1. What causes goose bumps?
Goose bumps (scientific name: piloerection) pop up when you're cold or afraid. A tiny muscle at the base of each body hair contracts; together, they appear as naked bumps on the flesh.
They made sense eons ago, when humans still had a natural "fur coat." Back then, fluffing your ruff would warm the body by trapping an insulating layer of air between the hairs.
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