Scientists have been fascinated with the idea of controlling gravity for over 200 years. In the mid-1990s, British aerospace manufacturer BAE Systems began a ground-breaking project code-named 'Green glow', which set about turning science fiction into reality. NASA was simultaneously running its own Breakthrough Propulsion Physics Project. Looking at these past projects and into the future, BBC's Horizon explores science's obsession with the idea of gravity control. Are flying cars and journeys to the stars still the stuff of dreams?