The Great Poisoning

The sky above you is orange. Not at sunset — always. There is no blue yet, because there is no oxygen yet, and the chemistry that makes sky blue requires the very thing the world is running out of time to produce. You are floating in a warm, shallow sea, and you are ancient beyond imagining, and you are about to commit the greatest catastrophe in the history of life on Earth — by accident.

You are a cyanobacterium. You are smaller than a thought. And you have just learned a trick no living thing has ever managed: you eat sunlight, and you exhale poison.

The poison is oxygen.

For a hundred million years, you and your descendants exhale quietly into the sea. The sea absorbs it — iron in the water grabs the oxygen and rusts, settling to the ocean floor in deep red bands of iron oxide that miners dig up today and call ore. But eventually the iron runs out. The ocean cannot soak up any more. The oxygen begins to leak into the sky.

Everything that breathes — everything alive — suffocates. Slowly, catastrophically, almost completely. The organisms that built the world for three billion years are killed by a gas they never needed and never asked for.

The sky turns blue. The dead settle into rock.

And somewhere in the survivors, something small discovers that the poison is actually the most powerful fuel the universe has on offer.