IV: Magnificent Desolation: The Moon
Even if you have not the least interest in astronomy or the Heavens, we’ve all seen the Moon in the sky. It’s impossible to miss, unless you happen to stay indoors and never venture outside at night, or only go out when the cloud cover is thickest. And even if so, you’ll still have seen it on the telly. Of all the celestial objects written about, it’s probably the one most featured in song, story, poetry, movies and television, and music. Even perhaps moreso than the Sun, the Moon has a certain romantic attraction for us, if only because it is the biggest and brightest thing in the sky at night, and so has become identified with night-time pursuits, from smuggling and robbery (to the practitioners of which it is an unwelcome intruder) to romance (where it is usually welcome). It’s a backdrop to the night for us, something across which bats or birds or - occasionally - a boy on a bicycle with his pet alien - travel, silhouetted briefly by the pale yellow disc. It’s been described as looking down, hiding, sailing on the clouds and many other poetic and lyrical themes have been afforded it.
It’s also the only - at the time of writing - other body in our solar system to which we have physically travelled ourselves, and on which we have set our feet. It represents humankind’s first tentative gropings out in the dark, our brief escape from our home planet, and our first manner foray into space. It exerts more than a romantic or fascinating influence on us though. The Moon controls the ebb and flow of the tides, allowing the Earth’s oceans to be regulated, and of course it usually lights up our night sky, a sort of natural light bulb that throws back the veil of darkness which would otherwise swallow us for anything from ten to twelve hours a day. It’s the nearest object to Earth, and therefore appears as the largest celestial object in our night sky, occasionally also visible during the day at certain times of the year and at certain latitudes. It features, not surprisingly, in most ancient mythologies, in which it is almost universally seen as being female, from Diana to Selene to Inanna, and usually the pale consort of the great god of the sky and ruler of the day, the mighty Sun.
The Moon is also said to exert a strange influence upon certain people, causing mood swings and sometimes madness - hence the term lunatic - and in legend invokes the process of lycanthropy, where someone bitten by a werewolf is doomed to become one at the rising of the full moon. As it rotates around the sun - taking roughly twenty-eight days to complete a rotation - the amount of visible light varies, showing in different aspects as seen from Earth, from a tiny sliver (new moon) to a full sphere (full moon). Here’s a cool video for kids that explains and shows the phases. Hey, it’s about our level, right?
Our home planet is the only one in the solar system with just the one moon, and though there are several theories as to how it formed, the mostly accepted one is that a large planet or body the size of Mars impacted the Earth about four million years ago (ah I remember it well!) and the resultant debris, formed in a ring around Earth, eventually coalesced into our own natural satellite. This is known in astronomical circles as the “giant impact hypothesis”. The Moon has no atmosphere or course, and originally was much closer to Earth than it is today, hanging huge in the sky above us, but over time tidal friction caused it to move further away, till it occupied the distance it does now, about 239,000 miles away.
Gravity is much lower on the Moon than on Earth, as anyone who has watched the Apollo missions will know, those of us old enough to remember Armstrong and Aldrin bouncing along as if they weighed nothing. Basically a big iron rock, the Moon has volcanic craters - one of them being the second-largest confirmed impact crater in the solar system - and ridges, and areas in between known as “maria”, Latin for seas, such as Mare Tranquilitatis and Mare Imbrium etc. Without an atmosphere to slow down and burn them up in, meteorites and asteroids have marked the surface of the Moon with many large craters, giving it a pock-marked appearance that can be seen almost with the naked eye, but certainly through a telescope. This probably gave rise to the old idea of the “Man in the Moon”, the face formed by features such as craters and maria.
Although it was believed there could be no water on the Moon, recent research suggests that, rather like Mercury, this may exist in some form, perhaps as ice, in areas near the poles which are in constant shadow. The Moon is surrounded by a permanent dust cloud, from the millions of comet particles that strike the surface, estimated at about five tons a day. With no wind to move them around and no atmosphere to absorb them, they remain above the surface of the Moon, rising to about 100 km. The coldest temperatures ever recorded in the solar system are not on Pluto, but the Moon, in dark, frozen caverns at the poles, where the temperature has been measured at - 238 degrees Celsius at the south pole and - 247 at the north.
Lunar Eclipse
We’ve discussed solar eclipses in the chapter on the Sun, but there are of course lunar eclipses, when the Moon is in Earth’s shadow and the two objects are more or less in a direct line with the Sun, in what is known as a state of syzygy. Because it is far closer to the Earth, though much smaller than the Sun, the Moon appears during a lunar eclipse to be the same size as our native star, and so can “block” it. Lunar eclipses only occur during a full moon, and unlike solar ones can be watched with the naked eye as they are nowhere near as bright. The moon at full eclipse does not turn black, as it does in a solar one, due to the sunlight passing through Earth’s atmosphere and being refracted, giving it a reddish colour, often called a “blood moon”. This is also used in Christian belief to signify the expected Second Coming of Christ and the Rapture (Judgement Day), tied in to a passage in the Book of Revelations in the Bible where John mentions the moon turning to blood.
Unlike solar eclipses, which occur but rarely, lunar eclipses happen at least twice and sometimes five times a year, though few of them are total eclipses.
Lunar eclipses were of course viewed with suspicion, dread and fear by our ancestors, most of whom believed some sort of beast or demon was swallowing or eating the moon, and it could only portend bad times ahead. The Hindus, though, believed that bathing in the Ganges after a lunar eclipse was opportune, as it would help them achieve salvation. Why? I have no idea. Ask them. A rather amusing, in a dark way, story comes from the Mesopotamians, always good for a laugh, who believed that a lunar eclipse was the result of seven demons attacking the moon, and fearful that the demons would then turn upon their king, they got someone to stand in so that he would be attacked instead of the king. Once the eclipse was over, this helpful gent was poisoned. I doubt there were too many applicants for
that job!
As late as the nineteenth century, the Chinese were still trying to ward off the dragon who was believed to eat the moon, and while traditionally this had been achieved through the ringing of bells, these modern lads used navy artillery to scare off the big lizard. That’ll show it who’s boss round here!
Moonwatching: Early Observation
Being the closest and most visible celestial object, the Moon has of course been studied since antiquity, and while Americans may have been the first to tread on its surface, I’m proud to say that the first ever depiction of the moon is in Ireland. In a burial passage in Knowth, in Drogheda, there is a representation on a rock which is believed to date back about five thousand years. In your
face, America! Of course the Babylonians, well known historical and scientific eggheads, had been studying the Moon since the fifth century BC, and those clever Chinese were already able to predict lunar eclipses a century later, and in 428 BC Asterix sorry Anaxagoras, an ancient Greek astronomer, sussed that the Moon was a big rock in space, and so was the Sun. Well, one out of two ain’t bad.
A pretty big deal in the second century BC was when Seleucus of Seleucia (did they name the city after him, or him after the city I wonder?) worked out that tides were controlled by the Moon. I mean, this was before anyone knew what a telescope was, or even what the Moon truly was. That’s mighty impressive. Not to be outdone, Aristarchus (who did not found Arista Records) gave working out the distance to the Moon a shot, and got it reasonably accurate, though later Ptolemy brushed up his figures and got more or less the correct measurement.
And then came our mate Galilieo.
It will come as no surprise to anyone that the Italian father of astronomy made big inroads into our understanding of our nearest and only satellite. He used his cool new invention, the Galileoscope (well, the telescope then), to make drawings of the surface of the Moon, and could prove that it wasn’t, as his predecessors had all thought, smooth and without features. In fact, he detected craters and basins and mountains, though it would be another two hundred and fifty years almost before a proper geological and topographical map of the Moon could be produced.
Because the Moon is in synchronous rotation with the Earth (you surely don’t need me to explain that term, do you?) the same face is always turned towards us. This gives rise to the idea of a dark side of the moon, but as yer man says on the Pink Floyd album, there is no dark side, it’s just that we only see one side, and so the other seems dark to us all the time. The actual, proper term for the two sides of the Moon is the near side and - wait for it - the far side. Although the Moon has no tectonic plates to crash into and move against one another as they do here, causing earthquakes, tidal stress means that there are frequent “Moonquakes”, though usually nothing on the order of even mild ones on Earth.