FYI -- Interstellar Economics explained... Krugman proves that interest rates on Earth & Asimov's Trantor are the same. http://krugman.blogs.nytimes.com/2008/03/11/economics-the-final-frontier/ March 11, 2008, 2:09 pm Economics: the final frontier Thirty years ago I was an oppressed assistant professor, caught up in the academic rat race. To cheer myself up I wrote  well, see for yourself. Joshua Gans of the University of Melbourne scanned a copy of the thing I wrote  back then academics did their work with typewriters, abacuses, and stone axes  and was good enough to send me a copy. Ladies and gentlemen, I give you The Theory of Interstellar Trade. www.princeton.edu/~pkrugman/interstellar.pdf Some of this is explained in the 1-hour video: Doing Business in Interstellar Space - Professor John D. Barrow http://blip.tv/greshamcollege/doing-business-in-interstellar-space-professor... or http://www.youtube.com/watch?v=OUlWkx0wdME --- A similar set of arguments shows that if time travel exists, then interest rates here on Earth will tend to zero. If we utilize an analogy of the Fermi Paradox, then our current _zero interest rates_ are proof of the existence of time travel. http://en.wikipedia.org/wiki/Fermi_paradox