Sunlight is far older than it looks

The energy warming you right now was born in the Sun's core, where fusion crushes hydrogen atoms at fifteen million degrees. From there to the surface is about 700,000 kilometres. At the speed of light, the trip should take just over two seconds.

But the Sun's interior is a monumental traffic jam. The energy staggers outward as matter absorbs and re-emits it over and over, in a chaotic zigzag with countless detours. According to calculations, escaping the Sun takes anywhere from thousands to more than a hundred thousand years.

Once outside, it's all speed: it crosses 150 million kilometres of vacuum in eight minutes and twenty seconds. So this morning's ray of sunshine is a fresh arrival — carrying a story older than the cave paintings of Altamira.