You are watching: Why are lines of longitude not parallel to each other
The meridians correspond to the natural truth that the sun reaches the zenith once a day all at once for a set of points that kind a right line native one pole to the other, cutting the equator in a right angle. Therefore meridians are not just synthetic lines, but correspond somehow to a herbal aspect, something that deserve to be measured. Even with your bare eye, without any instrument, you deserve to observe what time the the job it is best now. If you would certainly collect this info for a offered moment from civilization at diferent places anywhere the world, you could approximately say exactly how much to the east or west of your allude of monitoring every reporting observer is placed.
Compare with time-zones, they space slices from phibìc to south pole, indicating just how much come the eastern or west of a conventionally definned line they room located. If longitude to be parallel circles, you would have different points ~ above the exact same longitude with various day-time (somewhere midday, in other places morning). Together circles have no equivalent phenomenon in nature and also thus are pure standard lines, very daunting to measure (at the very least in pre-modern times).However, historically it to be very difficult to find adequate methods to measure longitude, also with the meridian system. Time was critical to uncover longitude. Until the 18th century, on pearl on the ocean, the was virtually impossible come determine exact longitude. There to be no clocks that ran specific enough. Longitude is characterized as the (angular) street (in levels or daytime) type a pre-defined meridian. It take it quite an effort (and numerous sunken ships) to be able to determine longitude appropriately (latitude in comparison was fairly easy to measure up on a ship v a sextant and other tools).
So think again: if the was virtually impossible to measure longitude from natural phenomenon (like sun and stars), that would have actually been even more difficult to measure up conventional, parallel one (that you propose) that execute not represent any natural phenomenon. So over there is some factor for the tradition. Parallel lines because that measuring longitude rather would have actually no real advantage.
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For more information, do an web search because that "finding longitude" or "history the longitude", there are additionally some good videos the end there that explain everything in information with lively animations.