This year marked the 40th anniversary of two momentous events related to space exploration. One, the Apollo 11 moon landing on July 20, 1969, was a hallmark technological achievement. The other, the complete first run of Stanley Kubrick’s remarkable movie 2001: A Space Odyssey, vividly depicted author Arthur C. Clarke’s vision of humans traveling the solar system with abandon.

Much of the related flurry of reporting noted the stark differences between reality—people have not been back to the lunar surface since the December 1972 visit—and Clarke’s idea. Articles also asked whether the nation is sufficiently committed to devoting the $200 billion or so to returning to the moon 10 years from now and perhaps, after that, spending even more money to send humans to Mars.

As a 15-year-old, I found the 1969 moon landing enthralling. I also charted the entire Apollo missions, built scale models and dreamed of being the first Canadian astronaut. Humankind’s travels promised to propel science forward. But since then, my perception of the proper role for human space exploration has changed.

I would still jump at the chance to go into space. But I now recognize, as I testified to Congress almost a decade ago (coincidentally along with Buzz Aldrin, from Apollo 11), that doing so would be for the adventure, not for advancing science. The most scientifically exciting knowledge we can gain about the universe and the solar system will involve unmanned space vehicles, robotic devices and a lot less money than lofting Americans beyond Earth’s orbit.

Human spaceflight has proved inordinately costly and far more dangerous than the Apollo program’s successes led us to believe. Moreover, the associated difficulties are far more mundane than TV and movie science fiction suggest. We are not held back for lack of a warp drive, although fuel costs are a reason why unmanned flights are so much cheaper; missions that carry humans must drag along the paraphernalia required to keep them alive. The chief obstacle to visiting Mars is cosmic radiation. During the 18 months or so that a round-trip journey would take, astronauts would very likely receive a lethal dose of radiation.

Our ultimate destiny may be in the stars, but the limitations imposed by physics and our biology suggest that this future probably is to be reserved for our mechanical progeny—robots—or perhaps for computers that can get organic life rebooted on some distant locale.

In the near term we still crave adventure, and the desire to travel to, and perhaps to colonize, the moon and maybe Mars seems irresistible, if financially daunting. I am not against sending humans into space for that reason (and would also encourage consideration of one-way missions, which seem to be ultimately more fiscally practical). But we should separate funding for science from the diversion of a costly manned space program.

We also should not waste huge amounts on boondoggles such as the $100-billion International Space Station, which purported to offer useful science beyond mere experience with how humans can live 200 miles above Earth’s surface for extended periods.

The Apollo program taught us that we may conquer even enormous technological problems if the nation is willing to focus for however long it takes to solve them and to devote tremendous resources. We now face many such challenges, from climate change to energy independence, which we need to tackle even as we juggle our hunger for space travel.

I do not believe that this is a zero-sum game. Maybe there is money to do it all: to send humans into space, to do the best fundamental science we can do and also to address pressing problems here on Earth. But we can only do that if we are honest about the costs, and possible benefits, of science for humanity. And we must not pretend that a base on the moon or Mars is a panacea for any of our significant problems back home.

Note: This article was originally printed with the title, "Space, the Final Frontier?"