Apparent motion of Polaris — direction at lower culmination on the meridian When the Pole Star (Polaris) is at lower culmination (crossing the meridian below the pole), its instantaneous apparent motion on the celestial sphere is predominantly in which direction?

Introduction / Context:
Due to Earth’s rotation from west to east, the entire celestial sphere appears to rotate from east to west. Polaris, lying close to the north celestial pole, describes a small diurnal circle about the pole. Understanding its motion at upper and lower culminations helps with timing and azimuth procedures in astro-surveying.

Given Data / Assumptions:

• Northern Hemisphere observation of Polaris.
• Consider the instantaneous apparent motion (tangent to the star’s diurnal circle).
• Earth’s rotation direction is fixed, giving consistent apparent westward motion of stars.

Concept / Approach:

All stars exhibit apparent westward motion due to Earth’s rotation. Near the pole, the diurnal circle is small; at both upper and lower culminations the motion remains westward along the small circle. The meridian crossing does not reverse the sense of motion; it only marks the instants of maximum and minimum altitude (culminations).

Step-by-Step Solution:

Verification / Alternative check:

Planetarium simulations or star charts show small counterclockwise motion about the pole (as seen from above), which corresponds to westward motion on the sky.

Why Other Options Are Wrong:

• Eastward would imply reversing Earth’s rotation sense.
• Northward/southward imply radial motion toward or away from the pole, which does not describe the diurnal track.
• “Stationary” is incorrect except at the mathematical pole, not at Polaris’s offset.

Common Pitfalls:

• Confusing altitude change (up or down) with the tangential direction of apparent motion on the sky.

Final Answer:

Westward.