* The really big question: what is motivating Putin?
* Paul Krugman advocates more daring economic reforms.
* The plan to break up California into six separate states.
* By the numbers: guns are far more likely to be used to commit suicide than to kill an assailant.
* Seeking scientific proof of bisexuality in humans.
* The implications of the near future of killer robots. Yes, really.
* Remembering the public life of Carl Sagan.
* New world order: why is Garth Brooks so popular in Ireland?