Thank you Stack, that is interesting. They seem to be saying that the horizon is at eye level but we can't see it because it disappears at a certain elevation/distance (Jeran cites 'science' as telling us we can't see the "real horizon" after we're more than a thousand feet up).
I guess the goalposts have shifted somewhat since the days of Rowbotham, Winship, and Piccard.
That was helpful - but was there a 'proof' in that video? Or just discussion on the topic?
Someone else sent me this:
It's a nice water level experiment, but done almost exactly at sea level. To that I replied:
"Thank you. Have you got anything from a higher altitude?"
I guess going by your kindly supplied information, Stack, the "higher altitude" will have to be less than 1000 feet.
PS I hear ya on the wiki but let's keep our focus.