Lesson 9: Other Worlds, Other Life 9.8 How To Make A Galactic Civilization There has been no lack of visionary thinking about what feats of engineering humans might aspire to. Generally, science fiction writers get their ideas from engineers and scientists and translate them into terms more entertaining to the public. We will just mention three examples: Dyson Spheres and Stellar Engineering In the 1976 a Princeton scientist, Gerard O'Neill captured our imaginations with daring yet seemingly feasible proposals to unite lunar materials and solar energy to fabricate giant habitable cylinders with all the comforts of home, including apartments, parks and streams. The banner of the feasible exploitation of near space is being carried on in books by U. of Az. Engineer John S. Lewis. Somewhat earlier, the imaginative physicist Freeman Dyson had conceived of what have come to be known as Dyson Spheres, completely capturing the radiation of a star (see also Khardashev II civilizations, below). There are of course some strength-of-materials concerns, especially over the solar poles, but one can imagine nested shells of spherical segments rotating about various axes. Figure 9.8.2 Artist's conception of a Dyson sphere. Rings of computer-controlled storage cells collect all of the energy emitted by a star and store it for later use. Finally, CalSpace at UCSD harbored in the 1980s a visionary named David Criswell who dreamed of extremely large magneto-hydrodynamic machines, perhaps boot-strapping to ever larger sizes, that might suck off some of the hydrogen from a star, therefore changing its spectral type and in the process prolonging its lifetime by billions of years. This seems like an introduction to the managing or "farming" of stars and ultimately black holes, first of stellar mass and ultimately of galactic mass, skills that will be necessary in the really really long term (see next sections). Khardashev Civilizations The Russian astrophysicist Nicolai S. Khardashev classified possible technologically advanced civilizations into three categories, according to the energy they have at their disposition. He then estimated the maximum information flow if they put most of their energy into interstellar communication. Type I: Technological level of present-day Earth Energy consumption: 4x1019 ergs/sec Communication potential: 140 books/sec across the galaxy Type II: Civilization capable of harnessing the energy of its own star Energy consumption: 4x1033 ergs/sec Communication potential: 1000 books/sec across the galaxy Type III: A civilization in possession of energy on the scale of its own galaxy Energy consumption: 4x1044 ergs/sec Communication potential: 33,000 books/sec between galaxies Note that since Khardashev made these estimates in the early 1960s, computer speeds have increased by a factor of perhaps 106, and this, not power available, would be the limiting factor in local transmissions. In addition, even in the Soviet system under which Khardashev worked, usage of all energy resources into a single transmission project would be unthinkable. A better number might be one millionth of the energy available. It is not hard to imagine renting Arecibo Radio Observatory nowadays for a few hours for less than $60,000 (this is 10-6 of a world GNP of $6x1010 or $60 trillion) to transmit the entire contents of the Library of Congress and similar repositories of knowledge to anywhere in our galaxy where they might have a similar dish for receiving it. Such is technical progress! Will we be still be human? It makes perfect sense to ask if human beings will still be recognizable in the distant future. Even if we were only subject to natural selection, it is to be expected that evolution would continue. Humans adapt to even very short periods of weightlessness by shedding bone mass. It is very easy to imagine and even expect that humans on planets or space vehicles with very different conditions than those under which we have evolved so far will show further evolution: lighter structures (bones) for less gravity and more massive structures for heavier gravity and changes in lung size and efficiency for different atmospheres, as well as changes in eye sensitivity and skin thickness or color, depending on the habitat (we've done his recently, in the last 100,000 years or so). More importantly, we stand at the threshold of gene manipulations that could vastly speed up the process of natural selection on humans - the same sort of "unnatural selection" that we have long practiced on domesticated plants and animals. A more basic question might be: will we be replaced by or become machines? It is easy to imagine increasing use of artificial "enhancements". Taken in progressive steps, it may become hard to tell humans from machines. Certainly robots are more suited to the task of exploring first our galaxy and ultimately the galaxy than are fragile flesh and blood beings. If we ever do meet another species, it may well be their mechanical surrogates that our robots first interact with. Machine intelligence may have a long way to go, but let us not forget that it is increasing far, far faster than human intelligence.