CAPF AC 2022 Q62: Geography – Astronomy & Earth - Sun System
- (a) Every great circle divides the Earth into equal halves.
- (b) Every great circle is a circumference of the Earth.
- (c) Great circles mark the longest travel routes between locations on the Earth’s surface.
- (d) Great circle is the largest circle that can be drawn around the Earth through two particular points.
Answer: (c) Great circles mark the longest travel routes between locations on the Earth’s surface.
Explanation
Great circles
How to think: a great circle is any circle on the globe whose centre is the centre of the Earth.
It cuts the Earth into two equal halves.
Its most useful property is that an arc of it is the shortest path between two places.
| Statement | Verdict |
|---|---|
| Every great circle divides the Earth into equal halves | True |
| Every great circle is a circumference of the Earth | True |
| Great circles mark the longest travel routes | False; they mark the shortest routes |
| It is the largest circle that can be drawn through two particular points | True |
Examples: the Equator is the only parallel of latitude that is a great circle.
Every meridian with its opposite meridian forms a great circle.
Use: ships and aircraft follow great circle routes to save fuel and time.
That is why flights from India to North America pass near the Arctic.
Answer: (c).
Why each option is right or wrong
- (a) Incorrect. This is true: a great circle halves the Earth.
- (b) Incorrect. This is true: its length equals the Earth's circumference.
- (c) CORRECT. This is wrong: great circles give the shortest, not the longest, routes.
- (d) Incorrect. This is true: it is the largest circle that can be drawn on the globe.
Key point
Great circle: centre at the Earth's centre, halves the globe, shortest distance between two points. The Equator and all meridian pairs are great circles; other parallels are small circles.
Remember
Great circle = shortest route on the globe.
Common mistakes
- Missing the single word longest in an otherwise familiar sentence.
- Thinking all parallels of latitude are great circles; only the Equator is.
- Believing a straight line on a flat map is the shortest route on the globe.
Exam tip
Educated guess: nobody plans the longest route on purpose. Great circle routes are famous in aviation precisely because they are the shortest.
Sources
- NCERT Class XI Geography — Practical Work in Geography (Latitude, Longitude and Time; Map Projections)
- G. C. Leong, Certificate Physical and Human Geography — The Earth and the Universe (great circle routes)