How much do we really know about the moon?

How much do we really know about the moon?

It's time for the moon. Not yet with Artemis 1, the demonstration mission of the homonymous program for the human return on our satellite, forced to a further delay and to return to the garage (in the Vehicle Assembly Building) by the devastating hurricane Ian. It's time for the Moon because on October 1st the International Moon Observation Night is staged, a widespread event, in presence and online, promoted to admire our satellite and learn about the projects that concern it. Because a large slice of space exploration has been dedicated to the Moon and an equally large one will dedicate itself to it in the future, primarily with the Artemis program. Because there is still a lot to discover, to explore, and also to know. Because maybe not everyone knows that ...

In the beginning it was “liquid”, perhaps

Let's start from the origins: we don't know exactly how the Moon was formed. NASA itself speaks of probability when you cite the most accredited hypothesis (also thanks to the analysis of the rock samples collected during the Apollo missions) to explain the birth of our satellite. According to this, the Moon was formed following the aggregation due to the effect of the gravity of the debris fired into Space after the collision of a planet the size of Mars with the Earth, about 4.5 billion years ago. In its earliest stages of life, the satellite infant would have been in a liquid, better fused state. Other alternative theories to that known as the big splash "- but more problematic in terms of scientific evidence - advanced to explain the origin of the Moon are those of multiple impact (ie the satellite would have been born from the debris of several objects and not just one that would have hit the Earth), that of fission (it would have detached from the Earth in rapid rotation), of capture (our planet would have grabbed it gravitationally), or of co-accretion (according to which the two bodies, Earth and Moon, formed at the same time as a binary system).

The Moon does not have a "dark face"

Let's continue addressing one of the most talked about aspects when it comes to the Moon and still die hard: our satellite does not have a dark face. We incorrectly call the part of the Moon that we do not see, since by using the Moon a rotation time on itself approximately equal to that of the revolution around the Earth, it always shows us the same face. What we do not see is not a dark face, but the face hidden from us. Until 1959, however: in that year the Soviet spacecraft Luna 3 sent back to Earth the first images of the hidden face of the Moon, then conquered for the first time by the Chinese probe Chang'e-4 in 2019.

We always see the same face of the Moon, but this is not just half face. In fact, as a result of a process known as libration, we are able to see almost 60% of the lunar surface overall. This is due to the combined effect of the tilt of the lunar axis and the orbit described by the Moon around the Earth, which makes it travel faster when closer and slower when farther away. In fact, this ensures that the visible portion of the satellite during its journey is more than 50%, adding pieces both in longitude and in latitude. To convey the idea with a clear metaphor - as Western Washington University does - it is as if the Moon, describing its orbit, moves its head up and down and here and there, revealing itself a little more.

It (almost never) changes size in our eyes

We have all experienced it: the Moon on the horizon seems enormous, and then decreases once it rises into the sky. In reality - also explains NASA - the Moon has the same size, it is we who perceive it as larger. In fact it is an optical illusion. Small differences instead we could notice them during the events of Superluna, in which the Moon appears larger and brighter (respectively by 14% and 30%) when it is in the phase of flooding at the perigee, but these are really minimal differences at a inexperienced eye, hardly noticeable.

On the Moon we could jump much higher

There is no trick and there is no deception, simple effect of the reduced lunar gravity, about a sixth of the terrestrial one. This also means that on our satellite we would weigh one sixth of what we weigh on Earth.

We have almost 400 kg of the Moon on Earth

The Apollo missions and Soviet spacecraft have made it possible to carry on Earth a considerable amount of moon rocks. It is 382 kg of the Moon to be precise, most of which is kept at the Lunar Sample Laboratory Facility of the Johnson Space Center in Houston. Not a museum, but rather a strictly controlled lunar sample library to protect the samples from contamination or environmental hazards. To these almost 400 kg of Moon will be added that will be collected during the Artemis III mission and coming from the regions near the south pole of the Moon.

There is also a "lunar flu"

Astronaut Harrison Schmitt called it "lunar dust hay fever", referring to the annoying reaction experienced after the exploration of the lunar soil. A sort of allergy, with sneezing and nasal congestion that according to the ESA would have actually affected all the astronauts who set foot on the lunar soil. The culprit would be precisely the lunar dust, extremely fine and very abrasive. It lifts easily and hangs for a long time, and sticks to everything. This is why NASA is also working to try to mitigate the problem of moon dust as much as possible. For the health of the astronauts and the functioning of the instruments that we will bring up there.

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