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[]
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[]
See also[]
Large numbers in science
Sagan's number · Avogadro's number · Eddington number · Planck units · Promaxima · Poincaré recurrence time · Universe size