It's impressive what they accomplished, even without technology (and by "technology" I include astrolabes and sextants, which have generally fallen out of commo

It's impressive what they accomplished, even without technology (and by "technology" I include astrolabes and sextants, which have generally fallen out of common use). Speaking of astrolabes & sextants, I recently read that higher-education 120-300 years ago featured "spherical trigonometry" as a course many students took ... because that was a core skill to navigate or even understand different locations / etc. Nowadays, the knowledge is there to be learned, but it's not commonly taught.