Spacecraft and satellites could in future be launched into space without the need for fuel, thanks to a revolutionary new theory. Dr Mike McCulloch, from the University of Plymouth, first put forward the idea of quantised inertia (QI) – through which he believes light can be converted into thrust – in 2007. He has now received $1.3million from the United States Defense Advanced Research Projects Agency (DARPA) for a four-year study which aims to make the concept a reality. The QI theory predicts that objects can be pushed by differences in the intensity of so-called Unruh radiation in space, similar...