subtend
61Snellen chart — A Snellen chart is an eye chart used by eye care professionals and others to measure visual acuity. Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862.DescriptionThe traditional Snellen chart… …
62Commelina — communis flower with typical arrangement of floral parts: 3 staminodes are present above, 3 fertile stamens below with the central one differing in size and form, and a single style emerging between them (curved in this species) …
63Rings of Jupiter — A schema of Jupiter s ring system showing the four main components The planet Jupiter has a system of rings, known as the rings of Jupiter or the Jovian ring system. It was the third ring system to be discovered in the Solar System, after those… …
64Human eye — Infobox Anatomy Name = Eye Caption = Schematic diagram of the human eye. The human eye is similar to most mammalian eyes.Dynamic rangeThe retina has a static contrast ratio of around 100:1 (about 6 1/2 stops). As soon as the eye moves (saccades)… …
65Moon illusion — The Moon illusion is an optical illusion in which the Moon appears larger near the horizon than it does while higher up in the sky. This optical illusion also occurs with the sun and star constellations. It has been known since ancient times, and …
66Kreutz Sungrazers — The Kreutz Sungrazers (pronEng|ˈkrɔɪts) are sungrazing comets of a particular family. They are believed to be fragments of one large comet that broke up several centuries ago and are named for the astronomer Heinrich Kreutz, who first… …
67Etendue — or étendue is a property of an optical system, which characterizes how spread out the light is in area and angle. The étendue can be defined in several equivalent ways. From the source point of view, it is the area of the source times the solid… …
68Arc length — Determining the length of an irregular arc segment is also called rectification of a curve. Historically, many methods were used for specific curves. The advent of infinitesimal calculus led to a general formula that provides closed form… …
69Visual angle — The visual angle is the angle a viewed object subtends at the eye, usually stated in degrees of arc.It also is called the object s angular size. The sketch helps to define it 1,2It shows an observer s eye looking at a frontal extent (the vertical …
70Big sky theory — General and commercial aviation In aviation, the Big Sky Theory is that two randomly flying bodies will likely never collide, as the three dimensional space is so large relative to the bodies. Certain aviation safety rules are based on this… …
