“American Idol” (8 p.m., Fox): Love it or hate it, the biggest show on the planet is

“American Idol” (8 p.m., Fox): Love it or hate it, the biggest show on the planet is back and rarin’ to go with a new judge (meet Kara DioGuardi) and some new twists (the semifinal round will consist of 36 singers, not 24). The changes come after “Idol” showed signs of waning popularity in Season 7. Still, the musical juggernaut is once again expected to crush everything in its path. And, as usual, it kicks off with the audition rounds, which too often prove to be an assault on both the ears and eyes.

“Homeland Security” (8 p.m., ABC): On a new episode of “Homeland Security,” a motorist is bewildered when border cops express concern over the human skull and handguns found in his possession. What, those aren’t standard features in vehicles, nowadays?

“The Ascent of Money” (9 p.m., PBS): Remember that stuff you probably had more of a year ago than you do today? Take a sentimental journey with “The Ascent of Money,” a two-hour documentary that traces the evolution of money through human history, and helps account for why money is the fulcrum of civilization. The film is written and presented by author, economist, historian and Harvard professor Niall Ferguson, based on his new book of the same title.