https://www.space.com/25325-fermi-paradox.html
https://en.m.wikipedia.org/wiki/Fermi_paradox
https://en.m.wikipedia.org/wiki/Enrico_Fermi
https://en.wikipedia.org/wiki/Billion
https://www.britannica.com/topic/large-numbers-1765137
https://www.britannica.com/science/Drake-equation
https://en.wikipedia.org/wiki/Drake_equation
https://en.wikipedia.org/wiki/Planetary_habitability_in_the_Solar_System
https://science.nasa.gov/resource/our-solar-system-2/
https://www.space.com/habitable-planets-common-sunlike-stars-milky-way