Antarctica

by Gabrielle Walker

  By now the sun will be touching the horizon, and the first colours will appear in the sky. Don’t expect deep spectacular reds; there is no dust in the air to scatter the setting sunlight, only crystals of ice that give colours that are paler and more subtle—pinks and mauves rather than crimson. On the side of the horizon opposite the Sun, you’ll see a purple haze like a visor, as the Earth casts its own shadow on to the air. And as the Sun dips deeper, you will have a better chance than most to see the famous green flash. In principle this can happen anywhere in the world at the end of a sunset. Light travels more quickly in the thin upper air than in the low dense air, so it tends to bend a little round the curved Earth. And since green light curves more than red, a flash of green is often still visible when the sun has disappeared over the horizon. In the tropics this might last a second. In the stretched-out saga of a polar sunset, a green stripe comes and goes over the course of a day or even two.

  Next come long days of a ghostly grey twilight. Half the sky darkens to deep blue, royal blue and then black, specked with stars, while the other half is still infused with leftover light from a sun that is only just over the horizon. As the sky turns, or rather you turn beneath it, the dark half moves, too, picking out different constellations like an inverse searchlight. And then you notice that the rest of the sky has also grown darker, and then there’s no light at all. This is the true winter, the crown jewel of an Antarctic stay. And it is now that the Dark Sector, home of the station’s telescopes, comes into its own.

  Tony Stark and I didn’t get off to the best of starts. Someone had already pointed him out to me so I knew he was a veteran astronomer from Harvard University, there at the Pole to work on one of the telescopes. One evening in the galley I went over to speak to him, but before I could introduce myself he made it obvious that he already knew what I was there for, and didn’t particularly approve. ‘I hope you’re going to do a good job,’ was his opening line, ‘because you’re taking the space of someone who could be critical to the scientific enterprise.’ (‘Charming to meet you, too,’ I thought, but luckily didn’t say.)

  Tony’s attitude wasn’t that uncommon among the scientists on the US Antarctic Program. Though many see the poetic and mysterious side of the continent where they work, others are at best irritated by the drama and the difficulties. Yes, yes, it’s an extreme place and all that, but we’re doing science, and that’s all that matters. If you’re here to help us do our science, that’s fine. If you’re not, then get out of the way.

  This seems particularly disingenuous at the Pole. There are some excellent scientific reasons for being here, especially to do astronomy. The cold, dry air and steady winter darkness provide a stability and clarity that make this one of the cleanest windows on Earth for peering out through the atmosphere into space. But it’s not perfect. Though the Pole lies at the geographic centre of the continent, it’s also on a slight slope. The winds on the continent are born on local high points and then spill down the sides till they reach the coasts with a furious flourish. And on the way, they pass by here, stirring up the air and muddying the view.

  But if you recall that the science in Antarctica also serves as a political placeholder, the reason for this location makes more sense. Before the Antarctic Treaty came into effect back in 1961, eleven nations had staked claims on various parts of the continent. Though these claims are now officially on hold, they have never been wiped from the record. And, significantly, they are all great wedges of land that meet at . . . the South Pole. The US has never staked a claim of its own, but it has built this station right at the touching point of all the other claims, an unofficial geopolitical finger poking into everyone else’s pies.

  Still, science was something that the South Pole was very good at, and Tony was one of its ablest practitioners. When he relented enough to take me back to his lab, in the Dark Sector, the stories he told me of their discoveries make me very happy that I bit my tongue when we first met.

  The Dark Sector, where the telescopes lived, was about a kilometre and a half away from the main station, but it seemed farther. Temperatures had still barely lifted above -58°F and the wind drew tears that instantly froze into globs of ice, gumming my eyelashes together, rendering me all but blind. As I rubbed at my eyes, I noticed belatedly that everyone else was wearing goggles. I thought they were only necessary if you were riding on a skidoo. I knew better now.

  The Dark Sector was separated from the main station to avoid any light and radio wave pollution when the darkness finally fell. There was one main building called the Martin A. Pomerantz Observatory (MAPO)7 and various smaller ones, some with towers and visible telescopes like classic radar dishes pointing up into the sky. Inside were offices, computers and banks and banks of electronics with spaghetti tangles of wires. And a gigantic poster of a mad-looking Jack Nicholson in The Shining. ‘Heeeeeeere’s Johnny!’ The Shining used to be one of the movies that the winterers watched on the day the last planes left, but lately they had been saving it for midwinter.

  Tony’s telescope was called AST/RO. The letters stood for ‘Antarctic Submillimetre Telescope and Remote Observatory’; the slash was to distinguish it from all the other telescopes whose owners have devised acronyms to be able to call them ASTRO. And as we sat in the main astronomical building in the Dark Sector, warming our hands with mugs of hot tea, he explained what AST/RO was looking for.

  The Galaxy in which we live, the Milky Way, is fairly typical, large and flat, shaped like a child’s drawing of a flying saucer with a bulge in the middle surrounded by a disk of spiral arms. Our home planet and the others in our Solar System inhabit a provincial spot in the outer part of one of these arms, some 30,000 light years from the bulge at the Galactic Centre. Though it sounds like a measure of time, a light year is actually the distance light can travel in a year, which is a shade less than ten trillion kilometres. Light moves so quickly it took humans until relatively recently to discover that it moves at all. Our own Sun is about eight light minutes away, the next nearest star about 4.2 light years. Thirty thousand light years seems almost unimaginably distant, but by the scale of the Universe, which was the scale Tony Stark lives and breathes, it’s still not that far. ‘I feel very at home in the Galaxy,’ he told me when casually tossing out these figures. ‘I think of it as if it were some kind of nearby real estate. I’m not overawed by it any more.’

  The problem when it comes to studying the centre of our Galaxy is not the distance, but the many intervening clouds blocking our view. The stars in the night sky are all relatively close by. It seems as if there are many of them, but there are a million times more packed into the Galactic Centre. We can’t see these because clouds of molecules like hydrogen, carbon monoxide, nitrogen and methane soak up all the light they emit, and cloak them from our view. ‘There are twenty-some magnitudes of visual extinction in the Galactic Centre,’ Tony said. ‘Not only can you not see it, but you can’t see it twenty times over.’

  So if we stuck with visible light, the sort of light that our weak human eyes can detect, the main activity of the Galaxy would be for ever out of view. But AST/RO’s eyes went beyond this. It could detect light coming in with longer wavelengths than the typical colours of the rainbow. In its preferred range of so-called ‘submillimetre’ (or far infrared) wavelengths, molecular clouds shone brightly, and the Galactic Centre was an open book.

  The trick for seeing with radio eyes is to have as little water vapour as possible between you and outer space. That’s why the South Pole is so very good at it. For every 10°F below freezing, the amount of water vapour in the air drops by half. When the temperatures here got cold enough, in the deep midwinter, AST/ RO could pick out the many molecular clouds that dot the night sky. But more than that, looking through this pristine Antarctic window it could see right into the heart of our Galaxy, to the bulging centre of commerce, activity and drama.

  And when it looked, AST/RO saw something that impressed even the phlegmatic Tony Stark. Spinning aro
und the centre of our Galaxy was a molecular cloud to dwarf all others. It was nearly a thousand light years across, and contained two million times as much material as our Sun. Like a storage ring it was soaking up dust and molecules dragged in from the rest of the Galaxy. And it was getting denser all the time. AST/RO showed that this massive ring was right on the edge of stability. It was so dense that after just one more tweak, in another few hundred thousand years at most (which in galactic terms was the merest twitch), it could tip over the edge. Then, as if you had dropped a mighty slug of vinegar into a giant galactic sauce, it would curdle and coagulate into blobs of gas that would fall in on themselves in a spectacular celestial light show. It would become a massive centre of star formation. At present there were only a handful of new stars created in the Galaxy each year. When this kicked off there could be thousands. They would be every colour and size, supermassive blue ones that blaze brightly but burn out quickly; more measured, smaller orange and red ones. As some were still barely switching on, others would be reaching the ends of their short lives and exploding dramatically, before new ones eventually reformed again from the material that was flung out.8

  That’s not all. Astronomers believe that at the true centre of the Galaxy, the point that everything else was rotating round, lies a supermassive black hole, some four million times heavier than the Sun. At the moment this is quiescent. Rather than performing the usual black hole habit of sucking in all the material around it, it is starved of nearby fuel and hence effectively switched off. But if the star formation kicked off, new material would fall into the black hole’s vicinity, activating it into a voracious monster. As dust and gas were dragged inwards, an accreting ring around it could shine like a thousand Suns, and giant jets of recycled stuff could burst out of its north and south poles and shoot out in magnetic maelstroms above and beyond the rim of the Milky Way and into intergalactic space. All of this would be hidden from us even if it were happening now, blocked by all the clouds in between. ‘But if you had radio eyes it would be fireworks.’9

  This was very dramatic, of course. But there was another more intimate reason why we should care about molecular clouds and bursts of newly formed stars. Tony called it the ‘ecology of the Galaxy’. As molecular clouds collapse into stars, some of the stars live much longer than others. But all in the end will die, either in massive explosions—supernovas—or in a gradual loss of form as the outermost parts are gently blown outwards in a streaming wind. And the material thrown out in this way goes on to make new molecular clouds, and ultimately new stars and planets.

  So our Galaxy is one massive exercise in recycling, mingling and reforming. But there’s more. From what we now understand about the lives of stars, we can tell where the material in our own Solar System came from. And that shows something extraordinary. Not only are we all made of stardust, but we are made of the dust from different stars. All the material around you—this book, your clothes, the tea bag that Tony Stark had just taken out of his mug—is made up of atoms that have been processed and recycled through a succession of stars. So has every atom in your body. And some of your atoms have been through a different set of stars than others.

  ‘So I have atoms next to each other in my body that have come from different stars, from different parts of the Galaxy?’

  ‘Yes.’

  ‘That is really spooky.’

  ‘That’s what star formation does.’

  Tony said all this in a matter-of-fact way. Perhaps he had grown used to it, the way he has grown used to the scale of the Galaxy. But I couldn’t. Even now, every time I think of this, it still blows my mind.

  Tony no longer spends winters at the Pole, but there are plenty of others who do. Unlike Larry and the other construction workers (whom he described as ‘indoor cats’), the astronomy technicians have no choice but to leave the comforts of the station and make the daily trek to the Dark Sector where the telescopes await their attention.

  German technician Robert Schwarz, a self-styled ‘telescope nanny’, was about to embark on his fourth winter. His hair was close-cropped, and he was inclined to be terse. (Typical conversation: ‘What’s it like here in the winter?’ ‘Cold, and dark.’) He had last year off, but had come back to the Pole to work on one of the biggest imaginable questions: the origin of the Universe.

  Robert’s telescope would be picking up the faint afterglow of the Big Bang itself. For the first few hundred thousand years after the Big Bang the entire Universe glowed hotter than the Sun. A roiling plasma of negatively charged electrons and positively charged ions circled around each other, eager to join forces and become neutralised, and yet constantly breaking apart as soon as they united, because of the searing heat. And all was bathed in a brilliant blaze of light.

  Eventually, as the Universe stretched and cooled, the electrons and ions fell into each other’s arms to become the atoms that make up the stars, the planets, and us.10 And the light streaked out across the Universe, bearing the slightest, almost imperceptible traces of erstwhile lumps in the cosmic maelstrom, here the light a little denser, there a little more insubstantial. This faint glow is still out there, its elongated wavelengths now too far from the visible rainbow for human eyes to see. But with the right telescope, in the right place, you can see through the dirty window of the Earth’s humid air and pick out, if you look hard enough, those traces of primordial structure. And if you do, you can calculate nothing less than the mass of the entire Universe.

  Astronomers call the afterglow of the Big Bang the ‘Cosmic Microwave Background’ (CMB). ‘Background’ because it exists in every direction in the sky; it is the canvas on which all the stars and galaxies are painted. ‘Microwave’ because the light that was once visible has now been stretched into roughly the same patch of the spectrum as the microwaves that power your oven, though it is feeble enough not to burn us all to a crisp. And ‘Cosmic’ because, well, that’s what it is.

  As for AST/RO, Robert and the other CMB researchers need air that is as devoid as possible of water. But unlike AST/RO they need to look away from the main body of the Galaxy—what the starburst people see as nascent star nurseries, the microwave background people dismiss as ‘galactic smog’. Instead, the CMB researchers angle their telescopes to look up and out of the flat plane of the Galaxy, where there are no spurs or arms or patches of molecular clouds to spoil the view. And then, thanks to the thin dry air at the Pole, the CMB researchers find themselves looking through one of the cleanest patches of sky in the world.

  It’s not perfect. To get the best results you need to look at the largest possible area—ideally the whole sky. As the Earth spins on its axis, a telescope at the equator sweeps through a huge area of sky every twenty-four hours, whereas the South Pole rotates constantly beneath the same relatively small patch. But with the long, cold, steady winters you can bore into that patch very deeply.

  Back in 1998 a South Pole telescope called VIPER, the brainchild of University of Pittsburgh researcher Jeff Peterson, performed measurements on the Microwave Background and picked up those almost imperceptible traces of ancient clumping. Added in with data from a telescope in the arid Atacama Desert in northern Chile, and a couple of balloon flights that set off from McMurdo and made long, slow circles around the Pole, the researchers came up with a number for the mass of the Universe. The answer was:

  100 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 000 tonnes.

  Give or take a few pounds.11

  Now the astronomers wanted to go deeper, to find out what the Microwave Background could tell us about the structure of the Universe, the strange invisible ‘dark energy’ that it seems to be filled with, how it truly began, and how it is likely to end. Next winter, Robert would be working on a new CMB instrument, and plans were already under way to build a whopping 10-m telescope here, the South Pole Telescope, that would have nothing but the Microwave Background in its sights.

  Robert’s friend and fellow telescope nanny Steffen Richter, who was
also German, would be on a much weirder kind of telescope called AMANDA, which stood for Antarctic Muon and Neutrino Detector Array.12 Unlike the other telescopes, which all looked like oversized TV satellite dishes, AMANDA was completely invisible. It was made up of strings of detectors that were buried hundreds of metres down in the ice. Any day now, construction was going to begin on a much bigger device called Ice Cube because it would stretch over a full cubic kilometre of ice, with AMANDA making up one small corner of this behemoth.13

  Both these telescopes were for studying spectacular astronomical occurrences: exploding stars, colliding black holes, gamma-ray bursts and the rest of the Universe’s biggest and most cosmic bangs. These all generate debris in the form of particles. But to do astronomy, you need to know exactly where they came from. And as they travel through space, most are hopelessly wayward. Cosmic rays are charged, so can be dragged about by any stray magnetic field. Free-flying neutrons fall apart within minutes.14 The only particles whose subsequent path through the Universe is straight and true are tiny, chargeless, faceless creatures called neutrinos.

  However, the same thing that makes them come to us so directly also makes them very hard to detect. Neutrinos don’t stop for anybody or anything. A magnetic field can’t turn them, gravity doesn’t bother them and they zip through solid objects without a backward glance. Trillions of neutrinos pass through your body every second. They are doing it now, and have been ever since you were born, but in your entire lifetime the chances are that only one of these will stop to wipe its feet.