APE CANAVERAL — A half-century ago, in the middle of a mean year of war, famine, violence in the streets and the widening of the generation gap, men from planet Earth stepped onto another world for the first time, uniting people around the globe in a way not seen before or since.

Hundreds of millions tuned in to radios or watched the grainy black-and-white images on TV as Apollo 11’s Neil Armstrong and Buzz Aldrin set foot on the moon on July 20, 1969, in one of humanity’s most glorious technological achievements.

Astronaut Michael Collins, who orbited the moon alone in the mother ship while Armstrong proclaimed for the ages, “That’s one small step for man, one giant leap for mankind,” was struck by the banding together of Earth’s inhabitants.

“It was a wonderful achievement in the sense that people everywhere around the planet applauded it: north, south, east, west, rich, poor, Communist, whatever,” Collins, now 88, told The Associated Press in a recent interview.

That sense of unity did not last long. But 50 years later, Apollo 11 — the culmination of eight years of breakneck labor involving a workforce of 400,000 and a price tag in the billions, all aimed at winning the space race and beating the Soviet Union to the moon — continues to thrill.

For the golden anniversary, NASA, towns, museums and other institutions are holding ceremonies, parades and parties, including the simultaneous launch of 5,000 model rockets outside the installation in Huntsville, Alabama, where the behemoth Saturn V moon rockets were born. Apollo 11K and Saturn 5K runs are “go” at NASA’s Kennedy Space Center.

Armstrong, who expertly steered the lunar module Eagle to a smooth landing with just seconds of fuel left, died in 2012 at 82. Aldrin, 89, who followed him onto the gray, dusty surface, was embroiled recently in a now-dropped legal dispute in which two of his children tried to have him declared mentally incompetent. He has kept an uncharacteristically low profile in the run-up to the anniversary.

Back in 1961, NASA had barely 15 minutes of human suborbital flight under its belt — Alan Shepard’s history-making flight — when President John F. Kennedy issued the Cold War-era challenge of landing a man on the moon by decade’s end and returning him safely.

At the time, the Soviets were beating America at every turn in the space race, with the first satellite, Sputnik, and the first spaceman, Yuri Gagarin.

Kennedy’s challenge struck John Tribe, one of Cape Canaveral’s original rocket scientists, as impossible.

“We were in the rocket business, so we were doing some weird and wonderful things back in those days. But, yes, it was an unbelievable announcement at that time,” he said. “It took a lot of guts.”

NASA’s Project Mercury gave way to the two-man Gemini flights, then the three-man Apollo program, dealt a devastating setback when three astronauts were killed in a fire during a 1967 test on the launchpad. The pace was relentless amid fears the Soviets would get to the moon first.

Cape Canaveral’s Bill Waldron remembers working “seven days a week, 12 hours a day, six months at a clip” on the lunar modules.

The pressure was so intense leading up to the flight that Collins developed tics in both eyes.

Launch day — Wednesday, July 16, 1969 — dawned with an estimated 1 million people lining the sweltering beaches and roads of what had been renamed Cape Kennedy in memory of the slain president.

At 9:32 a.m. EDT, the 363-foot Saturn V rocket roared off Pad 39A, its astronauts hurtling toward their destination and destiny 240,000 miles away. The command module, Columbia, and the attached lunar module reached the moon three days later. The next day, July 20, Armstrong and Aldrin descended to the surface in the lunar module.

Collins wasn’t overly concerned about Armstrong and Aldrin getting down to the moon. Rather, he worried about them getting off the moon and back to the mother ship. He kept his fears to himself.

“If it was unthinkable, it was unsayable also,” Collins told the AP. “We never discussed or hinted at their getting stranded on the moon. I mean, we were not fools, and we knew darn well that a lot of things had to go exactly right for them to ascend as they were supposed to do.”

President Richard Nixon even had a speech prepared in case of disaster: “Fate has ordained that the men who went to the moon to explore in peace will stay on the moon to rest in peace.”

As it turned out, descent proved more alarming than ascent.

With minutes remaining to touchdown, the Eagle was rattled by one computer alarm then another. Caution lights flashed. But flight controllers had rehearsed that very scenario right before the flight, and the mission pressed on.

Then a boulder-strewn crater appeared at the target landing site, and Armstrong had to keep flying, looking for somewhere safe to put down.

Finally came word from Armstrong: “Houston, Tranquility Base here. The Eagle has landed.”

The time was 4:17 p.m.

“You got a bunch of guys about to turn blue. We’re breathing again,” Mission Control radioed back.

Armstrong descended the nine-rung ladder first, touching the lunar surface at 10:56 p.m. Aldrin followed him out 18 minutes later.

Working in one-sixth Earth’s gravity, they gathered rocks, set up experiments and planted an American flag stiffened with wires to make it look as if it were waving in the windless vacuum.

Five more missions would take men to the surface of the moon — Apollo 13 had to be aborted because of an explosion — before Project Apollo came to a premature end, the last three flights on the schedule scrapped.

The first lunar landing, at least, lifted America’s spirits — indeed, the planet’s — when it needed it.

“The Vietnam War, civil strife, racial strife, all kinds of stuff going on that was bad, which I wasn’t paying much attention to because I was working so hard in the space world. The Cold War and all of that,” said JoAnn Morgan, Apollo 11’s lone female launch controller. “It was such a demonstration of the power and the passion of our country.”

She added: “I mean, literally, we did exactly what JFK said we would do.”

Follow AP’s full coverage of the Apollo 11 anniversary at: https://apnews.com/Apollo11moonlanding

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