Saturday, March 10, 2012

Making Stargates: The Physics of Traversable Absurdly Benign Wormholes

Getting around spacetime quickly has been a dream of some for more than a century. Until 1988, those dreamers were members of two distinct groups: aficionados interstellar spaceflight and fans of time travel. The technologies envisaged by these groups were distinct, for though space and time had been forged into spacetime by Einstein in his theories of relativity, space and time are sufficiently dissimilar that traveling in space was thought fundamentally different from traveling through time. Morris and Thorne’s work in 1988 changed that by showing that shortcuts in space and time require the same technology: traversable wormholes, macroscopic spacetime distortions connecting distant events (understood in the relativistic sense of a location in space and time) via very short structures in hyperspace. They found that a wide range of wormholes satisfy reasonable criteria for traversability. But most of them produce distortions that would seriously disrupt the surrounding spacetime over large distances. Morris and Thorne designated the class of wormholes that do not do this to their surrounding spacetime as “absurdly benign”.

From the practical point of view, the problem with absurdly benign wormholes of traversable dimensions is that they require “exotic” restmass matter – that is, real stuff you can stop in a laboratory that has negative mass. And you need a Jupiter mass – 2 X 1027 kg – concentrated in a region of small dimensions. A simple calculation assuming a throat diameter of, say, 10 meters and a wall thickness of a meter or so, leads to an exotic density of ~ 1022 gm/cm3, that is, on the order of seven orders of magnitude greater than nuclear density. Similar densities, as a matter of idle interest, are required to make the “warp drives” proposed several years later by Alcubierre.

Construction of devices that demand exotic matter of such densities seems, on its face, insuperable. The laws of physics as they are widely understood do not prohibit the existence of negative restmass matter as once thought. But its density and the amount required are breathtaking. And those laws seem not to even hint at where such stuff might be found and how it could be assembled into a stargate. Thorne has suggested that we must first master the so far vainly sought theory of quantum gravity before we have even the slimmest hope of figuring out how to make stargates. Nonetheless, if AAAs (arbitrarily advanced aliens) have actually built stagnates, presumably they have already done this. Should we want to build stargates, it seems that perhaps we should ask: What plausible physics must be true if absurdly benign wormholes are to be technically feasible? It may be there is no plausible physics, or that quantum gravity is required to answer this question. But we do not assume this before we investigate answers to the question since, improbable as it may seem, plausible physics may exist and quantum gravity may be irrelevant to the answer. ...

The key to the solution of the problem of making stargates is to be found in Equation 17 (see full pdf link below). Given some modest amount of everyday type matter, say a few hundred or thousand kilograms, all we have to do is enclose the matter within another presumably thin shell of matter wherein we can change its mass from positive to negative. It would have to become sufficiently negative to null the positive mass of the initial mass of the shell and the matter it encloses. But if we could do that, we would screen the gravitational influence of the matter in the rest of the universe on the matter within the thin shell. That would make [italic phi]u in Equation 17 zero for all of the elementary particles making up the enclosed matter. That, in turn, for distant observers, would render their masses negative and about 21 orders of magnitude larger than their original positive masses. And that would give us the Jupiter mass of exotic matter we need to make an absurdly benign wormhole. The really neat thing about this is that because both c and [italic phi] are locally measured invariants, the throat of the induced wormhole will look to you, the traversor, as though everything is completely normal, notwithstanding that someone outside the wormhole sees a major spacetime distortion present at the wormhole. ...

Plausibility, like truth and beauty, is often in the eye of the beholder – that is, you dear reader. So, the conclusion that you draw from the foregoing arguments will certainly depend on whether you think a reasonable case for the plausibility of Mach’s Principle and the negative bare mass ADM electron with accommodation for spin has been made. The Standard Model of particle physics is a profound, thoroughly developed, elegant theory of the structure and interactions of elementary particles. The version of the ADM model presented here is but a crude sketch of such a theory. And you may choose to ignore it. The point, however, is that if our hypothetical AAAs really have figured out how to make absurdly benign wormholes, the physics on which they have based their accomplishment cannot be the Standard Model. Or anything like it based on renormalizable quantum field theory. Quantum gravity as commonly understood will not save the day, for, as Ashtekar remarked many years ago, background independent quantum gravity theories are not renormalizable. Our AAAs must have found a theory of matter that contains latent exotic mass that can be exposed in some simple, relatively low energy fashion like that laid out above. As Peter Woit has remarked, “Finding . . . a new, deeper, and better way of thinking about fundamental physics is, however, an intellectually extremely demanding task. Unfortunately, it is not at all inconceivable that it is one that is beyond the capabilities of human beings if they are unaided by clues from experimentalists.” 

Faced with all this, we may ask: Is there any way forward? Yes. Experimental investigation of Mach effects – which turns out to be very much cheaper than building next generation accelerators – should illuminate whether stargates can in fact be built. Should that turn out to be possible, elaboration of the ADM model presented here might be worthy of some effort.

Making Stargates: The Physics of Traversable Absurdly Benign Wormholes (pdf)