Board Thread:Questions and Answers/@comment-25521424-20161130160919/@comment-1276416-20161201153532

My own interpretation based of the little information we have now, is that it is like a "tunnel" between dimensions. The tunnel is locked on the person, and is unaffected by the persons geographic location on the earth-realm. The person trapped in between can change their spatial location on the Earth-realm, but their position in the tunnel won't be affected by that. The tunnel is of course not visible to human senses.

The ghosts where only a little bit in the tunnel, as they could affect the Earth-realm, and the fear-touch the ghost had was energy from the unknown dimension sipping into the tunnel, that affected the mind of the victim.

Coulson, Fitz and Robbie, as stated in the episode, where deep in the tunnel, and could affect the Earth-realm to a little minimum. Coulson seemed to be deepest in his tunnel compared to the other three, as he was sucked in first. Perhaps because he was closest to Eli's machine when it went off. And, as Robbie was a bit away, he still had time to escape long after Coulson and Fitz were rescued, before he and the Rider were sucked in.

Interesting though that physical resistance helps a bit against being completely sucked in.