GEOGRAPHY OF WORLD
PHYSICAL FEATURES OF THE EARTH
The Earth in Space: The nine planets of the solar system Mercury, Venus, Earth, Mars, Jupiter, Saturn, Uranus, Neptune and Pluto are bound to the Sun by the forces of gravity. Their orbits are elliptical in shape and lie roughly in the place of the Sun’s equator.
Some Important Facts and Figures about the Earth Diameter: 7,926 miles (12,755 km) at the equator; 7,899 miles (12,712 km) at the poles; Circumference: 24,901 miles (40,074 km) at the equator; 24,857 miles (40,003 km) at the poles; Area: 196,940,400 sq. miles (510,073,270 sq. km), of which 70.8 per cent, is covered by water; Highest Point: Mount Everest 29,028 ft (8,848 m) above sea-level. Lowest Point: Challenger Deep (Pacific Ocean) 36,198 ft (11,033 M) below sea-level.
THE EARTH AND THE SOLAR SYSTEM
Movement of the Earth: The Earth moves in three main ways: (i) It revolves around the Sun once every 365 days, 5 hours, 48 minutes, and 46 seconds at a speed of 66,000 mph (106,200 kph). (ii) It spins on its axis at a speed of 1,038 mph (1,670 kph) at the equator. The tilt of the Earth’s axis is 23 Vz° from a line perpendicular to its path around the Sun. (iii) Together with the rest of the solar system, the Earth is moving around the Milky Way.
Earth’s Satellite; the Moon: .The Moon’s diameter is 2,160 miles (2,376 km)—about one-fourth the size of the earth. The Moon orbits the Earth at an average distance of 238,887 miles (384,400 km).
The Changing Year: In 1582, the Gregorian calendar was adopted. This calendar is based on the idea of a seven-day week. To eliminate the odd days, each year in the Gregorian calendar begins one day later in the week than the previous year. Leap years are fixed for every year that can be divided by four, such as 1976 and 1980.
Days and Time: The Earth takes 23 hours, 56 minutes, and 4.1 seconds to spin round once on its axis. Because the Earth is divided into 360°of longitude and it completes one spin on its axis in a day (24 hours), time alters by one hours for every 15° of longitude (36024).
International Date Line: The prime meridian, or 0° longitude, from which the time zones are measured, passes through Greenwich, England. A person travelling west of Greenwich for 180° of longitude would have to put his clock back by 12 hours.
Seasons: The tilt of the Earth’s axis is also responsible for seasons. Spring in the Northern Hemisphere begins on March 21, when the sun is overhead at the equator. March 21 is called the vernal equinox. After March 21, the overhead sun moves northwards until it reaches its northernmost point on June 21 (summer solstice). The overhead sun then moves south back towards the equator, where it is again overhead on a rjotit September 20, the autumnal equinox. On December 22, the winter solstice, the overhead sun reaches its southernmost point.
The Earth’s Structure: The Earth’s crust averages 20 miles (32 km) in thickness beneath the continents and about six miles (9.7 km) under the oceans. About 200 million years ago, the land masses were all grouped in one large continent, which geologists call Pangaea. This continent split into two parts, Lauraslia and Gondwanaland, which drifted northwards. These two smaller continents later broke up and moved slowly to their present positions. This movement called continental T drift, is still continuing.
There are several physical structures on the earth, such as mountains rocks and rivers.
STATISTICAL DATA OF THE EARTH
The Earth is the fifth largest planet in the solar system. Some important data relating to this planet are as follows:
Equatorial Diameter 12,756 km
Polar Diameter 12,714 km
Equatorial Circumference 40,077 km
Polar Circumference 40,009 km
3. Total Surface Area 510 million sq. km
29% covered by Continents;
71% covered by Oceans
4. Volume 1,000,000 million cu.
5. Mass metric tonnes 5.98 × 1021
6. Density 5.52 g/cm3
7. Age 4,550 million years
8. Mean Height of Land 29.2% of the total surface area
9. Water Area 756m
10. Mean Ocean Depth 70.8% of total surface area
11. Highest Land Point 8848m
12. Lowest Land Point 8,848m
13. Greatest Ocean Depth 397m
14. Mean Surface Temperature 14°C degree
15. Period of Rotation on 23 hr 56 min 4.09 sec.
16. Inclination of Polar Axis to 23°26′ 56″
Plane of Orbit about Sun
17. Sidereal Period (Time for 365.256 36 days
One Orbital Revolution
18. Orbital Speed About Sun . 29.8 km/sec
19. Eccentricity of Orbit 0.0167
20. Mean Distance from Sun
(1 astronomical unit) 149,598,500 km
21. Maximum distance from about 152 million km (at aphelion- between July 2 and July 5)
22. Minimum distance from Sun about 147 million km (at perihelion-between January 2 and January 5)
23. Temperature Highest - 58°C at Al-Aziziyah, Libya, Lowest-89.6°C at Antarctica Average 14°C.
24. Atmosphere Oxygen 21%, Nitrogen 78%, Argon and other gases 1%.
The Panchang (five limbs) is a book of tables, containing a calendar of months and days with astronomical data and calculations, days of festivals and auspicious times (mahurtams) and other useful information.
Every year, astronomers from all over India meet at the Jaipur Observatory and prepare the almanac with the help of various instruments built more than 250 years ago by Sawai Raja Jai Singh.
MONTHS OF THE HINDU CALENDAR
Hindu Months Western Months
1. Chaitra March-April
2. Vaishshakh April-May
3. Jyeshtha May-June
4. Ashadh June-July
5. Shravan July- August
6. Bhadrapad August-September
7. Ash win September-October
8. Kartik October-November
9. Margashirsha November-December
10. Poush December-January
11. Magh January-February
12. Phalgun February-March