If the Earth-Sun distance were halved and the orbit stayed circular, how many days would a year last?
Correct answer D. 129 days
Explanation
Kepler's third law gives T ∝ r^(3/2), so halving r multiplies the period by (1/2)^(3/2) ≈ 0.354, turning 365 days into about 129 days.
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