leo wrote:Some thoughts after my second viewing
Tars calls these humans from the future beings who live in the bulk. The bulk is a term used in recent physical theories related to string theory (see the wikipedia article on brane cosmology), and it refers to a hypothetical higher-dimensional space encompassing our conventional 4-dimensional space (3 spatial dimensions and 1 time dimension). Tars calls them 5-dimensional beings, so in Interstellar the bulk consists of one additional dimension. According to the theories only gravity would be able to travel between the bulk and our conventional dimensions. In Interstellar, Cooper communicates with Murph through gravity (that is how he moves the books, interacts with the watch and makes the dust pattern in Murph's room which Cooper interprets in the beginning as a gravitational anomaly).
In the bulk of Interstellar love is a physical, tangible reality, not just the unquantifiable emotion that it is in our conventional dimensions. Brand was right. The beings of the bulk (the humans from the future) hence physically perceive the love that links Cooper and Murph in her bedroom, through space and time, and the tesseract they have built enables Cooper to interact with the other end of that link. Apparently these beings are not able to directly interact gravitationally with our conventional dimensions (because if they did then why wouldn't they communicate directly with Murph themselves?), which then leaves the question who built the wormhole? If it is them then I do not yet understand why they couldn't help Murph directly the way Cooper did using gravity.
Cooper is sent back near Saturn through a wormhole once the beings of the bulk close down the tesseract. Cooper sees Brand in the wormhole, at the time when she was in the Endurance going through the wormhole for the first time. Cooper is the gravitational being she interacted with at that point. I suppose that the wormhole Cooper went through after the tesseract connected to the first wormhole at some point, but it is not clear to me why Cooper saw her inside the wormhole that she had went through 74 years earlier or so.
Cooper leaves at the end to reunite with Brand, who still believes she might be the last human alive, as she thinks plan A has failed and that Cooper died in the black hole. Until he reaches her she is on her own, trying to fulfill plan B and save humanity, by growing the fertilized eggs they had brought with them on the mission.
Answer
imo coop ends up in the dimension of the people who built the wormhole for us. He is not back in his reality or dimension. It's a snake biting his own self. They must send someone to communicate because they are lovedones and they have souvenirs and memories (i remember coop talking to Murphy about memories when they had the Talk right before he leaves). Knowing that it´s murphy's memories we are in a dimension in which murph has succeed. Well i understand myself but i should definitely make a drawing of this. It's a loophole with 3 parallel world and 4th one with "them"