Speed of sound

The speed of sound is the distance traveled per unit time by a sound wave propagating through an elastic medium. In dry air at 20 °C, the speed of sound is 343.2 metres per second (1,126 ft/s). This is 1,236 kilometres per hour (768 mph; 667 kn), or a kilometre in 2.914 s or a mile in 4.689 s.

The speed of sound in an ideal gas is independent of frequency, but does vary slightly with frequency in a real gas. It is proportional to the square root of the absolute temperature, but is independent of pressure or density for a given ideal gas. The speed of sound in air varies slightly with pressure only because air is not quite an ideal gas. Although, in the case of gas only the speed of sound is expressed in terms of a ratio of both density and pressure, these quantities cancel in ideal gases at any given temperature, composition, and heat capacity. This leads to a velocity formula for ideal gases which includes only the latter independent variables.

In common everyday speech, speed of sound refers to the speed of sound waves in air. However, the speed of sound varies from substance to substance. Sound travels faster in liquids and non-porous solids than it does in air. It travels about 4.3 times as fast in water (1,484 m/s), and nearly 15 times as fast in iron (5,120 m/s), as in air at 20 °C. Sound waves in solids are composed of compression waves (just as in gases and liquids), but there is also a different type of sound wave called a shear wave, which occurs only in solids. These different types of waves in solids usually travel at different speeds, as exhibited in seismology. The speed of a compression sound wave in solids is determined by the medium's compressibility, shear modulus and density. The speed of shear waves is determined only by the solid material's shear modulus and density.

Sounds Like

"Sounds Like" is the fourth episode of the second season of Masters of Horror. It is directed by Brad Anderson, and originally aired in North America on November 17, 2006.

Plot

Quality control supervisor Larry Pearce (Chris Bauer) spends his days monitoring the nuances of his tech support staff's telephone conversations. Listening is his life. However, after his young son's death, he experiences a supernaturally heightened sense of hearing, Larry is forced to take violent action to silence the horrific cacophony in his head. He comes home to find that everything, including the small appliances, creates insufferable noise.

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DNA

Deoxyribonucleic acid (ⁱ/diˈɒksiˌraɪboʊnjʊˌkliːɪk, -ˌkleɪɪk/;DNA) is a molecule that carries most of the genetic instructions used in the development, functioning and reproduction of all known living organisms and many viruses. DNA is a nucleic acid; alongside proteins and carbohydrates, nucleic acids compose the three major macromolecules essential for all known forms of life. Most DNA molecules consist of two biopolymer strands coiled around each other to form a double helix. The two DNA strands are known as polynucleotides since they are composed of simpler units called nucleotides. Each nucleotide is composed of a nitrogen-containing nucleobase—either cytosine (C), guanine (G), adenine (A), or thymine (T)—as well as a monosaccharide sugar called deoxyribose and a phosphate group. The nucleotides are joined to one another in a chain by covalent bonds between the sugar of one nucleotide and the phosphate of the next, resulting in an alternating sugar-phosphate backbone. According to base pairing rules (A with T, and C with G), hydrogen bonds bind the nitrogenous bases of the two separate polynucleotide strands to make double-stranded DNA. The total amount of related DNA base pairs on Earth is estimated at 5.0 x 10³⁷, and weighs 50 billion tonnes. In comparison, the total mass of the biosphere has been estimated to be as much as 4 TtC (trillion tons of carbon).

Speed

In everyday use and in kinematics, the speed of an object is the magnitude of its velocity (the rate of change of its position); it is thus a scalar quantity. The average speed of an object in an interval of time is the distance travelled by the object divided by the duration of the interval; the instantaneous speed is the limit of the average speed as the duration of the time interval approaches zero.

Like velocity, speed has the dimensions of a length divided by a time; the SI unit of speed is the metre per second, but the most common unit of speed in everyday usage is the kilometre per hour or, in the US and the UK, miles per hour. For air and marine travel the knot is commonly used.

The fastest possible speed at which energy or information can travel, according to special relativity, is the speed of light in a vacuum c = 7008299792458000000♠299792458 metres per second (approximately 7008299722222222222♠1079000000 km/h or 7008299963840000000♠671000000 mph). Matter cannot quite reach the speed of light, as this would require an infinite amount of energy. In relativity physics, the concept of rapidity replaces the classical idea of speed.

Sounds Like a Melody

"Sounds Like a Melody" is a song by the German group Alphaville, from the group's debut album Forever Young. The single was released on 14 May 1984.

The song was a big success in continental Europe and South Africa, reaching the Top 10; it topped the charts in Italy and Sweden.

Song background

Originally, Alphaville had planned to release "Forever Young" as their second single, to follow the success of "Big in Japan". However, record studio executives requested that Alphaville release an additional song between the two singles, and as a result "Sounds Like a Melody" was written and arranged in just two days. Of the experience, singer Marian Gold said "the whole affair felt like an insult to our naive hippie instincts. Writing music exclusively for the sake of commercial success seemed like the sell-out of our virtual beliefs. On the other hand, did this not open up possibilities for wonderful games to play in the brave new world of pop music?" This corporate pressure caused the band to dislike the song and they refused to play it live for over 10 years.