Hi Dave, lol, liked this vid!
I know, long time no see and all that, been busy but glad to be back on steem for now.
While i was watching this vid, it really gave me an idea since I am one of the brightest people on this planet. I really think you should maybe have Ariel pictures to get their head scratching about their answer.
The next time you ask some bright spark this question, you have to put the wording to them correctly or more accurately to get them scratching their heads.

Ask them this - If two light post or two buildings stand at ninety degrees on a tangent to the earth surface, at what distance will the co-interior angles be visible to prove the earths curvature.

All you would need for this is a beach ball with water bottles, at least five of them, one in the centre, the other four at north, east , west, south, glued on.

I'm sure a pic of a city like New York will do the trick, or the biggest city pick you can find.

Don't worry if you don't understand what i'm saying, they have to prove their theory is correct because you will have the proof of what you talking about.
If people break down emotionally, don't blame me, lol!

Chat again, when i Have time too, keep well my friend!