9 mind-expanding podcasts to listen to if you only have 30 minutes

The average morning commute in the US is $4.

That's no fun if you spend it in rush-hour traffic, but it's a good time to try out a new podcast, especially one that upends the way you see and think about the world.

From business to history to psychology, here are some of the most mind-expanding podcasts that you can gobble up in a half-hour or less.