Most reviews about Christopher Nolan's sci-fi masterpiece lazily suggest it is full of plot holes. Mark Kermode deigns the plot to be ludicrous, "...I can only accept the final 15 minutes if it’s all an illusion – which I suspect it isn’t". I suggest that most reviewers have misunderstood the film and especially misunderstood the scientific concepts that the film so wonderfully brings to life with its stunning visuals.
The Last 15 Minutes
Cooper decides to see what is inside a black hole and approach the singularity at its centre. He ejects from his ship and falls into what appears a infinite matrix of his daughter's bed room. The room is repeated ad infinitum in various directions (spatial dimensions) but each room shows a different time.
As explained in the film he is able to move around this matrix in various directions to visit the room at different times, in other words time travel. In Einstein's theory of Special Relativity there is a concept called Space-Time which states that space and time are the same, we exist in a 4 dimensional world that consists of 3 spacial dimensions and one time. In theory we should be able to move backwards and forwards through time, its our human perception of cause and effect that makes this idea seem bizarre. In fact there are philosophical musings that time actually runs backwards:
Retrocausality is primarily a thought experiment in philosophy of science based on elements of physics, addressing the question: Can the future affect the present, and can the present affect the past? Philosophical considerations of time travel often address the same issues as retrocausality, as do treatments of the subject in fiction, although the two terms are not universally synonymous."
Having said all of this the Second Law of Thermodynamics implies that time has a direction, entropy (disorder) increases with time, which in I my mind does separate time from the other spacial dimensions. In the film, Cooper suggests to TARS that he may actually be in a world with higher dimensions and that is how he is able to move to different points in time.
Cooper is able to communicate with the past using gravity. According to General Relativity, gravity is due to the curvature of space-time. The curvature in space-time is caused by mass, so it is feasible that Cooper's own mass will cause a tiny warping of the space-time in his daughter's room. Admittedly this will be tiny and it is very doubtful if he could even effect the motion of a falling speck of dust.
At the start of the film Cooper and his daughter receive mysterious messages that contain information about a secret NASA mission. In the final 15 minutes, it is Cooper himself who sent the messages and also information that allows his daughter to crack the Gravity problem (quantum theory of gravity?). So there are paradoxes and causality loops. Standard fare for any time travel film from The Terminator to Bill and Ted's Excellent Adventure!
For me the ending to 2001 A Space Odyssey's is still baffling but for Interstellar the ending made complete sense. In the cinema I was at edge of my seat as he entered the singularity, like when I first saw Disney's Black hole. Interstellar delivered a spectacular insight into the latest ideas of theoretical physics.
The worm hole is actually spherical, Kip Thorn and the CGI team have had two scientific papers published based on the theoretical physics and computation that went into the rendering of the Wormhole.
In a swipe at Creationism being taught in Schools, the Moon Landings have been removed from textbooks as they are now taught as having been faked, a PR stunt to win the Space Race.
The T.A.R.S. robot at first appeared to be naff but when he got going later in the film he moved in very interesting ways. Also his design is a nod to the 2001 monolith and certainly not HAL.
The character's in the film muse about why humans need to go into space instead of probes, as AI does not have the same survival instincts as humans. With the AI Singularity upon us, very interesting philosophical points.
A film that demands attention and intelligence, you'll be rewarded with new concepts and ideas presented with spectacular visuals. Looking forward to the DVD release with special features.