Take a look at the moon (pdf)Presentation Transcript
Take a look at the Moon An essay by David C, 2013
Take a look at the Moon and tell me what you see.They say that discoveries are made notso much by people who observe newthings but generally by people who lookat the same things that people havebeen looking at for centuries, andseeing details that no-one else had seenbefore.So look again at the Moon and see if there is something in its surface orits brightness or its position or its size or its ‘something-else’ that youmight not have noticed before.
Do you see a circle or a crescent?What colour is it?What makes its shape and colour and causes these things to changeover time?
A book will tell you, but so will a little bit of thought. The Moon near ourhorizon is sometimes red or yellow or gold, whereas it is a dazzlingwhite when it is high in the sky. Sometimes I’ve seen it in the middle ofthe afternoon when the half-eaten grey surface is stained blue by theatmosphere. Far up above the horizon, it is a tiny little thing, so small itis impossible to see until someone points you in the right direction.
At night, just above the rooftops, its presence is unavoidable. It dominates the entire neighbourhood, so much so that millions of people standing on a ring of twilight girdling the Earth, all at once will experience the same emotions as me: ‚Wow, look at the size of that thing!‛The Moon is whatever you want it to be: unimportant, romantic, irrelevant,a spotlight to navigate by in the darkness, a direction-finder for thosewho are lost, a decorative backdrop for a photograph, something to writesongs about for the lovesick.
It’s also something as loaded with information as our enquiring minds (orour un-enquiring minds) permit it to be.Look up at it again and see if you can see in it anything new.Do you know that the Moon tells you where the Sun is? See the Moon asthe bow from which an arrow could be launched. Put an arrow onto thebow and draw back the string. Whichever way the arrow flies is the waytowards the Sun.If the Sun is below the horizon, as it would be just before dawn or justafter sunset, the lunar arrow will guide you to where it will be when itrises or where it was when it set. In other words, the Moon can be usedlike a compass to find East and West.
Look again at the Moon. How big is the crescent?If the Moon is full and directly overhead, then it is close to midnight. If itis in the same position but only half-illuminated, then it’s about sixo’clock, am or pm. A half Moon is always six hours away from the Sun,either before it or after it by that much in its journey across the sky. Aquarter Moon is therefore three hours ahead of it or behind it. Learn toread the Moon like a clock and you can tell time by it.
Our ancestors used the Moon to great advantage. A group of scientistsin northern England, three hundred years ago called themselves theLunar Society, not because they studied the Moon but because theywould hold their meetings on the night of the full Moon. Were theyreligious fanatics? Werewolves? Not at all. The light of a full Moonenabled people living in a world without street lights to find their wayhome after a late-night meeting. That is all there is to it.
People such as these may have been the first to be called ‘lunatics’ bytheir less imaginative contemporaries. A lunatic to us is a madman. But alunatic back then may have been a scientist or an engineer or a wealthyentrepreneur who would rather go and hear the latest developments inscience each month than stay at home and stare at the empty spacewhere a TV set would one day be.So the Moon to some is a compass and a clock, and to others in thepast a guiding light.
We don’t need the Moon anymore and so we don’t see it, even when it’sin plain view. When asked whether the Moon was bigger or smaller thanan elephant, a contestant on a TV quiz show hesitated and eventuallyguessed the wrong answer, thereby fixing her place in history as a minorYoutube celebrity. Other people think the Moon only comes out at night.And if you dig deep enough into schmaltzy TV shows from the past,you’ll see the Moon depicted as a crescent shape on which people cansit, often with a fishing rod or a folk guitar. Go back a little further intocartoon history and you’ll see faces etched onto the Moon, smilingbrightly as the mice and ducks of this world go through their Disney andLooney Toons adventures.
The face in the Moon is something few of us can see today, not becauseit’s gone away but because it no longer interests us. Can you imaginepeople in prehistoric times wondering what the Moon was for, in thesame way that they might wonder what a tree was for or what a river wasfor? A tree grows and bears fruit. A river carries clean water to us anddirty water away from us. What does the Moon do? It gives us light in theabsence of the Sun. Maybe that’s its purpose, and why it was made.
But why does it have a face on it, and why does that face look so sad?With no Youtube to look at, no DVDs or TV shows to fill our evenings, alonely fellow might spend an evening looking at the Moon until he fellasleep, and dream of spirits in the sky who follow our lives as closely aswe follow Coronation Street.
The Moon sometimes grows and sometimes shrinks on its silent journeyacross the sky. Did the ancient people really think the Moon died when itdissolved into the Sun at sunset? And did they really think that a ‘NewMoon’ was a newborn Moon that split away from the Sun a few dayslater?
We know today that the Moon is simply The Moon, and always was andalways will be. But we know that largely because of what people tell us.Robbed of this cross-generational common sense, and similarly robbedof information from other reliable sources like Facebook and Twitter,would our descendants look at the Moon the way our ancestors did, andconclude that the Moon crashed into the Sun every month, and that whatemerged from the other side a few days later was the debris of thatcataclysm in the sky, reformed into a crescent that filled out with moredebris over time?
The Greeks were a little smarter than that. They observed that thegrowing and shrinking banana in the sky looked like a partly-illuminatedsphere, and furthermore that if you looked hard enough on a dark night,you could see a brown circle where the un-illuminated part of the Moonwas. The Moon was illuminated by the Sun, therefore, and the closer theMoon got to the source of this illumination, the narrower the band ofillumination got.
The Moon had to be a sphere that passed between the Sun and theEarth, an observation of such astounding simplicity that it makes nosense for priests a thousand years later to insist that it could be anythingelse. And yet there it is in our sky: still reddish brown on one side (if youlook hard enough on a really dark night) and blindingly white on theother side, the two parts together tracing out a perfect circle in the sky.
Our knowledge of the universe starts with this Moon. Four hundred yearsago, a fellow in Italy wrote a book about the Moon that he illustrated withfabulous pictures that he had drawn from his observations through atelescope. He became a literary celebrity for his efforts and his name iscelebrated even today, although generally for other reasons: GalileoGalilei, the renegade university lecturer who one day bought a device inthe market called a telescope, a device meant for observing ships at seaand decided instead to study the sky with it.
Was he the first person ever to do so? Almost certainly not! What personwho spends a small fortune on a device for observing ships at seadoesn’t at some stage also decide to spy on his neighbours with it, orlook at objects up there in the sky? Birds in flight, for example. Orclouds. Or planets? Very likely the fellow who sold the telescope thatGalileo bought also looked at the Moon one night just to see how itlooked up close; took a look, lost interest and went back to work.
What made Galileo different was that he was a fabulously good writerand could draw pictures and get a book published that would tickle theimagination of the average reader. Galileo gave us the Moon as if hehad once owned it, gave it to us fresh and renewed, now a world thatmight harbour people such as us, plying the lunar oceans in windsweptships in search of new markets to plunder.Galileo’s oceans are the eyes, nose and cheeks of the Man in the Moon.Their names reflect the passions and imagination of a man keen to makehis book a page-turner: Ocean of Storms, Sea of Tranquillity, Sea ofCrises,... where do such names come from, if not from the mind of a manwho could turn basalt and silicate into poetry?
And so those names exist in our science books today, lost amongstpages that few people ever read. Who should care about a clod of dirt,even if it does hang in the backyard sky every other night, even if it is asbig as Africa, even if it is as old as old ever gets, even if it can tell usthings we thought we’d never know about our own past. Who shouldcare?
Every now and then some scientist on Earth is handed a rock thatproves to be a remnant from Mars, spattered off the face of that planetmillions of years ago by an impacting comet that must have rattled it toits core and caused large parts of its surface to melt. Not even Marstoday looks like it did a couple of hundred million years ago, but thoserocks that fell to Earth do. Imagine if some of those rocks fell onto theMoon, as they surely must have done in more or less the same numbersas fell onto the Earth. Without wind and rain to smudge the details, wewould know even more about Mars’s history than we can tell from thosecooked and rotted fragments that fell to Earth. The Moon, therefore, is aspecimen jar for those that would make the effort to go and open it.
Are there fragments of the Earth to be found up there too? Almostcertainly so, since our best theories of the Moon’s formation require thatthe Moon was gouged out of the Earth by a passing comet. No othertheory can explain why a planet as small as the Earth can have acompanion as large as the Moon. The Earth (as it is today) simply isn’tlarge enough to attract the interest of an object as large as the Moon (asit is today). It would be as if a car travelled a little too close to a barn andwas drawn into orbit around it.
Ah, but what if the car actually smashed into the barn, reducing both ofthem to a cloud of debris which eventually settled into two heaps, onecalled the Earth and the other called the Moon? The Moon, therefore, notonly contains fragments of what the Earth used to be, it actually IS whatthe Earth used to be, the leftover bits that didn’t fall back to the groundto become Africa and Europe and so on.
Does this mean that the marks that make up the face of the Man in theMoon are scars left behind by this huge collision? Probably not, but whoreally knows? The Moon has been pounded again and again, a milliontimes over, a thousand million times over, by rocks as small as my hand,dust smaller than the dirt under my fingernails, and mega-rocks as bigas the country I live in. Those scars could be the result of the slowrecollection of dirt from the cloud surrounding the Earth, casting theMoon in the role of cosmic vacuum cleaner.
Whereas the Earth smoothed over most of its scars with the poo and thecarnage of biological activity, the Moon simply cooled down and frozeinto the landscape it has today. So when you look into the face of theMoon, you are looking back into history some 4.5 billion years. And if bysome mathematical magic we could resurrect those mega-rocks fromthe basins they formed, we could run time backwards and perhapsreconstruct the early solar system, or at least our little part of it.
When you look at the Moon in detail you see less of what it is and moreof what it means. The Moon means life on Earth, because it pulled theoceans back and forth and stranded some of our measly, slimyancestors on the beach. Would we have had ancestors who walkedinstead of swam if it wasn’t for the Moon? Perhaps we would, but thestory would be very different, and so would we.
We all know the story of the tides: the Moon pulls on the water of theEarth, making a bulge several metres high that stays put directly underthe Moon as the Earth spins on its axis beneath it. The tides are such acommonplace part of our experience that I can imagine ancestors whonever even bothered to ask why the tides should be as they are. Butfollowing the construction of a theory of gravitation, suddenly it waspossible to understand why the oceans rose and fell as they do, quitepossibly inspiring people to ask the question for the first time at thesame time that they answered it.
It all goes back to that fellow who sat under a tree one day and lookedup at the Moon and wondered why it didn’t fall down in the way that anapple would, and realised that perhaps it was falling down but (unlikethe apple) kept missing the Earth. The Earth after all is just a little roundworld very far away from the Moon, which is another little round world.On a smaller scale, the Earth and Moon are rather like two basketballs atopposite ends of a basketball court. The Earth therefore is not an easytarget to hit.So according to Isaac Newton, when we look up at the Moon at night,we are seeing gravity in action. We are seeing an apple that fell from atree but missed the ground and has found itself spiralling round theworld, trying to hit it ever since.
This observation was one of Newton’s great gifts to the world. Newton nomore created the force of gravity than he created the Moon, but bylooking at the Moon and seeing what no-one else had seen, he found away to explain why the planets moved in circles around the Sun, and(much later) why the stars moved in circles around the galaxy, and(much later still) why galaxies move in circles around each other. Hisexplanation was mathematical, which means his explanation could beused to predict the positions of the Moon and planets for years to come,so that it would be possible one day to fire a rocket into space and aim itat a spot where the Moon would be three days later.
I can remember the years when that first happened. I was nine years oldwhen people first walked on the Moon. I can remember going out theback door after watching the TV news one night and looking up at theMoon above our garage to see if I could see the spaceship on its way.Occasionally I’d see a flash of light on the Moon’s horizon and I’dwonder if it was sunlight reflecting off the side of Apollo. My brother toldme this couldn’t be so, and my knowledge of science since then hasproven him to be an expert.
But what were those flashes of light that I saw? Or thought I saw? Werethey necessarily illusions? Look up at the Moon and you just might seethem too, once in a long while. Like a window at sunset that is angledjust right to reflect the full glare of sunshine across a bay, perhaps aparticularly shiny hillside on the Moon near its edge is angled just rightfor a few moments to catch the sunlight and flash it across space to kidshere on Earth who just happen to look up at just the right moment to seeit.
The exploration of the Moon was like the exploration of the Antarctic.Shackleton, Scott, Armstrong, Aldrin, Amundsen, Conrad... We wentback to the Antarctic forty years after the famous pioneering trips withbetter technology and set up facilities there that make it possible for lessfamous adventurers to stay there forever. The same will happen to theMoon someday, and we might all be around to see it if we’re lucky.
Someday, it might happen that people looking up at the Moon will seepinpoints of light on its surface at night, showing where cities have beenbuilt. And people up there might begin to look at us in the same way thatwe have looked at them over the years: sometimes with fascination,sometimes with casual curiosity and sometimes with no interest at all.‚That green thing in the sky? Oh yeah...quite nice I suppose. But whatcan it teach us?‛