40 years ago marked the pinnacle of human space exploration. 500 million people around the world watched or listened as the first human to walk on the moon, Neil Armstrong, stepped out onto the dusty lunar surface, proclaiming “That’s one small step for man, one giant leap for mankind." Over the next three years, 11 other astronauts walked on the moon. At the time, most people viewed the Apollo Missions as merely the beginning of a bold new era of interplanetary exploration. Yet to this date we have never returned to the moon, nor have we attempted to set sail for more ambitious celestial destinations. NASA’s fraction of the U.S. GNP declined from 4% at the height of the cold war to its current low of .5%. Indeed, the cold war and the space race seemed to ascend, crescendo, and fizzle out in unison, leading one to believe that the moon missions were driven more by ephemeral political brinkmanship rather than any firm scientific or humanistic commitment to space exploration. Nowadays, the costs and risks associated with manned missions to the moon and beyond are viewed by both policymakers and the public at large as prohibitive, especially in this time of acute financial and environmental crises. Although former U.S. President G.W. Bush had declared his intention of putting humans back on the moon by 2020 and sending them on to Mars shortly thereafter (the cost of which has been estimated at over 150 billion dollars), the proposal is currently being reviewed and likely to be scrapped by the Obama administration in light of the latter’s ambitious and resource-draining domestic agenda.
In any case, what could justify spending a non-trivial fraction of an enormous GDP on “pure science” that has little foreseeable social and political benefit? Space exploration is a paradigm exemplar of pure science—work whose value is of largely theoretical interest without any immediate or obvious public payoff, apart from a few spectacular photo ops. Nevertheless, it is impossible to draw a sharp line between pure and applied science, since virtually all scientific endeavors have both theoretical and practical value in some ratio or another. Just as numerous unanticipated technologies emerged from the initial race to the moon, so too would many social benefits be likely to flow from a challenging space exploration program, such as a manned mission to Mars, even if the overarching mission itself were of largely theoretical or symbolic value. And of course, a better theoretical understanding of the causal structure of the universe enables us to more effectively manipulate the physical world, often in unanticipated ways, in order to achieve our common social goals (such as those relating to public health, medicine, energy, communication, civil infrastructure, defense, and so on). In addition to the incidental benefits of developing the technologies necessary for manned interplanetary exploration, studying Mars up close has other direct terrestrial benefits, such as providing unique insight into the process of irreversible climate change as it took place on a now bone-dry planet that once teamed with liquid water—which could help us understand the nature and magnitude of similar problems we may be confronting here at home. It is fairly easy to dream up potential ancillary benefits of manned space exploration; but it is by no means clear that they will outweigh competing terrestrial concerns such as poverty, drought, and infectious disease, with respect to which 150 billion dollars could have a substantial impact.
But even if there were absolutely no chance of deriving a practical benefit (either directly or further down the road) from some costly theoretical investigation, does this mean that the latter will almost never be justified, given the dilemma of triage in the distribution of public goods? Take, for example, the possibility of finding fossil or living microbial life on Mars. Understanding the origins of life here on Earth and on other worlds is one of the most profound and interdisciplinary scientific questions we can muster, and yet its value is almost entirely intrinsic. Are non-specialists, or lay people in general, sufficiently interested in questions relating to natural history, including cosmology, paleobiology, and the like, to fund such heady investigations at the expense of other more practical concerns? Would taxpayers prefer spending billions on a manned mission to Mars in lieu of using that money for other domestic programs such as healthcare? An Associated Press poll taken in 2004 at the time of President Bush’s proposal to revisit the moon showed that people were evenly split on the issue. More than half of respondents said that it would be better to spend money on domestic programs rather than on expanding the space program. It may be that taxpayers are simply not willing to spend billions of dollars on esoteric intellectual pursuits, such as the origins of life. But the notion that there are no practical benefits likely to accrue from a given publicly financed scientific endeavor is not a sufficient condition for ruling the latter out—lest we exclude a whole litany of academic disciplines from public support. I am not arguing that we should, all things considered, continue to fund manned (or for that matter robotic) space exploration; but I do believe that there is significant, non-instrumental value that comes from understanding our place in the cosmic scheme of things. And it is only by cultivating our primal sense of curiosity and adventure that we will continue to ask the hard questions, and be sufficiently moved to answer them.