FYI -- There are probably analogous examples of quantum superposition... http://www.bbc.co.uk/programmes/p023c98x Yemens Swap Marriages Duration: 25 minutes First broadcast: Tuesday 29 July 2014 Ill marry your sister if you marry mine. And if you divorce my sister, Ill divorce yours. That is Yemens Shegar, or swap marriage, an agreement between two men to marry each others sisters, thereby removing the need for expensive dowry payments. But the agreement also entails that if one marriage fails, the other couple must separate as well, even if they are happy. BBC Arabics Mai Noman returns to her native Yemen and hears the stories of two women who have loved and lost because of Shegar. Nadia lives in the village of Sawan on the outskirts of the capital Sanaa with her family. She was married off at the age of 22 and has three children. Nadia had to pay a high emotional price because of her familys decision to marry her off in the Shegar tradition. She was forced to divorce and now she and her mother have to live with the stigma that brings. Nora and her brother Waleed had little say in marrying their cousins through Shegar. But what happens when one siblings happiness depends on ending the marriage of the other? Could you choose your siblings happiness over your own? Stay in an unhappy marriage so your sibling can stay in a happy one? Mai asks why an old tradition that forces you to love only to force you to part, is still practised in Yemen. What do the religious authorities think of it? And is it tied to Islam? In Yemen, the heart of Arabia, ancient traditions and values have kept the fabric of society unchanged. They helped preserve Yemens unique charm and character, but also imprisoned Yemens people in the past. Shegar marriage is one such tradition. It helps poorer families to marry, but at what price?