Earth gets it blue skies through an effect known as Rayleigh scattering. Now astronomers have observed Rayleigh scattering in the atmosphere of a planet 100 light years away.

Put these three things together, and a blue sky is inevitable. Here's how it all comes together. Light of many different wavelengths, not all of which are visible, are emitted by the Sun.

This effect is called Rayleigh scattering. In this process, more of the bluer light, which has shorter wavelengths, ... making the small amount of light we see in the twilight sky blue.

Redder when the Sun sets and rises. Of course, the sky is not always blue. And Rayleigh scattering also explains why the sky tends to be reddish when the Sun is close to the horizon – at sunrise ...

They arise out of pollution, and they generate visual pollution—aircraft graffiti that can erase blue from the sky and light from the sun. All good reasons to despise these artificial clouds.

Well, that was quick. Less than 24 hours after the end of China’s massive military parade, Beijing is back to its usual smoggy self. Residents woke up Friday morning to find the crystal blue ...