It’s often thought it’s because of light reflected back into the sky from the blue sea. In fact, it’s the result of sunlight being scattered when it strikes the air molecules in the atmosphere.
Sunlight is made up of – literally – all the colours of the rainbow, and the complex physics of how light interacts with molecules means shorter-wavelength blue light is more strongly scattered than red light. As a result, it is blue-coloured light that ends up spread most widely across the sky, dominating its appearance.
- Is there any truth behind the saying ‘red sky at night, shepherd’s delight’?
- Why does the sky change colour on the brink of a hurricane?
- What colour is the sky on an exoplanet?
- What colour is space?