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International Date Line

Mapy
Source: licencja: CC 0.

Link to the lesson

Before you start you should know
  • that the Earth revolves around its own axis from west to east, making a full revolution in about 24 hours;

  • how to read the longitude from a map;

  • that at all times on Earth there are all different times of the day and night.

You will learn
  • indicate the solar time of a given place based on its longitude;

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Nagranie dźwiękowe dotyczy czasu uniwersalnego i linii zmiany daty.

What time does the new year begin? The simple answer is at 12 at night. But if you think about it, you will find that it can be at 00:00? In addition, on the eastern borders of our country, the New Year begins earlier than on the west, and we just agree that we welcome it at the same time.

Changes in the way of life of people on Earth in the 19th century, travel facilitation, telephone communication, radio and other forms of communication have forced the order of time. It was difficult to function in a situation where there was a different time in almost every place in each country. The concept of universal timeuniversal timeuniversal time was introduced. An international agreement was then adopted, according to which the 0 meridian passing through Greenwich in the United Kingdom is a universal time and all other meridians have a time appropriate to the difference in longitude.

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International Date Line. The course of the meridian 0⁰ in Greenwich in London is marked in the form of a line embedded in the sidewalk. There is also an astronomical observatory and a museum close to this place
Source: Randi Hausken, www.flickr.com, licencja: CC BY-SA 2.0.

At the moment when the Sun is towering highest on the Greenwich meridian it is midday, on the opposite side of the globe it is midnight. Therefore, it was considered that the day ended there. The end of the day means that the next day begins and the date changes. The 180⁰ meridian line was therefore considered the International Date LineInternational Date LineInternational Date Line. However, this meridian crosses inhabited areas, so the course of the date change line was moved in places so that there was no situation that two places lying on the same land that have two different dates. Crossing the date change line from west to east, we repeat the same day. However, if we cross it from east to west, we have to add one day.

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Ilustracja interaktywna. Koło z konturami kontynentów widzianymi od strony bieguna północnego. Na górze zaznaczono godzinę 12:00, na dole 24:00, po lewej stronie 18:00, po prawej 6:00. 1. Przykład dotyczy wtorku godziny 16:00 na południku 0 stopni., 2. Czerwona linia wskazuje umowną linię zmiany daty. Następne kolory oznaczają kolejne dni w kalendarzu. International Date Line 1. An example of the situation on Tuesday at 4 am on the meridian 0, 2. The red line indicates the contractual date change line. The following colors represent the next calendar days.
International Date Line
Source: GroMar Sp. z o.o., licencja: CC BY-SA 3.0.
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Exercise 1
Wprowadź datę w wyznaczonym miejscu. Enter the date in the designated place. Możliwe odpowiedzi: 1. September 21
Source: Wilfra, GroMar Sp. z o.o., licencja: CC BY-SA 3.0.
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Exercise 2
Evaluate the accuracy of the statements regarding the international date line.. When traveling from east to west, you must add one hour when crossing the international date line.. Możliwe odpowiedzi: True, False. Traveling from west to east when crossing the international date line you have to add one day.. Możliwe odpowiedzi: True, False. Traveling from east to west when crossing the international date line you have to add one day.. Możliwe odpowiedzi: True, False. Traveling from west to east when crossing the international date line you have to subtract one day.. Możliwe odpowiedzi: True, False

Summary

  • The 180⁰ meridian line became the basis for determining the date change line.

Keywords

solar time, universal time, International Date Line

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Exercise 3
Match the pairs: English words with Polish definition. universal time Możliwe odpowiedzi: 1. czas słoneczny południka zerowego, 2. umowna linia przebiegająca w przybliżeniu wzdłuż południka 180⁰ (z niewielkimi odchyleniami), po której obu stronach data różni się o 1 dobę International Date Line Możliwe odpowiedzi: 1. czas słoneczny południka zerowego, 2. umowna linia przebiegająca w przybliżeniu wzdłuż południka 180⁰ (z niewielkimi odchyleniami), po której obu stronach data różni się o 1 dobę

Glossary

universal time
universal time
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Nagranie dźwiękowe dotyczące słówka universal time.

czas uniwersalny – czas słoneczny południka zerowego

International Date Line
International Date Line
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Nagranie dźwiękowe dotyczące słówka international date line.

linia zmiany daty – umowna linia przebiegająca w przybliżeniu wzdłuż południka 180⁰ (z niewielkimi odchyleniami), po której obu stronach data różni się o 1 dobę