Exam-style question
Try this first
A spaceship travels at 0.99c for 10 years proper time. How much time passes on Earth?.
- A.70 years
- B.80 years
- C.100 years
- D.120 years
Model answer
What a good answer should say
- 70 years
Explanation
Why this works
γ = 1/√(1 − 0.99²) ≈ 1/√(1 − 0.9801) = 1/√0.0199 ≈ 7.09. The dilated time is Δt = γ Δτ = 7.09 × 10 ≈ 70.9 years, so approximately 70 years pass on Earth.
Common mistake
No common mistake is linked to this question yet.