On this date, Apollo 11 astronauts Buzz Aldrin and Neil Armstrong landed their moon module on a broad dark lunar lava flow, called the Sea of Tranquility. Six hours later, Neil Armstrong became the first human being to walk on the surface of a world beyond Earth. Today – July 20, 2015 – is the 46th anniversary of this great achievement. Armstrong and Aldrin spent 21.5 hours on the moon’s surface. They collected 47.5 pounds (21.5 kg) of moon rocks for return to Earth. Then they blasted off in their module from the lunar surface to meet up with Michael Collins in the command module orbiting overhead. They returned safely to Earth and landed in the Pacific Ocean on July 24.
In the video below, you can hear the excitement in Armstrong’s voice at the successful landing of Eagle on the moon’s surface as he says:
Tranquility Base here. The Eagle has landed.
An early concern of space engineers had been that the lunar regolith, the fine soil covering the moon, would be soft like quicksand. There was some fear that the Eagle lunar module would sink after landing. Hence Armstrong’s comment about the depth of the footpads in the lunar soil as he descended the ladder before stepping onto the moon.