中文简介：

世界各地数以百万计的人阅读并喜爱《假如？》，他们仍然有很多问题，而且这些问题越来越奇怪。谢天谢地，超热门科普漫画“xkcd”作家Randall Munroe来帮忙了。

打算骑着火杆从月球回到地球？最难的部分是着陆。希望通过同时打开每个人的冰柜门来冷却大气？也许是时候简单介绍一下热力学了。想知道如果你骑着直升机桨叶，建造一栋十亿层的大楼，用熔岩做一盏熔岩灯，或者在间歇泉爆发时跳上去会发生什么吗？好吧，如果你坚持想问的话。

在你开始宇宙公路旅行、把纽约市的居民喂给霸王龙、或在每个教堂里放满香蕉之前，一定要参考这本充满不切实际的想法的实用指南。Munroe不为荒谬所扰，查阅了从摆动装置物理学到客机弹射器设计等方面的最新研究，清楚而简洁地回答了读者的问题，并配以富有启发性、偶尔令人恐惧的插图。正如他一贯展示的那样，你可以从研究世界在非常具体的极端情况下如何运作中学到很多东西。

英文简介：

The millions of people around the world who read and loved What If? still have questions, and those questions are getting stranger. Thank goodness xkcd creator Randall Munroe is here to help.

Planning to ride a fire pole from the Moon back to Earth? The hardest part is sticking the landing. Hoping to cool the atmosphere by opening everyone's freezer door at the same time? Maybe it's time for a brief introduction to thermodynamics. Want to know what would happen if you rode a helicopter blade, built a billion-story building, made a lava lamp out of lava, or jumped on a geyser as it erupted? Okay, if you insist.

Before you go on a cosmic road trip, feed the residents of New York City to a T. rex, or fill every church with bananas, be sure to consult this practical guide for impractical ideas. Unfazed by absurdity, Munroe consults the latest research on everything from swing-set physics to airliner catapult–design to answer his readers' questions, clearly and concisely, with illuminating and occasionally terrifying illustrations. As he consistently demonstrates, you can learn a lot from examining how the world might work in very specific extreme circumstances.