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3.125: 1 Between 1 BC and AD 5: Liu Xin [7] [11] [12] Unknown method giving a figure for a jialiang which implies a value for π ≈ 162 ⁄ (√ 50 +0.095) 2. 3.1547... 1 AD 130: Zhang Heng (Book of the Later Han) [2] √ 10 = 3.162277... 736 ⁄ 232: 3.1622... 1 150: Ptolemy [2] 377 ⁄ 120: 3.141666... 3: 250: Wang Fan [2] 142 ⁄ 45: 3 ...
The Planck time, denoted t P, is defined as: = = This is the time required for light to travel a distance of 1 Planck length in vacuum, which is a time interval of approximately 5.39 × 10 −44 s. No current physical theory can describe timescales shorter than the Planck time, such as the earliest events after the Big Bang. [ 30 ]
This time happens to correspond roughly to the time of the formation of the Solar System and the evolutionary history of life. Stelliferous Era: 150 Ma ~ 100 Ta [19] 20 ~ −0.99: 60 K ~ 0.03 K: The time between the first formation of Population III stars until the cessation of star formation, leaving all stars in the form of degenerate ...
The number π (/ p aɪ / ⓘ; spelled out as "pi") is a mathematical constant, approximately equal to 3.14159, that is the ratio of a circle's circumference to its diameter.It appears in many formulae across mathematics and physics, and some of these formulae are commonly used for defining π, to avoid relying on the definition of the length of a curve.
where H is the hypervolume of a 3-sphere and r is the radius. S V = 2 π 2 r 3 {\displaystyle SV=2\pi ^{2}r^{3}} where SV is the surface volume of a 3-sphere and r is the radius.
k = +1, 0 or −1 depending on whether the shape of the universe is a closed 3-sphere, flat (Euclidean space) or an open 3-hyperboloid, respectively. [4] If k = +1 , then a is the radius of curvature of the universe.
Cosmic time [5]: 42 [6] is a measure of time by a physical clock with zero peculiar velocity in the absence of matter over-/under-densities (to prevent time dilation due to relativistic effects or confusions caused by expansion of the universe). Unlike other measures of time such as temperature, redshift, particle horizon, or Hubble horizon ...
The Chinese mathematician Liu Hui in 263 CE computed π to between 3.141 024 and 3.142 708 by inscribing a 96-gon and 192-gon; the average of these two values is 3.141 866 (accuracy 9·10 −5). He also suggested that 3.14 was a good enough approximation for practical purposes.