Question

The difference between a tropical year and a sidereal year is due to

A) the precession of Earth's rotation axis.
B) the tug of the Moon on Earth as it orbits the Sun.
C) the mismatch of the exact length of a year and 365 days.
D) the combination of Earth's rotation and Earth's orbital motion.

Answer 1

The difference between a tropical year and a sidereal year is due to the combination of Earth's rotation and orbital motion, causing the solar day to be longer than the sidereal day.

Step-by-step explanation:

The difference between a tropical year and a sidereal year is due to the combination of Earth's rotation and Earth's orbital motion.

Earth not only turns on its axis but also moves along its path around the Sun in a day. The movement of Earth along its orbit causes the Sun to not yet reach a position above the observer at the completion of one rotation with respect to the stars. To complete a solar day, Earth must rotate an additional amount, which is about 1/365 of a full turn or approximately 4 minutes. This makes the solar day about 4 minutes longer than the sidereal day.