Right now, deep inside you, there's a pool of acid strong enough to dissolve a razor blade. (Researchers tested this. The blade came out 37% lighter.) Naturally, this raises a question: why doesn't that acid dissolve your stomach? Part of the answer is that your stomach does something fairly drastic on a regular schedule. What is it? It briefly switches off its acid production every night while you sleep It grows itself a brand-new inner lining every few days It coats itself in a thin layer of fat that the acid can't penetrate It lowers its temperature to slow the acid down None You'd think the number of bones in a human body is a fixed thing — one of those facts you learn once and you're done. But it actually changes over your lifetime. Compared to a fully grown adult, how many bones does a newborn baby have? Far fewer — babies' skeletons aren't finished yet Exactly the same number More — babies are born with around 300 Twice as many None Somewhere in your head, right now, is the smallest bone you own — a bone roughly the size of a grain of rice. Where in the body is it? In the tip of your nose In your inner ear In your pinky fingertip At the base of your tongue None People love to claim the tongue is the strongest muscle in the body. It's a fun line at parties. It's also wrong. If you measure strength as raw force, which muscle actually wins? The bicep The calf muscle The jaw muscle The muscle in the front of the thigh None Here's one almost nobody gets right the first time. When a baby is born, there's one fairly important body part it doesn't really have yet — at least not as actual bone. What is it? Kneecaps Fingernails Eyelashes Earlobes None Time for a stumper. Your body is a walking ecosystem — it's home to trillions of bacteria. For years, the famous claim was that bacteria outnumber your own human cells 10 to 1. Then scientists actually ran the numbers. What's the real ratio, roughly? Still about 10 to 1 — the old number held up Around 100 to 1 — they badly undercounted Roughly 1 to 1 — about even About 1 bacterium for every 50 human cells None Time's up
