Why cats land on their feet. And 76 other paradoxes and puzzles

The title (plus subtitle) says it all. Although the author is a mathematics professor, the book is about physics rather than mathematics. All the reader is supposed to know are some elementary physical principles that are collected in an appendix. Things like Newton's laws, energy, center of mass, angular momentum, etc. Of course this involves some formulas and hence some mathematics, but secondary school knowledge suffices.

The example of the cat comes only in chapter 13 and explains why the cat manages to flip in a split second. Its trick is to squirm before making the roll movement, creating opposite spins. A surprising connection is made with winds that slow down the rotation of the earth. This phenomenon has extended a day, which is estimated to have originally lasted only 6.5 hours, to its current duration. Ant it is is basically a consequence of the same physical laws. These two items make it only a short chapter, but the other 12 chapters just keep going on applying the same thematic physical principle of the chapter in quite different situations. All of them are really surprising and keep you reading on. It is almost standard that the correct answer is opposite to what intuition predicts. Sometimes the wrong answer is explained according to apparently correct arguments and the reader is asked to find the flaw. In any case, the right arguments with the right answer are always given.

Some puzzles are practical like `how to sail against the wind?' or `why is it harder to suck up water through a straw than to blow it out?'. Others are academic like `if a water surface spinning in a bowl takes a parabolic shape, how should one steer a boat to navigate on the slope of this inclined sea?'.

Most chapters are centered around some physical principle or law like for example coriolis force: why goes fair weather with anticyclones and why do they rotate clockwise in the northern hemisphere and how do they link with trade winds at the equator? Or some topics related to a gyroscope: how does it manage to seemingly deny gravity and how can it be used to find out where is north? Or thermodynamics: how to mix two liquids of different temperature to end up with a mixture that has a temperature higher than the average?

Each chapter can be read in a few minutes time, say while you are drinking a cup of tea or coffee. It will give you a lot of inspiration to challenge or entertain your friends during a reception or another get-together with some different kind of beverages. Of course you will impress them only when they haven't read the book themselves already. Hence make sure that you are the first.


Adhemar Bultheel
KU Leuven
Book details

The author explains with elementary physical laws many phenomena observed in real life, but also gives answers to more academic puzzles. It's fun to read. It is addressed to a general intrigued and curious audience. Some elementary physical principles are added in an appendix.




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