Alastair Mayer’s T-Space Blog

One of the best things to happen for those of us who like both hard SF and space opera was Miguel Alcubierre’s 1994 paper demonstrating how General Relativity does allow for faster-than-light (FTL) travel, using “warped” spacetime. (Yes, Star Trek and all the SF writers before it seem to have guessed right, but Alcubierre did the math. See my article “Yes Virginia, There Really is a Warp Drive”.)

However, I see today on the Technology Review arXiv blog that a recent paper by Finazzi, Liberati and Barceló, “Semiclassical instability of dynamical warp drives”, applies quantum theory to Alcubierre’s analysis and comes up with two potential problems: Hawking radiation (the effect that makes small black holes “evaporate”) could be hazardous to the occupants, and the warp bubble itself might be unstable because of the “stress-energy tensor” growing exponentially. (No, I’m not exactly sure what that means either, I never got that far in my physics classes.)

Does that mean Finazzi et al. just killed Santa Claus? No. For one thing, they make some assumptions about the properties of the exotic matter needed to maintain the warp which may not hold. For another, it looks like they just analyzed an Alcubierre warp rather than Van Den Broek’s refinement (see the “Yes, Virginia” piece mentioned above for the difference), so the Hawking radiation may be confined to the “shell” in the latter case. Finally, instabilities can be overcome if you have a fast-responding control system. Maybe that means the controller needs a quantum computer.

Addendum: There may be another way to overcome Finazzi instability, depending on the physical constraints of how you generate the warp in the first place. The idea came to me in the course of writing a novel about the first Alpha Centauri expedition. The details are one of the plot points so I won’t go into it here (besides, I may just be handwaving — the math is beyond me), but consider the simplifying assumptions we can make to predict the behavior of large systems. — AM, 2010