As a young scientist searches for a way to save a dying Earth, she finds a connection with a man who's racing to catch the last shuttle off the planet.
I've thought that "Earth" is always used with "the" when we're referring to the planet we're living on because it's a unique object and "the" can be substituted with "this" here. But in that sentence, there's an "a" as if they are talking about SOME Earth. What am I missing here? Thanks.