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Q. I bike to class sometimes. It's annoying biking in the wintertime, because it's so cold. How fast would I have to bike for my skin to warm up the way a spacecraft heats up during reentry?
Q．我有时骑自行车去上课，但在冬天骑车实在是太冷了。如果我想让皮肤像太空飞船重返大气层时那样暖和起来，那么我需要骑多快？
-David Nai
——大卫•纳伊
A. REENTERING SPACECRAFT HEAT UP because they're compressing the air in front of them (not, as is commonly believed, because of air friction).
A．重返大气层的太空飞船表面温度上升，是因为它压缩了前方的空气，而不是像大多数人认为的那样是由于空气“摩擦”。
To increase the temperature of the air layer in front of your body by 20 degrees Celsius (enough to go from freezing to room temperature), you would need to be biking at 200 meters per second.
要想把你面前那层空气的温度提高20℃（足够从冰点上升到室温），你需要骑到每秒200米。
The fastest human-powered vehicles at sea levels are recumbent bicycles enclosed in streamlined aerodynamic shells. These vehicles have an upper speed limit near 40 m/s-the speed at which the human can just barely produce enough thrust to balance the drag force from the air.
目前最快的人力车是包裹在流线型空气动力学外壳里的躺式自行车，这种自行车的速度最快能达到将近每秒40米，再快人力就已经不足以抗衡空气阻力了。
Since drag increases with the square of the speed, this limit would be pretty hard to push any further. Biking at 200 m/s would require at least 25 times the power output needed to go 40 m/s.
由于空气阻力正比于速度的平方，因而要想再提高速度将会变得极为困难。以每秒200米的速度骑行所需要的动力是以每秒40米速度骑行时所需动力的25倍。
At those speeds, you don't really have to worry about the heating from the air-a quick back-of-the-envelope calculation suggests that if your body were doing that much work, your core temperature would reach fatal levels in a matter of seconds.
在这样的速度下，空气产生的加热效应已经不是你需要担心的东西了——简单计算一下就可以发现如果你的身体要产出这么多的能量，那么你的核心温度将在几秒钟内上升到致命的程度。
Q. How much physical space does the Internet take up?
Q．整个互联网占据多少物理体积？
-Max L
——马克思•L
A. THERE ARE A LOT of ways to estimate the amount of information stored on the Internet, but we can put an interesting upper bound on the number just by looking at how much storage space we (as a species) have purchased.
A．有很多种方法可以估算互联网上所有存储的信息的多少，我们可以通过全世界存储空间的购买量来确定互联网信息总量的上限。
The storage industry produces in the neighborhood of 650 million hard drives per year. If most of them are 3.5-inch drives, that's 8 liters (2 gallons) of hard drive per second.
硬盘行业每年能够生产约6.5亿块硬盘，如果它们之中绝大部分是3.5英寸硬盘的话，那么每秒生产出来的硬盘的体积为8立方分米。
This means the last few years of hard-drive production-which, thanks to increasing size, represents the majority of global storage capacity-would just about fill an oil tanker. So, by that measure, the Internet is smaller than an oil tanker.
这意味着最近几年硬盘的产量刚好只够塞满一艘油轮。得益于硬盘容量的不断增加，最近几年新增的存储空间占据了全球绝大多数的存储空间。这样看来，整个互联网还没有一艘油轮大。
Q. What if you strapped C4 to a boomerang? Could this be an effective weapon, or would it be as stupid as it sounds?
Q．如果我把C4炸药绑到回旋镖上会怎么样？它能摇身一变成为强力武器吗？还是会像它看起来的那样蠢？
-Chad Macziewski
——查德•马琴斯基
A. AERODYNAMICS ASIDE, I'M CURIOUS what tactical advantage you're expecting to gain by having the high explosive fly back at you if it misses the target.
A．撇开空气动力性能不说，我只是好奇，没击中目标就会自己飞回来的高爆炸药，你指望从中获得怎样的战术优势呢？
