What is the use of the standard meridian?
The standard meridian is used to establish a uniform time across a country. Since the Earth rotates, the sun rises earlier in the eastern parts and later in the western parts of a country. In India, there is a time difference of nearly two hours between the easternmost and westernmost parts due to a longitudinal variation of about 30 degrees.
Despite this natural time difference, the standard meridian ensures that all regions follow the same time. For example, while the sun rises in the northeastern states about two hours earlier than in Jaisalmer, the watches across India show the same time. This uniform time system facilitates coordination in administration, transportation, and communication throughout the country.
Explanation
The textbook explains that India has a longitudinal extent of about 30 degrees, causing a time difference of nearly two hours between its easternmost and westernmost parts. The standard meridian (82°30' E for India) is selected to create a single reference point for time across the country. This allows all regions to follow the same time (Indian Standard Time), which is essential for practical purposes like scheduling, administration, and communication. Countries with greater east-west extent like the USA may have multiple standard meridians (time zones) to accommodate larger time variations.