🔍 Key Concepts

• Difference between diurnal and annual phenomena in astronomy • Meaning of aberration of light (apparent shift in a celestial body’s position due to motion of the observer) • How the Earth’s motions (rotation vs revolution) affect observed star positions

💭 Think About

• First, decide what time scale the word diurnal refers to and which motion of the Earth happens on that time scale. • Ask yourself: in aberration of light, is the apparent shift caused by the Earth turning in place, or by it traveling along its orbit around the Sun? • Look at the choices and identify which option would instead be associated with annual aberration, then eliminate that from consideration for a diurnal effect.

✅ Before You Answer

• Confirm that diurnal means “daily” and connect that to the correct motion of the Earth. • Check which answer choice describes the Earth’s motion that takes about 24 hours versus about one year. • Make sure you are not confusing aberration (apparent shift due to motion of the observer) with a false horizon (a visual reference error near the horizon).