Moon shows same face — Assertion–Reason UPSC Prelims PYQ 2005
Consider the following statements:
- Assertion (A): The same face of the Moon is always presented to the Earth.
- Reason (R): The Moon rotates about its own axis in 27.3 days, which is about the same time that it takes to orbit the Earth.
Which of the statements is/are correct?
- Both (A) and (R) are individually true and R is the correct explanation of A
- Both (A) and (R) are individually true and R is not the correct explanation of A
- A is true, but R is false
- A is false, but R is true
Explanation
Option (a) is correct
- The Moon always shows nearly the same face to the Earth because it is in synchronous rotation (tidal locking). This means that the Moon takes approximately 27.3 days to complete one rotation on its axis and 27.3 days to complete one revolution around the Earth. Since these two periods are nearly identical, the same hemisphere of the Moon continuously faces the Earth. Therefore, both the Assertion and the Reason are true, and the Reason correctly explains the Assertion.
Answer: (a) Both (A) and (R) are individually true and R is the correct explanation of A
