A rainbow forms when sunlight passes through water droplets in the air, bending and reflecting inside the droplets to split white light into its component colors. The observer must have the sun behind them and water droplets in front of them to see a rainbow.

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Lightning forms when ice particles in storm clouds collide and create electrical charges that separate, building up until the charge difference becomes so large that it causes a giant spark between the cloud and ground. This spark is what we see as lightning.

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The ocean is salty because rivers and rain dissolve minerals from rocks and soil, carrying them into the sea over millions of years. These minerals, primarily salt, accumulate in the ocean and cannot easily escape, making the water increasingly salty.

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Onions make you cry because they release a chemical gas called syn-propanethial-S-oxide when their cells are cut open. This gas irritates your eyes and triggers tear production as a protective response.

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Spicy food tastes hot because capsaicin, a compound in chili peppers, activates pain receptors in your mouth that normally respond to heat. Your brain interprets these pain signals as a burning or hot sensation, even though the food isn't actually hot.

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