Did aliens in another universe create the universe we live in? It sounds like the theme for a new fall TV series. But it's a serious speculation put forth by physicist Edward R. Harrison of the University of Massachusetts at Amherst. As detailed in the September issue of the Quarterly Journal of Britain's Royal Astronomical Society, this is the latest twist in an intellectual game cosmically inclined scientists have played for many decades. They hope to gain new insight by looking at what they know about our physical universe from the perspective of a hypothetical creator. Our universe's basic physical laws seem finely tuned to support the rise of intelligent life. If gravity were a bit stronger, for example, stars would burn out too fast for organic life as we know it to arise. If the relative strengths of the ''strong'' force that holds atomic nuclei together and the electromagnetic force were different than we know them to be, our universe would lack elements organic life needs. As Einstein put it metaphorically, the central issue is whether or not God had any choice in designing the universe. Must the basic laws be exactly the same as the ones we know for a universe to support intelligent life, or is there some leeway in how these laws can operate? Explaining his thinking in a telephone interview, Professor Harrison said he is ''putting a rational layer'' between us and the concept of a primordial first cause. He noted that, if one merely says ''God did it,'' that ends rational discussion from a physicist's point of view. On the other hand, he says, many people find it unsatisfying merely to say, as some scientists do, that the universe exists because we exist, and if it were any other way we would not be here wondering about it. Harrison offers an alternative view based on the concept, widely held among physicists, that many universes can exist simultaneously. Without worrying about a first cause, he suggests that some universes contain advanced civilizations. One or more of these civilizations may experiment in creating other universes. Some of these new universes could also give rise to intelligent life that would, in turn, create more new universes, and so on. As Harrison puts it, ''Parent universes, by means of their intelligent inhabitants, give birth to offspring universes.'' These offspring would differ slightly in their basic laws. Some would be better homes for intelligent beings than others. This could lead to a process of evolution by which the kind of universe best suited for intelligent life would eventually arise. That could explain why our universe seems so finely tuned to support organic life. As for creating universes, Harrison says that, theoretically, ''we are beginning to see how'' this might be done. Compressing a small amount of matter - 10 kilograms or so - at a high energy can theoretically bring it to a point where, instead of collapsing farther, it inflates into a new universe. Such creative inflation now is part of standard cosmological theory. Physical laws as we know them allow such a process to create a universe with billions of galaxies of stars, measuring billions of light-years across, and enduring for billions of years. Harrison admits that, in proposing this, ''I have gone to the fringes of [scientific] cosmology.'' Yet that is where the discussion of our universe's remarkable fitness for life has been all along. Harrison now provides a way for scientists to think about it in evolutionary terms. They can think about how, given the tools to do it, they might create a new universe. What is the point of all this? Harrison says that ''it's a sort of game.'' And like most games, it exercises thinking. It helps thinkers loosen up and take fresh views of problems they tackle on Earth. That can be a very practical payoff from what might seem to be a most impractical kind of speculation.