Empty space is a hive of activity. Particle-antiparticle pairs are being created out of nothing, all the time and everywhere, and vanishing again before their energy can violate the uncertainty principle. A high-energy particle collision nearby may provide the energy to stabilize such a virtual pair, making it real.

What velocity, asks Daedalus, is a virtual pair born with? The obvious answer is that it is created stationary; but relativity makes this impossible. Empty space has no reference frame to be stationary relative to. The best it can do, says Daedalus, is to arrive with some random velocity relative to local matter. And a truly random velocity, somewhere between plus infinity and minus infinity, is almost certain to be very large indeed.

Indeed, such pairs might constitute the long-sought tachyons, which travel faster than light and backwards in time. But Daedalus reckons that to external observers, new pairs will merely seem to be moving extremely close to the speed of light. Relativistic time-dilation will therefore stretch their internal timescale enormously. Even if a pair cannot last more than 10−20 or 10−30 seconds before vanishing again, to external observers the time will seem much longer. At almost the speed of light, the pair could travel some distance before disappearing. It could even collide with something, and (just as in a violent particle collision) be transformed into something detectable.

Daedalus would like to test this bold theory. Several large-scale experiments, such as neutrino telescopes and proton-decay detectors, consist of a large volume full of something, surrounded by a dense array of detectors all looking in. Daedalus proposes to pump out such an experiment, leaving the detectors watching a vacuum. Any ray, particle or pair that enters from outside will collide with and trigger two detectors, at its entry and exit points. But one created within the vacuum will trigger only one.

A successful outcome would provide all sorts of new high-energy events. If it detects newly created hydrogen atoms, it would support the ‘continuous creation’ theory, in which a steady-state Universe is maintained by the continuous appearance of new hydrogen throughout space. And if it sees only pairs with a well-defined velocity with respect to local matter, it will disprove relativity and resurrect that universal inertial reference frame, the ether.