Centauri Dreams on the Air

by Paul Gilster on October 30, 2004

Theoretical physicist Michio Kaku interviewed me for his public radio show Explorations last Thursday. The show is to run November 1, but I’m told that some of the public stations that carry it are currently doing their fund-raising, so the schedule may be thrown off. Dr. Kaku’s Web page carries a list of stations, and the show will be available for download on the Web.

Michio KakuMichio Kaku is is the co-founder of String Field Theory, and is the author of international best-selling books such as Hyperspace, Visions, and Beyond Einstein. He also holds the Henry Semat Professorship in Theoretical Physics at the City University of New York.

Much of the conversation was devoted to interstellar propulsion concepts, with a few even more speculative issues thrown in. In particular, Kardashev’s three levels of civilization. A brief refresher:

Nikolai Kardashev was a Russian astronomer who sought to classify extraterrestrial civilizations based on energy output. A Type I civilization would be capable of harnessing the entire energy output of its planet. Type II would be able to draw on all the energy available from its star, while Type III would exploit the energy resources of its galaxy. In Kardashev’s view, the output of each stage is 10 billion times larger than the previous one. These are staggering numbers, but Kaku thinks they can be ‘bridged by any modestly expanding civilization.’

Listen to him in his book Visions (New York: Anchor Books, 1997):

Assume, for the moment, that our own world economy grows at a rather anemic rate of 1 percent per year, which is very conservative. Since economic growth is fueled by increased consumption of energy, we would find a corresponding growth in energy as well. Within a hundred to a few hundred years, our world will approach a planetary Type I civilization.

At such a growth rate, the transition from a planetary Type I civilization to a stellar Type II civilization will take longer, perhaps 2,500 years. A more realistic growth rate of 2 percent per year would reduce that figure to 1,200 years. And a 3 percent annual growth rate would reduce that even further to 800 years.

Eventually, the energy needs of a Type II civilization will outgrow even the energy output of its star. It will be forced to go to nearby star systems in search of resources and energy, eventually transforming it into a galactic civilization. (Visions, p. 323).

As to the transition to Type III, Dr. Kaku believes it will be a lengthy one, because it will require mastery of interstellar travel. But he thinks that within a hundred thousand to a few million years, a Type II civilization could make the transition to a Type III.

My view is that if a Type III civilization existed in our own galaxy, its presence would be blindingly obvious. Kaku disagrees; he says that would be like expecting ants along the side of a superhighway to understand that they were in the presence of an alien technology when, in fact, the most they would be looking for would be other, perhaps bigger, ants. Kaku’s speculations on how a Type II culture might grow into a Type III using self-replicating probes make for fascinating reading, and I want to return to them in the near future.

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