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Why Thunder Follows Lightning—But Seems Delayed
为什么打雷往往先于闪电被感知到（科普）
精读先不看文字，完整听一遍。
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Light travels nearly a million times faster than sound—about 300,000 km/s versus just 340 m/s in air.光速约为30万公里/秒，比声速（空气中约340米/秒）快近百万倍。
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So even though lightning and thunder happen simultaneously, light reaches you almost instantly while sound takes time.尽管闪电和雷声同时发生，但光几乎瞬间到达，而声音传播需要时间。
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Counting seconds between flash and boom lets you estimate distance: five seconds ≈ one mile (or three seconds ≈ one kilometer).从看到闪光到听到雷声的秒数可估算距离：5秒约1英里（或3秒约1公里）。
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Thunder rumbles because sound arrives from different parts of the lightning channel at slightly different times.雷声隆隆作响，是因为来自闪电通道不同部位的声音抵达时间略有差异。
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Temperature and wind layers in the atmosphere bend sound waves, sometimes making thunder inaudible even close by.大气中的温度与风层会使声波弯曲，有时即使近在咫尺也听不到雷声。
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High-frequency tones fade faster over distance, leaving low rumbles to travel farther—hence the ‘rolling’ quality.高频声音随距离衰减更快，低频隆隆声传得更远，因而呈现‘滚动’感。
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If you see lightning but hear no thunder, the strike was likely over 25 km away or blocked by terrain or buildings.若见闪电却未闻雷声，说明闪电可能发生在25公里以外，或被地形、建筑遮挡。
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Safety rule: when thunder roars, go indoors—even if the storm seems distant—because lightning can strike ahead of rain.安全守则：闻雷即入室——哪怕雷暴看似遥远，因闪电可在降雨前击中地面。
精读 · 大约 10 分钟
听 → 读 → 学表达 → 懂 → 今天会说这一句 → 跟读录音 → 自己说一句。
③ 学 · 重点表达
- High-frequency tones fade faster over distance, leaving low rumbles to travel farther—hence the ‘rolling’ quality. 高频声音随距离衰减更快，低频隆隆声传得更远，因而呈现‘滚动’感。
- Thunder rumbles because sound arrives from different parts of the lightning channel at slightly different times. 雷声隆隆作响，是因为来自闪电通道不同部位的声音抵达时间略有差异。
- Light travels nearly a million times faster than sound—about 300,000 km/s versus just 340 m/s in air. 光速约为30万公里/秒，比声速（空气中约340米/秒）快近百万倍。
④ 懂 · 选一选
⑤ 今天会说这一句
High-frequency tones fade faster over distance, leaving low rumbles to travel farther—hence the ‘rolling’ quality.
⑥ 跟读并录音
High-frequency tones fade faster over distance, leaving low rumbles to travel farther—hence the ‘rolling’ quality.
第一版：录下来、回听、再听标准音。系统打分以后再加。
⑦ 说 · 自己来一句
用今天的表达，自己说一句。
例子：High-frequency tones fade faster over distance, leaving low rumbles to travel farther—hence the ‘rolling’ quality.
已记下。连续天数以后会显示在课表里。
陈老师指导
课程开发中，敬请期待。成人和孩子都可以先自学听读、精读。
这边的讲解音轨还在做。想先跟着老师走完固定 30 课，可以去陈老师带读社（和自学通行不是同一份会员）。
课程开发中，敬请期待。