South Pole offers ideal location to observe the mysteries of the universe
Posted October 2, 2009
The South Pole is the most benign place on Earth. Just ask William L. Holzapfel, an astrophysicist at the University of California, Berkeley.
“This is the most benign environment on Earth,” he said as we climbed into the narrow indoor cavity housing the mount that once supported a couple of telescopes that helped astronomers refine our understanding of the universe.
“This is the most benign environment on Earth,” he repeated as we kicked at the miniature snowdrifts within the mammoth bowl-shaped telescope shield on the roof of that observatory.
The South Pole, of course, is also “the harshest environment on Earth,” Holzapfel acknowledged, as we rested in the control room for the South Pole Telescope (SPT), the instrument he oversaw at the Pole this past austral summer. “But,” he added, “it’s also the most benign.”
The weather the last week of 2008 had been unseasonably mild. Holzapfel made his daily treks to the Dark Sector — the portion of the South Pole complex that prohibits errant electromagnetic signals, so as not to interfere with the telescopes — wearing running shoes and jeans.
Temperatures didn’t dip lower than the minus single digits Fahrenheit all week, and once even peeped above zero to set a record high for the date. The participants in the traditional New Year’s Day group swimsuit photo at the ceremonial South Pole experienced only intense discomfort, not imminent hypothermia.
And certainly many of the amenities at the new science station feel more like a corporate retreat than a remote outpost. Little things like lobster on Christmas can even spoil you. When I learned that video-chatting with my wife and kids was available for only nine hours a day, because the communications satellites are below the horizon for the other 15 hours, I knew how Scott felt.
But when Holzapfel said “benign,” he wasn’t thinking of the relatively mild weather or the occasional luxurious living conditions. He was referring instead to the South Pole of global infamy, the one that comes with six months of darkness, 100-below temperatures, and a Michelin Man fashion sensibility. That’s the South Pole that indeed becomes the most conducive place on Earth to perform a certain kind of astronomy.
Or, as astronomers like to say, if you want better observing conditions, you’d have to go into space.
I had come to the Pole, courtesy of a grant from the National Science Foundation’s Antarctic Artists and Writers Program, to observe the astronomical facilities in the Dark Sector as part of the research for my next book (due for publication from Houghton Mifflin Harcourt in January 2011).
Although I don’t have a background in science, I write about science for a non-specialist audience. I try to use my initial ignorance and then my gradual learning process as a way to figure out how to present the necessary information to readers in a logical and accessible fashion. For this book, my topic is a mystery that many researchers feel might be the most significant and profound in science today: What comprises the vast majority of the universe?
In studying galaxies (including our own Milky Way), astronomers have consistently found that galaxies seem to be rotating far too rapidly for their own good. From what we can see of the amount and distribution of the visible matter, the galaxies should be deeply unstable. They’re spinning so fast that they should be shedding stars and gas in every direction — unless there’s something else out there stabilizing them. Something we can’t see but is nevertheless exerting a gravitational influence on the matter we can see.
Astronomers call this mysterious something “dark matter.” As for the kind of matter that makes up you, me, my laptop, Earth, planets, stars, and galaxies, it’s the exception in the universe, not the rule, a realization that has led some observers to call the discovery of dark matter “the ultimate Copernican revolution.”
The ultimate Copernican revolution
About 10 years ago, that revolution got, well, more ultimate (think of Spinal Tap’s 11 on the volume dial). Two rival teams of astronomers had spent much of the 1990s observing exploding stars, called supernovae, at distances up to halfway across the visible universe.
The universe is expanding, and matter (dark or otherwise) attracts other matter through gravity, so they set out to measure how much this mutual attraction is slowing down the expansion. In early 1998, however, the two teams independently reached the same conclusion: The expansion isn’t slowing down at all but seems to be speeding up. The universe appears to be accelerating under the influence of something that astronomers call, for lack of a better term, “dark energy.”
“Why should I believe you?” someone in the cafeteria at McMurdo asked me over breakfast during my stopover en route to the Pole, when I described the dark discoveries behind the science I would be observing.
Short answer: You shouldn’t. I’m not a scientist. But over the past decade, cosmologists (including a small army that has passed through Antarctica) have produced an enormous amount of corroborating data, until they have now arrived at an exquisitely precise rendering of the depths of our ignorance: 23 percent dark matter, 73 percent dark energy, and only 4 percent the stuff of us.
Particle physicists and theorists have come up with several possible but still hypothetical candidates for dark matter, including one they call the neutralino. The IceCube Neutrino Observatory now nearing completion at the South Pole — a square-kilometer network of sensors clinging to “strings” drilled thousands of meters into the polar ice — wasn’t specifically designed to find the neutralino. But if the interior of the sun is spewing forth these particles, as theorists speculate, then IceCube might be able to detect them.
As for dark energy, scientists aren’t trying to figure out what it is. Instead, they want to know what it’s like. Does dark energy change over space and time, and if so, by how much? Or does it stay constant, remaining at one single value, beginning at the Big Bang and continuing until the end of time?
And the end of time is precisely what hangs in the balance: how dark energy behaves will determine the fate of the universe. Will the universe ultimately collapse back on itself, in a reverse Big Bang that astronomers have christened the “Big Crunch”? Will it expand at a greater and greater rate of acceleration, pulling apart the cosmos like so much taffy, eventually ending in an atom-shredding “Big Rip”? Or will it just coast into a colder and colder, lonelier and lonelier, emptier and emptier eternity?
The global effort to solve that mystery is what brought me to the South Pole Telescope, the latest in a series of Antarctic experiments that astronomers hope will help them answer these questions.
Why, of all places, Antarctica? Because Holzapfel’s right: It’s the most benign environment on Earth — at least if you’re trying to study the Cosmic Microwave Background (CMB).
Lurking in the background
The CMB is the relic afterglow of the Big Bang. When the universe was about 380,000 years old, it had cooled enough for matter and radiation to decouple and go their separate ways. That relic radiation survives today, pervading our daily existence. In the pre-digital era, about one percent of the static on “blank” TV channels consisted of this echo from the Big Bang. The cosmologist’s job, in effect, is to sort through all the ambient static in the universe and isolate the CMB signal — and the South Pole is the best place on Earth to do just that.
Submillimeter, or microwave, radiation operates at a wavelength that happens to be particularly sensitive to water vapor. For the microwave astronomer, that sensitivity results in two distinct, equally complicating, problems.
First, even small amounts of atmospheric moisture can absorb incoming millimeter-wavelength CMB signals, meaning that those photons never even reach the telescope. Second, that same water vapor can emit its own millimeter-wavelength signals — photons at the same wavelength as the CMB — meaning that astronomers can find themselves mistaking humidity for history.
The Pole environment, fortunately, compensates for these potential problems. It’s high — more than 9,000 feet above sea level, so the atmosphere is thin. It’s dry — because the cold temperatures keep the amount of water vapor low. And during the austral winter, the atmosphere at the Pole is extremely stable, due to the absence of the heating and cooling effects of a rising and setting sun.
Because the CMB preserves the image of the universe in its infancy, scientists think of it as cosmic DNA. The grown-up universe now is identical genetically, so to speak, to the newborn universe. That universe was almost entirely smooth, but it did contain some irregularities, and through the gathering force of gravity, those seemingly minor fluctuations eventually coalesced into the cosmos we see today. They became the galaxies, the stars within those galaxies, the planets orbiting those stars, and the complex life forms populating those planets, such as human beings and NSF grant applications.
The discovery of the CMB itself, in 1965, led to one Nobel Prize in Physics, the verification of the CMB and then the discovery of its subtle bumps, in 1990 and 1992, to another. The scale of those fluctuations (as well as other defining features in the CMB) have been further refined by subsequent observations, including numerous balloon-borne detectors launched from McMurdo Station and such Dark Sector telescopes as the Degree Angle Scale Interferometer (DASI), QUEST at DASI (QUaD), and Background Imaging of Cosmic Extragalactic Polarization (BICEP), among others.
The mission of the South Pole Telescope, however, isn’t just to do more of the same, documenting the radiation from the Big Bang in greater and greater detail. Instead, the telescope is one of a new generation of experiments that uses the CMB not as an end in itself but as a means — a tool to investigate other phenomena.
Specifically, the South Pole Telescope uses the CMB to hunt for galaxy clusters. As CMB photons make their 13.7-billion-year journey from the primordial fireball to the ultra-cold spider web of gold at the heart of a Dark Sector receiver, they might interact with the hot gas of a galaxy cluster, an encounter that would bump them up in energy.
The clusters that Holzapfel and his colleagues discover by identifying this telltale change — they’re aiming for thousands — will then undergo further scrutiny from other telescopes to determine their distances. When astronomers piece together the abundance and distances of those clusters, they hope to see the influence of dark energy on the growth of large-scale structures throughout the history of the universe. And perhaps they’ll even find fresh clues as to whether dark energy has remained constant or changed with time.
Whether the South Pole is indeed the most benign environment on Earth depends on who’s defining “benign.” If you’re the winter-over who has to climb into the SPT’s 10-meter dish once a week to sweep out the snow, rather than the astrophysicist who gets to download six months’ worth of nonstop data at a desktop in Berkeley, the conditions at the Pole just might seem a bit harsh.
Even so, you can always content yourself with the knowledge that where you’re standing is not only the best place on earth to do CMB astronomy but a pretty good spot to stare at the heavens and contemplate the universe — and to wonder what the other 96 percent of it is.
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