What is Gatsby doing at the end of Chapter VII and why?

In Chapter VII, Daisy, confronted with the choice between Tom and Gatsby, chooses Tom and accidentally kills Myrtle, Tom's mistress. Later that night, Nick and Gatsby find themselves outside the Buchanan's house.  Nick encourages Gatsby to go home, but Gatsby wants to stay until Daisy goes to bed. He is worried about the earlier scene with Tom, since Tom is a brute and could harm Daisy. Nick is not concerned, as he is able to...

In Chapter VII, Daisy, confronted with the choice between Tom and Gatsby, chooses Tom and accidentally kills Myrtle, Tom's mistress. Later that night, Nick and Gatsby find themselves outside the Buchanan's house.  Nick encourages Gatsby to go home, but Gatsby wants to stay until Daisy goes to bed. He is worried about the earlier scene with Tom, since Tom is a brute and could harm Daisy. Nick is not concerned, as he is able to see Tom and Daisy through the window. He observes these two careless people go about their lives, happily eating dinner, with Tom covering Daisy's hand with his own at one point. Clearly they have have retreated into their insulated and irresponsible existence.  Nick leaves Gatsby there, on this moonlit night by the house, "watching over nothing" (Fitzgerald 153). This is an echo of the opening of the book, in which Nick observes Gatsby gazing longingly at the green light on another moonlit night.