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News: A rare Blood Moon appeared on September 7, 2025, longest since 2022, widely visible across Asia and Europe.
About Blood Moon
- A Blood Moon is the red glow of the Moon during a total lunar eclipse. It occurs at the full moon phase when Earth’s shadow covers the Moon.
- Occurring mechanism
- The Sun, Earth, and Moon align, with Earth between the Sun and the Moon.
- The Moon enters Earth’s umbra, blocking direct sunlight.
- Sunlight reaching the Moon is filtered through Earth’s atmosphere: shorter blue wavelengths scatter away, while longer red wavelengths bend toward the Moon, creating the reddish hue.
About Rayleigh Scattering
- Explained by John William Strutt (Lord Rayleigh).
- When light interacts with particles smaller than its wavelength, scattered intensity is inversely proportional to wavelength.
- Blue light scatters more strongly, which makes the sky appear blue.
- During an eclipse, this scattering removes blue light, letting red light pass through Earth’s atmosphere to illuminate the Moon.
