Amid the CBS Summer Press Tour this week, the subject came up about why the network had cancelled Without A Trace. It wasn't ratings, which is clearly the truth because just this past weekend, Without A Trace was pulling over six million viewers for a rerun, doubling the number of people who tuned in for the brand new ABC series, Defying Gravity. Therefore, if Without A Trace was still capable of besting the fodder produced by the competition, why on earth would CBS dump it?

"Every show has its own life cycle," said CBS Entertainment President Nina Tassler, who went on to explain that the shows the network had in development were just too good to wait. In other words, The Good Wife, Three Rivers and NCIS: Los Angeles, none of which are proven hits, were more important than an established success.

ABC is close to picking up 'Romantically Challenged,' a new comedy series starring Alyssa Mliano.

Also in the news today: Fox confirms Kara DioGuardi will return to 'American Idol,' while CBS reveals its plan for 'Flashpoint.'

See more of today's top TV headlines after the jump.

• Shark Week stars on Discovery Channel today.
• Travel Channel has a Man vs. Food marathon all night.
• At 7, NBC has a new Dateline, followed by a new Merlin and the conclusion of The Storm.
• At 8, ABC has Ty's British Adventure, then the series premiere of Defying Gravity.
• CBS has a new Big Brother at 8.
• At 8:30, Disney has a new Jonas.
• At 9, USA has a new Law and Order: CI, then a new In Plain Sight.
• Food Network has the season finale of Next Food Network Star at 9, followed by a new The Best Thing I Ever Ate.
• Lifetime has a new Drop Dead Diva at 9, then a new Army Wives.
• A&E has two new episodes of Gene Simmons' Family Jewels at 9.
• There's a new Ice Road Truckers on History Channel at 9, followed by two new episodes of Pawn Stars.
• G4 has a new Web Soup at 9.
• Also at 9: HBO has a new True Blood, then new episodes of Hung and Entourage.
• At 11:30, Cartoon Network has a new Robot Chicken.
• At midnight, Cartoon Network has a new Squidbillies.
• At 12:30am, Cartoon Network has a new Mighty Boosh.
  

Check your local TV listings for more.

Ron Livingston, who is probably best-known for his role as the lovable slacker, Peter Gibbons, in the cult classic, Office Space, is no stranger to television. He played the rakish captain Lewis Nixon on HBO's seminal miniseries, Band of Brothers, and will go down in Pop Culture history as Berger, the douche who broke up with Carrie via Post-It note on Sex and the City.

This summer, Livingston is starring in the new ABC drama, Defying Gravity, with a special two-hour premiere on Sunday, August 2, at 9:00. Described, to the dismay of many, as "Grey's Anatomy in Space," Gravity follows a group of astronauts on a planetary mission 40 years from now. While everybody's sleeping with their coworkers, they aren't quite as angst-ridden about it as their Grey's counterparts. These astronauts cut through all the BS and get down to the business of doing it in zero gravity, as any rational person would.

Recently, I was able to chat with Ron Livingston about Defying Gravity. We talk about some of the more mysterious elements of the show, how he prepared for the role, and why they're wearing t-shirts in the future, instead of Mylar jumpsuits.

(There aren't any major spoilers, but we do discuss the pilot, so keep that in mind).

Summer used to be a wasteland for TV, but now we see more and more shows debuting during the summer or having summer-only runs. Sometimes they're great, usually they're just reality shows. I haven't heard much about ABC's Defying Gravity (premiering August 2), other than it's about astronauts and from the producers of Grey's Anatomy. I hope it's more space/action-oriented than soap-oriented. I don't want to see a character named "McSpacey." It's stars Ron Livingston, Malik Yoba, and Laura Harris.

Jon Heder lands a new Comedy Central show, Ryan Seacrest is close to signing a three-year extension with 'American Idol,' Fox moves 'Dollhouse''s premiere date and more of today's top TV headlines.

FX schedules premiere dates for 'Nip/Tuck,' 'It's Always Sunny in Philadelphia' and others, 'Hung' has a big debut, Liza Minnelli is a 'Diva' and more TV news.