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Physics LibreTexts

3.20 Moon Landings

The flights to the Moon constituted one of the greatest human adventures of all time. The Cold War politically motivated the United States to beat the Russians to the Moon. The fear lurking in the background was nuclear weapons in space. Since the launch of Sputnik in 1957, the Soviets had gained a lead in the space race. They racked up an impressive string of firsts: first man in space, first woman in space, first space walk, first spacecraft landed on another planet. President John F. Kennedy captured the imagination of the American people and instigated an ambitious space program that put the first humans on the Moon in 1969. Before humans landed on the Moon, both the U.S. and U.S.S.R. performed extensive unmanned exploration. The Soviets sent the first of their Luna spacecraft as early as 1959. A series of American Ranger and Surveyor missions through the 1960s impacted, and later landed on, the lunar surface. The Apollo program was initiated with the express purpose of taking humans to the Moon and back. 


President John F. Kennedy speaks at Rice University and delivers his famous "We choose to go to the moon" speech. Click here for original source URL


Neil Armstrong (1930?2012), commander of NASA's Apollo 11 mission, descends the ladder of the Apollo Lunar Module (or Lunar Excursion Module, LEM) to become the first human to set foot on the surface of the Moon. Click here for original source URL.

On July 20, 1969, half a billion television viewers breathlessly watched Neil Armstrong's first step onto the Moon. The astronauts stood out in the bright, harsh sunlight as they bounced along uncannily in the Moon's low gravity. Buzz Aldrin described their landing spot, the Sea of Tranquility, as "magnificent desolation." They stayed on the surface for little more than two hours, then returned to the lunar module and blasted off the surface. A few days later, the astronauts successfully splashed down in the Pacific. 

The priority of the first Moon landing was simply getting the astronauts to the Moon and back safely — there wasn't much time for science. But five more Apollo missions successfully landed on the Moon. They returned thousands of photographs, planted seismometers to detect "Moonquakes," and studied the lunar topography, heat flow, magnetic field, and radiation environment. Astronauts also brought 382 kilograms (842 pounds) of Moon rocks and soil back to the Earth. New generations of scientists are still studying these samples, over thirty years later. Data from the Apollo program led to major scientific advances such as the theory of the Moon's origin and the age of the Solar System. The last Moon landing was in 1972, and humans have not been back since. 

Conspiracy theorists occasionally revive the idea that the Moon landings were faked. Most of the "evidence" for this hoax is based on misconceptions which result from not understanding the lunar environment — for example, things like dust and the American flag move differently on the Moon than we're accustomed to on Earth because they're in a vacuum. Proponents of the hoax point to unusual features in Apollo photographs, but they can easily be explained by the unique conditions at the lunar surface. For example, the reason there are no stars visible in most photographs taken on the surface of the Moon is that the lunar surface is so bright it overwhelms the faint stars in the background. Likewise, details are visible in shadows because the bright lunar ground reflects light everywhere, even in the Sun's shadow. Every purported claim by conspiracy theorists is easily debunked using common sense and knowledge of the lunar environment. Not only are there personal accounts by living astronauts that were on the Moon, we also have more than eight hundred pounds of Moon rocks. These are nothing like any terrestrial rocks, and hundreds of scientists all over the world have verified their lunar origin. The data from the Moon would be extremely difficult — if not impossible — to fake. In fact, it would have been easier for NASA scientists to go to the Moon in 1969 than to fake it.

More than forty years after the Apollo program, memories have faded and most Americans were not alive when astronauts last set foot on the Moon. Even at the time, attention faded; the last three Moon landings were scrapped and NASA's budget went into reverse as the country struggled with the Vietnam War and social unrest. But it was an extraordinary human achievement. The Apollo program was the most complex and challenging technical undertaking in history. Remember that your smartphone is a hundred times more powerful than the computer that guided Apollo to the Moon! The twelve astronauts who landed on the Moon are still the only people to set foot on another world.