Consider the following lines of Longitude and Latitude : 1. Prime Meridian 2. Tropic of Cancer 3. Equator Which of the above lines is/are a Great Circle ?

A great circle is defined as any circle that divides the Earth into two equal halves or hemispheres, passing through the center of the sphere [1]. Among the lines of latitude, only the Equator (0°) is a great circle because it is the largest circle and divides the Earth into the Northern and Southern Hemispheres [3]. Other parallels of latitude, such as the Tropic of Cancer (23½° N), are small circles because their planes do not pass through the Earth's center and they do not divide the globe into equal halves [4]. Regarding longitude, all meridians are semi-great circles that, when combined with their opposite meridian, form a complete great circle [1]. The Prime Meridian, being a meridian that radiates from pole to pole, is considered part of a great circle route [2]. Therefore, the Prime Meridian and the Equator are great circles, while the Tropic of Cancer is not.

Sources

1. [1] Certificate Physical and Human Geography , GC Leong (Oxford University press 3rd ed.) > Chapter 2: The Earth's Crust > Great Circle Routes > p. 14
2. [3] Exploring Society:India and Beyond. Social Science-Class VI . NCERT(Revised ed 2025) > Chapter 1: Locating Places on the Earth > b) Latitudes > p. 14
3. [4] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 18: Latitudes and Longitudes > Important Parallels of Latitudes > p. 240
4. [2] Physical Geography by PMF IAS, Manjunath Thamminidi, PMF IAS (1st ed.) > Chapter 18: Latitudes and Longitudes > 18.2. Longitude or Meridian > p. 242