Latitude, Longitude And Time Zones - NCERT Notes

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LATITUDE

1. Latitudes are angles measured from the center of the Earth.
2. Latitudes are lines drawn parallel to the equator.
3. The longest is on the equator, whose Latitude is zero. While, at the poles ( - at 90°N and 90°S ), the circle shrinks to a point.
4. No place on Earth can have Latitude more than 90°.
5. Each degree is subdivided into 60 mins and each men into 60 sec. ( 1° latitude = 60 minutes ), also ( 1° Latitude = 111km ).
6. The presentation of latitude

Equator = 0° latitude,

North Pole = 90°N,

South Pole = 90°S,

Tropic of Cancer = 23½°N

Tropic of Capricorn = 23½°S

Arctic circle = 66½°N, and

Antarctic circle = 66½°S.

LINES OF LATITUDE

The imaginary horizontal lines on the glove after called lines of latitude.

LONGITUDE

1. A longitude is the angular distance of a place from the center of the Earth.
2. These are measured to either East or West to the Prime meridian ( or 0° longitude ).
3. It plays an important role in determining local time in relation to Greenwich Mean Time ( GMT ).
4. At equator 1° longitude = 111 km, 30°N or 30°S = 96.5 km and goes on decreasing this way until it is zero at poles.
5. Earth moves about 15 degrees every 60 minutes - After 24 hours, it has completed a full circle rotation of 360 degrees ( 1hr = 15° & 4 min = 1° ).
6. Hence, planet is divided into 24 sections or time zones. Each time zone is 15 degrees of longitude wide.

LINES OF LONGITUDE

Imaginary lines from North to South between the poles is known as lines of latitude.

Note: All latitudes are parallel to each other whereas no longitude is parallel to each other, they have maximum distance at equator ( 111.33 km ) and zero at poles.

ANTIPODAL POINT

180° meridian ( International Date Line ) lies exactly opposite to 0° meridian ( Prime Meridian ). Such points are known as antipodal points.

LONGITUDE AND TIME

1. Longitude and Time are closely related to each other due to the Earth's rotation on its axis. As the Earth rotates, every place has its different sunset, sunrise and noon time.
2. 1 hour is 15°, hence, if two given places are located 15° apart in the East and the West of each other, then the difference in their time will be 1 hour.

NOON

When the sun is at its highest point in the sky, it is noon. The shadow is shortest at noon.

LOCAL TIME

1. The watches of a place is set at 12 O’clock when they are exactly below the sun, that is, when the sun is highest in the sky. The time indicated by these watches are local time.
2. All places located at a particular line of longitude have same local time.

STANDARD TIME

1. When the local time of a central place is taken as the time for the whole country, it is called standard time of that country or that area.
2. The whole world is divided into 24 standard time zones - Each zone is separated by 15° longitude or by one hour ( 1° = 4 min ).
3. Larger countries have to adopt several time zones - Russia currently has 11 time zones.

INDIAN STANDARD TIME (IST)

1. In India, the longitude of 82°30’E passing through Naini, Allahabad is considered the standard meridian.
2. When it is noon on this longitude, the time is taken noon for the whole country.

GREENWICH MEAN TIME ( GMT )

1. In order to maintain international uniformity, one uniform time, corresponding to the Prime meridian, is adopted by all countries.
2. This is called Greenwich Mean Time ( GMT ), that passes through Greenwich Observatory situated in London ( UK ).
3. It is the starting point of every time.

INTERNATIONAL DATE LINE

1. The line at which a day is lost or gained is called the International Date Line.
2. One who is crossing the date line from West to East repeats a day and travellers crossing it from East to West lose a day.
3. This line ( 180° ) deviates at Fiji, Soma and Gilbe island to avoid inconvenience to the travellers.

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