《那些古怪又讓人憂心的問題》第22期:短回答環節(3)

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．我有時騎自行車去上課，但在冬天騎車實在是太冷了。如果我想讓皮膚像太空飛船重返大氣層時那樣暖和起來，那麼我需要騎多快？

-David Nai

——大衛•納伊

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．重返大氣層的太空飛船表面溫度上升，是因爲它壓縮了前方的空氣，而不是像大多數人認爲的那樣是由於空氣“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.

要想把你面前那層空氣的溫度提高20℃（足夠從冰點上升到室溫），你需要騎到每秒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.

目前最快的人力車是包裹在流線型空氣動力學外殼裏的躺式自行車，這種自行車的速度最快能達到將近每秒40米，再快人力就已經不足以抗衡空氣阻力了。

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.

由於空氣阻力正比於速度的平方，因而要想再提高速度將會變得極爲困難。以每秒200米的速度騎行所需要的動力是以每秒40米速度騎行時所需動力的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.

在這樣的速度下，空氣產生的加熱效應已經不是你需要擔心的東西了——簡單計算一下就可以發現如果你的身體要產出這麼多的能量，那麼你的核心溫度將在幾秒鐘內上升到致命的程度。

Q. How much physical space does the Internet take up?

Q．整個互聯網佔據多少物理體積？

-Max L

——馬克思•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．有很多種方法可以估算互聯網上所有存儲的信息的多少，我們可以通過全世界存儲空間的購買量來確定互聯網信息總量的上限。

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.

硬盤行業每年能夠生產約6.5億塊硬盤，如果它們之中絕大部分是3.5英寸硬盤的話，那麼每秒生產出來的硬盤的體積爲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.

這意味着最近幾年硬盤的產量剛好只夠塞滿一艘油輪。得益於硬盤容量的不斷增加，最近幾年新增的存儲空間佔據了全球絕大多數的存儲空間。這樣看來，整個互聯網還沒有一艘油輪大。

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炸藥綁到迴旋鏢上會怎麼樣？它能搖身一變成爲強力武器嗎？還是會像它看起來的那樣蠢？

-Chad Macziewski

——查德•馬琴斯基

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．撇開空氣動力性能不說，我只是好奇，沒擊中目標就會自己飛回來的高爆炸藥，你指望從中獲得怎樣的戰術優勢呢？