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Why Do Astronauts Feel Weightless?
为什么宇航员会失重
精读先不看文字，完整听一遍。
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Astronauts feel weightless not because there’s no gravity in space—but because they’re in constant free fall.宇航员感觉失重，并非因为太空中没有引力，而是因为他们始终处于自由落体状态。
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The International Space Station orbits Earth at about 28,000 km/h, falling toward the planet while moving forward fast enough to miss it.国际空间站以约每小时2.8万公里的速度绕地球运行，在向地球下坠的同时，因水平速度足够快而始终‘错过’地球。
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Everything inside—including astronauts and floating tools—falls at the exact same rate, so nothing presses against anything else.舱内所有物体——包括宇航员和漂浮的工具——均以完全相同的速度下落，因此彼此间不产生压力。
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This creates the sensation of zero gravity, even though Earth’s pull is still about 90% as strong up there.这便产生了零重力的错觉，尽管此时地球引力仍约为地面的90%。
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Gravity weakens with distance, but astronauts only experience true microgravity because they’re falling continuously.引力随距离减弱，但宇航员体验到的真正微重力，源于他们持续不断的自由落体。
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Parabolic airplane flights mimic this feeling for about 20 seconds by following the same curved path as a thrown object.抛物线飞行的飞机通过模拟抛体运动的轨迹，可在约20秒内重现这种失重感。
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Long-term weightlessness affects muscles, bones, and fluid distribution, requiring daily exercise aboard the ISS.长期失重会影响肌肉、骨骼及体液分布，因此国际空间站上需每日锻炼。
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Without regular resistance training, astronauts can lose 1–2% of bone density per month in orbit.若缺乏规律的抗阻训练，宇航员每月在轨可能流失1%–2%的骨密度。
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Returning to Earth feels heavy at first, as gravity suddenly pushes blood downward and muscles readjust.返回地球初期会感到身体沉重，因重力突然将血液向下推压，肌肉亦需重新适应。
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Weightlessness is physics in action—not magic, but motion shaped by gravity itself.失重是物理定律的体现——并非魔法，而是引力塑造的运动状态。
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
- Weightlessness is physics in action—not magic, but motion shaped by gravity itself. 失重是物理定律的体现——并非魔法，而是引力塑造的运动状态。
- Gravity weakens with distance, but astronauts only experience true microgravity because they’re falling continuously. 引力随距离减弱，但宇航员体验到的真正微重力，源于他们持续不断的自由落体。
- Long-term weightlessness affects muscles, bones, and fluid distribution, requiring daily exercise aboard the ISS. 长期失重会影响肌肉、骨骼及体液分布，因此国际空间站上需每日锻炼。
④ 懂 · 选一选
⑤ 今天会说这一句
Weightlessness is physics in action—not magic, but motion shaped by gravity itself.
⑥ 跟读并录音
Weightlessness is physics in action—not magic, but motion shaped by gravity itself.
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：Weightlessness is physics in action—not magic, but motion shaped by gravity itself.
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。