Hi All

Having received email for some time from general relativists who have been working on the Warp-Drive I can summarise their current thoughts as virtually total scepticism. Most have given up on making the Alcubierre style warp-bubble work within physics as we know it. A recent analysis by Visser and Lobo has nailed the lid on the coffin so to speak, the chief problem being that the mass-energy of the warp-ring needed, even for sub-light travel, is a fraction approaching unity of the ship's rest mass - and is over unity for v > c. In otherwords it needs immense amounts of "negative mass" to work and no one is sure that's even physically possible.

However the good news is that Visser has proven that the negative energy needed to keep a wormhole traversable can be vanishingly small. It may even be possible to using negative energy to "open up" natural wormholes that have wrapped themselves in an event horizon (i.e. black holes) thus saving a lot of effort on actually making the wormhole itself.

Personally I think that the energy needed to actually expand a wormhole's horizon, which is equivalent to black hole mass energy, will keep the first wormholes as small as gamma-rays for a long time yet unless ways of minimising the energy needed can be found and realised. So wormholes might allow ~FTL comm-links but not mass transfers.

To actually get to the stars will require star-drives like Jordan Maclay's quantum starship which could conceivably be powered by the quantum vacuum itself. Alternatively Woodward's Machian analysis of Inertia could provide a means to propel vehicles without propellant. Both require materials with high tolerance of extreme levels of vibration which may provide a plot device since drive crystals may shatter inconveniently in the depths of space.

Another conceivable drive is the proton-decay ramjet. The chief problem of ramjets is the need to compress the interstellar medium to fusion conditions - this loses more energy than it gains according to a classic analysis by T.A.Heppenheimer. But the problem doesn't arise if the mass collected can be converted into energy which requires something that catalyses proton-decay i.e. monopoles. Monopoles are essentially knots of distorted space-time and in some particle theories they cause protons to fall apart into charged pions that can be directed with magnetic fields before they become gamma-rays. Light monopoles could conceivably be made by the Large Hadron Collider, so we may know more about such processes in just a few years time.

If so will it solve the energy crisis? A monopole dunked in water will probably cause the water to boil via proton-decay, but won't cause a massive detonation. High energy densities will only be achieved by ramming high-density matter down its super-symmetric throat. Fine for starships, crap for bombs... :o)

Adam

PS And ultimately monopoles will probably allow the Sun to be kept going for ~ 10^13 years, until its mass density is too low to sustain such a high reaction rate. Lower outputs will allow longer life times of course. Even more speculatively if a singularity can be exposed and wrapped in enough mass to thermalise it then we'd have a star with an ~ infinite life-time, barring quantum gravity complications.