Chapter 1 Solutions — Locating Places on the Earth

The Earth rotates 360° in 24 hours, so every 15° of longitude equals 1 hour (or every 1° equals 4 minutes).

India's standard meridian is 82°30'E (82.5°).

Time difference = 82.5° × 4 minutes = 330 minutes = 5 hours 30 minutes ahead of Greenwich.

So when it is 12:00 pm (noon) in London (Greenwich Mean Time), India's IST is 12:00 + 5:30 = 5:30 pm.

This is a personal observation activity. Face North (use a compass or the rising sun in the East as a guide), then identify what lies in each of the eight directions: North, South, East, West, North-East, North-West, South-East, South-West.

Model answer (for a school in a city): North — park; South — market; East — main road; West — residential houses; North-East — temple; North-West — school ground; South-East — bus stop; South-West — hospital.

Fill in your own observation for your actual home or school.

Local time is the time at a specific place based on the position of the Sun above that place's meridian. When the Sun is exactly overhead, it is 12 noon local time for that longitude.

Standard time is the officially adopted time for a whole country or region, based on one chosen meridian. It keeps everyone in the country following the same clock.

If every place used its own local time, timetables for trains, flights, and broadcasts would be impossible to manage — a train starting in Mumbai and arriving in Kolkata would need travellers to keep adjusting their watches.

India uses IST (Indian Standard Time), based on 82°30'E, so that the entire country shares one time. Similarly, the world uses time zones (each 15° wide) to group places under a common standard time.

Summary: local time = Sun's position at your exact location; standard time = the one fixed time all places in a region agree to use.