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. And standing your hair on end was intimidating to predators or enemies (picture a cat facing off with a...Full Story