十万个为什么·科学启蒙30篇（1）
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What Causes Thunder and Lightning?
雷声和闪电是如何产生的？
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Lightning is a giant spark of electricity that jumps between clouds, within a cloud, or from a cloud to the ground.
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It forms when rising and falling air currents cause ice particles and water droplets to collide inside storm clouds.
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These collisions separate positive and negative charges, building up huge voltage differences across regions of the cloud.
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When the electric field becomes strong enough, the air—normally an insulator—breaks down and conducts electricity suddenly.
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That rapid flow of electrons heats the air to around 30,000°C, which is five times hotter than the Sun’s surface.
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The superheated air expands explosively, creating a shock wave we hear as thunder.
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Because light travels faster than sound, we always see lightning before hearing thunder.
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You can estimate how far away lightning struck by counting seconds between flash and boom—every three seconds equals about one kilometer.
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Lightning rods don’t attract lightning but safely direct its current into the ground if a strike occurs nearby.
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About 100 lightning bolts hit Earth every second, yet fewer than 10% of them strike the ground directly.