Question

A generation is about one-third of a lifetime. Approximately how many generations have passed since the year 0 AD?

Length in Meters (m) Masses in Kilograms (kg) Time in Seconds (s) 10-15 m diameter of proton 10-14 m diameter of large nucleus 10-27 kg- mass of proton 10-10 m diameter of hydrogen atom 10-15 kg mass of bacterium 10-7 m diameter of typical virus 10-5 kg mass of mosquito 102 m pinky fingernail width 100 m height of 10-22 s = mean lifetime of very unstable nucleus 10-7 s time for single floating-point operation in a supercomputer 10-15 s time for one oscillation of visible light 10-13 s time for one vibration of an atom in a solid 10-3 s duration of a nerve impulse 10-30 kg mass of electron 10-2 kg mass of hummingbird 10° kg mass of liter of water 100 s time for one heartbeat 4 year old child 1 Lner 102 m length of football field 107 m diameter of Earth 1013 m diameter of solar system 022 kg mass of Moon 1016 m distance light travels 105 s one day 10 s - one year 109 s human lifetime 1011 s recorded human history 101 s age of Earth 102 kg mass of person 1019 kg mass of atmosphere in a year (one light-year) 1021 m Milky Way diameter 1026 m distance to edge of 1025 kg mass of Earth 1030 kg mass of Sun 1053 kg upper limit on mass of1018 s-age of the universe known universe

The answer is 10^2 generations. I don’t understand how they got this answer.

We are viewing this in the order of magnitude

Answer 1

Given, 10^7 s = One year 10^9 s = human lifetime, Year passed given the year OAD = 2018 Therefore No. of generations = 2018 times 10^7/10^9 times 3 [Because one lifetime = 3 generation] = 60.54 For approximation, 60.54 is nearest to 10^2 (from any power of 10) Therefore Approximate no. of generation = 10^2