Sunlight

Sunlight is light from the Sun. It travels at the speed of light, about 300,000 kilometres a second, and takes about eight minutes and twenty seconds to cover the 150 million kilometres to Earth.^[1] The Sun you see in the sky is therefore the Sun as it was eight minutes ago. If it had done anything interesting in the meantime, you would be the last to know.

An old journey

The light leaving the Sun's surface is only the last part of the story. The energy is produced deep in the core, and it takes a very long time, estimated at thousands to more than a hundred thousand years, to work its way out to the surface as it is absorbed and given off again countless times.^[2] It then crosses to Earth in eight minutes.

Sunlight therefore spends tens of thousands of years getting out of the Sun and about eight minutes doing the rest. It is the only journey in which the queue to leave the building takes longer than the trip.

Colour

Sunlight looks white or slightly yellow, but contains all the colours of the rainbow, as a prism or a rainbow shows. The Sun itself is, strictly, white. It looks yellow from the ground because the air scatters some of the blue light away, which is also why the sky is blue. The sky, in other words, is sunlight that took a detour.

See also

• Sun – where it comes from
• Rainbow – sunlight, sorted
• Shadow – where it isn't

References

1. Beam, B. (1999). Eight Minutes Late. Photon Press.
2. Core, C. (2008). “Getting Out of the Sun”. Solar Logistics 100,000: 1.
3. Prism, P. (1704). All the Colours. Fictional reprint.