Stardrives and Spinoza

There are several senses in which one may speak of limits in relation to Physics. For the purposes of this essay, it is most useful to begin with the technological limitations of practical human activity. In this context, Physics both provides positive and negative information. Physical laws tell us how to achieve some goals, and informs us that others are forever out of reach. An excellent historical example is the science of thermodynamics. On the one hand, it tells us how to construct heat engines, on the other, it provides us with the Carnotic limit on efficiency, and rules out perpetual motion machines of both kinds. So Physics both extends our limits and helps us to understand them. Despite the annoying tendency of popular authors to tell us that anything is possible, the laws of Physics act as negative limits, and this is one of the great services of science to humanity. One may also ask about the limits of our knowledge, i.e. of physical theory. Is it almost finished, as Feynman insisted, does it end in a non-predictive theory, as we sometimes hear from string theorists, or is there a final theory yet to be discovered? Finally, we can discuss the limits of Science in relationship to other intellectual disciplines, such as Philosophy and Theology. In this essay, we shall present possible end results of Physics in the different senses we discussed above: our practical possibilities, our understanding of nature, and the role of Physics in our intellectual and (for want of a better phrase) spiritual life; and show that they are closely interwoven. We shall outline this network of ideas here, then discuss them in detail in the rest of the essay. We begin by discussing a family of potential practical applications of Theoretical Physics, namely the creation of artificial black holes (ABH’s), and their use as powerplants and stardrives [1]. This is suggested by classical general relativity and quantum field theory, but in order to see if it is truly possible, we will need a quantum theory of gravity, and moreover, one which can be put in a certain form, as we shall discuss below. Black holes, according to Hawking, are not really black. They radiate a thermal bath because of quantum field effects on the boundary [2]. For astronomical black holes the power is minuscule, but for microscopic ones it can be enormous. We have investigated whether there is a size range which is both useful and possible to produce, and found that the answer is a qualified yes. This proposal is extremely difficult technically. However, it seems that it is actually the least difficult possible approach to transporting human beings to the