Most people have experienced lightning. Likewise, ask people if they have ever seen a rainbow and most will answer in the positive. Yet something which few have seen is the moment that a rainbow and lightning occur at the same time. Lightning frequently happens during heavy storms. The optical and meteorological phenomenon known as a rainbow, however, is generally formed after the rain has stopped. So, how did these pictures come about? Why can lightning and rainbows happen at the same time? We know how rainbows are formed. Water droplets in the air reflect and refract right. This results in a spectrum of light curving beautifully through the sky. This multi-colored arc always appears in the part of the sky opposite to the sun. Culturally, the rainbow has always been seen as a symbol of hope, from its appearance after the flood in the Genesis book of the Bible, to that elusive pot of Leprechaun gold. The rainbow flag, moreover, has been used a symbol of social change for hundreds of years. Lightning, on the other hand, does not enjoy such good press. Supernatural prominence has been ascribed to lightning in many cultures and generally it is seen as a sign of the anger of god(s). Its history on flags has something of a chequered history, too, with a number of extreme right wing movements adopting it as their symbol. Furthermore, scientists still can’t quite agree on what precisely causes lightning. One theory goes like this. Water often falls towards the earth in the form of drops of rain and ice – and it falls through the natural electric field in our atmosphere. It then becomes electrically polarized. The result – the brilliant hair-raising flashes we see in the sky, always accompanied by thunder. So, the one thing that lightning and rainbows have in common is water. The lightning which happens during heavy rain does so because of this aqueous precipitation. A rainbow, too, can only happen when the very same drops of water refract and reflect light. Perhaps the sight of a rainbow and lightning together is so rare, then, because during a storm there is often not enough light for the former to occur. Or possibly, they happen just when a storm is abating: still enough charge for lightning but enough sunlight for a rainbow. No one truly knows for sure. One thing we know is that it does not happen often. In mythology, likewise, the two are rarely seen together. There are any number of rainbow demons, few associated with lightning. Yet Indra, the god of war in Hindu mythology, had use for both. Although he mostly wielded thunderbolts alone as his primary weapon of choice, there were times when he used it in conjunction with a rainbow. The rainbow was his archer’s bow, the lightning his arrows. From these pictures, it is not difficult to imagine why this mythology could have sprung up.