When Neil Armstrong stepped onto the moon, the sky was the limit for space travel. Short-term priorities have changed now, but the challenge remains.
Exploration of space is a basic human drive
The death on Saturday of Neil Armstrong, at 82, reminds us how much has changed since the heady 1960s, when he became the first man on the Moon.
In 1969, scientific and engineering "progress" - a word generally used, then, without irony - had transformed much of the planet and was promising new worlds, beginning with the nearest celestial body of all, the one that had for millennia tantalised earthbound humanity no less than its tides tugged at the oceans.
But in recent years, manned space travel has reached a perigee. The last Moon landing was 40 years ago this December, the US Space Shuttle was retired last year and the Obama administration killed its replacement. And the International Space Station has funding only through 2020.
Look more closely, however, and you can see that space exploration, including manned flight, is far from dead. The rover Curiosity is sending back vivid new pictures of the Martian surface. China's space agency has spoken of a lunar base as a jumping-off point for a manned Mars mission. "Space tourism" is a reality and ready to expand rapidly.
True, the plan to mine asteroids for precious minerals is still over the horizon of technical capabilities. But so was a Moon landing, once. Indeed, in an era when governments are scrimping, it is natural that the private sector be relied upon to find new reasons and new ways to reach past Earth's atmosphere.
To be sure, the next steps in space will be dauntingly complicated, costly and slow. The first humans dispatched to Mars may well go in the full knowledge that it will be a one-way trip. That there would be eager volunteers for such a voyage reflects how deeply the urge to explore is rooted in the human spirit.
As for more distant destinations … well, Voyager 1, launched in 1977 to study the outer limits of the solar system, is only now preparing to pass that boundary.
Each generation faces - and welcomes - its own challenges. For decades, Armstrong personified the natural drive to "boldly go". He is gone, but human nature has not changed.
"We choose to go to the Moon," US President John F Kennedy said in 1962, " … because that goal will serve to organise and measure the best of our energies and skills." He spoke in the context of the Cold War's "space race", but today those words exhort humanity to work together, transcending national rivalries to rise to the next challenge.