Fourth

Fourth or 4th may refer to:

In music

See also

Fourth (Soft Machine album)

Fourth is the fourth studio album by the Canterbury band Soft Machine, released in 1971. The album is also titled Four or 4 in the USA.

Overview

The numeral "4" is the title as shown on the cover in all countries, but a written-out title appears on the spine and label. This was the group's first all-instrumental album, although their previous album Third had almost completed the band's move in this direction toward instrumental jazz, and a complete abandonment of their original self-presentation as a psychedelic pop group, or progressive rock group. It was also the last of their albums to include drummer and founding member Robert Wyatt who afterwards left to record a solo album, The End of an Ear (in which he described himself on the cover as an "out of work pop singer"), and then founded a new group, Matching Mole, whose name was a pun on "Soft Machine" as pronounced in French: "Machine Molle".

Like the previous Soft Machine album, this one uses session musicians who were not regarded as full group members, but toured with the band for live performances.

Degree (angle)

A degree (in full, a degree of arc, arc degree, or arcdegree), usually denoted by ° (the degree symbol), is a measurement of plane angle, representing ¹⁄₃₆₀ of a full rotation. It is not an SI unit, as the SI unit for angles is radian, but it is mentioned in the SI brochure as an accepted unit. Because a full rotation equals 2π radians, one degree is equivalent to π/180 radians.

History

The original motivation for choosing the degree as a unit of rotations and angles is unknown. One theory states that it is related to the fact that 360 is approximately the number of days in a year. Ancient astronomers noticed that the sun, which follows through the ecliptic path over the course of the year, seems to advance in its path by approximately one degree each day. Some ancient calendars, such as the Persian calendar, used 360 days for a year. The use of a calendar with 360 days may be related to the use of sexagesimal numbers.

Another theory is that the Babylonians subdivided the circle using the angle of an equilateral triangle as the basic unit and further subdivided the latter into 60 parts following their sexagesimal numeric system. The earliest trigonometry, used by the Babylonian astronomers and their Greek successors, was based on chords of a circle. A chord of length equal to the radius made a natural base quantity. One sixtieth of this, using their standard sexagesimal divisions, was a degree.