Apollo 11 — first footsteps on the Moon
On 20 July 1969 Apollo 11's lunar module Eagle landed on the Sea of Tranquility. Hours later Neil Armstrong became the first person to step onto the Moon, watched live on television by about 600 million people.
Available views: Orbit ✓ · Sky — (not visible in the sky)
The story
At 20:17 UT on 20 July 1969 the lunar module Eagle settled onto a broad plain on the Moon called the Sea of Tranquility. The last minutes were tense. The computer sounded an overload alarm, code 1202, several times, and the automatic guidance was steering toward a field of large boulders. So Neil Armstrong took over and flew on by hand to find level ground. After touchdown he reported: “Houston, Tranquility Base here. The Eagle has landed.”
Fuel was also short. At the time, mission control calculated that about 25 seconds of fuel remained. Later, more careful analysis suggested the real figure was closer to 50 seconds. Either way, the margin was less than a minute. That is why Charlie Duke, speaking for mission control, answered the landing call with: “You got a bunch of guys about to turn blue. We're breathing again.”
About six and a half hours later, at 02:56 UT on 21 July, Armstrong climbed down the ladder and left the first footprint on the Moon. His words were: “That's one small step for man, one giant leap for mankind.” The moment was broadcast live on black-and-white television around the world. An estimated 600 million people, about a fifth of the world's population at the time, watched. Buzz Aldrin followed him down nineteen minutes later.
The two men stayed on the Moon for 21 hours 36 minutes, and spent 2 hours 31 minutes of that outside the lander. In that short time they gathered 21.5 kg of rock and soil and set up experiments such as a seismometer and a laser reflector. Meanwhile Michael Collins circled the Moon alone in the command module, waiting for them. The orbit view reproduces the path from Earth to the Moon and the moment of landing.
Mission goals
Apollo 11 came out of the space race between the United States and the Soviet Union. When the Soviet cosmonaut Yuri Gagarin became the first person in space in 1961, President Kennedy announced that America would land a person on the Moon within the decade. Eight years later the promise was kept. The Soviets built their own giant Moon rocket, the N-1, but all four of its launches between 1969 and 1972 failed. The project began as a contest, yet what lasted longest was the science.
Apollo 11 through 17 brought back 382 kg of lunar rock in all. Studying it, scientists found that Moon rocks are remarkably similar to Earth rocks in several ways. That evidence helped establish the giant-impact hypothesis. In this idea, a body about the size of Mars struck the young Earth long ago, and the debris thrown out gathered to form the Moon. It is the explanation most widely accepted by scientists today.
The laser reflector left at the landing site is still in use. Scientists fire a laser from Earth and time how long the reflected light takes to return, which gives the distance to the Moon to within a few centimetres. Decades of these measurements show that the Moon is moving away from Earth by about 3.8 cm every year. That is roughly as fast as a fingernail grows.
Mission chronology and background
The landing site was chosen from photographs taken by Apollo 8 and 10, which had flown to the Moon earlier. The south-western part of the Sea of Tranquility was picked because it was flat and the approach was safe. Eagle, however, came down a few kilometres west of its target. As a result, right after landing even mission control did not know exactly where Eagle was, and Collins, orbiting overhead, could not spot it through his sextant.
Eagle was built in two parts. The upper part, the ascent stage, carried the two men off the Moon, met the command module and was then cast off; what happened to it afterwards is not known for certain. The lower part, the descent stage, served as a launch pad and still stands at the site. The crew left behind a patch and medals honouring American and Soviet space travellers who had died, and a small silicon disc carrying goodwill messages from leaders of 73 countries.
The Apollo programme landed on the Moon six times, ending with Apollo 17 in December 1972, and twelve people walked on its surface. For more than half a century afterwards, no one travelled beyond the orbits close to Earth. In April 2026 Artemis II carried a crew around the Moon and back. The first Moon landing in over fifty years is planned for Artemis IV.
Other milestones of this mission
Where to see it — sky and simulator
The Sea of Tranquility is a dark plain a little to the right of the Moon's centre, close to its equator, as seen from the northern hemisphere. This dark patch is easy to see with the naked eye or binoculars. The lower half of the lander, which still stands at the site, is far too small for any telescope on Earth. Instead, the Lunar Reconnaissance Orbiter, circling the Moon since 2009, has photographed the lander and the trails the astronauts left.
Select the Moon in the sky view to see its height, direction and phase from where you are. Move the date to 20 July 1969 and the view reproduces the Moon on landing day, a crescent growing toward half full. NASA has made the radio recordings and video of the landing public, so the 1202 alarm and the words “We're breathing again” can still be heard in the original voices.
See this for yourself — replay the moment in the orbit view
FAQ
How much fuel was left at landing?
Mission control calculated about 25 seconds' worth at the time; later analysis suggests it was closer to 50 seconds. Either way, the margin was under a minute.
How long were they on the Moon?
21 hours 36 minutes, of which 2 hours 31 minutes were spent outside the lander.
Is any of the equipment still in use?
The laser reflector is still used to measure the distance to the Moon to the centimetre. The seismometer stopped working in August 1969.
Can the landing site be seen?
Not with any telescope on Earth. Photographs from the Lunar Reconnaissance Orbiter, which circles the Moon, show the descent stage and the trails of footprints.
Related
- Apollo 11 launch
- Artemis III — docking test in Earth orbit
- Gagarin — first human in space
- The Moon — object index
- Earth — object index
Times and figures are approximate — verify with official sources when planning travel. Simulation uses J2000 mean elements.