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 picture info Density The density (more precisely, the volumetric mass density; also known as specific mass), of a substance is its mass per unit volume. The symbol most often used for density is ρ (the lower case Greek letter rho), although the Latin letter D can also be used. Mathematically, density is defined as mass divided by volume:[1] ${\displaystyle \rho ={\frac {m}{V}}}$ where ρ is the density, m is the mass, and V is the volume [...More Info...]       [...Related Items...] picture info Sea Ice Sea ice arises as seawater freezes. Because ice is less dense than water, it floats on the ocean's surface (as does fresh water ice, which has an even lower density). Sea ice covers about 7% of the Earth's surface and about 12% of the world's oceans.[1][2][3] Much of the world's sea ice is enclosed within the polar ice packs in the Earth's polar regions: the Arctic ice pack of the Arctic Ocean and the Antarctic ice pack of the Southern Ocean. Polar packs undergo a significant yearly cycling in surface extent, a natural process upon which depends the Arctic ecology, including the ocean's ecosystems. Due to the action of winds, currents and temperature fluctuations, sea ice is very dynamic, leading to a wide variety of ice types and features. Sea ice may be contrasted with icebergs, which are chunks of ice shelves or glaciers that calve into the ocean [...More Info...]       [...Related Items...] Bibcode (identifier) The bibcode (also known as the refcode) is a compact identifier used by several astronomical data systems to uniquely specify literature references. The Bibliographic Reference Code (refcode) was originally developed to be used in SIMBAD and the NASA/IPAC Extragalactic Database (NED), but it became a de facto standard and is now used more widely, for example, by the NASA Astrophysics Data System who coined and prefer the term "bibcode".[1][2] The code has a fixed length of 19 characters and has the form YYYYJJJJJVVVVMPPPPA where YYYY is the four-digit year of the reference and JJJJJ is a code indicating where the reference was published. In the case of a journal reference, VVVV is the volume number, M indicates the section of the journal where the reference was published (e.g., L for a letters section), PPPP gives the starting page number, and A is the first letter of the last name of the first author [...More Info...]       [...Related Items...] picture info Doi (identifier) A digital object identifier (DOI) is a persistent identifier or handle used to identify objects uniquely, standardized by the International Organization for Standardization (ISO).[1] An implementation of the Handle System,[2][3] DOIs are in wide use mainly to identify academic, professional, and government information, such as journal articles, research reports, data sets, and official publications. However, they also have been used to identify other types of information resources, such as commercial videos. A DOI aims to be "resolvable", usually to some form of access to the information object to which the DOI refers. This is achieved by binding the DOI to metadata about the object, such as a URL, indicating where the object can be found. Thus, by being actionable and interoperable, a DOI differs from identifiers such as ISBNs and ISRCs which aim only to identify their referents uniquely [...More Info...]       [...Related Items...] picture info Southern Hemisphere The Southern Hemisphere is the half of Earth that is south of the Equator. It contains all or parts of five continents[1] (Antarctica, Australia, about 90% of South America, one third of Africa, and several islands off the continental mainland of Asia), four oceans (Indian, South Atlantic, Southern, and South Pacific) and most of the Pacific Islands in Oceania. Its surface is 80.9% water, compared with 60.7% water in the case of the Northern Hemisphere, and it contains 32.7% of Earth's land.[2] Owing to the tilt of Earth's rotation relative to the Sun and the ecliptic plane, summer is from December to February (inclusive) and winter is from June to August (inclusive). September 22 or 23 is the vernal equinox and March 20 or 21 is the autumnal equinox [...More Info...]       [...Related Items...] picture info Northern Hemisphere The Northern Hemisphere is the half of Earth that is north of the Equator. For other planets in the Solar System, north is defined as being in the same celestial hemisphere relative to the invariable plane of the solar system as Earth's North Pole.[1] Owing to the Earth's axial tilt of 23.439281°, winter in the Northern Hemisphere lasts from the December solstice (typically December 21 UTC) to the March equinox (typically March 20 UTC), while summer lasts from the June solstice through to the September equinox (typically on 23 September UTC). The dates vary each year due to the difference between the calendar year and the astronomical year. Within the northern hemisphere, oceanic currents can change the weather patterns that affect many factors within the north coast [...More Info...]       [...Related Items...] picture info Salinity Salinity (/səˈlɪnɪti/) is the saltiness or amount of salt dissolved in a body of water, called saline water (see also soil salinity). This is usually measured in ${\displaystyle {\frac {g\ {\textrm {salt}}}{kg\ {\textrm {sea}}\ {\textrm {water}}}}}$ (note that this is technically dimensionless) [...More Info...]       [...Related Items...] picture info Polar Region The polar regions, also called the frigid zones, of Earth are the regions of the planet that surround its geographical poles (the North and South Poles), lying within the polar circles. These high latitudes are dominated by floating sea ice covering much of the Arctic ocean in the north, and by the Antarctic ice sheet on the continent of Antarctica in the South. The Arctic has various definitions, including the region north of the Arctic Circle (currently Epoch 2010 at 66°33'44" N), or the region north of 60° north latitude, or the region from the North Pole south to the timberline. The Antarctic is usually defined as south of 60° south latitude, or the continent of Antarctica [...More Info...]       [...Related Items...] picture info Etymological Etymology (/ˌɛtɪˈmɒlədʒi/)[1] is the study of the history of words.[1] By extension, the phrase "the etymology of [a word]" means the origin of a particular word.[2] For languages with a long written history, etymologists make use of texts, and texts about the language, to gather knowledge about how words were used during earlier periods, how they developed in meaning and form, or when and how they entered the language [...More Info...]       [...Related Items...] picture info Volume Volume is the quantity of three-dimensional space enclosed by a closed surface, for example, the space that a substance (solid, liquid, gas, or plasma) or shape occupies or contains.[1] Volume is often quantified numerically using the SI derived unit, the cubic metre. The volume of a container is generally understood to be the capacity of the container; i. e., the amount of fluid (gas or liquid) that the container could hold, rather than the amount of space the container itself displaces. Three dimensional mathematical shapes are also assigned volumes. Volumes of some simple shapes, such as regular, straight-edged, and circular shapes can be easily calculated using arithmetic formulas. Volumes of complicated shapes can be calculated with integral calculus if a formula exists for the shape's boundary [...More Info...]       [...Related Items...]