Earth's Shape, Axis, and Latitudes

• Earth is not a perfect sphere; it is slightly flattened and bulges in the middle
• A globe is a miniature model of Earth, showing countries, continents, and oceans in correct sizes
• Globes can vary in size and type and can be rotated like a top or potter's wheel

Axis, Poles, and the Equator

• The axis is a needle fixed through the globe in a tilted manner
• The two points where the needle passes through the globe are the North Pole and the South Pole
• The real Earth moves around its axis, which is an imaginary line, from west to east
• The equator is an imaginary line that divides the Earth into two equal halves
• The northern half is known as the Northern Hemisphere, and the southern half is the Southern Hemisphere

Parallels of Latitudes

• Parallels of latitudes are circular lines from the equator up to the poles, measured in degrees
• The equator represents 0 degrees latitude
• The distance from the equator to either pole is one-fourth of a circle, measuring 90 degrees
• 90 degrees north latitude marks the North Pole, and 90 degrees south latitude marks the South Pole
• Parallels north are called 'north latitudes', and parallels south are called 'south latitudes'
• Latitude values are followed by 'N' or 'S'
• Chandrapur is at 20° N, and Belo Horizonte is at 20° S
• As you move away from the equator, the size of the parallels of latitude decreases

Important Parallels

• Equator (0°)
• North Pole (90°N)
• South Pole (90°S)
• Tropic of Cancer (23½° N) in the Northern Hemisphere
• Tropic of Capricorn (23½°S) in the Southern Hemisphere
• Arctic Circle (66½° N) north of the equator
• Antarctic Circle (66½° S) south of the equator

Heat Zones of the Earth

• The area between the Tropic of Cancer and the Tropic of Capricorn receives maximum heat and is called the Torrid Zone because the sun is overhead at least once a year
• The sun never shines overhead beyond the Tropic of Cancer and Tropic of Capricorn
• 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 and are called Temperate Zones
• Areas 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 and are called Frigid Zones because the sun does not rise much above the horizon which mean less heat

Longitude

• Lines of reference running from the North Pole to the South Pole are called meridians of longitude which are necessary to fix the position of a place
• Meridians are measured in degrees of longitude, with each degree divided into minutes and seconds
• Meridians are semi-circles, and the distance between them decreases polewards, meeting at the poles
• Unlike parallels of latitude, all meridians are of equal length
• The count of meridians begins from the meridian which passes through Greenwich, where the British Royal Observatory is located, called the Prime Meridian
• The Prime Meridian is 0° longitude, counting 180° eastward and 180° westward
• The Prime Meridian and 180° meridian divide the Earth into the Eastern and Western Hemispheres
• Longitude values are followed by 'E' for east and 'W' for west
• 180° East and 180° West meridians are on the same line
• Dhubri in Assam is situated at 26° N latitude and 90° E longitude

Longitude and Time

• The best means of measuring time is by the movement of the Earth, the moon, and the planets because the sun rises and sets regularly every day
• Local time can be reckoned by the shadow cast by the sun
• When the Prime Meridian of Greenwich has the sun at the highest point in the sky which is mid noon
• Places east of Greenwich are ahead, and places west are behind, relative to Greenwich time
• The Earth rotates 360° in about 24 hours, which means 15° an hour or 1° in four minutes
• When it is 12 noon at Greenwich, it is 1 p.m. at 15° east and 11 a.m. at 15° west
• At 180°, it is midnight when it is 12 noon at Greenwich
• All places on a given meridian of longitude have the same local time

Standard Time

• The local time of places on different meridians differ
• A time-table for trains which cross several longitudes will be difficult to create with different times
• It is necessary to adopt the local time of some central meridian of a country as the standard time
• In India, the longitude of 82½° E (82° 30'E) is treated as the standard meridian
• The local time at this meridian is taken as the Indian Standard Time (IST)
• India is located east of Greenwich at 82°30'E which is 5 hours and 30 minutes ahead of GMT
• When it is 2:00 p.m. noon in London, it will be 7:30 p.m. in India
• Some countries have a great longitudinal extent and adopt more than one standard time like Russia with 11
• The Earth has been divided into twenty-four time zones of one hour each, with each zone covering 15° of longitude

Explore Earth's shape, axis, and latitude. Learn about the significance of the Equator, Northern and Southern Hemispheres, and parallels of latitude. Understand how these concepts define geographic measurements and divisions.