The 70th annual Venice Film Festival opened Wednesday with the world premiere of Alfonso Cuarón's 'Gravity,' the Mexican filmmaker's follow up to 2006's 'Children of Men.' While the film won't be released in theaters until Oct. 4, film critics have already given the sci-fi thriller rave reviews. 

'Gravity' stars Sandra Bullock and George Clooney as two stranded astronauts struggling to survive after flying debris crashes into their shuttle, sending them spiraling into outer space. Critics have praised both of the actors' performances, and have deemed the film a visual masterpiece, commending cinematographer Emmanuel Lubezki's camera work. 

Variety film critic Justin Chang praises Cuarón's filmmaking abilities and writes that the film will inspire astonishment from critics and audiences worldwide.

"While 'Gravity' is hardly the first film to send characters into orbit, few have so powerfully and subjectively evoked the sensation of floating right there with them," Chang writes. "The outstanding post-production 3D conversion enhances our sense of immersion in this foreign environment at every turn."

Todd McCarthy of The Hollywood Reporter deems the 90-minute thriller one of the most realistic movies ever set in space, and says the simple story is carried by two great performances. 

"It's a wonderful cinematic jolt to watch this film for the first time, as it looks as if it had been filmed, as it were, on location," McCarthy writes. "Clooney supplies both manly reliability and welcome lightness as a guy anyone would want in their corner in a pinch, while Bullock is aces in by far the best film she's ever been in."

Richard Corliss of TIME writes that the film "shows us the the glory of cinema's future." 

"And because Cuarón is a movie visionary of the highest order, you truly can't beat the view," he adds.

Aside from 'Gravity' and 'Children of Men,' Cuarón is also known for 1995's 'A Little Princess,' 2001's 'Y Tu Mamá También,' and 2004's 'Harry Potter and the Prizoner of Azkaban.' Both 'Y Tu Mamá También' and 'Children of Men' garnered him Oscar nominations.

Check out the thrilling teaser trailer for 'Gravity' below.