Magic.
It's the only explanation I can come up with for what happens to a theater space between the rehearsals and the first performance. I have been doing this for, ya know, a while now, and I am still amazed, both as an actor and an audience member, by the split realities taking place in one room when a play is in progress. It's like two alternate worlds have cozied up next to each other. They are sharing the same room but are still worlds away. I'm not (unsuccessfully) trying to be deep or poetic. I'm just trying to explain something that truly does delightfully baffle me.
Here's how it all goes down: During rehearsals, actors come into the theater each evening, dumping bags and coats on a seat in the house. They chatter, grab with they need to start rehearsal, fill up water bottles, go to the bathroom, etc. And then rehearsal begins, the actors moving between the house and the stage as required, the director and stage manager in the house watching and taking notes. While the show is being performed, at least for me, the space is clearly all one room. There is no barrier between the stage and the house.
But during performances, there IS a barrier! Not an actual physical barrier, but some kind of understood divide that exists between the stage and the first row of seats. As an actor, I know the audience is there. Actors are usually pretty in tune to the general vibe of the audience, sometimes even playing to each specific audiences' reactions. But while they are right there and maybe I can even see them, they are so far away. It's a fantastic split awareness - I'm in character and "in the moment" with my scene partner, but I'm aware of the many, many faces watching me from the other side of the shadows.
As an audience member, the same understanding exists. Depending on the theater, the first row seats could be within inches of the action on stage. If I'm in the first row, there have been times that the actors are close enough that I could reach out and touch them with very little effort. But I don't. Because while they are right there, they are so far away! They are in another world that I'm merely observing, dealing with a situation that I have become privy to without their knowing. If I did reach out to touch one of the characters, it seems as though my hand would likely slip right through them as though they were a projection on a wall of smoke.
If magic is to know logically what is true but to inexplicably believe what seems to be, then I believe in magic.
Let me also say, that I could write ALOT about freakish mysteries of a theater space...and I love it all, so I'm sure I'll get around to putting thought to keyboard eventually.
