Speaking of lines -I was reading a blurb by a flat-earther a while back on TS and one of the “reasons” he said supported the fact of the earth being flat was when airplanes fly, if they flew straight on a sphere, they’d go into space.
While true in a linear fashion, in FACT, taking into account drag (gravity and air resistance), thrust, lift, it is the balancing act of increasing thrust (inline of air screw) lift (also wing/elevator angle trim) to counter drag (while not ignoring the other two) which allows an airplane to remain at cruising altitude.
I explained that, never heard back from him.
A couple of Daves:
https://www.youtube.com/watch?v=GDShWTVNobY
https://www.youtube.com/@ProfessorDaveExplains/search?query=flat%20earth