Apollo 11 Anniversary And A Morning Moon Invitation

Astronaut Edwin E. Aldrin Jr., lunar module pilot, is photographed during the Apollo 11 extravehicular activity (EVA) on the lunar surface. In the right background is the lunar module. On Aldrin’s right is the Solar Wind Composition (SWC) experiment, already deployed. Credit: NASA

48 years ago today, humans walked on the moon for the first time. Neil Armstrong and Buzz Aldrin landed in the Sea of Tranquillity, an ancient lava plain, at 3:18 p.m. CDT July 20. About 6 ½  hours later at 9:56 p.m., Armstrong emerged from the lunar module; Aldrin followed some 20 minute later. The guys spent the next two and a half hours observing, photographing, gathering samples and setting up experiments. Aldrin return first to the module before Armstrong. 21 hours and 36 minutes after landing, the duo fired the ascent stage engine and returned to the command service module and fellow astronaut, Michael Collins.

This is how the moon appeared the evening that people first walked on the moon. The location near the terminator (the curve of at left where the sun is just rising over the lunar landscape) was important because Armstrong and Aldrin needed shadows to clearly read the landscape. Created with Stellarium

Beside experiments and equipment, Armstrong and Aldrin left commemorative medallions bearing the names of the three Apollo 1 astronauts who has lost their lives in a launch pad fire in January 1967, and two cosmonauts who also died in accidents, on the moon’s surface. A one-and-a-half inch silicon disk, containing micro miniaturized goodwill messages from 73 countries, and the names of congressional and NASA leaders, also stayed behind.


Footage from the Apollo 11 moonwalk with Aldrin and Armstrong that was partially restored in 2009

In recreating the moon phase, I was curious about lighting at the six Apollo landing locations. To provide the crew with the optimum visibility during the final phase of the descent and landing, the local sun angle had to be within 5° and 14° above the eastern horizon behind the lunar module lander. These lighting conditions allowed the crew to evaluate the landing area they were headed into and select the best location for touchdown.


Picking up a dropped hammer on the moon is no easy task!

If the lighting angle was too high, the view would have been washed out; too low and long shadows would have hidden much of the view. Moon phases varied for each landing from waxing crescent to waxing gibbous, but the angle and distance from the terminator always remained within that range.

Low sun angles also mean more moderate temperatures, the reason NASA planned landings in the early lunar morning before the sun had time to heat up the ground. Around local noon, the surface temperature’s around 250° F (120 C) and drops to around 200° below (-130 C) overnight. Picture yourself hiking in a desert landscape. You’d not only appreciate being there in the morning when temperatures are on the cool side but also when shadows make the landscape easier on the eye.

Drawing of the moon by Galileo. The Italian astronomer first observed the moon on November 30, 1609.

Think how many hundreds of thousands of years our ancestors looked up and wondered about the moon. Most people from the ancient Greeks through the time of Galileo considered the Earth to be imperfect (they were right about that!) and all other celestial bodies flawless perfection. That changed when the Italian astronomer Galileo trained his 20x scope on the moon in the fall of 1609 to begin an in-depth study. He found lots of imperfections. Mountains, valleys, peaks and “dark and light spots” (craters). Indeed, the moon looked a lot like Earth in all its beautiful imperfectitude.

This will be the scene facing northeast on Friday morning. The thin moon, with nice earthshine, joins the bright winter stars Aldebaran, Capella, Betelgeuse and Venus. Venus will stand about 14° or one and a half fists above the moon. Created with Stellarium

We can visit the moon anytime without the need for a bulky spacesuit or the lighting angle to be just so. Tomorrow morning, we’ll have the chance to catch a very thin, “old” crescent low in the northeastern sky about 40 minutes before sunrise. Look for it a little more than a fist below and left of Venus.

2 Responses

  1. caralex

    I remember watching it live on TV as a teenager on a school trip to France!

    It makes me very sad to have to acknowledge that there are a huge number of people out there – many who weren’t even born in 1969 – who think that this, mankind’s greatest achievement to date, was one big hoax. And sadly, their numbers are growing.

    1. astrobob

      Carol,
      It’s a sign of the Internet era and the lack of critical thinking skills to process so much information. Learning these should be an essential part of studies from middle school on up.

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