LOL @ fish…
For the real question, it depends on how specific you’re getting.
Here’s where we are now in regards to dream knowledge.
People can lucid dream. For some it comes naturally, for some it can be taught, and some people just aren’t any good at it. It’s like any other skill - it takes practice and effort, but it can be done. People lucid dreaming can communicate with the outside world through fMRI tech or by responding to stimulus with certain pre-ordained signals like rapid blinking. Lucid dreams are generally remembered better upon awakening, and often are more logical and orderly than normal dreams.
Dreams do NOT run in faster time than reality. That has been pretty solidly debunked in a set of experiments where they had dreamers and lucid dreamers count the seconds of their dream by blinking. All of the participants were blinking in actual seconds.
What most people accept (it is hard to prove) is that dreams progress faster because they skip all the in between and boring bits of real life. In other words, you get on a train, and then you’re immediately getting off at your destination. You go into a restaurant and are immediately at your table eating. The inbetweens are filled in by your mind, and you don’t notice them because your logic center is asleep.
On that point, dreams are weird as shit, and not anywhere as logical or coherent landscapes as Inception paints. People (usually) have their logic centers deactivated as a regular part of sleeping, so when you dream, you just accept whatever flows by as totally normal.
(there’s a good thread in Cafe about dreams as well - lots of good points)
Generally speaking, most people have learned that if they die in dreams, they tend to wake up. It has not been scientifically proven that I am aware of, but it’s a common enough “trope” (another one is the naked or lost in school before a test, another is stress-related; teeth falling out or rotten) - so many people dream those dreams and report having them that it’s simply accepted as a common dream theme.
On a personal note, dying in dreams is how I learned to lucid dream. (I didn’t want to have nightmares, so when I found myself in one, I just killed myself off. Eventually I got to where I could control the dream and keep the nightmares from forming, and from there on to where it’s like a big sandbox to play around in.)
As for implanting or removing ideas from dreamers, that’s a little hairy.
We know that it is possible to communicate with “locked-in” people (people stuck in a state where they are not able to move or access their body, but are awake and conscious) with fMRI. The one I’m remembering is a lady who was scanned and they could look at the active parts of her brain and see that she was imagining playing tennis, and then imagining swimming, because different parts lit up with each scenario. There was another where they asked a gentleman to construct a mental scene of his home and walk through it, and they could tell roughly where he was in that process through the same scanning techniques.
It is very expensive, time-consuming, hard as hell to interpret, and irradiates the patient in question, which really isn’t all that lovely. I don’t know that it has been done to anyone in a REM state, but based on people who don’t have their muscular and nervous systems shut down properly when they are asleep, we do act out our dreams (think all the sleepwalkers/eaters/sexers/drivers!) so it would make sense that they also would be apparent to a detailed brainscan.
As for implanting info, the closest analogue I can think of is hypnosis, and research on hypnosis isn’t my thing. All I can say is that from what I’ve seen hypnosis seems to work better with feelings, cravings, and physical hangups than for actual ideas and thoughts.
Shared dreaming is not possible today, at least not in the Inception sense. People can have shared experiences in the luminal state (when you’re in that drifty-half-asleep state right before you drop off or wake up), or in drugged states. In the cases I know of, the dreams are “shared” by the participants essentially narrating what’s going on and their brains incorporate both narratives (again, logic centers are out, so it totally makes sense!) into a seamless whole.
Lastly, people don’t fall asleep and instantly dream. Dreaming is actually one of the last sleep states you get to. One exception - if you take people and let them sleep, but wake them every time they get to REM to keep them from dreaming, they go a little nutso AND when they fall asleep in a REM-deprived state, they start hitting REM first. It appears to be extremely important to our mental state to experience regular dreaming.
So, Inception? Neat idea, based on some real science, sadly not really possible with today’s tech.
However - technology and the study of dreams is a really hot field right now. People are beginning to realize how important it is to humans, and how little we know scientifically about it. In the course of research and developing designer drugs to improve and help our dreams, we may find something that lets people share dreamstates, or to induce dreaming in someone artificially. It’s not that far-fetched.
What is far-fetched is the actual act of intruding into someone else’s dream, or importing someone else into your own dreams, with both of you remaining in a semi or totally lucid state. As far as I know, that’s still in the realm of utter science fiction.