Ok, this is definitely a silly question and is partly inspired by the last 20 minutes or so of the film The Avengers, so look to that if you can't picture the situation.
In the film a portal is opened up above new york, to somewhere in deep space. I.e. from an area where the gravitational field is effectively uniform and field lines would be parallel, to an area with negligible net gravitational acceleration.
My question is, assuming this portal has literally linked the two bits of space, it makes sense that the gravity of the earth would be transmitted through the portal in some way, but in what form would the field take on the other side of the portal?
Would it behave like a point source, or similarly to a diffraction slits? Would a mass slightly off to one side from the portal experience a force?
Let's ignore all the practical factors like the air rushing out into the vacuum and the question of what happens on the "other side" of the portal (the bit you'd be looking at if you flew up from new york to above the portal) although there's plenty of scope for interesting things happening there as well.