 In comparison, Earth's mass is 5.972 x 10 kilograms, the mass of the Milky Way Galaxy is estimated at 2.5 x 10 kilograms, and the mass of matter in the observable universe is estimated at 1.5 x 1053 kg.To put this in perspective, the mass of all such books required to write out a googolplex would be vastly greater than the masses of the Milky Way and the Andromeda galaxies combined (by a factor of roughly 2.0 x 10), and greater than the mass of the observable universe by a factor of roughly 7 x 1039.In pure mathematics, there are several notational methods for representing large numbers by which the magnitude of a googolplex could be represented, such as tetration, hyperoperation, Knuth's up-arrow notation, Steinhaus–Moser notation, or Conway chained arrow notation.