On this day 50 years ago, the Apollo astronauts who were being hailed as heroes didn't have all that much to do. They were a central part of a mission watched around the world, one which would define the century that followed, and which required intensive intelligence and ingenuity beyond our imagining – but at the moment they were engaged in housekeeping and sleeping.

Now is the anniversary of perhaps the most unusual part of the Moon mission: that intermediate period after astronauts had completed the all-important liftoff, and as they waited, quietly drifting through space, on their way to the Moon.

The launch happened on 16 July, 1969. The landing happened four days later, on 20 July.

Between those days were a strange and eerie silence, filled with activities that would be humdrum were they not happening inside of the most ambitious activity ever launched by humankind.

As the three astronauts – Neil Armstrong, Buzz Aldrin and Michael Collins – floated serenely through space, they began to think about what would happen at Earth. They were travelling at immense speed which meant that they had left the Earth quicker than many of those who had come along to watch would be able to get out of the parking lots they'd viewed it from.

Apollo 11 mission: Historic first moon landing in photos Show all 19 1 /19 Apollo 11 mission: Historic first moon landing in photos Apollo 11 mission: Historic first moon landing in photos Buzz Aldrin walks on the moon in an image taken by Apollo 11 commander Neil Armstrong. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Wernher von Braun in front of the Saturn V rocket, being readied for the lunar mission, in Cape Canaveral on 10 July 1969. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos The Saturn V rocket carries the Apollo 11 into space on 16 July 1969. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos The crew (from left): Neil Armstrong, Michael Collins and Buzz Aldrin. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos The launch control centre watches the rocket take off on 16 July 1969. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos The American flag flutters as the Apollo 11 heads into space. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos The interior of the landing module with its pilot, Buzz Aldrin, during the mission. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Earthrise viewed from the lunar landing module. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Flight controllers at the Space Centre in Houston as the landing module descends to the surface of the moon. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos The landing module in lunar orbit on 20 July 1969. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Buzz Aldrin's boot and footprint in lunar soil. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Buzz Aldrin standing by the US flag planted on the surface of the moon. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Crater 308 on the moon. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Buzz Aldrin’s boot print in the moon’s dust. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Aldrin deploys the passive seismic experiment package. To the left of the US flag in the background is the lunar surface television camera. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Buzz Aldrin stands next to a lunar seismometer. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Neil Armstrong works near the lunar landing module. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos Members of the Apollo 11 crew wait to be picked up by a helicopter from the USS Hornet on 24 July 1969. Nasa/EPA Apollo 11 mission: Historic first moon landing in photos US president Richard Nixon welcomes the Apollo 11 astronauts, confined to a mobile quarantine facility, aboard the USS Hornet. Nasa/EPA

"As we proceed outbound, this number will get smaller and smaller until the tug of the Moon's gravity exceeds that of the Earth's and then we will start speeding up again," Collins later said. "It's hard to believe that we are on our way to the Moon, at 1200 miles altitude now, less than three hours after liftoff, and I'll bet the launch-day crowd down at the Cape is still bumper to bumper, straggling back to the motels and bars."

Soon after that, they would get to the main work they had to do during the journey, which began early. Collins was assisted by his two colleagues to separate the command module from the third stage of the Saturn rocket, and then spin it around and connect with the lunar module known as Eagle that would be used to descend to the service.

"This of course was a critical maneuver in the flight plan," Aldrin later said. "If the separation and docking did not work, we would return to Earth.

"There was also the possibility of an in-space collision and the subsequent decompression of our cabin, so we were still in our spacesuits as Mike separated us from the Saturn third stage. Critical as the maneuver is, I felt no apprehension about it, and if there was the slightest inkling of concern it disappeared quickly as the entire separation and docking proceeded perfectly to completion.

"The nose of Columbia was now connected to the top of the Eagle and heading for the Moon as we watched the Saturn third stage venting, a propulsive maneuver causing it to move slowly away from us."

After that was completed, the really stressful work was over. The astronauts could get to sitting out the journey, waiting until they reached their distant target.

By the next day, the astronauts were able to darken the windows with covers that served as curtains, and try and get some sleep as the command module slowly rotated them through space. They'd spend the following days doing chores and talking with Earth.

During those intermediate days, there was considerably less activity on board the craft. Nasa's official timeline – which gives detailed information on absolutely everything the crew did – lists only a few activities over the course of the 17th and 18th, as the three astronauts floated through space.

On 17 July, for instance, the crew simply conducted three TV transmissions and did one small burn of their engines to correct their course. The day after, there was another TV transmission and a quick journey into the lunar module and back so that it could be inspected ahead of the landing.

But the day later, as they approached the Moon and, the atmosphere would change.

"Day four has a decidedly different feel to it," Collins later said. "Instead of nine hours' sleep, I get seven – and fitful ones at that.

"Despite our concentrated effort to conserve our energy on the way to the Moon, the pressure is overtaking us (or me at least), and I feel that all of us are aware that the honeymoon is over and we are about to lay our little pink bodies on the line."

At this point, everything became much more real: for one, the astronauts could once again see the Moon properly for the first time in nearly a day. They were now in orbit around the Moon, and it was vividly clear.

"The Moon I have known all my life, that two-dimensional small yellow disk in the sky, has gone away somewhere, to be replaced by the most awesome sphere I have ever seen," said Collins later.

"To begin with it is huge, completely filling our window. Second, it is three-dimensional. The belly of it bulges out toward us in such a pronounced fashion that I almost feel I can reach out and touch it. To add to the dramatic effect, we can see the stars again. We are in the shadow of the Moon now, and the elusive stars have reappeared."

At this point, the work to get ready to touch the lunar surface begins. The astronauts each carry out the checks that would try and ensure that the descent was as safe as possible, and that the lander that would carry them down was as secure as it could possibly be.