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夏天到了，遮阳伞、防晒霜、太阳镜等防御武器也跟着悄然登场了，夏日灼热的阳光似乎成了大家的公敌。太阳光的魔力真的那么厉害吗？能把我们原本雪白的皮肤晒成古铜色？
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Sunshine has what scientists call radiation. That's a type of energy, like electricity. The sun has three kinds of radiation -- visible, infrared（红外线的） and ultraviolet（紫外线的）. The warm feeling you get lying in the sun comes from the visible and infrared energy. (Visible light is the only light you can see. It makes things bright!) Ultraviolet energy reacts with chemicals in your skin to cause a sunburn.
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Here's what happens: You're outside on a sunny day. Your top layer of skin naturally blocks out about 10 percent of the ultraviolet light. The rest goes through and hooks up with cells called melanocytes（黑素细胞） in your second layer of skin. The melanocytes then produce a brown coloring called melanin（黑色素） -- and that's what gives you a tan and helps protect you from ultraviolet light.
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It’s no coincidence that the process of turning animal skins into leather is called tanning. When people tan, UV radiation from the sun breaks down protein in our skin cells and causes, over time, wrinkles and leathery-looking skin. According to the American Academy of Dermatology (AAD), most sun exposure occurs before the age of 18.
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