A chemical element is a pure chemical substance consisting of one type of atom distinguished by its atomic number, which is the number of protons in its nucleus. They are divided into metals and non-metals. Familiar examples of elements include carbon, oxygen (non-metals) together with aluminium, iron, copper, gold, mercury, and lead (metals).

As of November 2011, 118 elements have been identified, the latest being ununseptium in 2010. Of the 118 known elements, only the first 98 are known to occur naturally on Earth; 80 of them are stable, while the others are radioactive, decaying into lighter elements over various timescales from fractions of a second to billions of years. Those elements that do not occur naturally on Earth have been produced artificially as the synthetic products of man-made nuclear reactions.

Hydrogen and helium are by far the most abundant elements in the universe. However, iron is the most abundant element (by mass) making up the Earth, and oxygen is the most common element in the Earth's crust. Although all known chemical matter is composed of these elements, chemical matter itself constitutes only about 15% of the matter in the universe. The remainder is dark matter, a mysterious substance which is not composed of chemical elements since it lacks protons, neutrons or electrons.

Carl Edward Sagan ( /ˈseɪɡɪn/; November 9, 1934 – December 20, 1996) was an American astronomer, astrophysicist, cosmologist, author, science popularizer, and science communicator in astronomy and natural sciences. He published more than 600 scientific papers and articles and was author, co-author or editor of more than 20 books. He advocated scientifically skeptical inquiry and the scientific method, pioneered exobiology and promoted the Search for Extra-Terrestrial Intelligence (SETI).

Sagan is known for his popular science books and for the award-winning 1980 television series Cosmos: A Personal Voyage, which he narrated and co-wrote. The book Cosmos was published to accompany the series. Sagan wrote the novel Contact, the basis for a 1997 film of the same name.

Carl Sagan was born in Brooklyn, New York, to a Ukrainian Jewish family. His father, Sam Sagan, was an immigrant garment worker from Kamenets-Podolsk, Ukraine; his mother, Rachel Molly Gruber, a housewife. Carl was named in honor of Rachel's biological mother, Chaiya Clara, in Sagan's words, "the mother she never knew." Sagan graduated from Rahway High School in Rahway, New Jersey, in 1951.

Thomas Andrew Lehrer (born April 9, 1928) is an American singer-songwriter, satirist, pianist, and mathematician. He has lectured on mathematics and musical theater. Lehrer is best known for the pithy, humorous songs he recorded in the 1950s and 1960s.

His work often parodies popular song forms, though Lehrer usually creates original melodies when doing so. A notable exception is his song "The Elements", where he sets the names of the chemical elements to the tune of the "Major-General's Song" from Gilbert and Sullivan's Pirates of Penzance. Lehrer's earlier work typically dealt with non-topical subject matter and was noted for its black humor, seen in songs such as "Poisoning Pigeons in the Park". In the 1960s, he produced a number of songs dealing with social and political issues of the day, particularly when he wrote for the U.S. version of the television show That Was The Week That Was.

In the early 1970s, he retired from public performances to devote his time to teaching mathematics and music theatre at the University of California, Santa Cruz. He did two additional performances in 1998 at a London gala show celebrating the career of impresario Cameron Mackintosh.

Song In (in hangul 송인, in hanja 宋仁) was a civil official in the mid-Goryeo era who became the intermediary founder of the Jincheon Song clan. His highest post was munha pyeongjangsa (문하 평장사). This was the highest government position in the period. Song In was responsible for administration, judicial affairs and economy in the district.

As he performed meritorious deeds during the King, he was conferred with Chanhwagongsin and Jincheonbaek. Baek was a position of politicians who were responsible for administration, judicial affairs and economy in the district. As the government created him Jincheonbaek, his family started regarding Jincheon as their origin. Hence, the family origin became Jincheon Song.

When he was in the position of Sangsanbaek, he tried to be just and fair in all the administrative affairs and strived to enhance the welfare of his people. He also focused on education for the youth and courtesy for people, which made his district famous for most excellent behaviors in the nation. After that, the people have long paid tribute to his feats.

System of a Down, also known by the acronym SOAD and often shortened to System, is a rock band from Southern California, formed in 1994. It consists of Serj Tankian (lead vocals, keyboards, rhythm guitar), Daron Malakian (guitar, vocals), Shavo Odadjian (bass, background vocals) and John Dolmayan (drums).

The band achieved commercial success with the release of five studio albums; from which three debuted at number one on the Billboard 200. System of a Down has been nominated for four Grammy Awards, and won the award in 2006 for Best Hard Rock Performance for the song "B.Y.O.B.". The group went on hiatus in August 2006, but reunited in November 2010, embarking on a worldwide tour in 2011.

Serj Tankian, Daron Malakian, and Shavo Odadjian all attended Rose and Alex Pilibos Armenian School while children, although because of their eight-year age difference they did not meet until 1992 while working on separate projects at the same recording studio. They formed a band named Soil with Tankian on vocals and keyboards, Malakian on vocals and guitar, Dave Hakopyan (who later played in The Apex Theory/Mt. Helium) on bass and Domingo "Dingo" Laranio on drums. The band hired Shavo Odadjian (another Rose and Alex Pilibos alumnus) as manager, although he eventually joined Soil as rhythm guitarist. After three years, only one live show, and one jam session recording, Hakopyan and Laranio quit the band, feeling that it was not going anywhere.