Question

The duration of the day form the moment the sun is overhead today to the moment the sun will be overhead tomorrow is determined by

• A. the rotation of the earth's on its axis only.
• B. the revolution of the earth round the sun only.
• C. the rotation of the earth on its axis as well the revolution of the earth around the sun.
• D. the inclination of the axis of rotation of the earth to its plane of revolution.

Answer 1

The correct option is C the rotation of the earth on its axis as well the revolution of the earth around the sun.

The length of a solar day varies through the year, and the accumulated effect produces seasonal deviations of up to 16 minutes from the mean. The effect has two main causes. First, Earth's orbit is an ellipse, not a circle, so the Earth moves faster when it is nearest the Sun (perihelion) and slower when it is farthest from the Sun (aphelion) (see Kepler's laws of planetary motion). Second, due to Earth's axial tilt (known as the obliquity of the ecliptic), the Sun's annual motion is along a great circle (the ecliptic) that is tilted to Earth's celestial equator.