Nerd alert, nerd alert: Neil deGrasse Tyson has done us all a huge favor by methodically pointing out all the scientific impossibilities in “Gravity.”

The astrophysicist took to Twitter with the following: “Mysteries of #Gravity: Why [Sandra] Bullock’s hair, in otherwise convincing zero-G scenes, did not float freely on her head.”

He also asks why her character, who is a medical doctor, is sent into space to repair the Hubble Space Telescope.

Hey, it’s not rocket science: She was the only actress who fit the spacesuit after Natalie Portman, Angelina Jolie, Scarlett Johansson and Blake Lively took a pass.

By the way, Blake: Bad career move.

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QUICK TAKES

A really insensitive news anchor in Philadelphia sent the following tweet: “Thought ‘Breaking Bad’ was hot last Sunday? @FOX29philly see who’s breakin’ bad in SW Philly leavin’ 6 people SHOT — Tonight at Ten!”

Eminem’s daughter Hailie was crowned homecoming queen at her high school.

Miley Cyrus said on the “Today” show that people generally stop having sex by the age of 40.

Nielsen is launching a service that will track tweets about TV shows to try and measure how many people are watching.

“Bones” star David Boreanaz is rumored to be leaving the show after this season.

HAPPY BIRTHDAY

Actor Angus T. Jones (“Two and a Half Men”) is 20.

Actress Molly Quinn (“Castle”) is 20.

Singer-songwriter Bruno Mars is 28.

Actor Nick Cannon (“America’s Got Talent”) is 33.

Actor Matt Damon (“Elysium”) is 43.

Actress Stephanie Zimbalist (“Remington Steele”) is 57.

Actress Sigourney Weaver (“Alien”) is 64.

Pundit Dennis Kucinich is 67.

Actor Chevy Chase (“Caddyshack”) is 70.

Activist Jesse Jackson is 72.FeaturesGossipNeil deGrasse TysonSandra Bullock