Fifty years ago today, not only our nation, but nearly all of humanity, was agog at the announcement: “The Eagle has landed.”

With those words, Neil Armstrong announced the Apollo 11 Lunar Module had arrived safely on the moon — an accomplishment once thought impossible.

A few hours later, Armstrong, leaving the module to set foot on another world for the first time in human history, uttered what has become an even more-famous phrase: “That’s one small step for a man … one giant leap for mankind.”

And so it was. The Apollo 11 moon landing on July 20, 1969, is considered by many to be man’s greatest achievement. It’s inarguable the accomplishment stands alone in its audacity. Humans had pondered the sky and space for eons, wondering. Now, finally, answers were available. It was not the completion of a process, but a start.

Surely, the technology that brought Armstrong, Buzz Aldrin and Michael Collins to the moon and back was a marvel. As a 20th-century technological gain, it’s rivaled only by the harnessing of the power of the atom and the digital advances behind the Internet, smartphones and wireless networks.

Such huge steps do not come without fears, without the potential for great calamity. In the case of the Apollo program, the biggest fear at the time was simply failure: That we wouldn’t get there first, or at all, along with the chance that our astronauts would lose their lives. So far, the downsides of space exploration haven’t really been experienced, except in those very few cases where lives have been lost to tragedies such as Apollo 1 and the Challenger and Columbia shuttle disasters. But science fiction thrives on the negative possibilities, from the idea of overwhelming space-based weapons to bringing back deadly life forms from another planet to accidentally leaving Matt Damon on Mars.

Conversely, the real-life positives of the Apollo missions are plentiful. The technology that needed to be created to sustain life aboard a relatively compact spacecraft traveling at immense speed through uninhabitable space has brought us far more than Tang breakfast drink. It also resulted in propulsion and safety advances that are used in all sorts of environments today. It furthered medical knowledge regarding the limitations of the human body and inventions that include prescription medicine delivery systems and what became heart pacemakers. It brought us the technology of freeze-drying foods; new fabrics used in everything from firefighting to athletic shoes to building construction; cordless tools; quartz-based clocks and watches; the beginning of solar technology used to power everyday items; chemical concoctions that are used to treat pool water and more. And, yes, it made discoveries that have been used to benefit the military, both in making weapons better and in protecting troops.

Note the main thrust of the space program — to expand mankind’s footprint beyond Earth — has stalled in some ways in the past five decades. We’ve sent robotic missions clear out of our solar system, and landed vehicles and more on Mars, but thus far, no humans.

As for our other great technological achievements, it’s yet to be determined whether the upside of the Internet, social media and instant worldwide communications will outweigh its potential harm. We can only hope that 100 years from now, “It’s the greatest invention since the poop emoji” won’t be a go-to phrase. And the accessibility of our data — and control of the systems the technology runs — by anyone capable of hacking into a digital site may yet prove these advances a bigger problem than benefit.

Nuclear energy’s downsides were apparent from the start. Its very purpose, initially, was to be used for mass violence, and it remains a threat in that way even today. And while positive uses for the vast energy have been applied, incidents such as Chernobyl and Three Mile Island have made clear the fear is warranted.

A funny thing, fear. It spurred both the invention of nuclear weapons — to keep Germany from developing such a powerful weapon first — and the space race that led to Armstrong’s famous quotes.

After Russia announced it had sent Sputnik 1 into orbit in 1957, and cosmonaut Yuri Gagarin became the first human in space in 1961, the fear of our nation’s biggest rival reaching the moon first drove the founding of NASA and the U.S. space program to respond in spades.

And that may reveal the real legacy of Apollo 11, what makes it our greatest achievement to date. Humans are ever wondering, ever questioning, ever looking to find, or do, the next thing. But to make that “giant leap”? THAT was audacity.

Fifty years ago, Apollo 11 showed us, when properly motivated, we’re capable of almost anything.