In this video, discovery channel measures how much Earth curves at given distances using a telescope over water.
And as you hear from flat earthers again and again and again that "water finds it own level" (which is technically incorrect lol), you'll find that at the shore line, the helicopter clearly goes below.
The telescope is mounted straight and the helicopter goes below the horizon over water so the water curves. Proven categorically here.
But what's baffling me is the land you can see beyond the horizon.
(from 6m 42s)
If that's the horizon line (where helicopter goes below) then what's behind it? Have I missed something like the water line not being the actual horizon but just the curvature and beyond it is high lands i.e. not sea level?