Brent-- On Tue, Sep 15, 2015 at 7:47 PM, Brent <[email protected]> wrote:
> Michael; > > Ok, let's make it easier. > > On any day I want to stand in my backyard and look due east. > I don't want to travel anywhere. > > Do I look at where the sun will rise on the equinox or do I look slightly > to the left of that? (northern hemisphere) > You look at where the sun will rise on the equinox.. (but don't do it when the sun rises, because even if the rising or setting sun doesn't look very bright, due to mist or low altitude, the un-seen and un-felt infrared or UV could still do retinal-damage). > > If you tell me to look slightly to the left of where the sun will rise on > the equinox it would mean two things: > > 1. the sun doesn't rise due east on the equinox > 2. the east west line is not straight but curved > The equinox sun rises due east. But the east-west line is curved. But the curved-ness of the east-west line only matters if you want to travel on it. If you're, instead, just looking east, then, wherever you are, the direction you're looking is a straight line (a great circle). So, though you're looking due east, toward where the sun will rise, any places on the Earth that are in that line-of-sight will be slightly south of the parallel of latitude that you're on--even though they're due east from you. Their *direction* is due east. The *route* to them will soon have you going south of east instead of due east. So: Say the edge of a distant telephone-pole is due-east from you. Starting out toward it, you're starting out traveling due eastward. But, after you've proceeded even a little way, continuing in that same straight line toward the telephone-pole edge, you'll soon be traveling in a direction that's south of due east. Michael Ossipoff > > Thank you all for your replies. > brent > > > On 9/15/2015 4:00 PM, Michael Ossipoff wrote: > > Hi Brent-- > > The paradox involves what you mean by "travel due east'. > > If you travel due east, and keep on traveling due east at every point of > your journey, then you will indeed follow a parallel of latitude. > > If you were to drive your car in that fashion, always going due east, > along a parallel of latitude, then your car's wheels and steering-wheel > would have to be adjusted for a (slight) left-turn. ...as, for example, if > you wanted to drive east along the U.S-Canadian border. > > But there's another thing that you could mean by traveling due east: > > But, if you set out due east, and then travel in a straight line, without > letting your car's wheels curve your car left or right at all, then you're > not following a parallel, and, you'd indeed end up going farther and > farther south from your original latitude. > > As others have pointed out, a straight line on the Earth is also called a > "great circle". > > So, the paradox was just the result of two different meanings of "travel > due-east". > > Michael Ossipoff > > On Tue, Sep 15, 2015 at 10:10 AM, Brent <[email protected]> wrote: > >> I'm confused maybe. >> >> I live in the northern hemishpere and anticipating the equinox on the >> 23rd. >> >> Supposedly the sun will rise due east. >> >> So if due east is a right angle from north south and I traveled due east >> I would not follow my line of latitude. >> I would get further and further south of my latitude the further I >> traveled. >> >> So either the lines of latitude are not east west lines or due east is >> not a straight line but curved. >> I suspect lines of latitude are not east west lines? >> They would work fine if the earth was not tilted, but it is. >> >> Wouldn't it make sense to coordinate the globe so lines of latitude (or >> call them something else) are straight and a right angle >> from north south? >> >> brent >> >> >> >> --------------------------------------------------- >> https://lists.uni-koeln.de/mailman/listinfo/sundial >> >> >> > >
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