15 Million Degrees: A Journey to the Centre of the Sun by Lucie Green – review

Why does the sun shine? How does the star work? Why is it mostly plasma, not gas? Green gives us the latest mind-stretching facts, and tells the story of the heroes of solar science

We rarely look directly at it but we miss it when we can't see it. If it wasn't there at all, we'd be gone too. It delivers the food we eat, the air we breathe, the clothes we wear. We read by its light - on a screen, on paper, indoors or out - because it is the ultimate energy source: indeed, the only energy source. It powered the primeval forests of carboniferous ferns and conifers that became our fossil fuel just as it drives the winds for the electrical turbines that must one day replace coal and oil. Even the radioactive elements whose decay and fission keep the planet alive and self-renewing are stellar confections: fragments first forged in, and then recycled by supernovae, exploding giant suns.

That lucky old sun, the great Louis Armstrong sang, "has nothing to do but roll around heaven all day". In fact, it is the only thing in the solar system that really works hard: every second it converts 600m tonnes of hydrogen to 596m tonnes of helium and those missing 4m tonnes become the energy released by the thermonuclear reaction: a bonus of electromagnetic radiation distributed across the entire solar system.

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