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1×10 −1: multiplication of two 10-digit numbers by a 1940s electromechanical desk calculator [1] 3×10 −1: multiplication on Zuse Z3 and Z4, first programmable digital computers, 1941 and 1945 respectively; 5×10 −1: computing power of the average human mental calculation [clarification needed] for multiplication using pen and paper
Average cloudy sky [5] [12] 2.5 kcd/m 2: Moon surface [5] [6] 3–5 kcd/m 2: Clear sky [6] [12] 10 4: 5 kcd/m 2: Typical photographic scene in full sunlight [7] [9] 8 kcd/m 2: Average clear sky [5] [12] 10 kcd/m 2: Clear sky at noon [4] [12] 10 kcd/m 2: White illuminated cloud [6] 12 kcd/m 2: Fluorescent lamp [5] [6] 10 5: 75 kcd/m 2: Low ...
The type-generic macros that correspond to a function that is defined for only real numbers encapsulates a total of 3 different functions: float, double and long double variants of the function. The C++ language includes native support for function overloading and thus does not provide the <tgmath.h> header even as a compatibility feature.
For example, a magnitude 2.0 star is 2.512 times as bright as a magnitude 3.0 star, 6.31 times as magnitude 4.0, and 100 times magnitude 7.0. The brightest astronomical objects have negative apparent magnitudes: for example, Venus at −4.2 or Sirius at −1.46.
Consequently, a magnitude 1 star is about 2.5 times brighter than a magnitude 2 star, about 2.5 2 times brighter than a magnitude 3 star, about 2.5 3 times brighter than a magnitude 4 star, and so on. This is the modern magnitude system, which measures the brightness, not the apparent size, of stars.
The apparent magnitude is the observed visible brightness from Earth which depends on the distance of the object. The absolute magnitude is the apparent magnitude at a distance of 10 pc (3.1 × 10 17 m), therefore the bolometric absolute magnitude is a logarithmic measure of the bolometric luminosity.
Illuminance diagram with units and terminology. In photometry, illuminance is the total luminous flux incident on a surface, per unit area. [1] It is a measure of how much the incident light illuminates the surface, wavelength-weighted by the luminosity function to correlate with human brightness perception. [2]
[5] The brightness temperature provides "a more physically recognizable way to describe intensity". [6] When the electromagnetic radiation observed is thermal radiation emitted by an object simply by virtue of its temperature, then the actual temperature of the object will always be equal to or higher than the brightness temperature. [7]