Why does the Sun appear to rise about 2 minutes before it actually crosses the horizon?
Generated by claude-sonnet-4-6 · 2026-06-26 01:08 · grounding rag
Model Answer
The Sun appears to rise about 2 minutes before it actually crosses the horizon due to atmospheric refraction. As sunlight enters the Earth's atmosphere, it bends (refracts) towards the normal, making the Sun appear slightly higher than its actual position. Thus, we see the Sun before it has actually crossed the horizon.
Source: Chapter 10, Section 10.5 – Atmospheric Refraction (Advance sunrise and delayed sunset)
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Explanation
- The key concept is atmospheric refraction — light bends as it passes through layers of air of gradually changing density/refractive index.
- Examiners expect you to clearly state: (1) the cause (atmospheric refraction), and (2) the effect (Sun appears higher/visible before actual crossing of horizon).
- Mentioning "actual sunrise = actual crossing of the horizon" adds precision and shows you've read the definition carefully.
- Do not confuse this with scattering of light — that explains colours at sunrise/sunset, not the time difference.