North Pole and South Pole are two reference points on the Earth and with these two points, a line is drawn which lies exactly midway between the poles i. Further, we drawn a network of lines i. These lines intersect each other at right angles and create a network called a grid or graticule. These graticule helps us to locate places on the surface of the Earth accurately. Source: http: desktop.
The Earth takes 24 hours to rotate through degree longitude. Hence, two places that are 15 degree of longitude apart have a difference of one hour. As the Sun rises in the east and sets in the west.
This adds up to a difference of 24 hours or one day between east and west of degree line of longitude. But if it happens on same land mass , then same place would have different date in the same day. What is Cartography and how was the first map come to the modern World?
If we see this imaginary line, then we found, it is not straight but zig-zag line. But, if it is a straight line , then it demarcates the same land mass into two parts and then both places have different dates on the same day. It would be very inconvenient if one part of a country had one date of the week while another part would have the different date. Now you have to add a full 24 hours to your calculations and jump a full day ahead, making it 9 a. But you're not done yet. Because all the time calculations are taken from Greenwich, you must subtract four more hours from that time because Yakutsk sits four time zones west of the IDL.
So, when the time in San Francisco is p. President Chester A. Arthur convened the conference, which included representatives of 26 nations. The president, like other world leaders, saw the necessity of establishing standards for an international agreement on time and longitude.
By the end of the 19th century, as global commerce progressed, communication technologies grew more sophisticated and nations grew increasingly interdependent, it was imperative that all clocks be set to a world standard. With this in mind, the point of the conference, as summed up in the Protocols of the Proceedings , was "for the purpose of fixing upon a meridian proper to be employed as a common zero of longitude and standard of time-reckoning throughout the globe. The conference resulted in the recognition of the prime meridian in Greenwich, which had already been in use for several decades, as the world's single " initial meridian.
Petersburg and Oslo, for example, the Greenwich meridian was adopted primarily because over two-thirds of ships already used it for zero longitude. In all, seven resolutions were passed at the end of the conference. These ranged from adopting a universal solar day beginning at midnight in Greenwich and counted on a hour clock to the proposal that all nautical and astronomical days everywhere would begin at a.
The IDL was established as a result of the conference's Third Resolution , which stated: "That from this meridian longitude shall be counted in two directions up to degrees, east longitude being plus and west longitude minus. The logic behind this is that on a discrete sphere, the day and date have to be separated at two locations — you can't split a sphere into two parts with a single "cut" on one side.
You need a starting and an ending point. None of the resolutions, however, were binding. It was up to each country to enforce these proposals. Even today, for example, the IDL is not a matter of international law, nor is it enforced by the dictates of an international governing board.
It is accepted by all nations and has been adopted because it is crucial for global interconnectivity, instantaneous communication, time measurement and consistent international databases. An excellent way of visualizing the IDL is to think of it in terms similar to a line of longitude. In fact, it roughly follows the degree meridian, which is located halfway round the world from the prime meridian.
But the IDL, unlike a meridian line, does not run in a straight path. Since its inception, the IDL has undergone several major deviations, and it now swerves, zig-zags and jogs in a seemingly arbitrary pattern around prominent landmasses and certain Pacific islands.
Most of these deviations are the result of practical considerations, such as to avoid splitting a country into two time zones, or for political and economic reasons.
Although the islands are only separated by the narrowest of margins — just 2 miles 3. It then tracks back, following the degree meridian south again for several thousand miles, passing west of the Hawaiian Islands and east of the independent nation of the Marshall Islands, until reaching the Pacific island nation of Kiribati.
This deviation reaches nearly as far east as the degree meridian and forms a very large and noticeable hammerhead-looking configuration. Kiribati, which received its independence from the United Kingdom in , is a group of 33 mostly uninhabited islands and atolls that span a vast area encompassing no less than 1.
This caused considerable political and economic hardships as the nation tried to conduct normal everyday business with one half of its nation a day ahead and the other a day behind. In , Kiribati decided it had had enough of this arrangement, and seeking greater economic ties with Australia and New Zealand, extended the IDL eastward to encompass the nation's far-flung eastern islands, thus creating the odd configuration. Shifting the date line is a relatively easy matter, the BBC reported. The country can decide for itself.
It then swerves back sharply toward the degree meridian, but does not follow the meridian's exact path. Instead, it stays parallel to the meridian, keeping to the east of the line so that Tonga, the Kermadec Islands and New Zealand are all east of the IDL. It follows this path until reaching Antarctica, which has multiple time zones.
The IDL is not drawn into Antarctica on most maps. In essence, it is a more sophisticated version of GMT because it is still based on the zero degrees of latitude that passes through Greenwich but relies on atomic clocks. These devices, invented in the s, are incredibly accurate and are based solely on Earth's rotation.
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