科学与数学greenharbor.com
意外自由落体？一些生存技巧
Unplanned Freefall? Some Survival Tips
2017 — 2021，它一次次回到首页
黑点是上首页（≥ 50 分）的那次投稿，空心点是没冲上去的投稿，点越大分数越高。
导读
这是一篇幽默而认真的文章，讨论从高空坠落（如飞机失事）时如何提高生存几率的技巧，包括调整身体姿态、寻找缓冲物等建议。文章以轻松的口吻探讨一个极端罕见但引人好奇的话题。
为什么经久不衰：它把一个荒诞的假设性问题写得既有趣又有物理细节，多年来反复登上 HN 首页，说明这种'认真讨论不可能之事'的风格经得起时间考验。
HN 评论精选
文章的'分摊速度'计算在物理上不成立，能量按速度平方增长。
文章说'120 除以 5 等于 24 英里/小时，不比跳伞员着陆速度慢多少'，这物理上错了：能量与速度平方成正比，120 英里/小时意味着要耗散 25 倍的能量，即使完美的五点着陆，每次'接触'也相当于约 60 英里/小时的撞击。
sfeng查看英文原文
> 120 divided by 5 = 24. Not bad! 24 mph is only a bit faster than the speed at which experienced parachutists land. This is of course being a little silly, but it does get the physics wrong. Your energy is proportional to the square of your speed, so you have 25x more energy to dissipate at 120 mph, not 5x. Even if your five point landing was perfect, each of the five 'hits' is the equivalent of a landing at just under 60 mph, not 24.
实战角度：无经验者根本做不到文中动作，且生还几率极低。
作为有丰富跳伞经验的人：第一次从飞机上掉下去，你根本做不出这些动作，多半会失控翻滚。想学就去风洞练习。而且即使有经验，大概率还是会摔死——人体根本承受不了这种急减速，即使被安全带拦停（比如撞树），主动脉也可能断裂。
jmvoodoo查看英文原文
As someone with significant skydiving experience, good luck doing any of these things your first time out of a plane. Chances are you'll end up on your back, spinning out of control. If you are lucky you'll end up on your belly, spinning out of control. If you want to learn how to do any of these things, go to your local wind tunnel and practice. Without that practice, you should just enjoy the minute or so of spectacular views before you go splat. Also, even with that experience, you'll probably go splat. Best case your aorta will disconnect and you'll bleed out after a few seconds. This is common even when people are stopped by the harness (e.g. by hitting trees). Human body just wasn't designed to accelerate (decelerate) that quickly.
真实幸存者家属分享经历：极端处境下人性既闪光又迅速回归自私。
我父亲是 1985 年中华航空 006 航班事故的幸存者，飞机在 2.5 分钟内从 3 万英尺俯冲，在坠海前几十秒被机长改出。事后 FAA 制定了机组排班和强制休息的新规。他日记里写道：机舱里满是呕吐物和眼泪，但乘客间有深刻的关爱与联结；可落地几小时后，大家又立刻变回互相争抢的自私状态。他随后立刻又登机飞往洛杉矶，此后一生继续飞行。
neomantra查看英文原文
My father was a survivor of China Airlines Flight 006, which in 1985 fell 30,000 feet over 2.5 minutes and corrected tens of seconds before impact with the Pacific. The incident was caused by human error, but also recovered by the skill of the same Captain; after it, the FAA made new guidelines about crew schedules and mandatory rest times. Stephen passed away January 2021 from COVID (but had an amazing 85-year life) and I was just reading his diary from the incident. The gist: There was still an hour left before an emergency landing at SFO. The cabin was festering with vomit and tears, but there was a profound sense of love and connectedness and compassion among every passenger. Every one felt touched by a Divine Grace. However, after a only few hours at the terminal and people could finally leave, it was every person for themselves as they physically and verbally harassed each over to get to where they were going. So quickly back to being selfish humans... My Mom said she would drive from Los Angeles to get him, but he said that if he didn't get on a plane right then, he would never be able to fly again. So he courageously flew SFO->LAX right away, one of many flights he would continue to take throughout his life. [1] https://en.wikipedia.org/wiki/China_Airlines_Flight_006
文中'骑残骸'的建议在时间逻辑上站不住脚。
文章建议'寻找一块空气动力学合适的残骸骑上去'，但既然你已坠落 2 万英尺才醒来，任何'合适'的残骸要么在你上方，要么早已远去；连降落伞的终端速度都比你低，根本追不上。
Someone查看英文原文
“Look around for a proportionate personal vehicle—some large, flat, aerodynamically suitable piece of wreckage. Mount it and ride, cowboy” Given that you woke up after falling 20,000 feet, anything that in itself is “aerodynamically suitable” will be high above you by now (1) or, if it dropped of before you started falling, be miles behind you. Even that tightly packed parachute likely has lower terminal velocity, and will be out of reach by now. I guess your best (not one with good odds, but still best) bet is an airplane door with an uninflated glide that you can tie yourself to, remove from the door, and then inflate. (1) you can see that with rain showers: it’s the smaller droplets that hit the ground last
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