica, hardened and sintered in fire. Later, ceramics were glazed and fired to create smooth, colored surfaces, decreasing porosity through the use of glassy, amorphous ceramic coatings on top of the crystalline ceramic substrates. Ceramics now include domestic, industrial and building products, as well as a wide range of materials developed for use in advanced ceramic engineering, such as in semiconductors.


title: Ceramic

text: The word ""ceramic"" comes from the Greek word (), "of pottery" or "for pottery", from (), "potter's clay, tile, pottery". The earliest known mention of the root "ceram-" is the Mycenaean Greek , workers of ceramic written in Linear B syllabic script. The word ceramic can be used as an adjective to describe a material, product or process, or it may be used as a noun, either singular, or more commonly, as the plural noun "ceramics".


title: Ceramic

text: Ceramic material is an inorganic, non-metallic oxide, nitride, or carbide material. Some elements, such as carbon or silicon, may be considered ceramics. Ceramic materials are brittle, hard, strong in compression, and weak in shearing and tension. They withstand chemical erosion that occurs in other materials subjected to acidic or caustic environments. Ceramics generally can withstand very high temperatures, ranging from 1,000 °C to 1,600 °C (1,800 °F to 3,000 °F).


title: Ceramic

text: The crystallinity of ceramic materials varies widely. Most often, fired ceramics are either vitrified or semi-vitrified as is the case with earthenware, stoneware, and porcelain. Varying crystallinity and electron composition in the ionic and covalent bonds cause most ceramic materials to be good thermal and electrical insulators (researched in ceramic engineering). With such a large range of possible options for the composition/structure of a ceramic (nearly all of the elements, nearly all types of bonding, and all levels of crystallinity), the breadth of the subject is vast, and identifiable attributes (hardness, toughness, electrical conductivity) are difficult to specify for the group as a whole. General properties such as high melting temperature, high hardness, poor conductivity, high moduli of elasticity, chemical resistance and low ductility are the norm, with known exceptions to each of these rules (piezoelectric ceramics, glass transition temperature, superconductive ceramics). Many composites, such as fiberglass and carbon fiber, while containing ceramic materials are not considered to be part of the ceramic family.


title: Ceramic

text: Highly oriented crystalline ceramic materials are not amenable to a great range of processing. Methods for dealing with them tend to fall into one of two categories – either make the ceramic in the desired shape, by reaction "in situ", or by "forming" powders into the desired shape, and then sintering to form a solid body. Ceramic forming techniques include shaping by hand (sometimes including a rotation process called "throwing"), slip casting, tape casting (used for making very thin ceramic capacitors), injection molding, dry pressing, and other variations.


title: Ceramic

text: Many ceramics experts do not consider materials with amorphous (noncrystalline) character (i.e., glass) to be ceramics even though glassmaking involves several steps of the ceramic process and its mechanical properties are similar to ceramic materials. However, heat treatments can convert glass into a semi-crystalline material known as glass-ceramic.


title: Ceramic

text: Traditional ceramic raw materials include clay minerals such as kaolinite, whereas more recent materials include aluminum oxide, more commonly known as alumina. The modern ceramic materials, which are classified as advanced ceramics, include silicon carbide and tungsten carbide. Both are valued for their abrasion resistance and are therefore used in applications such as the wear plates of crushing equipment in mining operations. Advanced ceramics are also used in the medical, electrical, electronics, and armor industries.


title: Ceramic

text: Human beings appear to have been making their own ceramics for at least 26,000 years, subjecting clay and silica to intense heat to fuse and form ceramic materials. The earliest found so far were in southern central Europe and were sculpted figures, not dishes. The earliest known pottery was made by mixing animal products with clay and baked in kilns at up to 800°C. While actual pottery fragments have been found up to 19,000 years old, it was not until about ten thousand years later that regular pottery became common. An early people that spread across much of Europe is named after its use of pottery, the Corded Ware culture. These early Indo-European peoples decorated their pottery by wrapping it with rope, while still wet. When the ceramics were fired, the rope burned off but left a decorative pattern of complex grooves on the surface.


title: Ceramic

text: The invention of the wheel eventually led to the production of smoother, more even pottery using the wheel-forming technique, like the pottery wheel. Early ceramics were porous, absorbing water easily. It became useful for more items with the discovery of glazing techniques, coating pottery with silicon, bone ash, or other materials that could melt and reform into a glassy surface, making a vessel less pervious to water.


title: Ceramic

text: Ceramic artifacts have an important role in archaeology for understanding the culture, technology, and behavior of peoples of the past. They are among the most common artifacts to be found at an archaeological site, generally in the form of small fragments of broken pottery called sherds. Processing of collected sherds can be consistent with two main types of analysis: technical and traditional.


title: Ceramic

text: The traditional analysis involves sorting ceramic artifacts, sherds, and larger fragments into specific types based on style, composition, manufacturing, and morphology. By creating these typologies, it is possible to distinguish between different cultural styles, the purpose of the ceramic, and the technological state of the people among other conclusions. Besides, by looking at stylistic changes of ceramics over time is it possible to separate (seriate) the ceramics into distinct diagnostic groups (assemblages). A comparison of ceramic artifacts with known dated assemblages allows for a chronological assignment of these pieces.


title: Ceramic

text: The technical approach to ceramic analysis involves a finer examination of the composition of ceramic artifacts and sherds to determine the source of the material and through this the possible manufacturing site. Key criteria are the composition of the clay and the temper used in the manufacture of the article under study: the temper is a material added to the clay during the initial production stage, and it is used to aid the subsequent drying process. Types of temper include shell pieces, granite fragments, and ground sherd pieces called 'grog'. Temper is usually identified by microscopic examination of the tempered material. Clay identification is determined by a process of refiring the ceramic and assigning a color to it using Munsell Soil Color notation. By estimating both the clay and temper compositions, and locating a region where both are known to occur, an assignment of the material source can be made. From the source assignment of the artifact, further investigations can be made into the site of manufacture.


title: Ceramic

text: The physical properties of any ceramic substance are a direct result of its crystalline structure and chemical composition. Solid-state chemistry reveals the fundamental connection between microstructure and properties, such as localized density variations, grain size distribution, type of porosity, and second-phase content, which can all be correlated with ceramic properties such as mechanical strength σ by the Hall-Petch equation, hardness, toughness, dielectric constant, and the optical properties exhibited by transparent materials.


title: Ceramic

text: Ceramography is the art and science of preparation, examination, and evaluation of ceramic microstructures. Evaluation and characterization of ceramic microstructures are often implemented on similar spatial scales to that used commonly in the emerging field of nanotechnology: from tens of ångstroms (Å) to tens of micrometers (µm). This is typically somewhere between the minimum wavelength of visible light and the resolution limit of the naked eye.


title: Ceramic

text: The microstructure includes most grains, secondary phases, grain boundaries, pores, micro-cracks, structural defects, and hardness micro indentions. Most bulk mechanical, optical, thermal, electrical, and magnetic properties are significantly affected by the observed microstructure. The fabrication method and process conditions are generally indicated by the microstructure. The root cause of many ceramic failures is evident in the cleaved and polished microstructure. Physical properties which constitute the field of materials science and engineering include the following:


title: Ceramic

text: Mechanical properties are important in structural and building materials as well as textile fabrics. In modern materials science, fracture mechanics is an important tool in improving the mechanical performance of materials and components. It applies the physics of stress and strain, in particular the theories of elasticity and plasticity, to the microscopic crystallographic defects found in real materials in order to predict the macroscopic mechanical failure of bodies. Fractography is widely used with fracture mechanics to understand the causes of failures and also verify the theoretical failure predictions with real-life failures.


title: Ceramic

text: Ceramic materials are usually ionic or covalent bonded materials. A material held together by either type of bond will tend to fracture before any plastic deformation takes place, which results in poor toughness in these materials. Additionally, because these materials tend to be porous, the pores and other microscopic imperfections act as stress concentrators, decreasing the toughness further, and reducing the tensile strength. These combine to give catastrophic failures, as opposed to the more ductile failure modes of metals.


title: Ceramic

text: These materials do show plastic deformation. However, because of the rigid structure of crystalline material, there are very few available slip systems for dislocations to move, and so they deform very slowly.


title: Ceramic

text: To overcome the brittle behavior, ceramic material development has introduced the class of ceramic matrix composite materials, in which ceramic fibers are embedded and with specific coatings are forming fiber bridges across any crack. This mechanism substantially increases the fracture toughness of such ceramics. Ceramic disc brakes are an example of using a ceramic matrix composite material manufactured with a specific process.


title: Ceramic

text: If ceramic is subjected to substantial mechanical loading, it can undergo a process called ice-templating, which allows some control of the microstructure of the ceramic product and therefore some control of the mechanical properties. Ceramic engineers use this technique to tune the mechanical properties to their desired application. Specifically, strength is increased, when this technique is employed. Ice templating allows the creation of macroscopic pores in a unidirectional arrangement. The applications of this oxide strengthening technique are important for solid oxide fuel cells and water filtration devices.


title: Ceramic

text: To process a sample through ice templating, an aqueous colloidal suspension is prepared to contain the dissolved ceramic powder evenly dispersed throughout the colloid, for example Yttria-stabilized zirconia (YSZ). The solution is then cooled from the bottom to the top on a platform that allows for unidirectional cooling. This forces ice crystals to grow in compliance with the unidirectional cooling and these ice crystals force the dissolved YSZ particles to the solidification front of the solid-liquid interphase boundary, resulting in pure ice crystals lined up unidirectionally alongside concentrated pockets of colloidal particles. The sample is then simultaneously heated and the pressure is reduced enough to force the ice crystals to sublimate and the YSZ pockets begin to anneal together to form macroscopically aligned ceramic microstructures. The sample is then further sintered to complete the evaporation of the residual water and the final consolidation of the ceramic microstructure.


title: Ceramic

text: During ice-templating, a few variables can be controlled to influence the pore size and morphology of the microstructure. These important variables are the initial solids loading of the colloid, the cooling rate, the sintering temperature and duration, and the use of certain additives which can influence the microstructural morphology during the process. A good understanding of these parameters is essential to understanding the relationships between processing, microstructure, and mechanical properties of anisotropically porous materials.


title: Ceramic

text: Some ceramics are semiconductors. Most of these are transition metal oxides that are II-VI semiconductors, such as zinc oxide. While there are prospects of mass-producing blue LEDs from zinc oxide, ceramicists are most interested in the electrical properties that show grain boundary effects. One of the most widely used of these is the varistor. These are devices that exhibit the property that resistance drops sharply at a certain threshold voltage. Once the voltage across the device reaches the threshold, there is a breakdown of the electrical structure in the vicinity of the grain boundaries, which results in its electrical resistance dropping from several megohms down to a few hundred ohms. The major advantage of these is that they can dissipate a lot of energy, and they self-reset; after the voltage across the device drops below the threshold, its resistance returns to being high. This makes them ideal for surge-protection applications; as there is control over the threshold voltage and energy tolerance, they find use in all sorts of applications. The best demonstration of their ability can be found in electrical substations, where they are employed to protect the infrastructure from lightning strikes. They have rapid response, are low maintenance, and do not appreciably degrade from use, making them virtually ideal devices for this application. Semiconducting ceramics are also employed as gas sensors. When various gases are passed over a polycrystalline ceramic, its electrical resistance changes. With tuning to the possible gas mixtures, very inexpensive devices can be produced.


title: Ceramic

text: Under some conditions, such as extremely low temperature, some ceramics exhibit high-temperature superconductivity. The reason for this is not understood, but there are two major families of superconducting ceramics.


title: Ceramic

text: Piezoelectricity, a link between electrical and mechanical response, is exhibited by a large number of ceramic materials, including the quartz used to measure time in watches and other electronics. Such devices use both properties of piezoelectrics, using electricity to produce a mechanical motion (powering the device) and then using this mechanical motion to produce electricity (generating a signal). The unit of time measured is the natural interval required for electricity to be converted into mechanical energy and back again.


title: Ceramic

text: The piezoelectric effect is generally stronger in materials that also exhibit pyroelectricity, and all pyroelectric materials are also piezoelectric. These materials can be used to inter-convert between thermal, mechanical, or electrical energy; for instance, after synthesis in a furnace, a pyroelectric crystal allowed to cool under no applied stress generally builds up a static charge of thousands of volts. Such materials are used in motion sensors, where the tiny rise in temperature from a warm body entering the room is enough to produce a measurable voltage in the crystal.


title: Ceramic

text: In turn, pyroelectricity is seen most strongly in materials that also display the ferroelectric effect, in which a stable electric dipole can be oriented or reversed by applying an electrostatic field. Pyroelectricity is also a necessary consequence of ferroelectricity. This can be used to store information in ferroelectric capacitors, elements of ferroelectric RAM.


title: Ceramic

text: The most common such materials are lead zirconate titanate and barium titanate. Aside from the uses mentioned above, their strong piezoelectric response is exploited in the design of high-frequency loudspeakers, transducers for sonar, and actuators for atomic force and scanning tunneling microscopes.


title: Ceramic

text: Temperature increases can cause grain boundaries to suddenly become insulating in some semiconducting ceramic materials, mostly mixtures of heavy metal titanates. The critical transition temperature can be adjusted over a wide range by variations in chemistry. In such materials, current will pass through the material until joule heating brings it to the transition temperature, at which point the circuit will be broken and current flow will cease. Such ceramics are used as self-controlled heating elements in, for example, the rear-window defrost circuits of automobiles.


title: Ceramic

text: At the transition temperature, the material's dielectric response becomes theoretically infinite. While a lack of temperature control would rule out any practical use of the material near its critical temperature, the dielectric effect remains exceptionally strong even at much higher temperatures. Titanates with critical temperatures far below room temperature have become synonymous with "ceramic" in the context of ceramic capacitors for just this reason.


title: Ceramic

text: Optically transparent materials focus on the response of a material to incoming light waves of a range of wavelengths. Frequency selective optical filters can be utilized to alter or enhance the brightness and contrast of a digital image. Guided lightwave transmission via frequency selective waveguides involves the emerging field of fiber optics and the ability of certain glassy compositions as a transmission medium for a range of frequencies simultaneously (multi-mode optical fiber) with little or no interference between competing wavelengths or frequencies. This resonant mode of energy and data transmission via electromagnetic (light) wave propagation, though low powered, is virtually lossless. Optical waveguides are used as components in Integrated optical circuits (e.g. light-emitting diodes, LEDs) or as the transmission medium in local and long haul optical communication systems. Also of value to the emerging materials scientist is the sensitivity of materials to radiation in the thermal infrared (IR) portion of the electromagnetic spectrum. This heat-seeking ability is responsible for such diverse optical phenomena as night-vision and IR luminescence.


title: Ceramic

text: Thus, there is an increasing need in the military sector for high-strength, robust materials which have the capability to transmit light (electromagnetic waves) in the visible (0.4 – 0.7 micrometers) and mid-infrared (1 – 5 micrometers) regions of the spectrum. These materials are needed for applications requiring transparent armor, including next-generation high-speed missiles and pods, as well as protection against improvised explosive devices (IED).


title: Ceramic

text: In the 1960s, scientists at General Electric (GE) discovered that under the right manufacturing conditions, some ceramics, especially aluminium oxide (alumina), could be made translucent. These translucent materials were transparent enough to be used for containing the electrical plasma generated in high-pressure sodium street lamps. During the past two decades, additional types of transparent ceramics have been developed for applications such as nose cones for heat-seeking missiles, windows for fighter aircraft, and scintillation counters for computed tomography scanners.


title: Ceramic

text: Other ceramic materials, generally requiring greater purity in their make-up than those above, include forms of several chemical compounds, including:


title: Ceramic

text: For convenience, ceramic products are usually divided into four main types; these are shown below with some examples:


title: In Utero

text: In Utero is the third and final studio album by American rock band Nirvana. It was released on September 21, 1993, by DGC Records. After breaking into the mainstream with their second album, "Nevermind" (1991), Nirvana hired Steve Albini to record "In Utero", seeking a more complex, abrasive sound that was also reminiscent of their debut album, "Bleach" (1989). Frontman Kurt Cobain took heavy inspiration from his personal struggles for the album's lyrics, many of which express feelings of angst that were common on "Nevermind".


title: In Utero

text: The album was recorded over two weeks in February 1993 at Pachyderm Studio in Cannon Falls, Minnesota. Soon after recording began, rumors circulated that DGC might not release the album due to Albini's abrasive and uncommercial sound. In response, the label hired producer Scott Litt to remix the singles "All Apologies", "Heart-Shaped Box" and "Pennyroyal Tea", upsetting both Albini and the band.


title: In Utero

text: "In Utero" was a major commercial and critical success. Critics praised the album’s raw, unconventional sound and Cobain's lyricism. It reached number one on the US "Billboard" 200 and UK Albums Chart; "Heart-Shaped Box" and "All Apologies" reached number one on the "Billboard" Alternative Songs chart. The album is certified five-times platinum in the US and has sold 15 million copies worldwide. It was the final Nirvana album before Cobain's suicide in 1994. "Pennyroyal Tea", planned as a single prior to Cobain's death, was released in 2014 and reached number one on the "Billboard" Hot 100 Singles Sales chart.


title: In Utero

text: Nirvana broke into the mainstream with their second album, "Nevermind", in 1991. Despite modest sales estimates, "Nevermind" was a major commercial success, popularizing the grunge movement and alternative rock. Nirvana expressed dissatisfaction with the sound of the album, citing its production as too polished. Early in 1992, songwriter Kurt Cobain told "Rolling Stone" that Nirvana's next album would showcase "both of the extremes" of their sound, saying: "It'll be more raw with some songs and more candy pop on some of the others. It won't be as one-dimensional." The "Nevermind" producer, Butch Vig, said later that Cobain had needed to work with a different producer to "reclaim his punk ethics or cred".


title: In Utero

text: Cobain wanted to start work in mid-1992, but his bandmates lived in different cities, and Cobain and his wife, Courtney Love, were expecting the birth of their daughter, Frances Bean. Nirvana's record label, DGC Records, had hoped to release a new Nirvana album for the 1992 holiday season; instead, they released the compilation album "Incesticide".


title: In Utero

text: In a "Melody Maker" interview published in July 1992, Cobain said he was interested in recording with Jack Endino, who had produced Nirvana's 1989 debut album "Bleach", and Steve Albini, former frontman of the noise rock band Big Black, who had produced various independent releases. In Seattle in October 1992, Nirvana recorded several demos with Endino, mainly as instrumentals, including songs later rerecorded for "In Utero". Endino recalled that the band did not ask him to produce its next record, and that they constantly debated working with Albini. Nirvana recorded another set of demos while on tour in Brazil in January 1993. "Gallons of Rubbing Alcohol Flow Through the Strip" was recorded by Craig Montgomery at BMG Ariola Ltda in Rio de Janeiro, during the three-day demo session. The song was originally titled "I'll Take You Down to the Pavement", a reference to an argument between Cobain and Guns N' Roses singer Axl Rose at the 1992 MTV Video Music Awards.


title: In Utero

text: Nirvana ultimately chose Albini to record its third album. Albini had a reputation in the American independent music scene as being critical of the mainstream music industry and had a strict preference for analog recording than digital. He sent a disclaimer to the British music press denying rumors of his involvement with Nirvana, only to receive a call from Nirvana's management a few days later. Albini dismissed Nirvana as "R.E.M. with a fuzzbox" and "an unremarkable version of the Seattle sound". However, he accepted the job because he felt sorry for them, perceiving them as "the same sort of people as all the small-fry bands I deal with", at the mercy of their record company.


title: In Utero

text: Cobain said he chose Albini because he had produced two of his favorite records, "Surfer Rosa" (1988) by the Pixies and "Pod" (1990) by the Breeders. Cobain wanted to use Albini's technique of capturing the natural ambience of a room via the placement of several microphones, something previous Nirvana producers had been averse to trying. Before the recording, the band sent Albini a tape of the demos they had made in Brazil. In return, Albini sent Cobain a copy of the PJ Harvey album "Rid of Me" (1993) to give him an idea of the acoustics at the studio where they would record.


title: In Utero

text: Nirvana and Albini set a two-week deadline for recording. At the suggestion of Albini, who was wary of interference from DGC, Nirvana paid for the sessions with their own money. Studio fees totaled US$24,000, while Albini took a flat fee of $100,000. Though he stood to earn about $500,000 from royalties, Albini refused to accept them, as he considered taking royalties immoral and "an insult to the artist".


title: In Utero

text: In February 1993, Nirvana traveled to Pachyderm Studio in Cannon Falls, Minnesota. Albini did not meet them until the first day of recording, though he had spoken to them beforehand about the type of album they wanted to make; he observed that "they wanted to make precisely the sort of record that I'm comfortable doing". The group stayed in a house on the studio grounds. Novoselic compared the isolated conditions to a gulag; he said, "There was snow outside, we couldn't go anywhere. We just worked." For most of the sessions, only the band, Albini, and technician Bob Weston were present. Nirvana made it clear to DGC and their management company Gold Mountain that they wanted no intrusion, and did not play their work in progress for their A&R representative. Albini instituted a policy of ignoring everyone except for the band members; he said that everyone associated with Nirvana were "the biggest pieces of shit I ever met".


title: In Utero

text: Nirvana arrived at Pachyderm Studio without their equipment and spent much of the first three days waiting for it to arrive by mail. Once recording began, on February 13, work moved quickly. On most days, the group began work around midday, took breaks for lunch and dinner, and worked until midnight. For most songs, Cobain, Novoselic, and Grohl recorded their basic instrumental tracks together as a band. For faster songs, such as "Very Ape" and "Tourette's", the drums were recorded separately in a kitchen for its natural reverb. Albini surrounded Grohl's drum kit with about 30 microphones. Cobain added additional guitar tracks to about half of the songs, then guitar solos, and finally vocals. The band did not discard takes and kept virtually everything they recorded.


title: In Utero

text: Albini saw himself more as an engineer than a producer; despite his personal opinions, he let the band choose takes. He said, "Generally speaking, [Cobain] knows what he thinks is acceptable and what isn't acceptable [...] He can make concrete steps to improve things that he doesn't think are acceptable." Cobain reportedly recorded all his vocal tracks in six hours. Albini said that Cobain, who had struggled with drug addiction, was focused and sober in the studio.


title: In Utero

text: Recording was completed in six days; Cobain had anticipated disagreements with Albini, whom he had heard "was supposedly this sexist jerk", but called the process "the easiest recording we've ever done, hands down". The only disruption occurred a week into the sessions, when Love arrived because she missed Cobain. Weston's girlfriend, the studio's chef, said that Love created tension by criticizing Cobain's work and was confrontational with everyone present.


title: In Utero

text: The initial mix of "In Utero" took five days. This was quick by Nirvana's standards, but not for Albini, who was used to mixing albums in a day or two. When work on a mix was not producing desired results, the band and Albini took the rest of the day off to watch nature videos, set things on fire and make prank calls. The sessions were completed on February 26.


title: In Utero

text: After the recording sessions were completed, Nirvana sent unmastered tapes of the album to several individuals, including Gold Mountain and Ed Rosenblatt, the president of DGC's parent company Geffen Records. When asked about the feedback he received, Cobain told Michael Azerrad, "The grown-ups don't like it." He said he was told his songwriting was "not up to par", the sound was "unlistenable", and that there was uncertainty that mainstream radio would accept Albini's production. Few at Geffen or Gold Mountain had wanted the band to record with Albini, and Cobain felt he was receiving an unstated message to scrap the sessions and start again.


title: In Utero

text: Cobain was upset and said to Azerrad, "I should just re-record this record and do the same thing we did last year because we sold out last year—there's no reason to try and redeem ourselves as artists at this point. I can't help myself—I'm just putting out a record I would like to listen to at home." However, a number of Nirvana's friends liked the album, and by April 1993, Nirvana was intent on releasing "In Utero" as it was. According to Cobain, "Of course, they want another "Nevermind", but I'd rather die than do that. This is exactly the kind of record I would buy as a fan, that I would enjoy owning."


title: In Utero

text: The band began to have doubts about the record. Cobain said, "The first time I played it at home, I knew there was something wrong. The whole first week I wasn't really interested in listening to it at all, and that usually doesn't happen. I got no emotion from it, I was just numb." The group concluded that the bass and lyrics were inaudible and asked Albini to remix the album. He declined; as he recalled, "[Cobain] wanted to make a record that he could slam down on the table and say, 'Listen, I know this is good, and I know your concerns about it are meaningless, so go with it.' And I don't think he felt he had that yet ... My problem was that I feared a slippery slope." The band attempted to address their concerns during the mastering process with Bob Ludwig at his studio in Portland, Maine. Novoselic was pleased with the results, but Cobain still did not feel it was perfect.


title: In Utero

text: Soon afterward, in April 1993, Albini told the "Chicago Tribune" that he doubted Geffen would release the album. Years later, Albini said: "I wasn't there when the band was having their discussions with the record label. All I know is ... we made a record, everybody was happy with it. A few weeks later I hear that it's unreleasable and it's all got to be redone." While Albini's remarks in the article drew no reply from Nirvana or Geffen, "Newsweek" ran a similar article soon afterwards that did. Nirvana wrote a letter to "Newsweek" denying any pressure to change the album and saying the author had "ridiculed our relationship with our label based on totally erroneous information". The band reprinted the letter in a full-page ad in "Billboard". Rosenblatt insisted in a press release that Geffen would release anything Nirvana submitted, and label founder David Geffen made the unusual move of calling "Newsweek" to complain.


title: In Utero

text: Nirvana considered working with producer Scott Litt and remixing some tracks with Andy Wallace, who had mixed "Nevermind". Albini vehemently disagreed, and said the band had agreed not to modify the tracks without his involvement. He initially refused to give the master tapes to Gold Mountain, but relented after a phone call from Novoselic. The band eventually had Litt remix songs intended as singles; "Heart Shaped Box" and "All Apologies" were remixed at Seattle's Bad Animals Studio in May 1993.


title: In Utero

text: "I Hate Myself and Want to Die" was omitted as Cobain felt the album already contained too many "noise" songs. The rest of the album was left unaltered aside from a remastering. Albini was critical of the final mix; he said, "The record in the stores doesn't sound all that much like the record that was made, though it's still them singing and playing their songs, and the musical quality of it still comes across." According to Albini, "In Utero" made him unpopular with major record labels, and he faced problems finding work in the year following its release.


title: In Utero

text: Albini sought to produce a record that sounded nothing like "Nevermind". He felt the sound of "Nevermind" was "sort of a standard hack recording that has been turned into a very, very controlled, compressed radio-friendly mix [...] That is not, in my opinion, very flattering to a rock band." Instead, he intended to capture a more natural and visceral sound. Albini refused to double-track Cobain's vocals and instead recorded him singing in a resonant room. He noted the intensity of Cobain's vocals on some tracks; he said, "There's a really dry, really loud voice at the end of 'Milk It' ... that was also done at the end of 'Rape Me', where [Cobain] wanted the sound of him screaming to just overtake the whole band." Albini achieved the sparse drum sound by placing several microphones around Grohl, picking up the natural reverberation of the room. Albini said, "If you take a good drummer and put him in front of a drum kit that sounds good acoustically and just record it, you've done your job."


title: In Utero

text: Azerrad asserted in his 1993 biography "" that "In Utero" showcased divergent sensibilities of abrasiveness and accessibility that reflected the upheavals Cobain experienced prior to the album's completion. He wrote, "The Beatlesque 'Dumb' happily coexists beside the all-out frenzied punk graffiti of 'Milk It,' while 'All Apologies' is worlds away from the apoplectic 'Scentless Apprentice.' It's as if [Cobain] has given up trying to meld his punk and pop instincts into one harmonious whole. Forget it. This is war." Cobain believed, however, that "In Utero" was not "any harsher or any more emotional" than any of Nirvana's previous records. Novoselic agreed that the album leaned more towards the band's "arty, aggressive side"; he said, "There's always been [Nirvana] songs like 'About a Girl' and there's always been songs like 'Paper Cuts'... "Nevermind" came out kind of 'About a Girl'-y and this [album] came out more 'Paper Cuts'". Cobain cited "Milk It" as an example of the more experimental and aggressive direction in which the band's music had been moving in the months prior to the sessions at Pachyderm Studio. Novoselic viewed the album's singles "Heart-Shaped Box" and "All Apologies" as "gateways" to the more abrasive sound of the rest of the album, telling journalist Jim DeRogatis that once listeners played the record, they would discover "this aggressive wild sound, a true alternative record".


title: In Utero

text: Several songs on "In Utero" were written years prior to recording; some dated to 1990. Cobain favored long song titles, such as "Frances Farmer Will Have Her Revenge on Seattle", in reaction to contemporary alternative rock bands that used single-word titles. He continued to work on the lyrics while recording. He told Darcey Steinke in "Spin" in 1993 that, in contrast to "Bleach" and "Nevermind", the lyrics were "more focused, they're almost built on themes". Azerrad asserted that the lyrics were less impressionistic and more straightforward than in previous Nirvana songs. Azerrad also noted that "virtually every song contains some image of sickness and disease". In a number of songs, Cobain made reference to books; "Frances Farmer Will Have Her Revenge on Seattle" was inspired by "Shadowland", a 1978 biography of actress Frances Farmer, with whom Cobain had been fascinated ever since he read the book in high school. "Scentless Apprentice" was written about "Perfume: The Story of a Murderer", a historical horror novel about a perfumer's apprentice who attempts to create the ultimate perfume by killing virgin women and taking their scent.


title: In Utero

text: Cobain described "In Utero" as "very impersonal". He also told "Q" that the infant and childbirth imagery on the album and his newfound fatherhood were coincidental. However, Azerrad argued that much of the album contains personal themes, noting that Grohl held a similar view. Grohl said, "A lot of what he has to say is related to a lot of the shit he's gone through. And it's not so much teen angst any more. It's a whole different ball game: rock star angst." Cobain downplayed recent events and told Azerrad that he did not want to write a track that explicitly expressed his anger at the media; Azerrad countered that "Rape Me" seemed to deal with that very issue. While Cobain said the song was written long before his addiction problems became public, he agreed that the song could be viewed in that light. "Serve the Servants" comments on Cobain's life. The opening lines "Teenage angst has paid off well / Now I'm bored and old" were a reference to Cobain's state of mind in the wake of Nirvana's success. Cobain dismissed the media attention given to the effect his parents' divorce had on his life with the line "That legendary divorce is such a bore" from the chorus, and directly addressed his father with the lines "I tried hard to have a father / But instead I had a dad / I just want you to know that I don't hate you any more / There is nothing I could say that I haven't thought before". Cobain said he wanted his father to know he did not hate him, but had no desire to talk to him.


title: In Utero

text: According to journalist Gillian G. Gaar, "Gallons of Rubbing Alcohol Flow Through the Strip" was the kind of improvisational jam Nirvana frequently performed in the studio, but had rarely recorded during earlier sessions, when the priority had been to record as quickly as possible. She wrote that it featured "Cobain alternating between seemingly disconnected singing and spoken-words sections, with Novoselic and Grohl providing a steady background accompaniment, punctuated by bursts of noisy guitar." Journalist Everett True described the song's mood as "playful", with "the instruments engaging in a game of cat and mouse, almost daring each other to explode in fury". Novoselic said it was an example of the band "just fucking around".


title: In Utero

text: Cobain originally wanted to name the album "I Hate Myself and I Want to Die", a phrase that had originated in his journals in mid-1992. At the time, he used the phrase as a response whenever someone asked him how he was doing. Cobain intended the album title as a joke; he stated he was "tired of taking this band so seriously and everyone else taking it so seriously". Novoselic convinced Cobain to change the title due to fear that it could potentially result in a lawsuit. The band then considered using "Verse Chorus Verse"—a title taken from its song "Verse Chorus Verse", and an earlier working title of "Sappy"—before eventually settling on "In Utero". The final title was taken from a poem written by Courtney Love.


title: In Utero

text: The art director for "In Utero" was Robert Fisher, who had designed all of Nirvana's releases on DGC. Most of the ideas for the artwork for the album and related singles came from Cobain. Fisher recalled that "[Cobain] would just give me some loose odds and ends and say 'Do something with it.'" The cover of the album is an image of a Transparent Anatomical Manikin, with angel wings superimposed. Cobain created the collage on the back cover, which he described as "Sex and woman and "In Utero" and vaginas and birth and death", that consists of model fetuses, a turtle shell and models of turtles, and body parts lying in a bed of orchids and lilies. The collage had been set up on the floor of Cobain's living room and was photographed by Charles Peterson after an unexpected call from Cobain. The album's track listing and re-illustrated symbols from Barbara G. Walker's "The Woman's Dictionary of Symbols and Sacred Objects" were then positioned around the edge of the collage.


title: In Utero

text: Mannequins of the angel-winged anatomical figure were used as stage props on Nirvana's concert tour supporting "In Utero". One such mannequin later featured at the Experience Music Project museum's exhibition "Nirvana: Taking Punk to the Masses", which ran from April 2011 through 2013 and showcased memorabilia celebrating the band's music and history.


title: In Utero

text: To avoid over-hyping the album, DGC Records took a low-key approach to promoting "In Utero"; their head of marketing told "Billboard" before the album's release that they were planning a campaign similar to that of "Nevermind", and the label would "set things up, duck, and get out of the way". The label aimed its promotion at alternative markets and press, and released the album on vinyl as part of this strategy. In contrast to "Nevermind", DGC did not release any of "In Utero"'s singles commercially in the United States. DGC sent promo copies of the album's first single, "Heart-Shaped Box", to American college, modern rock, and album-oriented rock radio stations in early September, but did not target Top 40 radio. The band was convinced that "In Utero" would not be as successful as "Nevermind". Cobain told Jim DeRogatis, "We're certain that we won't sell a quarter as much, and we're totally comfortable with that because we like this record so much."


title: In Utero

text: "In Utero" was released on September 13, 1993, on vinyl record and cassette tape in the United Kingdom, and on September 14 on vinyl in the United States, with the American vinyl pressing limited to 25,000 copies. It was issued on CD in the U.K. on September 14, and in other formats on September 21. European and Australian versions of "In Utero" released that same month included "Gallons of Rubbing Alcohol Flow Through the Strip" as a hidden bonus track, with a sticker on the cover reading "Exclusive International Bonus Track", although the booklet referred to the song as a "Devalued American Dollar Purchase Incentive Track". According to Novoselic, DGC did not want the European version to compete with the US version, and so added the extra track.


title: In Utero

text: "In Utero" debuted at number one on the US "Billboard" 200, selling 180,000 copies. The retail chain stores Wal-Mart and Kmart refused to sell it; according to "The New York Times", Wal-Mart said this was due to lack of consumer demand, while Kmart representatives said the album did not fit with their "merchandise mix". In truth, both chains feared that customers would be offended by the artwork on the back cover. DGC issued a new version to the stores in March 1994, with edited album artwork, "Rape Me" retitled "Waif Me", and the Scott Litt remix of "Pennyroyal Tea". A spokesperson for Nirvana explained that the band decided to edit the packaging because they wanted their music available to "kids who don't have the opportunity to go to mom-and-pop stores". "In Utero" also debuted at number one in the United Kingdom where according to "NME", "Nirvana confirmed their status as the seminal band of the time".


title: In Utero

text: In October 1993, Nirvana began their first American tour in two years to promote the album. A second single, a split release that featured "All Apologies" and "Rape Me", was issued in December in the United Kingdom. The band began a six-week European leg in February 1994, but it was canceled after Cobain suffered a drug overdose in Rome on March 6. Cobain agreed to enter drug rehabilitation, but went missing soon afterward. On April 8, he was found dead in his Seattle home, having shot himself. A third single from "In Utero", "Pennyroyal Tea", was canceled in the wake of Cobain's death and the subsequent dissolution of Nirvana; limited promotional copies were released in Britain. Three days after Cobain's body was discovered, "In Utero" moved from number 72 to number 27 on the "Billboard" charts, with a 122% sales increase of 40,000 copies sold compared to 18,000 in the week before.


title: In Utero

text: "In Utero" has been certified five times platinum by the Recording Industry Association of America for shipments of over five million units, and has sold 4,258,000 copies in the United States, according to Nielsen SoundScan. For the album's 20th anniversary, DGC reissued "In Utero" in several formats in September 2013.


title: In Utero

text: "In Utero" received critical acclaim from critics. "Time"s Christopher John Farley stated in his review, "Despite the fears of some alternative-music fans, Nirvana hasn't gone mainstream, though this potent new album may once again force the mainstream to go Nirvana." "Rolling Stone" reviewer David Fricke said that the album is "a lot of things – brilliant, corrosive, enraged and thoughtful, most of them all at once. But more than anything, it's a triumph of the will." "Entertainment Weekly" reviewer David Browne commented "Kurt Cobain hates it all", and noted that the sentiment pervades the record. Browne argued, "The music is often mesmerizing, cathartic rock & roll, but it is rock & roll without release, because the band is suspicious of the old-school rock clichés such a release would evoke."


title: In Utero

text: "NME" writer John Mulvey had doubts about the record; he concluded, "As a document of a mind in flux – dithering, dissatisfied, unable to come to terms with sanity – Kurt should be proud of [the album]. As a follow-up to one of the best records of the past ten years it just isn't quite there." "Plugged In" was not enthusiastic; reviewer Bob Waliszewski wrote, ""In Utero" is noxious noise with no redeeming value." Ben Thompson of "The Independent" commented that in spite of the more abrasive songs, ""In Utero" is beautiful far more often than it is ugly ... Nirvana have wisely neglected to make the unlistenable punk-rock nightmare they threatened us with." "Q" felt that the album showcases Cobain's songwriting abilities and wrote, "If this is how Cobain is going to develop, the future is lighthouse-bright."


title: In Utero

text: Several critics ranked "In Utero" one of the best releases of the year; it placed first and second in the album categories of the "Rolling Stone" and "Village Voice" Pazz & Jop year-end critics' polls. "The New York Times" included it on its list of the top ten albums of the year. It was nominated for Best Alternative Music Album at the 1994 Grammy Awards. The guitar riff from "Very Ape" was sampled by British electronic band the Prodigy for their 1994 single "Voodoo People".


title: In Utero

text: "In Utero" has continued to perform commercially and gather critical praise. In a 2003 "Guitar World" article for the album's tenth anniversary, Cobain biographer Charles R. Cross argued that "In Utero" was "a far better record than ["Nevermind"] and one that only 10 years later seems to be an influential seed spreader, judging by current bands. If it is possible for an album that sold four million copies to be overlooked, or underappreciated, then "In Utero" is that lost pearl." That year, "Pitchfork" named "In Utero" the 13th best album of the 1990s. "Rolling Stone" ranked it number 435 on its list The 500 Greatest Albums of All Time, and 173 in its 2020 updated list. It also ranked it the seventh best album of the 90s.


title: In Utero

text: In 2004, "Blender" named "In Utero" the 94th greatest American album, and in 2005, "Spin" named it the 51st best album of the previous 20 years. In 2005, "In Utero" was ranked number 358 in "Rock Hard's" book of "The 500 Greatest Rock & Metal Albums of All Time". In 2013, Diffuser.fm named "In Utero" the fourth best album of 1993, while "NME" ranked it at number 35 on its list "The 500 Greatest Albums of All Time". The album was also included in the book "1001 Albums You Must Hear Before You Die". In May 2017, "Loudwire" ranked it at number six on its list "The 30 Best Grunge Albums of All Time". In April 2019, "Rolling Stone" placed it at number eight on its 50 Greatest Grunge Albums list.


title: Toilet-Bound Hanako-kun

text: Kamome Academy is famous for its rumors regarding its Seven Wonders and supernatural occurrences. Nene Yashiro, a first-year high-school student who loves the occult and wishes for a boyfriend, summons the Seventh and most famous Wonder, "Hanako-san of the Toilet", the spirit of a girl who allegedly haunts the bathroom and can grant wishes for the right price. Upon summoning her, Nene discovers that "Hanako-san" is nothing like the rumors say; Hanako-san is a boy. With a turn of events, she is spiritually bound to Hanako and becomes his assistant, helping him destroy evil supernaturals and change rumors in order to maintain the balance between the spirit world and the human world. Along the way, Nene learns about her connection to the spirit world and the dark secrets regarding Hanako and his past.


title: Toilet-Bound Hanako-kun

text: The Seven Wonders of Kamome Academy are the seven most famous supernatural rumors in the school, and their corresponding supernaturals serve to maintain the students' safety from murderous supernaturals. Leading them is Hanako, who is the Seventh and most famous school Wonder. Each one has their own Boundary, a " divine yorishiro", and an aspect of the school that they control. Their Boundary is a section of the school where their power is the strongest. Boundaries are the 'sea' between the "Near Shore," where the living reside, and the "Far Shore", where other apparitions exist and thus contain a small amount of water on the ground. A" divine yorishiro" is an item they cherish that acts as the source of their power. When a "yorishiro" is destroyed (by removing its seal), the Wonder's designated seat as a School Wonder and their power is removed. Thus, they are usually kept in the deepest region of the Boundary or safeguarded by the wonder themselves.


title: Toilet-Bound Hanako-kun

text: Apart from the Seven Mysteries, there are other, less powerful supernaturals that roam the school. They rely on student rumors to gain power, unlike the Mysteries who already have theirs so popular and widespread among the student body.


title: Toilet-Bound Hanako-kun

text: "Toilet-Bound Hanako-kun" is written and illustrated by AidaIro. The series started in the July 2014 issue of Square Enix's "Monthly GFantasy", published on June 18, 2014. Square Enix has compiled its chapters into individual "tankōbon" volumes. The first volume was published on May 22, 2015. A volume 0 was released on December 27, 2019. As of August 26, 2022, eighteen volumes have been published.


title: Toilet-Bound Hanako-kun

text: In North America, Yen Press announced in July 2017 that they would publish the manga digitally. In July 2019, Yen Press announced the print release of the series.


title: Toilet-Bound Hanako-kun

text: An spin-off titled "Hōkago Shōnen Hanako-kun" launched on August 27th 2019. It was licensed by Yen Press under the title "After-School Hanako-kun" and released in April 2021.


title: Toilet-Bound Hanako-kun

text: An anime television series adaptation was announced in the April issue of "Monthly GFantasy" magazine on March 18, 2019. The series is animated by Lerche and directed by Masaomi Andō, with Yasuhiro Nakanishi handling series composition, and Mayuka Itou designing the characters. Hiroshi Takaki composed the music. It premiered from January 9, 2020, to March 26, 2020, on TBS, SUN, CBC, and BS-TBS. Jibaku Shōnen Band performed the series' opening theme song "No.7", while Akari Kitō performed the series' ending theme song "Tiny Light." The series has run for 12 episodes. Funimation had licensed the series for a simuldub. Following Sony's acquisition of Crunchyroll, the series was moved to Crunchyroll.


title: Toilet-Bound Hanako-kun

text: In a review of the anime for "NEO", Alex Jones praised the series and characters for being engaging, as well as the unique visuals, comparing "Hanako-kun" to a comic book brought to life, utilizing thick outlines, vibrant colors and distinct character proportions. However, he felt the series left on an unsatisfying note, noting there were several questions unanswered by the end of the series.


title: Cosmic microwave background

text: In Big Bang cosmology the cosmic microwave background (CMB, CMBR) is electromagnetic radiation that is a remnant from an early stage of the universe, also known as "relic radiation". The CMB is faint cosmic background radiation filling all space. It is an important source of data on the early universe because it is the oldest electromagnetic radiation in the universe, dating to the epoch of recombination when the first atoms were formed. With a traditional optical telescope, the space between stars and galaxies (the background) is completely dark (see: Olbers' paradox). However, a sufficiently sensitive radio telescope shows a faint background brightness, or glow, almost uniform, that is not associated with any star, galaxy, or other object. This glow is strongest in the microwave region of the radio spectrum. The accidental discovery of the CMB in 1965 by American radio astronomers Arno Penzias and Robert Wilson was the culmination of work initiated in the 1940s, and earned the discoverers the 1978 Nobel Prize in Physics.


title: Cosmic microwave background

text: CMB is landmark evidence of the Big Bang origin of the universe. When the universe was young, before the formation of stars and planets, it was denser, much hotter, and filled with an opaque fog of hydrogen plasma. As the universe expanded the plasma grew cooler and the radiation filling it expanded to longer wavelengths. When the temperature had dropped enough, protons and electrons combined to form neutral hydrogen atoms. Unlike the plasma, these newly conceived atoms could not scatter the thermal radiation by Thomson scattering, and so the universe became transparent. Cosmologists refer to the time period when neutral atoms first formed as the "recombination epoch", and the event shortly afterwards when photons started to travel freely through space is referred to as photon decoupling. The photons that existed at the time of photon decoupling have been propagating ever since, though growing less energetic, since the expansion of space causes their wavelength to increase over time (and wavelength is inversely proportional to energy according to Planck's relation). This is the source of the alternative term "relic radiation". The "surface of last scattering" refers to the set of points in space at the right distance from us so that we are now receiving photons originally emitted from those points at the time of photon decoupling.


title: Cosmic microwave background

text: Precise measurements of the CMB are critical to cosmology, since any proposed model of the universe must explain this radiation. The CMB has a thermal black body spectrum at a temperature of . The spectral radiance "dE"/"dν" peaks at 160.23 GHz, in the microwave range of frequencies, corresponding to a photon energy of about . Alternatively, if spectral radiance is defined as "dE"/"dλ", then the peak wavelength is 1.063 mm (282 GHz, photons). The glow is very nearly uniform in all directions, but the tiny residual variations show a very specific pattern, the same as that expected of a fairly uniformly distributed hot gas that has expanded to the current size of the universe. In particular, the spectral radiance at different angles of observation in the sky contains small anisotropies, or irregularities, which vary with the size of the region examined. They have been measured in detail, and match what would be expected if small thermal variations, generated by quantum fluctuations of matter in a very tiny space, had expanded to the size of the observable universe we see today. This is a very active field of study, with scientists seeking both better data (for example, the Planck spacecraft) and better interpretations of the initial conditions of expansion. Although many different processes might produce the general form of a black body spectrum, no model other than the Big Bang has yet explained the fluctuations. As a result, most cosmologists consider the Big Bang model of the universe to be the best explanation for the CMB.


title: Cosmic microwave background

text: The high degree of uniformity throughout the observable universe and its faint but measured anisotropy lend strong support for the Big Bang model in general and the ΛCDM ("Lambda Cold Dark Matter") model in particular. Moreover, the fluctuations are coherent on angular scales that are larger than the apparent cosmological horizon at recombination. Either such coherence is acausally fine-tuned, or cosmic inflation occurred.<ref name="hep-ph/0309057"></ref>


title: Cosmic microwave background

text: Other than the temperature and polarization anisotropy, the CMB frequency spectrum is expected to feature tiny departures from the black-body law known as spectral distortions. These are also at the focus of an active research effort with the hope of a first measurement within the forthcoming decades, as they contain a wealth of information about the primordial universe and the formation of structures at late time.


title: Cosmic microwave background

text: The cosmic microwave background radiation is an emission of uniform, black body thermal energy coming from all parts of the sky. The radiation is isotropic to roughly one part in 100,000: the root mean square variations are only 18 μK, after subtracting out a dipole anisotropy from the Doppler shift of the background radiation. The latter is caused by the peculiar velocity of the Sun relative to the comoving cosmic rest frame as it moves at some 369.82 ± 0.11 km/s towards the constellation Leo (galactic longitude 264.021 ± 0.011, galactic latitude 48.253 ± 0.005). The CMB dipole and aberration at higher multipoles have been measured, consistent with galactic motion.


title: Cosmic microwave background

text: In the Big Bang model for the formation of the universe, inflationary cosmology predicts that after about 10 seconds the nascent universe underwent exponential growth that smoothed out nearly all irregularities. The remaining irregularities were caused by quantum fluctuations in the inflation field that caused the inflation event. Long before the formation of stars and planets, the early universe was smaller, much hotter and, starting 10 seconds after the Big Bang, filled with a uniform glow from its white-hot fog of interacting plasma of photons, electrons, and baryons.


title: Cosmic microwave background

text: As the universe expanded, adiabatic cooling caused the energy density of the plasma to decrease until it became favorable for electrons to combine with protons, forming hydrogen atoms. This recombination event happened when the temperature was around 3000 K or when the universe was approximately 379,000 years old. As photons did not interact with these electrically neutral atoms, the former began to travel freely through space, resulting in the decoupling of matter and radiation.


title: Cosmic microwave background

text: The color temperature of the ensemble of decoupled photons has continued to diminish ever since; now down to , it will continue to drop as the universe expands. The intensity of the radiation corresponds to black-body radiation at 2.726 K because red-shifted black-body radiation is just like black-body radiation at a lower temperature. According to the Big Bang model, the radiation from the sky we measure today comes from a spherical surface called "the surface of last scattering". This represents the set of locations in space at which the decoupling event is estimated to have occurred and at a point in time such that the photons from that distance have just reached observers. Most of the radiation energy in the universe is in the cosmic microwave background, making up a fraction of roughly of the total density of the universe.


title: Cosmic microwave background

text: Two of the greatest successes of the Big Bang theory are its prediction of the almost perfect black body spectrum and its detailed prediction of the anisotropies in the cosmic microwave background. The CMB spectrum has become the most precisely measured black body spectrum in nature.


title: Cosmic microwave background

text: The cosmic microwave background was first predicted in 1948 by Ralph Alpher and Robert Herman, in close relation to work performed by Alpher's PhD advisor George Gamow. Alpher and Herman were able to estimate the temperature of the cosmic microwave background to be 5 K, though two years later they re-estimated it at 28 K. This high estimate was due to a misestimate of the Hubble constant by Alfred Behr, which could not be replicated and was later abandoned for the earlier estimate. Although there were several previous estimates of the temperature of space, these suffered from two flaws. First, they were measurements of the temperature of space and did not suggest that space was filled with a thermal Planck spectrum. Next, they depend on our being at a special spot at the edge of the Milky Way galaxy and they did not suggest the radiation is isotropic. The estimates would yield very different predictions if Earth happened to be located elsewhere in the universe.


title: Cosmic microwave background

text: The 1948 results of Alpher and Herman were discussed in many physics settings through about 1955, when both left the Applied Physics Laboratory at Johns Hopkins University. The mainstream astronomical community, however, was not intrigued at the time by cosmology. Alpher and Herman's prediction was rediscovered by Yakov Zel'dovich in the early 1960s, and independently predicted by Robert Dicke at the same time. The first published recognition of the CMB radiation as a detectable phenomenon appeared in a brief paper by Soviet astrophysicists A. G. Doroshkevich and Igor Novikov, in the spring of 1964. In 1964, David Todd Wilkinson and Peter Roll, Dicke's colleagues at Princeton University, began constructing a Dicke radiometer to measure the cosmic microwave background. In 1964, Arno Penzias and Robert Woodrow Wilson at the Crawford Hill location of Bell Telephone Laboratories in nearby Holmdel Township, New Jersey had built a Dicke radiometer that they intended to use for radio astronomy and satellite communication experiments. On 20 May 1964 they made their first measurement clearly showing the presence of the microwave background, with their instrument having an excess 4.2K antenna temperature which they could not account for. After receiving a telephone call from Crawford Hill, Dicke said "Boys, we've been scooped." A meeting between the Princeton and Crawford Hill groups determined that the antenna temperature was indeed due to the microwave background. Penzias and Wilson received the 1978 Nobel Prize in Physics for their discovery.


title: Cosmic microwave background

text: The interpretation of the cosmic microwave background was a controversial issue in the 1960s with some proponents of the steady state theory arguing that the microwave background was the result of scattered starlight from distant galaxies. Using this model, and based on the study of narrow absorption line features in the spectra of stars, the astronomer Andrew McKellar wrote in 1941: "It can be calculated that the 'rotational temperature' of interstellar space is 2 K." However, during the 1970s the consensus was established that the cosmic microwave background is a remnant of the big bang. This was largely because new measurements at a range of frequencies showed that the spectrum was a thermal, black body spectrum, a result that the steady state model was unable to reproduce.


title: Cosmic microwave background

text: Harrison, Peebles, Yu and Zel'dovich realized that the early universe would require inhomogeneities at the level of 10 or 10. Rashid Sunyaev later calculated the observable imprint that these inhomogeneities would have on the cosmic microwave background. Increasingly stringent limits on the anisotropy of the cosmic microwave background were set by ground-based experiments during the 1980s. RELIKT-1, a Soviet cosmic microwave background anisotropy experiment on board the Prognoz 9 satellite (launched 1 July 1983) gave upper limits on the large-scale anisotropy. The NASA COBE mission clearly confirmed the primary anisotropy with the Differential Microwave Radiometer instrument, publishing their findings in 1992. The team received the Nobel Prize in physics for 2006 for this discovery.


title: Cosmic microwave background

text: Inspired by the COBE results, a series of ground and balloon-based experiments measured cosmic microwave background anisotropies on smaller angular scales over the next decade. The primary goal of these experiments was to measure the scale of the first acoustic peak, which COBE did not have sufficient resolution to resolve. This peak corresponds to large scale density variations in the early universe that are created by gravitational instabilities, resulting in acoustical oscillations in the plasma. The first peak in the anisotropy was tentatively detected by the Toco experiment and the result was confirmed by the BOOMERanG and MAXIMA experiments. These measurements demonstrated that the geometry of the universe is approximately flat, rather than curved. They ruled out cosmic strings as a major component of cosmic structure formation and suggested cosmic inflation was the right theory of structure formation.


title: Cosmic microwave background

text: The second peak was tentatively detected by several experiments before being definitively detected by WMAP, which has tentatively detected the third peak. As of 2010, several experiments to improve measurements of the polarization and the microwave background on small angular scales are ongoing. These include DASI, WMAP, BOOMERanG, QUaD, Planck spacecraft, Atacama Cosmology Telescope, South Pole Telescope and the QUIET telescope.


title: Cosmic microwave background

text: The cosmic microwave background radiation and the cosmological redshift-distance relation are together regarded as the best available evidence for the Big Bang event. Measurements of the CMB have made the inflationary Big Bang model the Standard Cosmological Model. The discovery of the CMB in the mid-1960s curtailed interest in alternatives such as the steady state theory.


title: Cosmic microwave background

text: In the late 1940s Alpher and Herman reasoned that if there was a Big Bang, the expansion of the universe would have stretched the high-energy radiation of the very early universe into the microwave region of the electromagnetic spectrum, and down to a temperature of about 5 K. They were slightly off with their estimate, but they had the right idea. They predicted the CMB. It took another 15 years for Penzias and Wilson to discover that the microwave background was actually there.


title: Cosmic microwave background

text: According to standard cosmology, the CMB gives a snapshot of the hot early universe at the point in time when the temperature dropped enough to allow electrons and protons to form hydrogen atoms. This event made the universe nearly transparent to radiation because light was no longer being scattered off free electrons. When this occurred some 380,000 years after the Big Bang, the temperature of the universe was about 3,000 K. This corresponds to an ambient energy of about , which is much less than the ionization energy of hydrogen. This epoch is generally known as the "time of last scattering" or the period of recombination or decoupling.


title: Cosmic microwave background

text: Since decoupling, the color temperature of the background radiation has dropped by an average factor of 1,090 due to the expansion of the universe. As the universe expands, the CMB photons are redshifted, causing them to decrease in energy. The color temperature of this radiation stays inversely proportional to a parameter that describes the relative expansion of the universe over time, known as the scale length. The color temperature "T" of the CMB as a function of redshift, "z", can be shown to be proportional to the color temperature of the CMB as observed in the present day (2.725 K or 0.2348 meV):


title: Cosmic microwave background

text: For details about the reasoning that the radiation is evidence for the Big Bang, see Cosmic background radiation of the Big Bang.


title: Cosmic microwave background

text: The anisotropy, or directional dependency, of the cosmic microwave background is divided into two types: primary anisotropy, due to effects that occur at the surface of last scattering and before; and secondary anisotropy, due to effects such as interactions of the background radiation with intervening hot gas or gravitational potentials, which occur between the last scattering surface and the observer.


title: Cosmic microwave background

text: The structure of the cosmic microwave background anisotropies is principally determined by two effects: acoustic oscillations and diffusion damping (also called collisionless damping or Silk damping). The acoustic oscillations arise because of a conflict in the photon–baryon plasma in the early universe. The pressure of the photons tends to erase anisotropies, whereas the gravitational attraction of the baryons, moving at speeds much slower than light, makes them tend to collapse to form overdensities. These two effects compete to create acoustic oscillations, which give the microwave background its characteristic peak structure. The peaks correspond, roughly, to resonances in which the photons decouple when a particular mode is at its peak amplitude.


title: Cosmic microwave background

text: The peaks contain interesting physical signatures. The angular scale of the first peak determines the curvature of the universe (but not the topology of the universe). The next peak—ratio of the odd peaks to the even peaks—determines the reduced baryon density. The third peak can be used to get information about the dark-matter density.


title: Cosmic microwave background

text: The locations of the peaks give important information about the nature of the primordial density perturbations. There are two fundamental types of density perturbations called "adiabatic" and "isocurvature". A general density perturbation is a mixture of both, and different theories that purport to explain the primordial density perturbation spectrum predict different mixtures.


title: Cosmic microwave background

text: The CMB spectrum can distinguish between these two because these two types of perturbations produce different peak locations. Isocurvature density perturbations produce a series of peaks whose angular scales ("ℓ" values of the peaks) are roughly in the ratio 1 : 3 : 5 : ..., while adiabatic density perturbations produce peaks whose locations are in the ratio 1 : 2 : 3 : ... Observations are consistent with the primordial density perturbations being entirely adiabatic, providing key support for inflation, and ruling out many models of structure formation involving, for example, cosmic strings.


title: Cosmic microwave background

text: Collisionless damping is caused by two effects, when the treatment of the primordial plasma as fluid begins to break down:


title: Cosmic microwave background

text: These effects contribute about equally to the suppression of anisotropies at small scales and give rise to the characteristic exponential damping tail seen in the very small angular scale anisotropies.


title: Cosmic microwave background

text: The depth of the LSS refers to the fact that the decoupling of the photons and baryons does not happen instantaneously, but instead requires an appreciable fraction of the age of the universe up to that era. One method of quantifying how long this process took uses the "photon visibility function" (PVF). This function is defined so that, denoting the PVF by "P"("t"), the probability that a CMB photon last scattered between time "t" and is given by "P"("t")"dt".


title: Cosmic microwave background

text: The maximum of the PVF (the time when it is most likely that a given CMB photon last scattered) is known quite precisely. The first-year WMAP results put the time at which "P"("t") has a maximum as 372,000 years. This is often taken as the "time" at which the CMB formed. However, to figure out how it took the photons and baryons to decouple, we need a measure of the width of the PVF. The WMAP team finds that the PVF is greater than half of its maximal value (the "full width at half maximum", or FWHM) over an interval of 115,000 years. By this measure, decoupling took place over roughly 115,000 years, and when it was complete, the universe was roughly 487,000 years old.


title: Cosmic microwave background

text: Since the CMB came into existence, it has apparently been modified by several subsequent physical processes, which are collectively referred to as late-time anisotropy, or secondary anisotropy. When the CMB photons became free to travel unimpeded, ordinary matter in the universe was mostly in the form of neutral hydrogen and helium atoms. However, observations of galaxies today seem to indicate that most of the volume of the intergalactic medium (IGM) consists of ionized material (since there are few absorption lines due to hydrogen atoms). This implies a period of reionization during which some of the material of the universe was broken into hydrogen ions.


title: Cosmic microwave background

text: The CMB photons are scattered by free charges such as electrons that are not bound in atoms. In an ionized universe, such charged particles have been liberated from neutral atoms by ionizing (ultraviolet) radiation. Today these free charges are at sufficiently low density in most of the volume of the universe that they do not measurably affect the CMB. However, if the IGM was ionized at very early times when the universe was still denser, then there are two main effects on the CMB:


title: Cosmic microwave background

text: Both of these effects have been observed by the WMAP spacecraft, providing evidence that the universe was ionized at very early times, at a redshift more than 17. The detailed provenance of this early ionizing radiation is still a matter of scientific debate. It may have included starlight from the very first population of stars (population III stars), supernovae when these first stars reached the end of their lives, or the ionizing radiation produced by the accretion disks of massive black holes.


title: Cosmic microwave background

text: The time following the emission of the cosmic microwave background—and before the observation of the first stars—is semi-humorously referred to by cosmologists as the Dark Age, and is a period which is under intense study by astronomers (see 21 centimeter radiation).


title: Cosmic microwave background

text: Two other effects which occurred between reionization and our observations of the cosmic microwave background, and which appear to cause anisotropies, are the Sunyaev–Zeldovich effect, where a cloud of high-energy electrons scatters the radiation, transferring some of its energy to the CMB photons, and the Sachs–Wolfe effect, which causes photons from the Cosmic Microwave Background to be gravitationally redshifted or blueshifted due to changing gravitational fields.


title: Cosmic microwave background

text: The cosmic microwave background is polarized at the level of a few microkelvin. There are two types of polarization, called E-modes and B-modes. This is in analogy to electrostatics, in which the electric field ("E"-field) has a vanishing curl and the magnetic field ("B"-field) has a vanishing divergence. The E-modes arise naturally from Thomson scattering in a heterogeneous plasma. The B-modes are not produced by standard scalar type perturbations. Instead they can be created by two mechanisms: the first one is by gravitational lensing of E-modes, which has been measured by the South Pole Telescope in 2013; the second one is from gravitational waves arising from cosmic inflation. Detecting the B-modes is extremely difficult, particularly as the degree of foreground contamination is unknown, and the weak gravitational lensing signal mixes the relatively strong E-mode signal with the B-mode signal.


title: Cosmic microwave background

text: Cosmologists predict two types of B-modes, the first generated during cosmic inflation shortly after the big bang, and the second generated by gravitational lensing at later times.


title: Cosmic microwave background

text: Primordial gravitational waves are gravitational waves that could be observed in the polarisation of the cosmic microwave background and having their origin in the early universe. Models of cosmic inflation predict that such gravitational waves should appear; thus, their detection supports the theory of inflation, and their strength can confirm and exclude different models of inflation. It is the result of three things: inflationary expansion of space itself, reheating after inflation, and turbulent fluid mixing of matter and radiation.


title: Cosmic microwave background

text: On 17 March 2014 it was announced that the BICEP2 instrument had detected the first type of B-modes, consistent with inflation and gravitational waves in the early universe at the level of , which is the amount of power present in gravitational waves compared to the amount of power present in other scalar density perturbations in the very early universe. Had this been confirmed it would have provided strong evidence for cosmic inflation and the Big Bang


title: Cosmic microwave background

text: and on 19 September 2014 new results of the Planck experiment reported that the results of BICEP2 can be fully attributed to cosmic dust.


title: Cosmic microwave background

text: The second type of B-modes was discovered in 2013 using the South Pole Telescope with help from the Herschel Space Observatory. In October 2014, a measurement of the B-mode polarization at 150 GHz was published by the POLARBEAR experiment. Compared to BICEP2, POLARBEAR focuses on a smaller patch of the sky and is less susceptible to dust effects. The team reported that POLARBEAR's measured B-mode polarization was of cosmological origin (and not just due to dust) at a 97.2% confidence level.


title: Cosmic microwave background

text: Subsequent to the discovery of the CMB, hundreds of cosmic microwave background experiments have been conducted to measure and characterize the signatures of the radiation. The most famous experiment is probably the NASA Cosmic Background Explorer (COBE) satellite that orbited in 1989–1996 and which detected and quantified the large scale anisotropies at the limit of its detection capabilities. Inspired by the initial COBE results of an extremely isotropic and homogeneous background, a series of ground- and balloon-based experiments quantified CMB anisotropies on smaller angular scales over the next decade. The primary goal of these experiments was to measure the angular scale of the first acoustic peak, for which COBE did not have sufficient resolution. These measurements were able to rule out cosmic strings as the leading theory of cosmic structure formation, and suggested cosmic inflation was the right theory. During the 1990s, the first peak was measured with increasing sensitivity and by 2000 the BOOMERanG experiment reported that the highest power fluctuations occur at scales of approximately one degree. Together with other cosmological data, these results implied that the geometry of the universe is flat. A number of ground-based interferometers provided measurements of the fluctuations with higher accuracy over the next three years, including the Very Small Array, Degree Angular Scale Interferometer (DASI), and the Cosmic Background Imager (CBI). DASI made the first detection of the polarization of the CMB and the CBI provided the first E-mode polarization spectrum with compelling evidence that it is out of phase with the T-mode spectrum.


title: Cosmic microwave background

text: In June 2001, NASA launched a second CMB space mission, WMAP, to make much more precise measurements of the large scale anisotropies over the full sky. WMAP used symmetric, rapid-multi-modulated scanning, rapid switching radiometers to minimize non-sky signal noise. The first results from this mission, disclosed in 2003, were detailed measurements of the angular power spectrum at a scale of less than one degree, tightly constraining various cosmological parameters. The results are broadly consistent with those expected from cosmic inflation as well as various other competing theories, and are available in detail at NASA's data bank for Cosmic Microwave Background (CMB) (see links below). Although WMAP provided very accurate measurements of the large scale angular fluctuations in the CMB (structures about as broad in the sky as the moon), it did not have the angular resolution to measure the smaller scale fluctuations which had been observed by former ground-based interferometers.


title: Cosmic microwave background

text: A third space mission, the ESA (European Space Agency) Planck Surveyor, was launched in May 2009 and performed an even more detailed investigation until it was shut down in October 2013. Planck employed both HEMT radiometers and bolometer technology and measured the CMB at a smaller scale than WMAP. Its detectors were trialled in the Antarctic Viper telescope as ACBAR (Arcminute Cosmology Bolometer Array Receiver) experiment—which has produced the most precise measurements at small angular scales to date—and in the Archeops balloon telescope.


title: Cosmic microwave background

text: On 21 March 2013, the European-led research team behind the Planck cosmology probe released the mission's all-sky map (565x318 jpeg, 3600x1800 jpeg) of the cosmic microwave background. The map suggests the universe is slightly older than researchers expected. According to the map, subtle fluctuations in temperature were imprinted on the deep sky when the cosmos was about years old. The imprint reflects ripples that arose as early, in the existence of the universe, as the first nonillionth of a second. Apparently, these ripples gave rise to the present vast cosmic web of galaxy clusters and dark matter. Based on the 2013 data, the universe contains 4.9% ordinary matter, 26.8% dark matter and 68.3% dark energy. On 5 February 2015, new data was released by the Planck mission, according to which the age of the universe is billion years old and the Hubble constant was measured to be .


title: Cosmic microwave background

text: Additional ground-based instruments such as the South Pole Telescope in Antarctica and the proposed Clover Project, Atacama Cosmology Telescope and the QUIET telescope in Chile will provide additional data not available from satellite observations, possibly including the B-mode polarization.


title: Cosmic microwave background

text: Raw CMBR data, even from space vehicles such as WMAP or Planck, contain foreground effects that completely obscure the fine-scale structure of the cosmic microwave background. The fine-scale structure is superimposed on the raw CMBR data but is too small to be seen at the scale of the raw data. The most prominent of the foreground effects is the dipole anisotropy caused by the Sun's motion relative to the CMBR background. The dipole anisotropy and others due to Earth's annual motion relative to the Sun and numerous microwave sources in the galactic plane and elsewhere must be subtracted out to reveal the extremely tiny variations characterizing the fine-scale structure of the CMBR background.


title: Cosmic microwave background

text: The detailed analysis of CMBR data to produce maps, an angular power spectrum, and ultimately cosmological parameters is a complicated, computationally difficult problem. Although computing a power spectrum from a map is in principle a simple Fourier transform, decomposing the map of the sky into spherical harmonics,


title: Cosmic microwave background

text: where the formula_2 term measures the mean temperature and formula_3 term accounts for the fluctuation, where the formula_4 refers to a spherical harmonic, and "ℓ" is the multipole number while "m" is the azimuthal number.


title: Cosmic microwave background

text: By applying the angular correlation function, the sum can be reduced to an expression that only involves "ℓ" and power spectrum term formula_5 The angled brackets indicate the average with respect to all observers in the universe; since the universe is homogeneous and isotropic, therefore there is an absence of preferred observing direction. Thus, "C" is independent of "m". Different choices of "ℓ" correspond to multipole moments of CMB.


title: Cosmic microwave background

text: In practice it is hard to take the effects of noise and foreground sources into account. In particular, these foregrounds are dominated by galactic emissions such as Bremsstrahlung, synchrotron, and dust that emit in the microwave band; in practice, the galaxy has to be removed, resulting in a CMB map that is not a full-sky map. In addition, point sources like galaxies and clusters represent another source of foreground which must be removed so as not to distort the short scale structure of the CMB power spectrum.


title: Cosmic microwave background

text: Constraints on many cosmological parameters can be obtained from their effects on the power spectrum, and results are often calculated using Markov chain Monte Carlo sampling techniques.


title: Cosmic microwave background

text: When , the formula_3 term reduced to 1, and what we have left here is just the mean temperature of the CMB. This "mean" is called CMB monopole, and it is observed to have an average temperature of about with one standard deviation confidence. The accuracy of this mean temperature may be impaired by the diverse measurements done by different mapping measurements. Such measurements demand absolute temperature devices, such as the FIRAS instrument on the COBE satellite. The measured "kT" is equivalent to 0.234 meV or . The photon number density of a blackbody having such temperature is formula_7. Its energy density is \approx \mathrm{0.260\,eV{\cdot}cm^{-3}}</math>,}} and the ratio to the critical density is .


title: Cosmic microwave background

text: CMB dipole represents the largest anisotropy, which is in the first spherical harmonic (). When , the formula_3 term reduces to one cosine function and thus encodes amplitude fluctuation. The amplitude of CMB dipole is around . Since the universe is presumed to be homogeneous and isotropic, an observer should see the blackbody spectrum with temperature "T" at every point in the sky. The spectrum of the dipole has been confirmed to be the differential of a blackbody spectrum.


title: Cosmic microwave background

text: CMB dipole is frame-dependent. The CMB dipole moment could also be interpreted as the peculiar motion of the Earth toward the CMB. Its amplitude depends on the time due to the Earth's orbit about the barycenter of the solar system. This enables us to add a time-dependent term to the dipole expression. The modulation of this term is 1 year, which fits the observation done by COBE FIRAS. The dipole moment does not encode any primordial information.


title: Cosmic microwave background

text: From the CMB data, it is seen that the Sun appears to be moving at relative to the reference frame of the CMB (also called the CMB rest frame, or the frame of reference in which there is no motion through the CMB). The Local Group — the galaxy group that includes our own Milky Way galaxy — appears to be moving at in the direction of galactic longitude , . This motion results in an anisotropy of the data (CMB appearing slightly warmer in the direction of movement than in the opposite direction). The standard interpretation of this temperature variation is a simple velocity redshift and blueshift due to motion relative to the CMB, but alternative cosmological models can explain some fraction of the observed dipole temperature distribution in the CMB.


title: Cosmic microwave background

text: A 2021 study of Wide-field Infrared Survey Explorer questions the kinematic interpretation of CMB anisotropy with high statistical confidence.


title: Cosmic microwave background

text: The temperature variation in the CMB temperature maps at higher multipoles, or , is considered to be the result of perturbations of the density in the early Universe, before the recombination epoch. Before recombination, the Universe consisted of a hot, dense plasma of electrons and baryons. In such a hot dense environment, electrons and protons could not form any neutral atoms. The baryons in such early Universe remained highly ionized and so were tightly coupled with photons through the effect of Thompson scattering. These phenomena caused the pressure and gravitational effects to act against each other, and triggered fluctuations in the photon-baryon plasma. Quickly after the recombination epoch, the rapid expansion of the universe caused the plasma to cool down and these fluctuations are "frozen into" the CMB maps we observe today. The said procedure happened at a redshift of around .


title: Cosmic microwave background

text: With the increasingly precise data provided by WMAP, there have been a number of claims that the CMB exhibits anomalies, such as very large scale anisotropies, anomalous alignments, and non-Gaussian distributions.<ref name="arXiv:astro-ph/0511666"></ref><ref name="arXiv:astro-ph/0503213"></ref> The most longstanding of these is the low-"ℓ" multipole controversy. Even in the COBE map, it was observed that the quadrupole (, spherical harmonic) has a low amplitude compared to the predictions of the Big Bang. In particular, the quadrupole and octupole () modes appear to have an unexplained alignment with each other and with both the ecliptic plane and equinoxes. A number of groups have suggested that this could be the signature of new physics at the greatest observable scales; other groups suspect systematic errors in the data.


title: Cosmic microwave background

text: Ultimately, due to the foregrounds and the cosmic variance problem, the greatest modes will never be as well measured as the small angular scale modes. The analyses were performed on two maps that have had the foregrounds removed as far as possible: the "internal linear combination" map of the WMAP collaboration and a similar map prepared by Max Tegmark and others. Later analyses have pointed out that these are the modes most susceptible to foreground contamination from synchrotron, dust, and Bremsstrahlung emission, and from experimental uncertainty in the monopole and dipole.


title: Cosmic microwave background

text: A full Bayesian analysis of the WMAP power spectrum demonstrates that the quadrupole prediction of Lambda-CDM cosmology is consistent with the data at the 10% level and that the observed octupole is not remarkable. Carefully accounting for the procedure used to remove the foregrounds from the full sky map further reduces the significance of the alignment by ~5%.


title: Cosmic microwave background

text: Recent observations with the Planck telescope, which is very much more sensitive than WMAP and has a larger angular resolution, record the same anomaly, and so instrumental error (but not foreground contamination) appears to be ruled out. Coincidence is a possible explanation, chief scientist from WMAP, Charles L. Bennett suggested coincidence and human psychology were involved, "I do think there is a bit of a psychological effect; people want to find unusual things."


title: Cosmic microwave background

text: Assuming the universe keeps expanding and it does not suffer a Big Crunch, a Big Rip, or another similar fate, the cosmic microwave background will continue redshifting until it will no longer be detectable, and will be superseded first by the one produced by starlight, and perhaps, later by the background radiation fields of processes that may take place in the far future of the universe such as proton decay, evaporation of black holes, and positronium decay.


title: Muskrat

text: The muskrat ("Ondatra zibethicus") is a medium-sized semiaquatic rodent native to North America and an introduced species in parts of Europe, Asia, and South America. The muskrat is found in wetlands over a wide range of climates and habitats. It has important effects on the ecology of wetlands, and is a resource of food and fur for humans.


title: Muskrat

text: Adult muskrats weigh , with a body length of . They are covered with short, thick fur of medium to dark brown color. Their long tails, covered with scales rather than hair, are their main means of propulsion. Muskrats spend most of their time in the water and can swim under water for 12 to 17 minutes. They live in families, consisting of a male and female pair and their young. To protect themselves from the cold and from predators, they build nests that are often burrowed into the bank with an underwater entrance. Muskrats feed mostly on cattail and other aquatic vegetation but also eat small animals.


title: Muskrat

text: "Ondatra zibethicus" is the only species in the genus "Ondatra" and tribe Ondatrini. It is the largest species in the subfamily Arvicolinae, which includes 142 other species of rodents, mostly voles and lemmings. Muskrats are referred to as "rats" in a general sense because they are medium-sized rodents with an adaptable lifestyle and an omnivorous diet. They are not, however, members of the genus "Rattus". They are not closely related to beavers, with which they share habitat and general appearance.


title: Muskrat

text: The muskrat's name probably comes from a word of Algonquian (possibly Powhatan) origin, "muscascus" (literally "it is red", so called for its colorings), or from the Abenaki native word "mòskwas", as seen in the archaic English name for the animal, "musquash". Because of the association with the "musky" odor, which the muskrat uses to mark its territory, and its flattened tail, the name became altered to musk-beaver; later it became "muskrat" due to its resemblance to rats.


title: Muskrat

text: Similarly, its specific name "zibethicus" means "musky", being the adjective of "zibethus" "civet musk; civet". The genus name comes from the Huron word for the animal, "ondathra", and entered New Latin as "Ondatra" via French.