A typical sentiment expressed on the 40th anniversary of a historic milestone is to observe how far humanity has progressed since then.

Today marks the four decades that have passed since Neil Armstrong set foot on the moon. In terms of mankind venturing off toward our galaxy's other worlds, it's disheartening to note that we've barely moved at all.

There are reasons for that, of course, some of them even good ones. The catastrophic loss of life in the Challenger and Columbia shuttle disasters injected a great deal of caution in the National Aeronautics and Space Administration approach to risky endeavors. And the mounting costs of the space program in the context of competing demands on American resources have not extinguished the space-exploration flame but has certainly put a damper on it.

But today is not a time for reflecting on the perils. Rather, the U.S. should take note of everything space exploration has given us in the past, and its bright promise for the future.

Of course, the legacies the space program already yielded include our computers and many other elements among our technological advancements. And the unmanned missions to Mars and beyond have expanded the boundaries of science immensely.

However, it's the urge to continue manned missions that must be reinvigorated. The drive to explore our world and our universe is one of the impulses that set human beings apart; our ambitions for exploration have fueled research, technology and more.

Forty years after the heroes of Apollo 11 made their indelible mark, their achievement should be seen as a foundation, not as a footnote.

Yes, we have other, more pressing problems here on Earth. But that's no cause to abandon the opportunity for learning, international cooperation and exploration that a robust space program represents.