Unit                          Symbol                    Value    

光速                             c                 299 792 458 ms-1

光年                             ly                0.3066 pc = 0.946x1016m

秒差距(天文距離單位之一)         pc                3.261 ly = 3.085 677x1016m

太陽亮度                         L                3.826x1026 J/s

太陽質量                         M               1.989x1030 kg

太陽赤度半徑                     R                6.96x108 m

哈伯參數                         H0                100 h km/s Mpc=h/9.78 Gyr

引力常數                         G                6.672 59x10-11 m3/kg s2

普朗克常數                       =h/2          6.582 122x10-22 MeV s

普朗克質量                       Mp=       1.221x1019 GeV/c2

普朗克時間                       tp=       5.31x10-44 s

開爾文常數                       k                8.617x10-5 eV/K

史特凡-波茲曼常數                a=    7.56x10-16 J/m3k4

宇宙臨界密度                     =3H     2.8x1011 h2 Msun/Mpc3=10.6 h2 GeV/m3