4 ms·
That's pedantic. Most people will realise that "straight line" means constant bearing.
by cup-of-tea 8y ago
That's pedantic. Most people will realise that "straight line" means constant bearing.
- sandworm101 8y agoBut, unless you are passing over a pole, a great circle doesn't use a constant bearing.
- mikeash 8y agoFrom 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 8y 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 8y agoDon't apologize. Your use is perfectly correct, you're obviously not referring to compass bearing.
- deleted 8y ago[deleted]
- pbhjpbhj 8y 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 8y agoWalk (or drive, or sail) without turning and you’ll follow a great circle.
- pbhjpbhj 8y agoStay perpendicular to North/South and you follow a parallel. None of these things is of course possible IRL.
- mikeash 8y agoStaying perpendicular to north/south requires turning, unless you’re on the equator.
- pbhjpbhj 8y agoOr listing (ie leaning); still it seems straight, YMMV.
- mikeash 8y 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.
- deleted 8y ago[deleted]
- pbhjpbhj 8y agoWhat sort of constant bearing - magnetic bearings will vary along a map-based bearing. There's an arbitrary choice involved. We're probably not looking at changes in sea-level that put us off line - is a necessarily idealised system in which the question makes sense.