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Size in general is themagnitude ordimensions of a thing. More specifically,geometrical size (orspatial size) can refer to threegeometrical measures:length,area, orvolume. Length can be generalized to other linear dimensions (width,height,diameter,perimeter). Size can also be measured in terms ofmass, especially when assuming adensity range.
In mathematical terms, "size is a concept abstracted from the process of measuring bycomparing a longer to a shorter".[1] Size is determined by the process of comparing or measuring objects, which results in the determination of the magnitude of a quantity, such as length or mass, relative to a unit ofmeasurement. Such a magnitude is usually expressed as a numerical value ofunits on a previously establishedspatial scale, such asmeters orinches.
The sizes with which humans tend to be most familiar are body dimensions (measures ofanthropometry), which include measures such ashuman height andhuman body weight. These measures can, in the aggregate, allow the generation of commercially useful distributions of products that accommodate expected body sizes,[2] as with the creation ofclothing sizes andshoe sizes, and with the standardization ofdoor frame dimensions,ceiling heights, andbed sizes. The human experience of size can lead to a psychological tendency towards size bias,[3] wherein the relative importance or perceived complexity of organisms and other objects is judged based on their size relative tohumans, and particularly whether this size makes them easy to observe without aid.
Humans most frequently perceive the size of objects throughvisual cues.[4] One common means of perceiving size is to compare the size of a newly observed object with the size of a familiar object whose size is already known.Binocular vision gives humans the capacity fordepth perception, which can be used to judge which of several objects is closer, and by how much, which allows for some estimation of the size of the more distant object relative to the closer object. This also allows for the estimation of the size of large objects based on comparison of closer and farther parts of the same object. The perception of size can be distorted by manipulating these cues, for example through the creation offorced perspective.
Some measures of size may also be determined bysound. Visually impaired humans often useecholocation to determine features of their surroundings, such as the size of spaces and objects. However, even humans who lack this ability can tell if a space that they are unable to see is large or small from hearing sounds echo in the space. Size can also be determined bytouch, which is a process ofhaptic perception.
The sizes of objects that can not readily be measured merely by sensory input may be evaluated with other kinds ofmeasuring instruments. For example, objects too small to be seen with the naked eye may be measured when viewed through amicroscope, while objects too large to fit within thefield of vision may be measured using atelescope, or throughextrapolation from known reference points. However, even very advanced measuring devices may still present a limitedfield of view.
Objects being described by their relative size are often described as being comparatively big and little, or large and small, although "big and little tend to carry affective and evaluative connotations, whereas large and small tend to refer only to the size of a thing".[5] A wide range of other terms exist to describe things by their relative size, with small things being described for example as tiny, miniature, or minuscule, and large things being described as, for example, huge, gigantic, or enormous. Objects are also typically described as tall or short specifically relative to their vertical height, and as long or short specifically relative to their length along other directions. People who have experienced excessive growth and height significantly above average are described as havinggigantism. Outside of humans,deep-sea gigantism (or abyssal gigantism) is the tendency for species of deep-sea dwelling animals to be larger than their shallower-water relatives across a large taxonomic range, andisland gigantism (or insular gigantism) is a biological phenomenon in which the size of an animal species isolated on an island increases dramatically in comparison to its mainland relatives.
Although the size of an object may be reflected in itsmass or itsweight, each of these is a different concept. In scientific contexts, mass refers loosely to the amount of "matter" in an object (though "matter" may be difficult to define), whereas weight refers to theforce experienced by an object due togravity.[6] An object with a mass of 1.0 kilogram will weigh approximately 9.81 newtons (newton is the unit of force, whilekilogram is the unit of mass) on the surface of theEarth (its mass multiplied by thegravitational field strength). Its weight will be less onMars (where gravity is weaker), more onSaturn, and negligible in space when far from any significant source of gravity, but it will always have the same mass. Two objects of equal size, however, may have very different mass and weight, depending on thecomposition anddensity of the objects. By contrast, if two objects are known to have roughly the same composition, then some information about the size of one can be determined by measuring the size of the other, and determining the difference in weight between the two. For example, if two blocks of wood are equally dense, and it is known that one weighs ten kilograms and the other weighs twenty kilograms, and that the ten kilogram block has a volume of one cubic foot, then it can be deduced that the twenty kilogram block has a volume of two cubic feet.
The concept of size is often applied to ideas that have no physical reality. Inmathematics,magnitude is the size of amathematical object, which is anabstract object with no concrete existence. Magnitude is a property by which the object can be compared as larger or smaller than other objects of the same kind. More formally, an object's magnitude is anordering (or ranking) of theclass of objects to which it belongs. There are various other mathematical concepts of size for sets, such as:
Instatistics (hypothesis testing), the "size" of the test refers to the rate offalse positives, denoted by α. Inastronomy, themagnitude of brightness or intensity of a star is measured on alogarithmic scale. Such a scale is also used to measure the intensity of anearthquake, and this intensity is often referred to as the "size" of the event.[7] In computing,file size is a measure of the size of acomputerfile, typically measured inbytes. The actual amount ofdisk space consumed by the file depends on thefile system. The maximum file size a file system supports depends on the number ofbits reserved to store size information and the total size of the file system in terms of its capacity to store bits of information.
Inphysics, thePlanck length, denotedℓP, is a unit oflength, equal to1.616199(97)×10−35 metres. It is a unit in the system ofPlanck units, developed by physicistMax Planck. The Planck length is defined in terms of threefundamental physical constants: thespeed of light, thePlanck constant, and theNewtonian constant of gravitation. In contrast, the largest observable thing is theobservable universe. Thecomoving distance – the distance as would be measured at a specific time, including the present – betweenEarth and the edge of theobservable universe is 46 billion light-years (14×10^9 pc), making thediameter of the observable universe about 91 billion light-years (28×10^9 pc).
Inpoetry,fiction, and otherliterature, size is occasionally assigned to characteristics that do not have measurable dimensions, such as the metaphorical reference to the size of a person's heart as a shorthand for describing their typical degree ofkindness orgenerosity. With respect to physical size, the concept ofresizing is occasionally presented infairy tales,fantasy, andscience fiction, placing humans in a different context within their natural environment by depicting them as having physically been made exceptionally large or exceptionally small through some fantastic means. A famous example is associated with the fictional character, theGrinch, who was said in the story to have been born with a heart that they say was "two sizes too small", such that when he is later redeemed, his heart grows "three sizes that day", leading cardiologist David Kass to humorously suggest that the rapid growth of the Grinch's heart at the end of the story indicates that the Grinch has the physiology of aBurmese python.[8]
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