Rod (unit)

The rod or perch or pole is a surveyors tool and unit of length equal to 5¹⁄₂ yards, 16¹⁄₂ feet, ¹⁄₃₂₀ of a statute mile or one-fourth of a surveyor's chain and 5.0292 meters. The rod is useful as a unit of length because whole number multiples of it can equal one acre of square measure. The 'perfect acre' is a rectangular area of 43,560 square feet, bounded by sides 660 feet by 66 feet long (660 ft long × 66 ft wide), or 220 yards by 22 yards long (220 yd/ long × 22 yd wide), or 40 rods by 4 rods long. Thus, an acre is 160 square rods. Since the adoption of the international yard on 1 July 1959, the rod has been equal to exactly 5.0292 meters.

A rod is the same length as a perch, also sometimes called a pole which measure using cordage or wood, slightly antedated the use of both rods and surveyors chains, made of more dimensionally regular materials. The measure also has a relationship to the military pike of about the same size and both measures date from the sixteenth century, when that weapon was still utilized in national armies. The tool, normally configured as a metal rod with eye-ends (loops that could be hooked together), was used commonly until quite recently, when it was supplanted by electronic tools such as surveyor lasers (Lidar) and optical target devices for surveying lands. Surveyors rods and chains are still utilized in rough terrains with heavy overgrowth where laser or other optical measurements are difficult or impossible. In old English, the term lug is also used.

Length

In geometric measurements, length is the most extended dimension of an object. In the International System of Quantities, length is any quantity with dimension distance. In other contexts "length" is the measured dimension of an object. For example, it is possible to cut a length of a wire which is shorter than wire thickness.

Length may be distinguished from height, which is vertical extent, and width or breadth, which are the distance from side to side, measuring across the object at right angles to the length. Length is a measure of one dimension, whereas area is a measure of two dimensions (length squared) and volume is a measure of three dimensions (length cubed). In most systems of measurement, the unit of length is a base unit, from which other units are defined.

History

Measurement has been important ever since humans settled from nomadic lifestyles and started using building materials, occupying land and trading with neighbours. As society has become more technologically oriented, much higher accuracies of measurement are required in an increasingly diverse set of fields, from micro-electronics to interplanetary ranging.

Length (phonetics)

In phonetics, length or quantity is a feature of sounds that have distinctively extended duration compared with other sounds. There are long vowels as well as long consonants (the latter are often called geminates).

Many languages do not have distinctive length. Among the languages that have distinctive length, there are only a few that have both distinctive vowel length and distinctive consonant length. It is more common that there is only one or that they depend on each other.

The languages that distinguish between different lengths have usually long and short sounds. According to some linguists, Estonian and some Sami languages have three phonemic (meaning-distinguishing) lengths for consonants and vowels. Some Low German/Low Saxon varieties in the vicinity of Hamburg and some Moselle Franconian and Ripuiarian Franconian varieties do, too.

Strictly speaking, a pair of a long sound and a short sound should be identical except for their length. In certain languages, however, there are pairs of phonemes that are traditionally considered to be long-short pairs even though they differ not only in length, but also in quality, for instance English "long e" which is /iː/ (as in feet /fiːt/) vs. "short i" which is /ɪ/ (as in fit /fɪt/) or German "long e" which is /eː/ (as in Beet /beːt/ 'garden bed') vs. "short e" which is /ɛ/ (as in Bett /bɛt/ 'sleeping bed'). Also, tonal contour may reinforce the length, as in Estonian, where the over-long length is concomitant with a tonal variation resembling tonal stress marking.

Horse length

A horse length, or simply length, is a unit of measurement for the length of a horse from nose to tail, approximately 8 feet (2.4 m).

Use in horse racing

The length is commonly used in Thoroughbred horse racing, where it describes the distance between horses in a race. Horses may be described as winning by several lengths, as in the notable example of Secretariat, who won the Belmont Stakes by 31 lengths (248 feet (76 m)). More often, winning distances are merely a fraction of a length, such as half a length.

Other measures

Distances smaller than that are similarly described in reference to the equine body with terms such as a "neck", and a "head", a "short head" or "nose", the smallest possible named advantage by which a horse can win. In the United Kingdom and Ireland a margin of more than 30 lengths is described as a "distance". In France the term "short neck" is used for a margin intermediate between a head and a neck. Harness race finishing margins are typically measured in meters.

Rod

Rod, Ród, Rőd, Rød, Röd, ROD, or R.O.D. may refer to:

Devices

Media

Rod (optics)

"Rods" (sometimes known as "skyfish", "air rods", or "solar entities") is a term used in cryptozoology, ufology, and outdoor photography to refer to elongated artifacts in the form of light-rods produced by cameras. Videos of rod-shaped objects moving quickly through the air were claimed by some ufologists and cryptozoologists to be alien life forms, "extradimensional" creatures, or very small UFOs. Subsequent experiments showed that these rods appear in film because of an optical illusion/collusion (especially in interlaced video recording), and are typically traces of a flying insect's wingbeats.

Optical analysis

Various paranormal interpretations appeared in the popular culture, and one of the more outspoken proponents of rods as alien life forms is Jose Escamilla, who claims to have been the first to film them on March 19, 1994 at Roswell, New Mexico, while attempting to film a UFO. Since then, Escamilla has made additional videos and embarked on lecture tours to promote his claims.

Rod cell

Rod cells, or rods, are photoreceptor cells in the retina of the eye that can function in less intense light than the other type of visual photoreceptor, cone cells. Rods are concentrated at the outer edges of the retina and are used in peripheral vision. On average, there are approximately 90 million rod cells in the human retina. More sensitive than cone cells, rod cells are almost entirely responsible for night vision. However, because they have only one type of light-sensitive pigment, rather than the three types that human cone cells have, rods have little, if any, role in color vision (which is why colors are much less apparent in darkness).

Structure

Rods are a little longer and leaner than cones but have the same structural basis. The opsin or pigment is on the outer side, lying on the Retinal pigment epithelium, completing the cell's homeostasis. This epithelium end contains many stacked disks. Rods have a high area for visual pigment and thus substantial efficiency of light absorption.