Some context: Iron Maiden are an English heavy metal band formed in Leyton, East London, in 1975 by bassist and primary songwriter Steve Harris. The band's discography has grown to thirty-eight albums, including sixteen studio albums, twelve live albums, four EPs, and seven compilations. Pioneers of the new wave of British heavy metal, Iron Maiden achieved initial success during the early 1980s. After several line-up changes, the band went on to release a series of UK and US platinum and gold albums, including 1982's The Number of the Beast, 1983's Piece of Mind, 1984's Powerslave, 1985's live release Live
On New Year's Eve 1978, Iron Maiden recorded a demo, consisting of four songs, at Spaceward Studios in Cambridge. Hoping the recording would help them secure more gigs, the band presented a copy to Neal Kay, then managing a heavy metal club called "Bandwagon Heavy Metal Soundhouse", located in Kingsbury Circle, northwest London. Upon hearing the tape, Kay began playing the demo regularly at the Bandwagon, and one of the songs, "Prowler", eventually went to No. 1 in the Soundhouse charts, which were published weekly in Sounds magazine. A copy was also acquired by Rod Smallwood, who soon became the band's manager, and, as Iron Maiden's popularity increased, they released the demo on their own record label as The Soundhouse Tapes, named after the club. Featuring only three tracks (one song, "Strange World", was excluded as the band were unsatisfied with its production) all five thousand copies were sold out within weeks.  In December 1979, the band secured a major record deal with EMI and asked Dave Murray's childhood friend Adrian Smith of Urchin to join the group as their second guitarist. Smith declined as he was busy with his own band, Urchin, so Iron Maiden hired guitarist Dennis Stratton instead. Shortly afterwards, Doug Sampson left due to health issues and was replaced by ex-Samson drummer Clive Burr at Stratton's suggestion on 26 December. Iron Maiden's first appearance on an album was on the Metal for Muthas compilation (released on 15 February 1980) with two early versions of "Sanctuary" and "Wrathchild". The release led to an ensuing tour which featured several other bands linked with the new wave of British heavy metal.  Iron Maiden's eponymous 1980 release, Iron Maiden, debuted at No. 4 in the UK Albums Chart. In addition to the title track (a live version of which would be one of the first music videos aired on MTV), the album includes other early favourites such as "Running Free", "Transylvania", "Phantom of the Opera", and "Sanctuary" - which was not on the original UK release but appeared on the US version and subsequent remasters. The band set out on a headline tour of the UK, before opening for Kiss on their 1980 Unmasked Tour's European leg as well as supporting Judas Priest on select dates. Iron Maiden also appeared, to much acclaim, at the Reading Festival 1980. They were second to top of the bill on the Saturday, with UFO headlining. After the Kiss tour, Dennis Stratton was dismissed from the band as a result of creative and personal differences, and was replaced by Adrian Smith in October 1980.  In 1981, Iron Maiden released their second album, entitled Killers. Containing many tracks written prior to their debut release, only two new songs were written for the record: "Prodigal Son" and "Murders in the Rue Morgue" (the latter's title was taken from the short story by Edgar Allan Poe). Unsatisfied with the production on their debut album, the band hired veteran producer Martin Birch, who would go on to work for Iron Maiden until his retirement in 1992. The record was followed by the band's first world tour, which included their debut performance in the United States, opening for Judas Priest at The Aladdin Casino, Las Vegas.
was their album successful?
A: one of the songs, "Prowler", eventually went to No. 1 in the Soundhouse charts,

Some context: Zhang Heng (Chinese: Zhang Heng ; AD 78-139), formerly romanized as Chang Heng, was a Han Chinese polymath from Nanyang who lived during the Han dynasty. Educated in the capital cities of Luoyang and Chang'an, he achieved success as an astronomer, mathematician, scientist, engineer, inventor, geographer, cartographer, artist, poet, statesman, and literary scholar. Zhang Heng began his career as a minor civil servant in Nanyang. Eventually, he became Chief Astronomer, Prefect of the Majors for Official Carriages, and then Palace Attendant at the imperial court.
Zhang Heng's mechanical inventions influenced later Chinese inventors such as Yi Xing, Zhang Sixun, Su Song, and Guo Shoujing. Su Song directly named Zhang's water-powered armillary sphere as the inspiration for his 11th-century clock tower. The cosmic model of nine points of Heaven corresponding with nine regions of earth conceived in the work of the scholar-official Chen Hongmou (1696-1771) followed in the tradition of Zhang's book Spiritual Constitution of the Universe. The seismologist John Milne, who created the modern seismograph in 1876 alongside Thomas Gray and James A. Ewing at the Imperial College of Engineering in Tokyo, commented in 1886 on Zhang Heng's contributions to seismology. The historian Joseph Needham emphasized his contributions to pre-modern Chinese technology, stating that Zhang was noted even in his day for being able to "make three wheels rotate as if they were one." More than one scholar has described Zhang as a polymath. However, some scholars also point out that Zhang's writing lacks concrete scientific theories. Comparing Zhang with his contemporary, Ptolemy (83-161) of Roman Egypt, Jin Guantao, Fan Hongye, and Liu Qingfeng state:  Based on the theories of his predecessors, Zhang Heng systematically developed the celestial sphere theory. An armillary constructed on the basis of his hypotheses bears a remarkable similarity to Ptolemy's earth-centered theory. However, Zhang Heng did not definitely propose a theoretical model like Ptolemy's earth-centered one. It is astonishing that the celestial model Zhang Heng constructed was almost a physical model of Ptolemy's earth-centered theory. Only a single step separates the celestial globe from the earth-centered theory, but Chinese astronomers never took that step.  Here we can see how important the exemplary function of the primitive scientific structure is. In order to use the Euclidean system of geometry as a model for the development of astronomical theory, Ptolemy first had to select hypotheses which could serve as axioms. He naturally regarded circular motion as fundamental and then used the circular motion of deferents and epicycles in his earth-centered theory. Although Zhang Heng understood that the sun, moon and planets move in circles, he lacked a model for a logically structured theory and so could not establish a corresponding astronomical theory. Chinese astronomy was most interested in extracting the algebraic features of planetary motion (that is, the length of the cyclic periods) to establish astronomical theories. Thus astronomy was reduced to arithmetic operations, extracting common multiples and divisors from the observed cyclic motions of the heavenly bodies.
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