Bananas contain potassium-40, a naturally occurring isotope that makes them slightly radioactive. But before you swear off smoothies, know this: you’d have to eat millions of bananas in one sitting to be at any risk. Still, it’s wild to think that your breakfast might be giving off tiny doses of radiation—just one of nature’s odd little quirks.

2. You’re Mostly Made of Empty Space

The atoms that make up your body are 99.9999999% empty space. The nucleus is tiny compared to the full atom, and electrons orbit so far out that, proportionally, you’re more "nothing" than "something." It's one of those facts that’ll break your brain if you think too hard about it—because it means even solid things aren’t really solid.

3. Octopuses Have Three Hearts and Blue Blood

These deep-sea aliens pump blood through three hearts—two for the gills and one for the rest of the body. Their blood is blue because it uses copper-based hemocyanin instead of iron-based hemoglobin. And get this: when they swim, the heart that pumps to the body actually stops. No wonder they’re considered some of the weirdest, smartest animals in the ocean.

4. There’s a Planet Where It Rains Glass—Sideways

HD 189733b is a planet outside our solar system with 5,400 mph winds and storms that rain molten glass. Sideways. It’s only 63 light-years away, but it makes Earth’s worst weather look like a drizzle. Space is metal—and terrifying—and this is just one of thousands of extreme exoplanets scientists are now discovering.

5. Your Stomach Lining Replaces Itself Every Few Days

Stomach acid is strong enough to dissolve metal, so how does it not burn through you? Simple—your body replaces your stomach lining every 3 to 4 days. Without that rapid regeneration, your own digestive system would start digesting itself. It’s a little gruesome, but also pretty genius.

Conclusion: The Universe Is Way Weirder Than Your Textbook Let On

Science isn’t just lab coats and formulas—it’s full of jaw-dropping facts that make the world feel stranger (and cooler) than fiction. Whether it’s radioactive fruit or storms of sideways glass, there’s always something new to learn—and it’s rarely what you expect.