Why is Luke Skywalker missing?

This has been bugging me since they revealed the official poster for The Force Awakens.... where is Luke? He's not in the poster and he's not in the official trailer. What are your theories?

I have one theory that might be a bit, mmm, drastic. Though they've named the villain in the movie, Kylo Ren, we haven't seen his face (which we probably won't for a long time) I am forced to wonder if perhaps "Kylo Ren" is actually Luke Skywalker. I know, I know, it sounds crazy. I'm just connected the dots, even if they don't make a sensible picture.

Maybe they just want it to be a surprise when we finally see Luke. Maybe he doesn't play a large part in the movie. There are many possibilities, but I have to consider if maybe the film makers wanted to throw us a curve ball. Is it a stretch of the imagination that Luke could have turned to the dark side later in life? Even if it doesn't make a lot of sense, I can't eliminate that theory just yet.

So what do YOU think? Why is Luke missing?

I don't think Luke is Kylo as we've seen him without his headwear from on-set pics. It seems pretty certain Adam Driver is playing him. Unless this is a bluff and he's just another of the Knights of Ren...

However who's pulling Kylo's strings? It's quite possible Luke has fallen, and is masterminding the "finishing what Vader started". Perhaps Kylo has prominence amongst the Knights of Ren because Luke is his father?

Either way, it would make sense that we don't see Luke in trailers, posters etc if he has "dark side" appearance now. But that seems a little easy to me... making Luke follow the path of his father. I'm still hoping they're keeping us guessing because Luke has some other part to play. Either way, I'm not expecting much screen time from him.

New trailer!!

I think Luke went into hiding. My feeling is that he understood what a small group of force-users are capable of, the tremendous harm and imbalance, and he took his power out of the game.

Luke has killed thousands of people. He's not the only one, and he did it in the context of a war, but the fact remains. And that fact would sit heavily on my shoulders. Consider that in every piece of fiction, whatever regualr people were doing, in whatever vast numbers, history was always decided by a handful, or a single, force-user. Good guys, bad guys, they all thought they were doing what was best. They all thought they were right.

So, if I were Luke, and not completely sold on the idea that my judgement was perfect, and I was aware of my power, I might remove myself from the board.

Luke WAS in the trailer... you can see him placing his hand on R2-D2

Potential Major Spoiler About Luke Skywalker

Along with the question about Luke's absence, there's a raging debate going on about the appearance of a new Skywalker.

Loads of information and pictures here: http://www.denofgeek.us/movies/star-wars/235168/star-wars-the-force-awakens-news-new-official-poster-trailers-release-date

I think the forest world we see them on might be Endor. We assume that, because we saw the mask early on, that it must be there the whole film. I wonder if he does not go get it in the middle.