Keeping humans alive is key to asteroid deflection and space colonization---preserving 100 trillion years of animal life

In contrast, I assume here that moral value is a function of both the quality and number of lives in a history.[3] This view is consistent with most people’s intuition about extinction (that it’s bad) and with moral theories under which life is considered a benefit to those who have it, or under which life is a necessary condition for producing things of value (Broome, 2004; Hare, 1993; Holtug 2001, Ng, 1989; Parfit 1984; Sikora, 1978). For instance, some moral theories value things like experiences, satisfied preferences, achievements, friendships, or virtuous acts, which take place only in lives. On this view, an early death is bad (at least in part) because it cuts short the number of these valuable things. Similarly, on this view, an early extinction is bad (at least in part) because it cuts short the number of these valuable things. I think this view is plausible and think our best reasons for believing an early death is bad are our best reasons for believing an early extinction is bad. But such a view is controversial and I will not settle the controversy here. I start from the premise that we ought to increase moral value by increasing both the quality and number of lives throughout history. I also take it, following Singer (2002), this maxim applies to all sentient beings capable of positive subjective feelings. Life’s prospects The human population is now 6 billion (6 x 109). There are perhaps another trillion (1012) sentient animals on Earth, maybe a few orders more, depending on where sentience begins and ends in the animal kingdom (Gaston, Blackburn, and Goldewijk, 2003; Gaston and Evans, 2004). Animal life has existed on Earth for around 500 million years. Barring a dramatic intervention, all animal life on Earth will die in the next several billion years. Earth is located in a field of thousands of asteroids and comets. 65 million years ago, an asteroid 10 kilometers in size hit the Yucatan , creating clouds of dust and smoke that blocked sunlight for months, probably causing the extinction of 90% of animals, including dinosaurs. A 100 km impact, capable of extinguishing all animal life on Earth, is probable within a billion years (Morrison et al., 2002). If an asteroid does not extinguish all animal life, the Sun will. In one billion years, the Sun will begin its Red Giant stage, increasing in size and temperature. Within six billion years, the Sun will have evaporated all of Earth’s water, and terrestrial temperatures will reach 1000 degrees -- much too hot for amino acid-based life to persist. If, somehow, life were to survive these changes, it will die in 7 billion years when the Sun forms a planetary nebula that irradiates Earth (Sackmann, Boothroyd, Kraemer, 1993; Ward and Brownlee, 2002). Earth is a dangerous place and animal life here has dim prospects. If there are 1012 sentient animals on Earth, only 10^21 life-years remain. The only hope for terrestrial sentience surviving well beyond this limit is that some force will deflect large asteroids before they collide with Earth, giving sentients another billion or more years of life (Gritzner and Kahle, 2004); and/or terrestrial sentients will colonize other solar systems, giving sentients up to another 100 trillion years of life until all stars begin to stop shining (Adams and Laughlin, 1997). Life might survive even longer if it exploits non-stellar energy sources. But it is hard to imagine how life could survive beyond the decay of nuclear matter expected in 1032 to 1041 years (Adams and Laughlin, 1997). This may be the upper limit on the future of sentience.[4] Deflecting asteroids and colonizing space could delay the extinction of Earth-originating sentience from 109 to 10^41 years. Assuming an average population of one trillion sentients is maintained (which is a conservative assumption under colonization[5]), these interventions would create between 1021 and 1053 life-years. At present on Earth, only a human civilization would be remotely capable of carrying out such projects. If humanity survives the next few centuries, it’s likely we will develop technologies needed for at least one of these projects. We may already possess the technologies needed to deflect asteroids (Gritzner and Kahle, 2004; Urias et al., 1996). And in the next few centuries, we’re likely to develop technologies that allow colonization. We will be strongly motivated by self-interest to colonize space, as asteroids and planets have valuable resources to mine, and as our survival ultimately requires relocating to another solar system (Kargel, 1994; Lewis, 1996). Extinction risks Being capable of preserving sentient life for another 10^41 years makes human survival important. There may be nothing more important. If the human species is extinguished, all known sentience and certainly all Earth-originating sentience will be extinguished within a few billion years. We ought then pay more attention to what Bostrom (2002) has called “existential risks” -- risks “where an adverse outcome would either annihilate Earth-originating intelligent life or permanently and drastically curtail its potential.”