Anti-gravity, the taboo of the science and aerospace communities, takes a step into the limelight of respectability this week with news that Boeing, the world’s biggest aircraft-maker, is exploring concepts that could one day – perhaps even soon – overturn a century of propulsion technology. Boeing’s interest in anti-gravity is encapsulated in a company project known as Grasp – Gravity Research for Advanced Space Propulsion. A Grasp document, obtained by Jane’s Defence Weekly, the defence industry magazine, spells out what Boeing believes to be at stake if it can succeed in engineering real hardware. “If gravity modification is real,” it says, “it will alter the entire aerospace business.”