Chapter 33, Problem 3RQ

To determine

The reason behind the appearance of stars on an imaginary north-south axis once every $24\text{ hours}$.

Answer to Problem 3RQ

The appearance of stars on an imaginary north-south axis once every $24\text{ hours}$ is due to Earth’s rotation from west to east due to which the celestial bodies have motion from east to west.

Explanation of Solution

The stars appear on an imaginary north-south axis once every $24\text{ hours}$. This is called the diurnal motion of stars.

Earth rotates daily on its axis from west to east, which results in the motion of celestial sphere from east to west.

This can be explained by the movement of the Big Dipper constellation. North star appears at the end of the Big Dipper. The stars appear to move in circles around North star. North star appears stationary as the celestial sphere rotates because it lies very close to the projection of Earth’s rotational axis. After $24\text{ hours}$ stars come at their position again, but the position of North star appears to be stationary.

Conclusion:

Therefore, the appearance of stars on an imaginary north-south axis once every $24\text{ hours}$ is due to Earth’s rotation from west to east due to which the celestial bodies have motion from east to west.