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an object of diameter 1 AU (149 597 871 km) at a distance of 1 parsec (pc) Thus, the angular diameter of Earth's orbit around the Sun as viewed from a distance of 1 pc is 2″, as 1 AU is the mean radius of Earth's orbit. The angular diameter of the Sun, from a distance of one light-year, is 0.03″, and that of Earth 0.0003″. The angular ...
The historical evolution of metric systems has resulted in the recognition of several principles. A set of independent dimensions of nature is selected, in terms of which all natural quantities can be expressed, called base quantities. For each of these dimensions, a representative quantity is defined as a base unit of measure.
The solid angle of a sphere measured from any point in its interior is 4 π sr. The solid angle subtended at the center of a cube by one of its faces is one-sixth of that, or 2 π /3 sr. The solid angle subtended at the corner of a cube (an octant) or spanned by a spherical octant is π /2 sr, one-eight of the solid angle of a sphere. [1]
This system has largely been replaced by defining the weapon in terms of the measurement of the calibre, which is the standard today for most weapon systems in use by the world's armed forces. The 18th century standards were based on a projectile's weight, which dates back to use of muzzle loaded cannons that fired solid cannonballs. The bore ...
The stokes (St) is a unit of kinematic viscosity equal to 1 cm 2 ⋅s −1 (100 mm 2 ⋅s −1). [3] The stilb (sb) is a unit of luminance equal to 1 cd⋅cm −2 (10 kcd⋅m −2). [4] The phot (ph) is a unit of illuminance equal to 1 lm⋅cm −2 (10 klx). [3] The rayl is a unit of specific acoustic impedance, equal to 1 dyn⋅s⋅cm −3 (10 ...
Since an mrad is an angular measurement, the subtension covered by a given angle (angular distance or angular diameter) increases with viewing distance to the target. For instance the same angle of 0.1 mrad will subtend 10 mm at 100 meters, 20 mm at 200 meters, etc., or similarly 0.39 inches at 100 m, 0.78 inches at 200 m, etc.
The French scale measures the outer diameter of the catheter, not the size of the internal drainage channel (inner diameter). For instance, a two-way catheter of 20 Fr and a three-way catheter of 20 Fr have the same outer diameter, but the three-way catheter has an additional channel for irrigation, reducing the size of its drainage channel.
22 cm = 2.2 dm – diameter of a typical association football (soccer ball) 30 cm = 3 dm – typical school-use ruler length (= 300 mm) 30.48 cm = 3.048 dm – 1 foot (measure) 60 cm = 6 dm – standard depth (front to back) of a domestic kitchen worktop in Europe (= 600 mm) 90 cm = 9 dm – average length of a rapier, a fencing sword [30]