The possibility of a certain thing is only limited by the mind. Once the mind commands that he is capable of defying what has not able to occur, he surpassed the gamut of Power ever known to humanity.
The impossible might be defined if a huge number of people cannot accomplish such thing. Thousand years ago, it could be lunatic to think that it is possible for a piece of metal to float in the air or perhaps in water but when the Egyptians was able to make a way to travel through water, and when the Wright Brothers didn’t bother being lunatic, the concept of possibility has been exposed.