
IPFS News Link • Space Travel and Exploration
What causes the strange green flash at sunset and sunrise on Earth?
• https://www.space.com By Joe RaoHere is something that you might remember from your high school earth science class: As sunlight — which appears to be pure white — passes through a glass prism, it refracts or bends. Different wavelengths of light are bent by different amounts. In this way a prism can spread out a ray of white light into the rainbow spectrum.
The spread of refractive colors can be observed in poor-quality binoculars and telescopes. In such inexpensive instruments the optics tend to be not aligned properly so sometimes you'll see the full moon appearing with a yellow-orange tinge on one side and a bluish tinge on the opposite side.
Once again, however, remember that the sun and also the moon — because it reflects direct sunlight back toward Earth — is really composed of a "stack" of different colored images. Perhaps you can recall the fictitious name "Roy G. Biv," where each letter represents a color in the spectral lineup: Red, Orange, Yellow, Green, Blue, Indigo and Violet.