> It's certainly arguable that a particular namable someone first found some way to communicate the concept that the earth is spherical to someone else...
If you mean "it's not likely everyone thought it was flat until someone said 'wait, it's round!'", yeah, sure, I agree. If you don't, what do you mean?
> Its easy enough to say "the earth is a ball" because you've been told, but how can you prove it?
Same way Eratosthenes did in 3rd century BC to get his fairly impressively accurate estimate (39,060-40,320 km; real is 40,075km) for the Earth's circumference. Or do the laser shining through holes in boards on the salt flats. Or go to that huge long lake in Canada and note that you can't see the other side unless you raise your camera. Any of those will give you results that show it to be roughly spherical.
If you mean "it's not likely everyone thought it was flat until someone said 'wait, it's round!'", yeah, sure, I agree. If you don't, what do you mean?
> Its easy enough to say "the earth is a ball" because you've been told, but how can you prove it?
https://ui.adsabs.harvard.edu/abs/2018EGUGA..20.5417K/abstra...
Same way Eratosthenes did in 3rd century BC to get his fairly impressively accurate estimate (39,060-40,320 km; real is 40,075km) for the Earth's circumference. Or do the laser shining through holes in boards on the salt flats. Or go to that huge long lake in Canada and note that you can't see the other side unless you raise your camera. Any of those will give you results that show it to be roughly spherical.