FYI -- There are probably analogous examples of quantum superposition... http://www.bbc.co.uk/programmes/p023c98x Yemen’s Swap Marriages Duration: 25 minutes First broadcast: Tuesday 29 July 2014 ‘I’ll marry your sister if you marry mine. And if you divorce my sister, I’ll divorce yours.’ That is Yemen’s ‘Shegar’, or swap marriage, an agreement between two men to marry each other’s 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 Arabic’s 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 Sana’a 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 family’s 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 sibling’s happiness depends on ending the marriage of the other? Could you choose your sibling’s 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 Yemen’s unique charm and character, but also imprisoned Yemen’s people in the past. Shegar marriage is one such tradition. It helps poorer families to marry, but at what price?