We explain what length is in physics and geography, what they have in common in both disciplines and its relationship with other concepts.
What is length?
Length can designate different notions, depending on the specific area, but always in the sense of a flat and linear distance. In fact, the Dictionary of the Spanish Language defines it as a “physical magnitude” and as the “linear dimension of a flat surface.”
Length is a metric concept, with which distances can be accounted for.
It is used in physics and geography, and in the latter it may have a different meaning, with regard to the Geographic Coordinate System.
In general terms, the term length is used to measure the distance or length of things or phenomena, as in “wavelength”, “length jump”, etc.
See also: Reference system
Physical length
In the field of physics, the length It is considered one of the fundamental magnitudes of the universe from which other different ones derive, but which cannot be explained by them. It serves as a frame of reference for distances, and from it comes the length or dimensional length of objects, real or imaginary.
Initially, it was proposed as the distance of straight segments, and then proceeded to measure the length of the curves or circumferences. As long as it is linear, we can speak of length since other magnitudes such as area or volume imply two and even three simultaneous dimensions.
However, these notions about length were questioned by Albert Einstein in the 20th century because, According to the Theory of Relativity, the length depends on the measurements made by its observers that is, it is not intrinsic to objects and spaces.
Length measurements
length It is commonly measured in meters (m) and its multiples and submultiples according to the International System of Units (SI). The most used on a daily basis are kilometers, centimeters and millimeters.
However, to measure particularly large lengths, such as those in outer space, units such as the light year are used (the distance that light travels in one year, that is, about 9,460,730,472,580.8 km), or the Astronomical Unit (AU, equivalent to the average distance between the Earth and the Sun, that is, 149,597,870,700 meters) or the parsec (parallax of one arc second, equivalent to 206,265 AU).
geographic longitude
In the geographical and cartographic field, however, length is understood the angular distance between any point on the globe and the zero meridian (or Greenwich meridian), which divides the planet into two hemispheres: western (west) and eastern (east). This distance is measured with respect to the closest parallel and with the center of the Earth as its center.
It is, therefore, an imaginary construction that allows any point to be located on the horizontal axis of the globe and that forms, together with latitude, a coordinate system used in geolocation.
length It is measured in sexagesimal degrees, from 0° to 360° along the equatorial plane and indicates the hemisphere you are in: West (W, sometimes W) or East (E).
Longitude and latitude
Together with latitude, longitude forms an angular geographic coordinate system. From them the planetary position of any point on the Earth's surface is established. This system is used by technologies such as GPS (Global Positioning System). It is expressed in sexagesimal degrees, for both latitude and longitude, in parentheses.
For example: The latitude and longitude of the city of Hong Kong, China, is 22 degrees, 15 minutes and 00 seconds north latitude (N) and 114 degrees, 10 minutes and 00 seconds east longitude (E). Or what is the same: (22° 15' 00'' N; 114° 10' 00'' E).
References
- “Length” in Wikipedia.
- “Longitude (cartography)” on Wikipedia.
- “Longitude” in the Language Dictionary of the Royal Spanish Academy.
- “Longitude” at Monterrey Institute.
- “Longitude (geography)” in The Encyclopaedia Britannica.
