Planets as a Species

While popular magazines come out well before their cover dates, science journals arrive at my place late. But there's time enough for you to look up April's Physics Today and enjoy its special issue on planetary diversity. David Stevenson, who edited the collection of articles, wrote a masterful introduction showing how Earth, the solar system and the planets newly found around distant stars all shed light on--and deep into--each other. And that's just the start.