It isn't only physicists who are fascinated by light. Poets too have been entranced by its powers. Photons have mysterious properties. Perhaps this is why we like to light candles when we're feeling contemplative.

Li-Fi, short for "Light Fidelity" is a wireless technology that uses LED light to share data. It is faster and safer than regular WiFi. And it could soon be put into practice.

Blanketing the Antarctic ice sheet in artificial snow might sound outlandish. But could geoengineering help to counteract runaway climate change? One thing is clear: many of the ideas could be very risky.