4 ms·
Isn't "straight line" somewhat arbitrary? How about "the longest circle you could sail without hitting land" or some other reasonably smooth shape?
by sorokod 9y ago
Isn't "straight line" somewhat arbitrary? How about "the longest circle you could sail without hitting land" or some other reasonably smooth shape?
- yitchelle 9y agoI was just thinking this. If it is allow to sail over the same places more than once, they must be a route that is just a circle. Maybe along one of the southern parallels?
- algorithm_dk 9y agoYes, "straight" is misguiding.
- cup-of-tea 9y agoThat's pedantic. Most people will realise that "straight line" means constant bearing.
- sandworm101 9y agoBut, unless you are passing over a pole, a great circle doesn't use a constant bearing.
- mikeash 9y 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 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.
- deleted 9y ago[deleted]
- pbhjpbhj 9y 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.
- Retra 9y agoLife is arbitrary. Your question is equally interesting, except for the fact that you haven't offered up an answer to it.