Think of how Albert Einstein changed our understanding of time and space by fantasizing about people going to the center of time in order to freeze their lovers or their children in century-long embraces. This space he imagined is clearly reminiscent of a black hole, where, theoretically, gravity would stop time. Einstein also fantasized about a woman’s heart leaping and falling in love two weeks before she has met the man she loves, which lead him to the understanding of acausality, a feature of quantum mechanics. A caricature of special relativity (the relativistic idea that people in motion appear to age more slowly) is based on his fantasy of a world in which all the houses and offices are on wheels, constantly zooming around the streets (with advance collision-avoidance systems).
Even the “Many worlds” interpretation which is espoused by some physicists, including Stephen Hawkins is based on Einstein’s fantasy of a world where time has three dimensions, instead of one, where every moment branches into three futures. Einstein summarized value of using your imagination to fantasize best when he said “The gift of fantasy has meant more to me than my talent for absorbing positive knowledge.”