The existence of love and its nature is something that has troubled philosophers for centuries, but a pair of scientists believe they have a set of questions that yield "clear empirical evidence" of it, or at least whether your relationship will end in divorce. They are: 'How happy are you in your marriage relative to how happy you would be if you weren't in the marriage?' and 'How do you think your spouse answered that question?' University of Virginia economists Leora Friedberg and Steven Stern asked this to 4,242 couples twice, six years apart, and analysing th...