GLOBE : LATITUDES AND LONGITUDES

-->Globe is a true model (miniature form) of the earth.You will notice that a needle is fixed through the globe in a tilted manner, which is called its axis. Two points on the globe through which the needle passes are two poles – North Pole and South Pole. The globe can be moved around this needle from west to east just as the earth moves. But, remember there is a major difference. The real earth has no such needle. It moves around its axis, which is an imaginary line.

-->Another imaginary line running on the globe divides it into two equal parts. This line is known as the equator. The northern half of the earth is known as the Northern Hemisphere and the southern half is known as the Southern Hemisphere.They are both equal halves.

-->The equator is an imaginary circular line.All parallel circles from the equator up to the poles are called parallels of latitudes. Latitudes are measured in degrees.

-->The equator represents the zero degree latitude. Since the distance from the equator to either of the poles is one-fourth of a circle round the earth, it will measure 1⁄4 th of 360 degrees, i.e. 90°. Thus, 90 degrees north latitude marks the North Pole and 90 degrees south latitude marks the South Pole.

-->all parallels north of the Figure 2.2 : Latitude equator are called ‘north latitudes.’ Similarly all parallels south of the equator are called 'south latitudes.'

-->Besides the equator (0°), the North Pole (90°N) and the South Pole (90° S), there are four important parallels of latitudes– (i) Tropic of Cancer (23*1⁄2° N) in the Northern Hemisphere. (ii) Tropic of Capricorn (23*1⁄2° S) in the Southern Hemisphere. (iii) Arctic Circle at 66*1⁄2° north of the equator. (iv) Antarctic Circle at 66*1⁄2° south of the equator.

-->The mid-day sun is exactly overhead at least once a year on all latitudes in between the Tropic of Cancer and the Tropic of Capricorn. This area, therefore, receives the maximum heat and is called the Torrid Zone.

-->The mid-day sun never shines overhead on any latitude beyond the Tropic of Cancer and the Tropic of Capricorn. The angle of the sun’s rays goes on decreasing towards the poles. As such, the areas bounded by the Tropic of Cancer and the Arctic Circle in the Northern Hemisphere, and the Tropic of Capricorn and the Antarctic Circle in the Southern Hemisphere, have moderate temperatures. These are, therefore, called Temperate Zones.

-->Areas lying between the Arctic Circle and the North Pole in the Northern Hemisphere and the Antarctic Circle and the South Pole in the Southern Hemisphere, are very cold. It is because here the sun does not rise much above the horizon. Therefore, its rays are always slanting and provide less heat. These are, therefore, called Frigid Zones (very cold).

-->Tonga Islands (in the Pacific Ocean) and Mauritius Islands (in the Indian Ocean) are situated on the same latitude (i.e., 20° S).

-->To fix the position of a place, it is necessary to know something more than the latitude of that place.in order to locate them precisely, we must find out how far east or west these places are from a given line of reference running from the North Pole to the South Pole. These lines of references are called the meridians of longitude,and the distances between them are measured in 'degrees of longitude.' Each degree is further divided into minutes, and minutes into seconds. They are semi-circles and the distance between them decreases steadily polewards until it becomes zero at the poles,where all the meridians meet.

-->Unlike parallels of latitude, all meridians are of equal length. Thus, it was difficult to number the meridians. Hence, all countries decided that the count should begin from the meridian which passed through Greenwich, where the British Royal Observatory is located. This meridian is called the Prime Meridian. Its value is 0° longitude and from it we count 180° eastward as well as 180° westward. The Prime Meridian and 180° meridian divide the earth into two equal halves, the Eastern Hemisphere and the Western Hemisphere. Therefore, the longitude of a place is followed by the letter E for the east and W for the west. It is, however, interesting to note that 180° East and 180° West meridians are on the same line.

-->earth rotates from west to east, those places east of Greenwich will be ahead of Greenwich time and those to the west will be behind it.

-->The rate of difference can be calculated as follows. The earth rotates 360° in about 24 hours, which means 15° an hour or 1° in four minutes. Thus, when it is 12 noon at Greenwich, the time at 15° east of Greenwich will be 15 × 4 = 60 minutes, i.e., 1 hour ahead of Greenwich time, which means 1 p.m. But at 15° west of Greenwich, the time will be behind Greenwich time by one hour, i.e., it will be 11.00 a.m. Similarly, at 180°, it will be midnight when it is 12 noon at Greenwich.

-->In India, the longitude of 82*1⁄2° E (82° 30 ' E) is treated as the standard meridian. The local time at this meridian is taken as the standard time for the whole country. It is known as the Indian Standard Time (IST).

-->India located east of Greenwich at 82 ° 30 ' E is 5 hours and 30 minutes ahead of GMT.

-->In Russia, there are as many as eleven standard times. The earth has been divided into twenty-four time zones of one hour each. Each zone thus covers 15° of longitude.

Tick the correct answers.
(a) The value of the prime meridian is
(i) 90°
(ii) 0°
(iii) 60°

(b)The frigid zone lies near
(i) the Poles
(ii) the Equator
(iii) the Tropic of Cancer

(c)The total number of longitudes are
(i) 360
(ii) 180
(iii) 90

(d)The Antarctic circle is located in
(i) the Northern hemisphere
(ii) the Southern hemisphere
(iii) the Eastern hemisphere

(e)Grid is a network of
(i) parallels of latitudes and merdians of longitudes
(ii) the Tropic of Cancer and the Tropic of Capricorn
(iii) the North Pole and the South Pole

Fill in the blanks.
(a) The Tropic of Capricorn is located at _________________.
(b) The Standard Meridian of India is ____________________.
(c) The 0° Meridian is also known as ____________________.
(d) The distance between the longitudes decreases towards___________.
(e) The Arctic Circle is located in the ____________ hemisphere.