During the Steam Age Victorian times, a politician allegedly said something along the lines of, ''We know so much now, is it possible to know anything more?''I don't think so. Not many fantasies become reality. Only a small subset of fantasies are capable of becoming real. We are quite capable of imagining things that don't and will not and cannot ever exist and the ones that can become real do so for tangible (economic/security/defense) reasons. There are real limits that no amount of imagination can overcome. We don't necessarily know where all those limits are yet - but some big ones are quite well known and as science progresses closer to a true and complete understanding of the universe we inhabit it becomes increasingly possible to know beforehand if something imaginary is possible. New knowledge can open up new possibilities but it can and does close off imaginary possibilities that are not based in reality.
Our present scientists are in the same situation, they dont know how much more there is to learn about our universe. They are constantly finding new things that were previously considered impossible.
As to ''Reality'' what is reality?
We dont even know IF our universe is reality, or just a hologram.
What is fantasy now, could become reality in the future.
There are still many unknowns in our science.
''We don't necessarily know where all those limits are yet,'' says it all.