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Apollo 11 Moon landing
July 20, 1969· Event· Transport & space
Well documentedSolid records, physical evidence or scientific consensus.
The first crewed Moon landing: Neil Armstrong and Buzz Aldrin walked on the surface while Michael Collins orbited above.
See it on the Technology & Medicine map →How it works
A Saturn V rocket launched the three astronauts from Florida on July 16, 1969. On July 20 the lunar module Eagle landed in the Sea of Tranquility with little fuel to spare, after its computer flashed overload alarms. Hours later Armstrong stepped out: 'That's one small step for man, one giant leap for mankind.' The two spent about two and a half hours outside, collected 21.5 kg of rock, and splashed down safely on July 24.
Why it mattered
It met Kennedy's 1961 goal and effectively ended the Space Race. Twelve men walked on the Moon by 1972, still the only other world humans have visited.
How we know
Mission recordings and telemetry, 382 kg of samples from all Apollo landings studied worldwide, Soviet tracking, mirrors on the surface still used for laser ranging, and 2009 orbiter photos of the sites.
Still unknown or debated
Armstrong said he meant 'one small step for a man'; whether the 'a' was lost in transmission is still argued. Hoax claims are contradicted by all the evidence.
Connections (6)
▸Newton's Principia supplied the orbital mechanics for the Apollo 11 Moon landingWell documented
The connection
Newton's laws of motion and gravity, published in 1687, are what NASA used to plan Apollo's path: the burn to leave Earth orbit, the coast to the Moon, entry into lunar orbit and the return. Einstein's corrections were too small to matter. Newton himself imagined a cannonball fired fast enough to circle the Earth.
When and how
Principia: London, 1687. Apollo trajectories: computed in the 1960s by NASA and MIT engineers and mathematicians, including NASA's Katherine Johnson.
How we know
Apollo's navigation documents and its guidance software, now public, are built on Newtonian equations of motion and gravity.
Debates and open questions
Not disputed. Newton's physics still needed two centuries of refinement by Euler, Lagrange, Gauss and others, plus computers, before it could steer a spacecraft.
▸Television carried live pictures of the Apollo 11 Moon landingWell documented
The connection
A small black-and-white camera on the lunar module sent live pictures of Armstrong's first step. Its unusual format had to be converted for broadcast at receiving stations in California and Australia, which cost picture quality. An estimated 530 to 650 million people, about a sixth of humanity, watched live.
When and how
Sea of Tranquility, July 20, 1969, US time (July 21 in universal time); signals received at Goldstone, California, and at Honeysuckle Creek and Parkes in Australia, then relayed worldwide.
How we know
Broadcast recordings survive, and NASA, network and station logs document the relay; Parkes's role was later dramatized in the 2000 film 'The Dish.'
Debates and open questions
NASA's original higher-quality tapes of the broadcast were apparently erased and reused; a 2009 NASA search concluded they were lost.
▸Integrated circuit (microchip) flew in the guidance computer of the Apollo 11 Moon landingWell documented
The connection
The Apollo Guidance Computer was one of the first computers built from integrated circuits: about 2,800 identical chips, each holding a few transistors. It steered the spacecraft and helped fly the landing. When it overloaded during descent, flashing '1202' alarms, its software dropped low-priority tasks and kept running.
When and how
MIT Instrumentation Laboratory in Cambridge, Massachusetts, 1961–1969, led by Charles Stark Draper, with software led by Margaret Hamilton; chips from Fairchild and Philco.
How we know
The computer's design documents and full software listings are public, and surviving units have been restored to working order.
Debates and open questions
How much Apollo and Minuteman missile purchases drove the early chip industry, versus commercial demand, is debated; claims that Apollo bought most US chips are disputed.
▸V-2 rocket led, via von Braun, to the Apollo 11 Moon landingWell documented
The connection
Wernher von Braun led Germany's V-2 program, the first large liquid-fuel rocket, built partly by concentration-camp prisoners; by most estimates, more of them died making it than its attacks killed. In 1945 the US brought him and over 100 of his engineers to America. In the 1960s his team designed Apollo 11's Saturn V, scaling up that know-how.
When and how
Peenemünde, Germany, 1936–1945; Fort Bliss, Texas, from 1945; then Huntsville, Alabama, where NASA's Marshall Space Flight Center developed the Saturn V in the 1960s.
How we know
Records of Operation Paperclip, the US program that recruited them, and NASA histories document the team's move from Peenemünde to Huntsville; the Saturn V's giant F-1 engines, though, were designed by the US firm Rocketdyne.
Debates and open questions
How much von Braun knew of and bore responsibility for the forced labour is debated, as is the US decision to overlook his Nazi Party and SS membership.
▸Yuri Gagarin, first human in space spurred the US goal of the Apollo 11 Moon landingWell documented
The connection
Gagarin's flight on April 12, 1961, five days before the failed Bay of Pigs invasion, left the Kennedy administration looking for a dramatic win. On May 25, 1961, Kennedy asked Congress to land a man on the Moon 'before this decade is out.' Apollo 11 met the goal with five months to spare.
When and how
Washington, April–May 1961: on April 20 Kennedy asked Vice President Lyndon Johnson where the US could beat the Soviets in space; a crewed Moon landing was the answer.
How we know
Kennedy's memo, Johnson's reply and the May 25 speech are in the presidential archives and refer directly to Soviet space successes.
Debates and open questions
Kennedy's commitment wavered: recorded meetings show doubts about the cost, and in 1963 he proposed a joint Moon mission with the Soviets at the United Nations.
▸Apollo 11 Moon landing used expendable rockets, unlike Reusable rocketsWell documented
The connection
Each Saturn V flew once: its stages fell into the ocean or were left in space, and only the small capsule came home. A launch cost about $185 million in 1969 dollars, over $1 billion today. The Space Shuttle was partly reusable but costly to refurbish; modern reusable rockets land their boosters and fly them again.
When and how
Saturn V launches from Florida, 1967–1973; Blue Origin's first suborbital booster landing in Texas, November 2015; SpaceX's first orbital-class booster landing at Cape Canaveral, December 21, 2015.
How we know
NASA budget records document Apollo's costs; launch records show some SpaceX boosters reflown more than 20 times.
Debates and open questions
How much reuse lowers costs is debated, since SpaceX does not publish full figures; whether expendable rockets were a necessity of Apollo's era or a choice is also argued.