Still needs to include a way to get to know what a 'second' is, like the Hyperfine transition of neutral hydrogen on the https://en.wikipedia.org/wiki/Pioneer_p

Still needs to include a way to get to know what a 'second' is, like the Hyperfine transition of neutral hydrogen on the https://en.wikipedia.org/wiki/Pioneer_plaque https://en.wikipedia.org/wiki/Pioneer_plaque