# Regions

The clear areas within the brown region correspond to the potential development of eyespot foci. Credit: Mike Serfas.

A region is a division or part of an area or volume having definable characteristics but not always fixed boundaries.

The origin of the word may be from regere which means 'to rule, direct'.

## Theory of regions

Def. "[a]ny considerable and connected part of a space or surface; specifically, a tract of land or sea of considerable but indefinite extent; a country; a district; in a broad sense, a place without special reference to location or extent but viewed as an entity for geographical, social or cultural reasons"[1] is called a region.

"Region is most commonly found as a term used in terrestrial and astrophysics sciences also an area, notably among the different sub-disciplines of geography, studied by regional geographers. Regions consist of subregions that contain clusters of like areas that are distinctive by their uniformity of description based on a range of statistical data, for example demographic, and locales."[2]

## Astronomy

This is a composite image of the central region of our Milky Way galaxy. Credit: NASA/JPL-Caltech/ESA/CXC/STScI.

Any considerable and connected part of a space or surface studied in astronomy is an entity in regional astronomy.

"In celebration of the International Year of Astronomy 2009, NASA's Great Observatories -- the Hubble Space Telescope, the Spitzer Space Telescope, and the Chandra X-ray Observatory -- have produced a matched trio of images of the central region of our Milky Way galaxy. Each image shows the telescope's different wavelength view of the galactic center region, illustrating the unique science each observatory conducts."[3]

"In this spectacular image, observations using infrared light and X-ray light see through the obscuring dust and reveal the intense activity near the galactic core. Note that the center of the galaxy is located within the bright white region to the right of and just below the middle of the image. The entire image width covers about one-half a degree, about the same angular width as the full moon."[3]

## Dusty regions

This is a Hubble Space Telescope image of Arp 220. Credit: NASA, ESA, the Hubble Heritage (STScI/AURA)-ESA/Hubble Collaboration, and A. Evans (University of Virginia, Charlottesville/NRAO/Stony Brook University).
RCW 120 is a region of hot gas and glowing dust. Credit: NASA/JPL-Caltech/GLIMPSE-MIPSGAL Teams.

"Arp 220 [at right] appears to be a single, odd-looking galaxy, but is in fact a nearby example of the aftermath of a collision between two spiral galaxies. It is the brightest of the three galactic mergers closest to Earth, about 250 million light-years away in the constellation of Serpens, the Serpent. The collision, which began about 700 million years ago, has sparked a cracking burst of star formation, resulting in about 200 huge star clusters in a packed, dusty region about 5,000 light-years across (about 5 percent of the Milky Way's diameter). The amount of gas in this tiny region equals the amount of gas in the entire Milky Way Galaxy. The star clusters are the bluish-white bright knots visible in the Hubble image. Arp 220 glows brightest in infrared light and is an ultra-luminous infrared galaxy. Previous Hubble observations, taken in the infrared at a wavelength that looks through the dust, have uncovered the cores of the parent galaxies 1,200 light-years apart. Observations with NASA s Chandra X-ray Observatory have also revealed X-rays coming from both cores, indicating the presence of two supermassive black holes. Arp 220 is the 220th galaxy in Arp's Atlas of Peculiar Galaxies."[4] Bold added.

At lower right is a "glowing emerald nebula seen by NASA's Spitzer Space Telescope ... Named RCW 120, this region of hot gas and glowing dust can be found in the murky clouds encircled by the tail of the constellation Scorpius. The ring of dust is actually glowing in infrared colors that our eyes cannot see, but show up brightly when viewed by Spitzer's infrared detectors. At the center of this ring are a couple of giant stars whose intense ultraviolet light has carved out the bubble, though they blend in with other stars when viewed in infrared."[5]

"The green ring is where dust is being hit by winds and intense light from the massive stars. The green color represents infrared light coming from tiny dust grains called polycyclic aromatic hydrocarbons. These small grains have been destroyed inside the bubble. The red color inside the ring shows slightly larger, hotter dust grains, heated by the massive stars."[5]

"This bubble is far from unique. ... Spitzer has found that such bubbles are common and can be found around O stars throughout our Milky Way galaxy. The small objects at the lower right area of the image may themselves be similar regions seen at much greater distances across the galaxy."[5]

"RCW 120 can be found slightly above the flat plane of our galaxy, located toward the bottom of the picture. The green haze seen here is the diffuse glow of dust from the galactic plane."[5]

"This is a three-color composite that shows infrared observations from two Spitzer instruments. Blue represents 3.6-micron light and green shows light of 8 microns, both captured by Spitzer's infrared array camera. Red is 24-micron light detected by Spitzer's multiband imaging photometer."[5]

## Astrophysics

Main source: Astrophysics
The Tarantula Nebula is the dominant feature in our satellite galaxy the Large Magellanic Cloud (LMC). It is one of the largest known star formation regions anywhere. Credit: 2MASS/T. Jarrett, R. Hurt, NASA.

"In astrophysics some regions have science-specific terms such as galactic clusters."[2]

## Geography

Main sources: Locations/Geography and Geography

"In Geography, regions can be broadly divided by physical characteristics (physical geography), human impact characteristics (human geography), and the interaction of Humanity and the environment (environmental geography). Geographic regions and subregions are mostly described by their imprecisely defined, and sometimes transitory boundaries, except in human geography where jurisdiction areas such as national borders are clearly defined in law."[2]

"Apart from the global continental regions, there are also hydrospheric and atmospheric regions that cover the oceans, and discrete climates above the land and water masses of the planet. The land and water global regions are divided into subregions geographically bounded by large geological features that influence large-scale ecologies, such as plains and steppes, forested massifs, deserts, or mountainous regions. Subregions describe the areas within regions that are easily distinguished in both the geological and ecological observable features."[2]

"A region has its own nature that could not be moved. The first nature is its natural environment (landform, climate, etc.). The second nature is its physical elements complex that were built by people in the past. The third nature is its socio-cultural context that could not be replaced by new immigrants."[2]

## Governments

With the origin of the word region being regere 'to rule' or 'ruling', a region is more than a part or a division. It is any entity, source, or object, for example, or a part of any of these where ruling is possible in some form.

That which may be said to be the ruling is the connection between two or more elements of the open set. Two or more elements that are connected are a group, though not all groups need be composed of elements having a connection.

## Mathematics

Main source: Mathematics

Def. "a subset of ${\displaystyle \mathbb {R} ^{n}}$ that is open (in the standard Euclidean topology), connected and non-empty"[6] is called a region, or region of ${\displaystyle \mathbb {R} ^{n}}$, where ${\displaystyle \mathbb {R} ^{n}}$ is the n-dimensional real number system.

Theorem any connected, non-empty topology that maps to, or can be mapped to, a subset of ${\displaystyle \mathbb {R} ^{n}}$ is also a region, or region of ${\displaystyle \mathbb {R} ^{n}}$.

If the theorem is true, or at least sufficient portions of it are, then any field (not just a mathematical field) may have a region within it.

More generally, a region may be a division or part not necessarily of an area or volume having definable characteristics such as connectivity but not always fixed boundaries.

## Hypotheses

Main source: Hypotheses
1. Regions exist without dominant groups.
2. Dominant groups may not exist without regions.
3. In order for a dominant group to rule a subordinate group there must be a region within which the two groups co-exist.
4. A group wanting to rule another group may create a region of overlap that results in the ruling of the second group.