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Around 2 billion years ago, uranium deposits at Oklo, in what is now Gabon, sustained natural fission reactions, long before humans existed. Concentrated uranium, the right rock and groundwater came together naturally; the water slowed neutrons, helping the chain reactions continue. The evidence was discovered in 1972, when scientists noticed unusual proportions of uranium isotopes and found traces left by fission. Surviving rock samples preserve the story of these natural reactors.

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Carnegie Mellon researchers fashioned experimental seed carriers from wood veneer. With no motor or battery, moisture makes the wood twist, helping each carrier work its way into soil. The design takes inspiration from Erodium plants: their seeds have coiled appendages that move as moisture changes. Three tails help the wooden carrier stand upright before it burrows, bringing this plant-inspired mechanism to other seeds.

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Found at Yanghai in western China, these trousers are more than 3,000 years old and among the oldest known surviving trousers. Their patterned knees look familiar. The wearer was buried with horse equipment and weapons associated with mounted warriors. The wool garment combines weaving techniques and allows room at the crotch for legs to spread while riding. Archaeologists examined it and made full-size reconstructions to test how it worked.

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Nearly 4,000 years ago, Babylonians recorded recipes in cuneiform on clay. One surviving tablet contains 25 stew recipes. A Yale–Harvard team translated and tested recipes from the tablets. Their reconstructions included lamb with beetroot, lamb stew with milk and grain cakes, and a vegetarian dish enriched with beer bread. The food shown is a modern reconstruction of meals people planned almost 4,000 years ago.

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Some clouds begin with dust from meteors. Noctilucent clouds, electric-blue clouds, form when tiny ice crystals grow around particles left high in the atmosphere, roughly 80 kilometres above Earth, far higher than ordinary weather clouds. NASA detected meteoric material inside their ice crystals. They can catch sunlight after the ground below has gone dark. Their night-time glow is sunlight scattered by ice high above the shadowed landscape.

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