On 20 July 1969, humans set foot on another world for the first time. The Apollo 11 mission was the culmination of nearly a decade of work by hundreds of thousands of people, and its details remain remarkable.
Key takeaways
- Apollo 11 launched on 16 July 1969 and landed on the Moon on 20 July.
- Neil Armstrong and Buzz Aldrin walked on the surface, while Michael Collins orbited above.
- They landed in the Sea of Tranquility and spent about two and a half hours outside.
- The crew brought back about 21.5 kilograms of lunar samples.
- A mirror-like device left on the surface is still used by scientists.
The crew
Commander Neil Armstrong, lunar module pilot Edwin "Buzz" Aldrin and command module pilot Michael Collins were the three astronauts. Armstrong and Aldrin descended in the lunar module, called Eagle, while Collins stayed in orbit in the command module, Columbia, and waited for them to return.
Launch and journey
A Saturn V rocket, still the most powerful rocket to have flown successfully, launched the spacecraft from Kennedy Space Center in Florida. The journey to the Moon took about three days. After entering lunar orbit, Armstrong and Aldrin separated in Eagle and began the descent.
The landing
The landing was tense. Alarms from the guidance computer sounded during the descent, which were later explained as the computer being overloaded with tasks, and Armstrong took manual control to avoid a boulder-strewn area. Eagle touched down with only a small amount of fuel left, at about 4:17 p.m. Eastern time. Armstrong radioed, "Houston, Tranquility Base here. The Eagle has landed."
First steps
Armstrong stepped onto the surface about six and a half hours later, at around 10:56 p.m. Eastern time, saying, "That's one small step for man, one giant leap for mankind." He later said he intended to say "for a man", and there has been discussion about whether the "a" was lost in transmission. Aldrin joined him shortly after. An estimated 600 million people watched the broadcast worldwide.
On the surface
The two astronauts spent about two and a half hours outside. They planted a US flag, set up scientific experiments, took photographs and collected rocks and soil. They left a plaque stating that they came in peace for all mankind, along with other items, including a patch commemorating the Apollo 1 crew.
Science left behind
They set up a seismometer, a solar wind experiment and a laser retroreflector, an array of mirrors that reflects laser beams back to Earth. Scientists still bounce lasers off the retroreflector to measure the distance to the Moon very precisely, and these measurements have shown that the Moon is moving away from Earth by a few centimetres a year.
The return
After about 21 hours on the surface, Eagle lifted off, rejoined Columbia, and the crew returned to Earth, splashing down in the Pacific Ocean on 24 July 1969. The astronauts were kept in quarantine for a few weeks as a precaution. The Moon rocks they brought back have been studied for decades and have helped scientists understand the Moon's age and origin.
Computing power
The Apollo guidance computer had only a few kilobytes of memory and far less processing power than a modern smartphone. Its success came from careful programming and engineering, led in part by teams such as that of Margaret Hamilton at MIT.
The Apollo programme
Apollo 11 was the first of six missions that landed astronauts on the Moon between 1969 and 1972. In total, twelve people have walked on the Moon. No humans have returned since Apollo 17, though new missions are planned.
Why the Moon, and why then
The Apollo programme grew out of the Cold War competition between the United States and the Soviet Union. The Soviet Union launched the first satellite in 1957 and sent the first person into space in 1961. Weeks later, President John F. Kennedy told the US Congress that the nation should commit to landing a person on the Moon and returning them safely before the end of the decade. The goal combined scientific ambition, national prestige and technological challenge, and it drew on the work of around 400,000 people across government, universities and companies.
The lunar module and the descent
The lunar module, Eagle, had two stages. The descent stage held the landing engine, fuel tanks and legs, and stayed on the Moon. The ascent stage carried the astronauts back into orbit. Because there was no backup for the ascent engine, its reliability was critical, and engineers designed it to be as simple as possible. During the descent, Armstrong looked out of the window and saw that the planned landing spot was strewn with boulders. He flew horizontally for a short distance to find a smoother area while fuel ran low, which made the final minutes of the landing especially tense.
What the samples revealed
The astronauts collected about 21.5 kilograms of rock and soil on Apollo 11, and later missions brought back several hundred kilograms more. Analysis showed that the Moon's rocks are similar to Earth's mantle in some ways but contain far less water and few volatile elements. Radioactive dating gave ages of around 3.6 to 4.4 billion years, showing that the lunar surface is ancient. These findings supported the giant-impact hypothesis, the leading explanation that the Moon formed from debris after a Mars-sized body collided with the early Earth. Samples are still studied today with new instruments, and some have been kept sealed for future techniques.
The wider legacy
Apollo drove advances in computing, materials, engineering and project management, and it created a lasting cultural image of Earth seen from space. Photographs taken during the Apollo missions, including Earthrise from Apollo 8 and the Blue Marble from Apollo 17, shaped how many people thought about the planet. After Apollo 17 in 1972, no crewed mission went beyond low Earth orbit for decades, mainly because of cost and shifting priorities. Today, space agencies are planning new crewed lunar missions, with the aim of building a longer-term presence and preparing for journeys farther out.
Frequently asked questions
Was the landing faked?
No. Evidence includes independent tracking from other countries, retroreflectors still in use, lunar samples studied worldwide and orbital images of landing sites.
How far is the Moon?
About 384,000 kilometres on average.
Who was the first woman to go to the Moon?
None has yet. Future missions aim to include women.
Did the American flag really fall over when Eagle took off?
Aldrin reported seeing the flag knocked over by the exhaust from the ascent engine. Later missions placed their flags farther from the lander. Images from orbit show that some Apollo flags are still standing at other landing sites.
Can the landing site be seen from Earth?
No telescope on Earth can see the equipment on the Moon, because it is far too small. Orbiting spacecraft, such as NASA's Lunar Reconnaissance Orbiter, have photographed the landing sites, showing the descent stages, tracks and equipment.
Why haven't people returned to the Moon since 1972?
Apollo was expensive and was driven by a particular political moment. After the first landings, priorities shifted toward the space shuttle, space stations and robotic exploration. New programmes now aim to return crews to the Moon with international partners.
Sources and further reading
Written by
FactNest Editorial Team
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