3 ms·
From the maps they show, it’s pretty clearly a great circle (the obvious meaning for “straight line” on the surface of a sphere), not constant bearing.
by mikeash 9y ago
From the maps they show, it’s pretty clearly a great circle (the obvious meaning for “straight line” on the surface of a sphere), not constant bearing.
- cup-of-tea 9y agoWhoops, turns out I didn't actually understand what "constant bearing" meant. What I actually meant was "no rudder/steering" which is exactly what people would imagine as travelling in a straight line. A constant bearing actually gives a Rhumb line: https://en.wikipedia.org/wiki/Rhumb_line https://en.wikipedia.org/wiki/Rhumb_line
- Luc 9y agoDon't apologize. Your use is perfectly correct, you're obviously not referring to compass bearing.
- deleted 9y ago[deleted]
- pbhjpbhj 9y agoObvious perhaps, in a mathematically idealised system that's idealised according to axioms that are unstated ... a non-equitorial latitudinal line on a sphere is straight.
- mikeash 9y agoWalk (or drive, or sail) without turning and you’ll follow a great circle.
- pbhjpbhj 9y agoStay perpendicular to North/South and you follow a parallel. None of these things is of course possible IRL.
- mikeash 9y agoStaying perpendicular to north/south requires turning, unless you’re on the equator.
- pbhjpbhj 9y agoOr listing (ie leaning); still it seems straight, YMMV.
- mikeash 9y agoConsider the degenerate case where you’re ten feet away from the North Pole. You’ll need to go in a tight circle. The situation at more moderate latitudes is the same, just less extreme. It only seems straight because we’re usually at moderate latitudes and the rate of turning is low.