A smile is infectious, as the saying goes, and now scientists have proven it. In spades. A study published today in British Medical Journal shows that happiness acts like a blessed disease: it can spread from person to person through social channels. On average, the study finds, every happy friend increases your own chance of being happy by 9 percent.
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Science is reinventing play, from extreme sports to gamification to ridiculous roller coasters to the playgrounds of tomorrow, and this issue is chock full of fun. Also, on a less fun note: Did global warming destroy my hometown?