This book provides the answers to these and dozens of other questions about our natural world and how some of its inhabitants use polarised light instinctively. We humans cannot see when light is polarised and this leads to unfortunate misapprehensions about this aspect of nature. Even scientists who should know better often assume that it is an obscure topic of specialised interest in only a few rather isolated areas ; in fact it is a universal feature of our world and most natural light is at least partially polarised. In the Animal Kingdom, insects and other animals exploit such natural polarisation in some fascinating ways, since they do not share this human deficiency and can both detect and analyse polarisation. It may be our unfamiliarity with this aspect of light that also makes many people think it is a 'difficult' subject, yet the basis is extremely simple. When these misconceptions are overcome, the phenomena associaled with polarisation are found to be important throughout science and technology - in physics, astronomy, natural history, geology, chemistry and several branches of engineering, as well as crafts such as glass-blowing and jewellery. They also involve some very beautiful effects, most of which are easy to demonstrate. Our general unawareness of what we are missing is indeed a great pity. This book hopes to put all this right and enrich its readers' perception of their world.