Radioactivity: Friend or Foe?

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One of the first things that comes to mind when thinking of radioactivity is often a nuclear accident or dangerous rays. But radioactivity is in fact a much more varied phenomenon, one that can bring us great benefits as well as put us in danger. With help from three experts, Rajan Datar looks for a more nuanced picture of the role radioactivity plays in our lives. Photo: A symbol for radioactivity is visible on a radioactively-contaminated container. (Getty Images)