Now that we've had time to hear the predictable cracks about President Bush wanting to send human beings to live on the Moon and Mars ("Maybe he'll find the WMD up there," etc.), let's analyze the cost-benefit ratio of the proposal. The argument that the money would be better spent here on earth lacks logic. NASA appropriations are less than one percent of the annual federal budget. For every dollar we put into space exploration, we spend dozens on social programs and other earthly needs. NASA's costs, measured as either a portion of the Gross Domestic Product or the federal budget, are tiny. It would seem we could earmark that relatively small amount money for scientific inquiry without starving any orphans or forcing senior citizens to eat dog food.
Having said that, it must be noted that most arguments in favor of space exploration are almost as lame as the arguments against it. We can't count on discovering vast new resources of anything useful out there, and so far as providing humanity with alternative survival environments, human nature doesn't change through travel, no matter how far we go. If we are inclined to poison the planet and blow ourselves up on Earth, it's reasonable to believe colonists on the Moon or Mars will carry the seeds of the same madness with them.
There's just one good reason to send people to explore and possibly colonize other worlds: A reinvigorated space program will generate spinoff benefits that will pay its own costs, and then some. Historically, that dynamic has been working for decades.
Consider: Human productivity has been greatly increased through applications of the info-tech revolution. Those advances were initially made affordable through the huge decrease in the cost of computer chips, paired with a massive increase in the amount of data they hold. The chips got cheap and efficient because the Department of Defense needed a lot of them for high-tech military equipment, while NASA had to make everything on spacecraft smaller and lighter in order to increase mission payloads (space exploration and national defense have been joined at the hip since the 1950s, for reasons we'll get into later). The big costs of any new technology are the startup expenses, the research and development. Once you've got a production line cranking out a given item, the per-unit cost soon drops from dollars to cents.
So it's reasonable to postulate that because the U.S. poured money into improved technology for defense and the space race, the standard of living for everyone in America, and indeed the world, has been improved. The reason so little credit for that increased productivity (and, by logical extension, wealth) has accrued to expenditures on space and defense is, the money goes out in large, identifiable chunks and trickles back in, via higher profits and salaries, through thousands of private companies.
The thing to remember is, no science occurs in a vacuum. For instance, when former Senator Jesse Helms decried the millions spent researching AIDS, a disease which kills fewer Americans than heart disease or cancer, he was technically correct, but also incredibly short-sighted. AIDS researchers study viruses and how they break down the human immunological system, so what they learn has instant crossover implications for virology and immunology. With deadly viruses locked in a perpetual arms race against human ingenuity, aren't we glad all that money was spent on AIDS research?
What too few of us understand is that when scientists publish their findings in order to get the credit they're due, other scientists read those publications, then use the information in their own projects. And we all profit thereby.
Back to the defense-space program relationship: When Sputnik began orbiting, as explained in Tom Wolf's "The Right Stuff," the U.S. military was very concerned with potential Soviet domination of "the high ground." Our space program has its historical roots in military necessity, which in and of itself is enough to make some of us despise it. It's no coincidence that many of the same people who would de-fund NASA also think too much is spent on our military.
Also, while scientists have said for years that unmanned missions were safer and cheaper than manned ones, Congress wouldn't fund exclusively unmanned programs. That's because we, the taxpaying public, has never had the enthusiasm for robots that we've had for our astronauts. Or, as appropriations committee members used to remark, "No bucks without Buck Rogers."
All that notwithstanding, increased human productivity through the side benefits of the first four-and-a-half decades of human space exploration have expanded human knowledge while creating bonus wealth to help pay for all the things we need on Earth, including feeding orphans and keeping senior citizens from having to eat dog food. Who knows what unanticipated benefits lurk within a Mars colony?