A significant part of our nightscape, the Moon has been the subject of myths, alternative conceptions and conspiracies for decades. Let’s take a look at some of the most popular alternative conceptions and why we’ve yet to colonise the big wheel of cheese in the sky.
The phases and the ‘dark side’
When the Moon is on the same side of Earth as the Sun, we cannot see it. This is because the illuminated side of the lunar surface is facing away from us, and only the shadowed side is visible. This is the phase called new Moon. When it is on the opposite side of Earth from the Sun, we see the fully illuminated side, and this phase is called full Moon. The periods between new Moon and full Moon are when we see it appear to change its shape or go through phases.
The dark side of the Moon is a common alternative conception. In fact, it’s not dark at all. During new Moon, the dark side is the illuminated side facing the Sun, which is technically called the far side. As the Moon orbits Earth, it always faces us with the same side, so its rotational period is equal to its orbital period. We had no idea what was on the other side of the Moon until the Soviet Union sent a space probe in the 1950s and returned with images. Speculation was that it could be the location of an alien base! More recently, NASA’s Deep Space Climate Observatory satellite captured a new image of the sunlit far side of the Moon with Earth in the background.
Moon phases from the Southern Hemisphere
The phases of the moon relate to the amount of light you see (waxing and waning) on the Moon’s surface as it orbits the Earth. This image shows the moon phases – from the new Moon (Whiro) to the full Moon (Te Rākaunui) – from the Southern Hemisphere.
This image is not to scale.
Moon, sun and Earth images courtesy of NASA.
The Moon in the southern versus northern hemisphere
Another common alternative conception is that, on the same day, different countries see different phases of the Moon. In fact, we see the same Moon phases simultaneously but upside down to one another. In New Zealand, we see the constellations upside down to those in the northern hemisphere. and the same applies to the Sun and Moon, we see them upside down also. When the Moon goes through its phases, New Zealand sees the crescent Moon appear on the left, get larger (waxing), reach full Moon and then fade out on the right (waning). The northern hemisphere sees the opposite. If you want to know what the Moon looks like in the northern hemisphere, all you need to do is a handstand!
Comparing sizes of the Moon
Have you ever noticed that the Moon appears larger when it is closer to the horizon compared to when it’s straight over our heads? There are two alternative conceptions often used to explain this unusual perspective. The first is that the atmosphere acts like a lens, magnifying the Moon’s size. The second is that objects such as buildings, trees or people in the foreground make the Moon look large by comparison. The actual reason for the difference in appearance is known as the Moon illusion - or more specifically a Ponzo illusion. When we look at the Moon on the horizon, our brains make the assumption that it must be further away than when the Moon is over our heads. Our brains then compensate for this assumption by increasing the Moon’s size. The same illusion happens with the Sun when it rises and sets.
Colonising the Moon
Often people think that there is no gravity on the Moon. There is gravity on the Moon, but it is a lot less than Earth, which is why, when watching astronauts walking on the Moon, they jump and float to the surface slowly. If humankind colonised the Moon, we would have to do lots of weightlifting to keep up our muscle mass. If you bench press 50 kg on Earth, you would have to bench press 300 kg on the Moon to have an equivalent workout.
The Moon’s atmosphere is very different to Earth’s. It contains no oxygen, so we would be unable to breathe without a spacesuit and oxygen tanks or a sealed, oxygenated area to inhabit. The Moon day and night takes 1 month, and because there is so little atmosphere, temperatures on the Moon are extreme. Daytime temperatures on the Moon can reach 100°C, and during night, temperatures drop to around minus 170°C.
The lunar surface
Any future missions to the Moon would require extensive mapping of the lunar surface. When you look up at the Moon, you can see dark and light patches. The dark patches are ancient lava fields called maria, which are smooth and ideal spots for landing. A mission needs to land on a smooth surface to minimise the risk of the lunar module breaking or tipping and the crew on board not being able to tip it back upright.
During the Apollo 11 mission to the Moon, Neil Armstrong had to make an emergency landing after almost landing in the wrong lunar area. With only 30 seconds of fuel left, he managed to land the Eagle (where the phrase “the Eagle has landed” comes from) on the edge of the designated landing maria. Not only was Armstrong the first person on the Moon, he was also the first person to navigate an emergency landing on another planet. Had he not executed the landing successfully, the crew would have run out of fuel and would have been unable to return to Earth. When on the Moon with few others and no immediate outside help or available resources, everyone must be a problem solver.
Testing a return to the Moon
Discover how in 2022 a tiny CubeSat called CAPSTONE is playing a key role in returning humans to the Moon.
Useful links
For a wide range of Moon resources see the Our Moon Pinterest board that we created.
This website has 21 activities to help you teach about Moon phases.
Read about the Moon illusion in these articles from Sky & Telescope and NASA. They have great images and matter-of-fact explanations.
This article and interactive map from the Smithsonian magazine's website provides information about the 21 successful moon landings.
Acknowledgement
This article has been written by Stardome Observatory and Planetarium, which has been operating since 1967. It is a place of exploration, research and sharing of knowledge and hosts New Zealand’s first and still largest planetarium theatre. Stardome Observatory and Planetarium celebrates its 50th anniversary in 2017.
