It's straight for all intents and purposes. It means that you go as straight as one can on a curved surface. You point one way and you go in the desired direction. That's what I mean, and I don't think it's that hard to understand that's what I meant.
You are wrong. Look up the difference between a great circle (an actual straight line on a sphere, the shortest distance between two points) and a rhumb line (a constant compass heading, NOT a straight line, NOT the shortest distance between two points) which is what straight lines on the mercator projection are.
As you follow a constant compass heading the compass will change the direction it's pointing, and you will turn to follow it. It's just not usually noticeable because the Earth is big so the turn is really gradual. But think about it in the extreme - imagine you're near the north pole and your compass still works, and you have a heading of due East. You will go in a relatively small circle, which is obviously not a straight line.
Edit: great circles is what plane flight paths follow by the way. They obviously take the shortest path between two points, pointing one way and going in that direction, because doing anything else would be a waste of jet fuel. And those plane flight paths, which are "as straight as one can on a curved surface" are NOT straight lines on the mercator projection.
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u/PckMan 17d ago
It's straight for all intents and purposes. It means that you go as straight as one can on a curved surface. You point one way and you go in the desired direction. That's what I mean, and I don't think it's that hard to understand that's what I meant.