A huge landmass of South Asia is flanked by new fold towering mountains on the northwest, north and northeast. The Arabian sea lies to its southwest, the Bay of Bengal to its southeast and the Indian Ocean to its south. This well defined South Asian landmass is called Indian sub-continent.
This sub-continent consists of the countries of India, Pakistan, Bangladesh, Nepal and Bhutan including Sri Lanka, an island narrowly separated by the Palk Strait. India alone covers about three-fourths of the area of this sub-continent and has common frontier with each one of them.
She along with her five neighbours, forms a clearly identifiable geographical unit, with certain common cultural parameters. Since old times, the country has been known by various names such as Aryavarta, Bharat, Hindustan and lately India. The Indian Ocean or Hind Mahasagar has also been named after India - the only country to be so. According to the Constitution of India, the country is known as Bharat or India.
India lies wholly in the Northern Hemisphere. The Indian mainland extends between 8°4'N to 37°6' N latitudes and from 68°7' E to 97°25' E longitudes. Thus, the latitudinal and longitudinal extent of India is of about 29 degrees. It measures about 3,214 km from north to south, and 2,933 km from east to west.
Though the latitudinal and longitudinal extent is almost the same, the actual distances do differ considerably. This is because the east-west distance between two successive meridians of longitude along the equator is at its maximum - 111 km. This, however, goes on decreasing as one moves from the equator to the poles, where it is zero. This is because all the meridians of longitude merge in a single point at the poles - both North and South. On the other hand, the north-south distance between any two successive parallels of latitude along any meridian of longitude remains almost uniform, i.e., 111 km.
The northern most point of the Indian mainland lies in the state of Jammu and Kashmir and the southern most point is Kanyakumari in Tamilnadu. However, the southern most point of the country as a whole lies further south in Andaman and Nicobar Islands. It is now called Indira Point. It is situated at 6°30'N latitude. The westernmost point of lndia lies in Gujarat and the eastern most in Arunachal Pradesh.
The northern parts of the country are quite far off from the equator. Therefore, the rays of the sun strike those parts more obliquely. Consequently, this part of the country receives lesser amount of insolation and has cold climate unlike the southern parts.
Secondly, the difference between the length of day and right in southern most part of India is much less only about 45 minutes as they are situated near the equator, This difference between day and night in the northern parts of India steadily goes on increasing till it becomes as much as 5 hours.
The Tropic of Cancer passes almost halfway through the country. Thus, half of the country to the south of the Tropic of Cancer is situated in the Tropical or Torrid zone and the other half lying north of the Tropic of Cancer falls in the Sub-tropical zone.
The earth takes 24 hours to complete one rotation on its axis. The Sun rises first in the east and then in the west because the earth rotates from west to east. The earth’s longitudinal expanse of 360° is thus covered in 24 hours, at the pace of 15° per hour. As the longitudinal extent of India is nearly 29°, the real time difference in India between its eastern and western extremities is roughly of two hours. While at the eastern extremity of India the day may have just broken out, the western extremity would take nearly another two full hours to do so.
To iron out this big chunk of time difference, India, like all other countries of the world, follows the local time of its relatively central meridian as the standard time for the whole country. For the convenience of all, each country chooses its standard meridian in a multiple of 7°30'. Accordingly, the standard meridian of India has been chosen to be 82°30' E.
The north-central part of India is broad while the southern part tapers down towards the Indian Ocean in the south. Thus, the northern part of the Indian Ocean has been divided into two, by the sheer presence of Indian Peninsula. The western part of northern Indian Ocean is called the Arabian Sea while the eastern part is called the Bay of Bengal.
The total length of the coastline of India including the island groups is about 7,516.6 km. The Palk Strait separates Indian mainland from Sri Lanka. Structurally, Sri Lanka is an extension of the peninsular block of India.