Question 5
- With the aid of a diagram, explain eclipse of the moon.
- State three characteristics of Great Circles.
- Outline three uses of Great Circles.
This question was popular among the candidates and quite a good percentage of those who answered the question were able to draw a diagram illustrating the eclipse and explained what it was. However, a significant percentage of those who answered it were not able to state the characteristics and uses of Great Circle. The characteristics of Great Circle are:
- imaginary circular lines drawn on maps or globes
- they run in all directions
- they are limitless in number
- any line that divides the earth into two equal parts is a Great Circle
- the centre of Great Circles is also the centre of earth
- the Equator is the only latitude that is a Great Circle
- the shortest distance between any two points on the earth’s surface lies along the circumference of the Great Circle
- it is capable of dividing the earth into two equal halves
- each halve is called hemisphere
- any two opposite longitudes form a Great Circle, e.g. Longitudes 900E & 900W; 180o & 00
- they are equal in length
The uses of Great Circles are:
- for locating places on the earth’s surface
- in determining approximate distances between places
- serves as the shortest distance between two points on the earth’s surface
- in determining directions
- by commercial aircrafts for long distance journeys
- in saving time in aviation and navigation
- by ship for navigation
- in cutting fuel cost in aviation and navigation