Great Tree, Great Axe巨树与巨斧\tFrom what-if.xkcd.com

The Sea

If all the seas were combined into one sea， it would look pretty much like the Pacific Ocean， only a little bigger.

The Tree

Real trees can't grow taller than around 130 meters， thanks to physical limits on their ability to transport water. If they found a way around those limits， they'd face issues of fundamental physical strength; a kilometers-tall tree would crush3) itself.

Let's set aside4) these limits and imagine that we built a single standard tree out of all the material in all the world's trees. For our \"standard tree\"， we'll use the oak tree from the Sylva Foundation's5) OneOak project. The project extensively documents every detail of a single oak tree. As part of the project， the tree was cut down in 2010. Frankly， I'm not sure what to make of6) the whole thing， but it's as good a candidate as any for our model \"standard tree\".

The OneOak tree was 23.9 meters tall and weighed 14.385 tons. By comparison， one paper estimates that the world's forests have an aboveground7) plant mass of about 470 billion tons.

If—ignoring the physical constraints—we combined this mass into a single tree， modeled on the OneOak， the trunk would be two kilometers in diameter8). The upper branches would stretch about 75 kilometers above the surface—most of the way to space.

The Human

If we used the same approach to combine every living human into a single body—again， ignoring the obvious physical constraints—that person would be close to 3 kilometers tall. Proportionally9)， the person would have grown slightly less than the tree.

The Axe

How many axes are there in the world? Thanks to multiple meanings of the word \"axes\"， this is a hard problem to Google. Instead， let's try to get a reasonable guess through Fermi estimation10).

Since there's no central clearing house11) of axe-related information， I thought I'd try asking friends how many axes they had.

But this might miss a lot of axes; for example， some axes—like fire axes—are owned by organizations. To get a slightly fairer sample， I asked a bunch of friends around the country to estimate the number of axes and number of humans in their general vicinity12).

Some people were in houses with sheds， and had a 2:1 human-to-axe ratio. Other people were in large offices with hundreds of people and at best13) one or two fire axes. The average seemed to be around 50:1—much lower than I expected.

Of course， surveying random Internet-connected people who I know is hardly representative; rural people probably have more axes， while the very poor might not have any. But it also wouldn't make sense for there to be substantially14) more axes than people， if for no other reason than that humans can only really use one axe at a time.

But absent any other data， I'm guessing the ratio of humans to axes is probably somewhere between 50:1 and 5:1.

This means that our combined axe would be a little small for our combined person. It would be only a little over half a kilometer long—barely more than a flimsy15) hatchet16).

If an experienced axe user can chop down an eight-inch tree in 15 minutes， then chopping down our giant tree—if the rate is proportional to the axe size and square of the tree's diameter—would most likely take a few weeks of chopping.

巨海

如果所有的海洋都汇成一片海，那么这个新大洋会和太平洋没什么两样，只不过大了一点而已。

巨树

真实的树木最高长不过130米左右，这是因为树的水分输送能力受到了物理限制。就算树能设法突破这些限制，它们将面临至关重要的物理力量问题：一棵几千米高的树会将自己压垮。

让我们把这些限制放在一边，并假设我们用全世界所有树木的所有部分合成一棵标准树。我们会选用英国林木基金会“一棵橡树”项目的那棵橡树作为我们的“标准树”。“一棵橡树”项目详细地记录了一棵橡树的各个细枝末节。按照该项目的计划，这棵橡树于2010年被砍伐。老实说，我没太搞明白这整个项目，但用这棵橡树作为我们的“标准树”模型是再好不过了。

这棵橡树高23.9米，重14.385吨。相比之下，根据一篇论文的估计，全世界所有森林地上部分的重量加起来约为4700亿吨。

如果——忽略那些物理限制——我们将这4700亿吨的树木参照那棵橡树的样子合成一棵树，那么这棵树的树桩直径将达2000米，而上层枝叶将离地面约75千米，直冲太空。

巨人

假如我们用同样的方法，将所有活着的人合成一个人——再次忽略那些显而易见的物理限制——那么这个人将会有近3000米高。按比例来说，这个巨人会稍微不如那棵巨树成长得茁壮。

巨斧

世界上有多少把斧头？都怪“axes”这个单词具有多重含义，我们难以通过谷歌搜索获得答案。作为代替，让我们尽力通过费米估算得到一个合理的估计值。

由于没有与斧头相关信息的中央统计机构，我想我应该试着问问朋友他们有多少把斧头。

但是，这样可能会遗漏很多斧头。例如，有些斧头——像消防斧这样的斧头——只有那些机构才拥有。为采集到一个稍微客观一些的样本，我请我在全国各地的一些朋友帮忙，让他们估计一下他们那一带的斧头数量和居民数量。

他们有些住在带牲口棚的房子里，这些地方人与斧的比例为2:1。其他人则在可容纳数百人的办公大楼里，这些地方最多只有一两把消防斧。这样看起来人与斧的平均比例约为50:1，远远低于我的预期。

当然，随机调查的这些我认识的网友难具代表性；农村居民可能拥有更多的斧头，而太穷的人家可能连一把斧头也没有。但斧头数量也不会大大超过人口数量，这不合情理，只因为我们每次真的只能用一把斧头。

不过，由于没有任何其他数据，我在想人与斧头的比例很可能在50:1到5:1之间。

这就是说，合成的这把巨斧对合成的这位巨人来说会有点小，长度可能仅500米出头——充其量只是一把不算结实的小斧头。

假如一位娴熟的伐木工砍倒一棵8英寸(编注：约20厘米)粗的树需要15分钟，那么砍倒我们这棵巨树——如果砍伐速度与斧头大小和树干直径的平方成正比的话——很可能要花几个星期的时间。1.splish-splash: 水花四溅声

2.Mother Goose: 《鹅妈妈童谣》，是英国民间的童谣集。这些民间童谣流传时间相当久，总数约有八百多首，包括幽默故事、游戏歌曲、儿歌、谜语、字母歌、绕口令等。

3.crush [kr#652;#643;] vt. 压断

4.set aside: 把……置于一旁，不顾

5.Sylva Foundation: 林木基金会，英国的一个慈善机构，旨在复兴英国的林业文化，推动和提升森林的可持续管理。

6.make of: 理解；解释

7.aboveground: 在地面上的

8.diameter [da#618;#712;#230;m#618;t#601;(r)] n. 直径

9.proportionally [pr#601;#712;p#596;#720;#643;#601;nli] adv. 按比例地

10.Fermi estimation: 费米估算，以美国物理学家恩利克·费米(Enrico Fermi， 1901~1954)命名，是在科学研究中用来做量纲分析、估算和清晰地验证一个假设的估算问题，比如“芝加哥有多少钢琴调琴师？”，这是费米提出的一个经典的费米问题。

11.clearing house: 信息交换所；信息交换机构

The Sea

If all the seas were combined into one sea， it would look pretty much like the Pacific Ocean， only a little bigger.

The Tree

Real trees can't grow taller than around 130 meters， thanks to physical limits on their ability to transport water. If they found a way around those limits， they'd face issues of fundamental physical strength; a kilometers-tall tree would crush3) itself.

Let's set aside4) these limits and imagine that we built a single standard tree out of all the material in all the world's trees. For our \"standard tree\"， we'll use the oak tree from the Sylva Foundation's5) OneOak project. The project extensively documents every detail of a single oak tree. As part of the project， the tree was cut down in 2010. Frankly， I'm not sure what to make of6) the whole thing， but it's as good a candidate as any for our model \"standard tree\".

The OneOak tree was 23.9 meters tall and weighed 14.385 tons. By comparison， one paper estimates that the world's forests have an aboveground7) plant mass of about 470 billion tons.

If—ignoring the physical constraints—we combined this mass into a single tree， modeled on the OneOak， the trunk would be two kilometers in diameter8). The upper branches would stretch about 75 kilometers above the surface—most of the way to space.

The Human

If we used the same approach to combine every living human into a single body—again， ignoring the obvious physical constraints—that person would be close to 3 kilometers tall. Proportionally9)， the person would have grown slightly less than the tree.

The Axe

How many axes are there in the world? Thanks to multiple meanings of the word \"axes\"， this is a hard problem to Google. Instead， let's try to get a reasonable guess through Fermi estimation10).

Since there's no central clearing house11) of axe-related information， I thought I'd try asking friends how many axes they had.

But this might miss a lot of axes; for example， some axes—like fire axes—are owned by organizations. To get a slightly fairer sample， I asked a bunch of friends around the country to estimate the number of axes and number of humans in their general vicinity12).

Some people were in houses with sheds， and had a 2:1 human-to-axe ratio. Other people were in large offices with hundreds of people and at best13) one or two fire axes. The average seemed to be around 50:1—much lower than I expected.

Of course， surveying random Internet-connected people who I know is hardly representative; rural people probably have more axes， while the very poor might not have any. But it also wouldn't make sense for there to be substantially14) more axes than people， if for no other reason than that humans can only really use one axe at a time.

But absent any other data， I'm guessing the ratio of humans to axes is probably somewhere between 50:1 and 5:1.

This means that our combined axe would be a little small for our combined person. It would be only a little over half a kilometer long—barely more than a flimsy15) hatchet16).

If an experienced axe user can chop down an eight-inch tree in 15 minutes， then chopping down our giant tree—if the rate is proportional to the axe size and square of the tree's diameter—would most likely take a few weeks of chopping.

巨海

如果所有的海洋都汇成一片海，那么这个新大洋会和太平洋没什么两样，只不过大了一点而已。

巨树

真实的树木最高长不过130米左右，这是因为树的水分输送能力受到了物理限制。就算树能设法突破这些限制，它们将面临至关重要的物理力量问题：一棵几千米高的树会将自己压垮。

让我们把这些限制放在一边，并假设我们用全世界所有树木的所有部分合成一棵标准树。我们会选用英国林木基金会“一棵橡树”项目的那棵橡树作为我们的“标准树”。“一棵橡树”项目详细地记录了一棵橡树的各个细枝末节。按照该项目的计划，这棵橡树于2010年被砍伐。老实说，我没太搞明白这整个项目，但用这棵橡树作为我们的“标准树”模型是再好不过了。

这棵橡树高23.9米，重14.385吨。相比之下，根据一篇论文的估计，全世界所有森林地上部分的重量加起来约为4700亿吨。

如果——忽略那些物理限制——我们将这4700亿吨的树木参照那棵橡树的样子合成一棵树，那么这棵树的树桩直径将达2000米，而上层枝叶将离地面约75千米，直冲太空。

巨人

假如我们用同样的方法，将所有活着的人合成一个人——再次忽略那些显而易见的物理限制——那么这个人将会有近3000米高。按比例来说，这个巨人会稍微不如那棵巨树成长得茁壮。

巨斧

世界上有多少把斧头？都怪“axes”这个单词具有多重含义，我们难以通过谷歌搜索获得答案。作为代替，让我们尽力通过费米估算得到一个合理的估计值。

由于没有与斧头相关信息的中央统计机构，我想我应该试着问问朋友他们有多少把斧头。

但是，这样可能会遗漏很多斧头。例如，有些斧头——像消防斧这样的斧头——只有那些机构才拥有。为采集到一个稍微客观一些的样本，我请我在全国各地的一些朋友帮忙，让他们估计一下他们那一带的斧头数量和居民数量。

他们有些住在带牲口棚的房子里，这些地方人与斧的比例为2:1。其他人则在可容纳数百人的办公大楼里，这些地方最多只有一两把消防斧。这样看起来人与斧的平均比例约为50:1，远远低于我的预期。

当然，随机调查的这些我认识的网友难具代表性；农村居民可能拥有更多的斧头，而太穷的人家可能连一把斧头也没有。但斧头数量也不会大大超过人口数量，这不合情理，只因为我们每次真的只能用一把斧头。

不过，由于没有任何其他数据，我在想人与斧头的比例很可能在50:1到5:1之间。

这就是说，合成的这把巨斧对合成的这位巨人来说会有点小，长度可能仅500米出头——充其量只是一把不算结实的小斧头。

假如一位娴熟的伐木工砍倒一棵8英寸(编注：约20厘米)粗的树需要15分钟，那么砍倒我们这棵巨树——如果砍伐速度与斧头大小和树干直径的平方成正比的话——很可能要花几个星期的时间。DThe Fall

The tree would weigh between 1% and 10% as much as the Chicxulub asteroid17) that killed the dinosaurs. It would strike the ocean with much less speed than the Chicxulub asteroid， and the energy release would be much less substantial. However， it would still be moving at kilometers per second， and would be able to displace a gigantic18) amount of water.

The Chicxulub impact created a giant tsunami19). There have been some beautiful simulations20) of the Chicxulub tsunami. The exact details of the tsunami depend on a lot of factors， but it seems safe to say that waves at least tens or hundreds of meters high would inundate21) every coastline and destroy virtually every coastal city and many farther inland.

In other words， the Mother Goose poem in John's question probably wouldn't wipe out the human race， but it would probably be the deadliest single disaster in our species' history. Even by the ghastly22) standards of old children's fairy tales， that's pretty bad.巨树之倒

这棵巨树的重量为导致恐龙灭亡的希克苏鲁伯小行星重量的1%~10%。巨树倒向海洋的速度要比希克苏鲁伯小行星撞向海洋的速度小很多，而且释放的能量也要少很多。不过，巨树的倒落速度仍将达到数千米每秒，并会激起滔天的海浪。

希克苏鲁伯小行星的撞击引发了一场巨大的海啸，对于这场海啸已有一些精彩的模拟。虽然海啸的各项具体情况取决于多种因素，但有一点似乎可以肯定——最少高达几十米或几百米的海浪将淹没所有海岸，并将摧毁几乎所有的沿海城市和许多更远一些的内陆地区。

换句话说，约翰提出的关于《鹅妈妈童谣》里那首诗的问题可能不会造成人类灭亡，但却可能是人类历史上最致命的一次灾难。即便是按照古老的儿童童话故事的恐怖程度来衡量，这场灾难也够可怕的。In closing， I offer my favorite piece of axe-related legal trivia23): Lawyer Kevin Underhill， of the legal blog Lowering the Bar， highlighted the wonderful 1998 case People v. Foranyic24). In this case， he writes， appeals court ruled25) \"that there was probable cause for police to detain26) someone they see riding a bike at 3 a.m.， carrying an axe\".

So if you're two miles tall and heading toward the coast to cut down the world's only tree ... watch out for cops.

最后，我要提一下我最喜欢的一段关于斧头的法律小插曲：法律博客“降低律师门槛”的博主凯文·昂德希尔律师专门强调了这起精彩绝伦的1998年福伦伊克公诉案。他写道，在该案中，上诉法院判定“若是发现有人在凌晨3:00携带一把斧头骑自行车，警方有可以成立的理由拘留当事人”。

因此，如果你身高两英里(编注：约3000米)，正要到海边去砍倒世上唯一的一棵树……可得小心警察。In closing， I offer my favorite piece of axe-related legal trivia23): Lawyer Kevin Underhill， of the legal blog Lowering the Bar， highlighted the wonderful 1998 case People v. Foranyic24). In this case， he writes， appeals court ruled25) \"that there was probable cause for police to detain26) someone they see riding a bike at 3 a.m.， carrying an axe\".

So if you're two miles tall and heading toward the coast to cut down the world's only tree ... watch out for cops.

最后，我要提一下我最喜欢的一段关于斧头的法律小插曲：法律博客“降低律师门槛”的博主凯文·昂德希尔律师专门强调了这起精彩绝伦的1998年福伦伊克公诉案。他写道，在该案中，上诉法院判定“若是发现有人在凌晨3:00携带一把斧头骑自行车，警方有可以成立的理由拘留当事人”。

因此，如果你身高两英里(编注：约3000米)，正要到海边去砍倒世上唯一的一棵树……可得小心警察。12.vicinity [v#601;#712;s#618;n#601;ti] n. 附近

13.at best: 至多，充其量

14.substantially [s#601;b#712;st#230;n#643;#601;li] adv. 大量地

15.flimsy [#712;fl#618;mzi] adj. 脆弱的；易损坏的；劣质的

16.hatchet [#712;h#230;t#643;#618;t] n. 短柄小斧

17.Chicxulub asteroid: 希克苏鲁伯小行星，其直径至少有10千米，在6500万年前撞击了今天墨西哥境内的希克苏鲁伯地区，形成了一个撞击陨石坑，即希克苏鲁伯陨石坑(Chicxulub crater)。

18.gigantic [d#658;a#618;#712;ɡ#230;nt#618;k] adj. 巨大的，庞大的

19.tsunami [tsu#720;#712;nɑ#720;mi] n. 海啸

20.simulation [#716;s#618;mju#712;le#618;#643;n] n. 模拟；模仿

21.inundate [#712;#618;n#652;nde#618;t] vt. 淹没

22.ghastly [#712;ɡɑ#720;stli] adj. 可怕的；恐怖的

23.trivia [#712;tr#618;vi#601;] n. 小事；琐事

24.People v. Foranyic: 福伦伊克公诉案。被告福伦伊克(全名Robert Francis Foranyic)凌晨3:00拿着斧子、骑着车子在路上，一名警察觉得福伦伊克可能会进行犯罪活动因而将其逮捕。福伦伊克进行了上诉，不过法院最后判定该警察的行为是合理且合法的。

25.rule [ru#720;l] vt. 裁决；裁定

26.detain [d#618;#712;te#618;n] vt. 拘留；扣押