Faster than Light?

F AR out at the edges of the solar system, the motions of two spacecraft, Pioneer 10 and Pioneer 11, appear to be breaking all known laws of physics. Some mysterious source of energy is causing them to speed up. They are millions of miles apart, but both of them are experiencing the same tiny amount of acceleration. It is no more than a billionth of a metre per second every second, but its cumulative effect has put them 300,000 miles further from Earth than Newton's laws say they should be after 35 years of cruising. This "Pioneer Anomaly'' was cited at a recent seminar of the British Interplanetary Society entitled "Warp Drive, Faster than Light, Breaking the Interstellar Distance Barrier.'' It might reveal a form of energy unknown to conventional physics, enabling spaceships to make instantaneous journeys by manipulating space itself.

Some space enthusiasts are impatient with the absolute prohibition of faster than light travel decreed by Einstein's special relativity of 1905. There is hope for their ideas since the special theory speaks only of travel through normal space. There is now a search for new physics that would overrule this interdiction. For the equations of Einstein's much more complex general theory of 1916 raise the possibility of travelling instantaneously through some other dimension. A ship could thus effectively disappear in one place and reappear immediately afterwards in another. Long used in science fiction where it is called the "Jump through hyperspace'', such superluminal transport might one day be possible in reality. This is no project for the next fiscal year or decade. It is an attempt to answer the far-off question: What things do the laws of nature permit an infinitely advanced civilisation to do, and what things do those laws forbid? Merely academic today, in two centuries time this may become be the most important of all crises facing the human race. Its solution will decide which of two vastly different futures our descendants will face. If no possibility of faster than light travel exists, then space travel will be essentially restricted to a few nearby star systems. In these circumstances the human race will in the long term become culturally dead. But if, on the contrary, instantaneous travel becomes feasible, then there is no limit to the voyages that can be undertaken. The galaxy could be explored and colonised by manned spaceships from end to end. Humanity could solidify into a single galactic community. Discovering this will be tremendously difficult. A new generation of supercomputers may be needed to explore all the ramifications of general relativity.  It is not so much what the equations say as what they mean.  In almost a century only a modest amount of progress has been made in unravelling these mysteries, that one scientist calls "Einstein's outrageous legacy.'' As Michio Kaku remarks, within the 1916 equations lurk all sorts of strange "goblins and demons'', black holes, wormholes, time travel and other universes. Eventually a theoretical solution may be found, and half the battle will have been won. Engineers can do the rest. As Arthur C. Clarke says: "Anything that is theoretically possible will be achieved in practice, no matter what the technical difficulties, if it is desired greatly enough.''