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These are examples of objective criteria globe-earthers have presented to flat-earthers to demonstrate how the objective evidence supports the sphericity of earth, and flat-earthers have provided no substantive answers, rather, they attempt to change the subject or criticize the objective criteria on the basis of some re-definition of words or an abstract, contrived fantasy for which they have no credible evidence.
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Why a straight line track on earth for large distances is not possible:
---- Flat-earthers have no answer to this. The best they can muster is "perspective!" (Redefinition of perspective!)
Why two courses initially set parallel one mile apart will converge after 300 miles and cross paths
---- No response from flat-earthers!
If they ever do respond, it will be to deny this ever happens, or it's trickery: we're being lied to!
What the shortest distance is between any two points on the earth
---- Again, flat-earthers have no answer to this. They want to say, "straight line," but they're afraid of the rejoinder.
Shorter arc of circle passing through both points + this circle has largest radius possible
---- The best flat-earthers can do here is to say that an arc is a straight line because the earth is a flat plane. (They like to say, "plain," like where the rain mainly falls in Spain.)
This video also covers why navigators do not generally use GC route plan but series of short Rhumb line segments
---- Flat-earthers cannot muster the gumption to pronounce "rhumb" because they deny its existence, like "ellipsoid."
The reason is GC course execution is not practical, since it requires constant course adjustment to port and/or starboard rudder
---- Flat-earthers don't know what GC means, nor do they care. It's not endemic to their flat-earth thinking.
Short segments of Rhumb lines, however, only need occasional adjustment with steady rudder settings in between
---- This is ENTIRELY OVER THE HEADS of flat-earthers. Entirely Over Their Heads. EOTH.
TLDR (flat-earthers won't read this - But years from now they'll ask, "Why didn't you say this before?" Well, I did.)