At a lecture I went to some years ago, astrophysicist Trevor Weekes compared garden-variety elementary particles to mosquitoes. They are plentiful and easy to find—indeed, they find you. But ultra-high-energy gamma rays, he said, are like elephants. They are fairly rare, but among the greatest of creatures. They often roam in spectacular habitats. Their sheer [...]

Two years ago several of my Sci Am colleagues and I had an intense email exchange over a period of weeks, trying to figure out what to make of a new paper by string theorist Erik Verlinde. I don’t think I’ve ever been so flummoxed by physicists’ reactions to a paper. Mathematically it could hardly [...]