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Square miles should not be confused with miles square, a square region with each side having a length of the value given. For example, a region which is 20 miles square (20 miles × 20 miles) has an area of 400 sq mi; a rectangle of measuring 10 miles × 40 miles also has an area of 400 sq mi, but is not 20 miles square.
An adult human foot is about 28 cm (11 in) long. The decimetre ( SI symbol: dm ) is a unit of length in the metric system equal to 10 −1 metres ( 1 / 10 m = 0.1 m ). To help compare different orders of magnitude , this section lists lengths between 10 centimeters and 100 centimeters (10 −1 meter and 1 meter).
Snellen chart is used to estimate visual acuity (last three rows are 20/15, 20/13 and 20/10) A Snellen chart is an eye chart that can be used to measure visual acuity . Snellen charts are named after the Dutch ophthalmologist Herman Snellen who developed the chart in 1862 as a measurement tool for the acuity formula developed by his professor ...
A reference value above which visual acuity is considered normal is called 6/6 vision, the USC equivalent of which is 20/20 vision: At 6 metres or 20 feet, a human eye with that performance is able to separate contours that are approximately 1.75 mm apart. [9] Vision of 6/12 corresponds to lower performance, while vision of 6/3 to better ...
Humans have a slightly over 210-degree forward-facing horizontal arc of their visual field (i.e. without eye movements), [4] [5] [6] (with eye movements included it is slightly larger, as you can try for yourself by wiggling a finger on the side), while some birds have a complete or nearly complete 360-degree visual field. The vertical range of ...
The English long continued the Roman computations of the mile as 5,000 feet, 1,000 paces, or 8 longer divisions, which they equated with their "furrow's length" or furlong. [ 20 ] The origins of English units are "extremely vague and uncertain", [ 21 ] [ citation needed ] but seem to have been a combination of the Roman system with native ...
Hidden 100 feet below Earth's surface is a one-of-a-kind playground for the explorer in all of us. North Wales in the UK is home to an underground cavern, covered in lights, trampoline-like nets ...
The Egyptian equivalent of the foot—a measure of four palms or 16 digits—was known as the djeser and has been reconstructed as about 30 cm (11.8 in). The Greek foot (πούς, pous) had a length of 1 / 600 of a stadion, [12] one stadion being about 181.2 m (594 ft); [13] therefore a foot was, at the time, about 302 mm (11.9 in). Its ...