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Sagan's number, named after Carl Sagan, is the number of stars in the observable universe, currently estimated to be 70 sextillion or \(7 \times 10^{22}\).[1]

A related term, the sagan, is defined as four billion.[2]

Approximations Edit

Notation Lower bound Upper bound
Scientific notation \(7\times10^{22}\)
Arrow notation \(80\uparrow12\) \(43\uparrow14\)
Steinhaus-Moser Notation 18[3] 19[3]
Copy notation 6[23] 7[23]
Taro's multivariable Ackermann function A(3,72) A(3,73)
Pound-Star Notation #*(0,1,3,2)*5 #*(4,1,6,10)*4
BEAF {80,12} {43,14}
Hyper-E notation 7E22
Bashicu matrix system (0)(0)(0)[717] (0)(0)(0)[718]
Hyperfactorial array notation 23! 24!
Fast-growing hierarchy \(f_2(69)\) \(f_2(70)\)
Hardy hierarchy \(H_{\omega^2}(69)\) \(H_{\omega^2}(70)\)
Slow-growing hierarchy \(g_{\omega^{\omega2+2}7}(10)\)

Sources Edit

  1. http://www.numericana.com/answer/sagan.htm. Retrieved April 2013.
  2. http://www.neatorama.com/2009/11/09/10-neat-facts-about-carl-sagan

See also Edit

Large numbers in science