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HyperPhysics: Blue Sky and Rayleigh Scattering

The brilliant blue color of the sky is due to scattering by molecules in the atmosphere.

- Visit HyperPhysics: Blue Sky and Rayleigh Scattering for detailed explanations about why the sky is blue and an overview of different kinds of scattering.
- See this University of California article to learn why the sky appears blue, not violet.

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Why is the Sky Blue?

Perform a scattering experiment on your own to learn why the sky is blue during the day but reddish at sunset.

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Why isn't the Martian sky blue like the Earth's?

The Martian sky is butterscotch, not blue like our own--the butterscotch color is produced by light scattering from dust particles blown into the atmosphere by the strong Martian winds. For more on the Martian sky, see this NASA Q & A.

(This feature was updated on July 28, 2011.)

Atmospheric Optics: Rays and Shadows

See pictures and detailed explanations of atmospheric phenomena at Atmospheric Optics:  Rays and Shadows. Many of the optical effects are caused by scattering sunlight.