U of T cosmologists are piecing together the epic table of how the universe has evolved over 14 billion years
Inside the old Molson brewery on Toronto’s Lake Shore Boulevard, Barth Netterfield has built a time machine. To be sure, the spindly aluminum structure bears little resemblance to the souped-up DeLorean that carried Michael J. Fox into the 1950s in the film Back to the Future. Instead, it’s a high-tech telescope that will provide a glimpse of how our universe appeared billions of years ago, when the first stars and galaxies were forming and the cosmos we see today was beginning to take shape.
The telescope is called BLAST – for Balloon-Borne Large Aperture Sub-Millimetre Telescope. A NASA balloon will hoist BLAST into the stratosphere next year, an event for which Netterfield, a professor in U of T’s department of astronomy and astrophysics, has already spent a year preparing. Because the university lacks the kind of high-ceiling facility that such an instrument needs, he had to settle for the brewery, with its leaky roof, rusting support columns and complete absence of temperature control. What’s more, the building, like so many others in the now trendy “west of SkyDome” neighbourhood, is about to metamorphose into condominiums – and the developer gave Netterfield a mere two weeks’ notice. BLAST was already scheduled for shipment to a lab at the University of Pennsylvania for final preparations; now, with eviction imminent, that move will have to come sooner.
But Netterfield and graduate students Carrie MacTavish (MSc 2000) and Don Wiebe (MSc 2001) have made the best of their no-frills workspace, plugging in space heaters in the winter and electric fans in the summer. “It’s been far from ideal,” concedes Netterfield, “but it gets the job done.” Overhead, the giant pipes that once carried grain for the brewery poke out of the ceiling; a blue tarp protects the computer workstations from the elements. As the months passed, Netterfield’s unconventional laboratory grew on him. “I think it’s aesthetically rather nice,” he says, “in a weird kind of way.”
The brewery-lab may seem low-tech, but BLAST itself – a joint venture with scientists from the United States, Mexico and Britain – will be state-of-the-art. As we walk around the BLAST gondola, Netterfield explains the role of each component: the two-metre concave mirror, an array of detectors, a computer and an assortment of gyroscopes and flywheels. Soon, the whole machine will be circling the globe at an altitude four times that of Mount Everest. It will give scientists their first detailed look at the early universe in the barely explored “sub-millimetre” wavelengths – longer than waves of infrared light but shorter than microwaves or radio waves. It will be able to hold its aim to within four arc-seconds – equivalent to aiming at a dime half a kilometre away. With 288 individual detectors, BLAST “will be the biggest sub-millimetre array on any telescope to date,” Netterfield says. “I really hope it’s going to revolutionize the field.”
Netterfield and his colleagues have high hopes for BLAST, but the project is merely the latest chapter in the new and compelling story of modern cosmology, a discipline that explores how the universe we see today evolved from the primordial fireball of the big bang some 14 billion years ago. It is a mind-boggling transformation: back then, the universe was indescribably hot, dense and nearly perfectly smooth; today, it is enormous, cold and full of structure. Back then, it was a soup of subatomic particles and pure radiation; today, it contains stars and galaxies, planets and people. Astronomers and physicists at U of T are helping to piece together this epic tale – and, incredibly, they’re beginning to attach precise numbers to theories that were little more than conjecture just a couple of decades ago.
Those numbers, known as cosmological parameters, include quantities such as the age of the universe, its density, its expansion rate and its total energy content. Fitting those numbers together into a cohesive cosmological picture also requires a strong theoretical framework. That framework rests on the big bang, of course, but also on a refinement of the basic theory: developed in the early 1980s, it is known as inflation. According to inflation, the universe underwent a brief spurt of exponential growth in a minuscule fraction of a second after the initial explosion. Physicists believe that during that brief moment, tiny fluctuations in the fabric of the early universe inflated into the seeds of the first structures to develop in the cosmos. So far, inflation appears to be spot-on: it seems to predict exactly the values that astronomers are now measuring for those cosmological parameters. “We really have a very, very strong case that the basic paradigm is working,” says Richard Bond, the director of the Canadian Institute for Theoretical Astrophysics (CITA), headquartered at U of T.
And yet the cosmos continues to surprise us. Physicists have learned that the universe is awash in bizarre entities such as dark matter and dark energy – entities that inflation can accommodate but not explain. “Obviously, there’s a tremendous amount of euphoria that things are working as well as they are,” Bond says of inflation’s success. But, he observes, “instead of sitting back and resting on our laurels, we have to do a remarkable amount of new work.”
You might think that all evidence of the big bang must have long since vanished. Surprisingly, though, it’s all around us, if only we know where to look. Turn on your TV, disconnect the cable and tune in one of the in-between channels: about seven per cent of that “fuzz” is from radiation produced by the big bang. That radiation, which astronomers call the CMB, for cosmic microwave background, was discovered by accident in the mid-’60s; it appears as a “glow” that seems to radiate from every direction in the sky. Astronomers now recognize the CMB as the microwave “echo” of the big bang – a burst of radiation released when matter and energy first went their separate ways, about 400,000 years after the initial explosion.
That all-sky glow holds a treasure trove of information about the early universe, and no one is more skilled at teasing that data out of the CMB than Bond, a leading authority on the physics of the microwave background. (Bond won two prestigious awards in 2002: he received the Heineman Prize from the American Institute of Physics, and was elected to the Royal Society of London – an honour that, he jokes, is “still rarely given to scientists from the colonies.” Currently at the California Institute of Technology, he is in the midst of a busy sabbatical year that will later take him to Paris and Cambridge, where he’ll confer with some of the world’s top cosmologists.) Over the past few years, Bond and his colleagues have worked on a series of ground-based, balloon-borne and satellite-based telescopes designed to probe the microwave background in ever increasing detail – and they’ve used that data to piece together a remarkably detailed picture of the early universe.
The structure of the microwave background began to show itself in the early 1990s. At that time, the COBE satellite (Cosmic Background Explorer) mapped the largest of the faint “ripples” in the CMB, which appear as subtle differences between its “hot” and “cold” regions. A decade later, a balloon-borne telescope known as Boomerang captured more detailed views of the CMB. (The telescope circled the globe – hence its name – above Antarctica, and will fly again this winter. Netterfield leads the project’s Canadian contingent.) Using data from Boomerang, scientists were able to determine the “power spectrum” of those ripples in the CMB – essentially finding the intensity of the ripples as a function of how large a swath of sky they cover. The shape of that spectrum again seemed to match perfectly the predictions of the inflation model. (The Boomerang data also agreed with data from two U.S. experiments, known as DASI and Maxima, reported at about the same time.) Recent experiments, including the Chile-based Cosmic Background Interferometer – in which U of T scientists again played a leading role – reveal even more detailed structure in that spectrum. A Toronto team is also helping to plan a European satellite known as Planck, to be launched in 2007; Planck will map the CMB across the entire sky in minute detail.
Physicists are thrilled to have the first high-resolution images of the microwave background radiation, and they’re glad to see those cosmological parameters being pinned down. But they admit that the numbers seem to describe a peculiar, highly counterintuitive universe. For starters, only about five per cent of the energy content of the universe is in the form of “ordinary” matter – the kind that makes up stars, planets and galaxies. About 30 per cent is tied up in “dark matter” – non-luminous and detectable only through its gravitational effects. The bulk of the universe – some 65 per cent – is “dark energy,” a mysterious entity of unknown origin that fills the entire universe.
And yet, scientists are gradually learning to navigate this peculiar cosmos. Beginning this winter, astronomers will use the Canada-France-Hawaii Telescope (CFHT) to map the distribution of dark matter in unprecedented detail. The project, known as the CFHT Legacy Survey, will reveal the subtle bending of light from distant galaxies as it passes massive objects en route to Earth. This bending – astronomers call it “gravitational lensing” – was predicted by Albert Einstein and has already been observed in numerous deep-sky images. The CFHT survey will be the first to use gravitational lensing to systematically hunt for dark matter and record its distribution.
“Our survey will be directly mapping where it is and what it is doing,” says CITA cosmologist Ue-Li Pen. Peering deeper than any previous survey of its kind, the CFHT will show where the dark matter is lurking. “Dark matter is not as dark as it used to be,” Pen jokes. Yet the actual makeup of the dark matter remains unknown. The survey will show where it is, he explains, but not what it’s composed of. The best guess, he says, is that most of it is made up of exotic, ultra-heavy particles produced in the big bang. Smaller amounts may be due to neutrinos – tiny particles whose mass is nearly, but not quite, zero – or to primordial black holes.
Dark matter may be weird, but dark energy is even stranger. It’s the name astronomers have given to the mysterious force that seems to be pushing every galaxy away from its neighbours. The case for dark energy has been building since the mid-’90s, when observations of supernovas in distant galaxies showed that those galaxies weren’t just receding, they were accelerating. The recession by itself is not surprising; the big bang gave every galaxy a “push,” which we still observe. But gravity ought to be slowing those galaxies. What could possibly be causing them to speed up? At the moment, the best explanation for the acceleration is something called the “cosmological constant” – a kind of anti-gravity force first put forward by Einstein in 1917. (He introduced it as a fudge factor in his theory of gravity, known as general relativity, adding the term to his equations to make sure they described a “static” universe. When astronomers discovered a decade later that the universe wasn’t static but was actually expanding, Einstein lamented the fudge as his “greatest blunder.” If the universe really is accelerating, however, Einstein’s cosmological constant may be resurrected.)
Scientists speculate that the cosmological constant might result from the “vacuum energy” of empty space – an energy field created as countless subatomic particles wink fleetingly in and out of existence. “I certainly find it very weird,” admits Pen. “Maybe next year we’ll have a new Isaac Newton coming along and giving order – giving a single picture in which we can understand all [of these phenomena]. Maybe there is no dark energy. Maybe it’s a mental crutch we are using to describe something much more profound. That, I think, would be a very exciting possibility,” says Pen.
Inflation has been an invaluable theory, but it is probably not the final word. Ultimately, physicists would like to see a theory that embraces Einstein’s relativity as well as quantum mechanics – the two pillars of modern physics – in one unified framework. If they’re lucky, the new theory will explain the mechanism behind inflation, as well as the nature of dark energy.
So far, the leading contender is a framework known as string theory – an outgrowth of particle physics in which matter and energy, at the deepest level, are thought to be made up of tiny, vibrating strings (or perhaps multi-dimensional membranes), billions of times smaller than an atomic nucleus. String theorists, including U of T physicists Amanda Peet and Kentaro Hori, have been working closely with cosmologists such as Bond and inflation expert Lev Kofman, also at CITA, in an effort to see what evidence for string theory can be found in observations of the early universe. The Canadian Institute for Advanced Research (CIAR) – Bond is one of its directors – is also playing a key role. Thanks to the efforts of Bond and his colleagues, this nationwide think-tank now boasts one of the world’s top cosmology and gravity programs. The resulting cross-fertilization of ideas has been enormously beneficial to all parties, keeping the astronomers up to speed on the latest theoretical studies, and keeping the theoreticians focused on ideas that can actually be put to the test. Such collaborations “are exactly what makes a bridge between string theory – early universe theories – and cosmological observations,” notes Kofman. “We are always asking, ‘What are the signatures of early universe physics in present-day observations?’ ”
Will string theory eventually revolutionize our view of the early universe? That remains to be seen. In the meantime, cosmologists are enjoying the current golden age, in which both theory and experiment are leaping ahead at breakneck speed and much of the universe’s 14-billion-year history is beginning to make sense. That success is especially impressive when we remember that cosmology is one of the youngest of the sciences – much younger than either astronomy or physics, from which it emerged less than a century ago. “It’s quite an exciting period,” says Bond, “with remarkable experimental efforts converging with grand theorizing.”
Back at the former Molson brewery, meanwhile, Netterfield is preparing BLAST for its move to Pennsylvania. The two graduate students, MacTavish and Wiebe, are busy dismantling computer equipment and rolling up cables. On this day, they don’t seem particularly sad to be vacating the Molson building. The garage-style doors are open, and the remnants of Hurricane Isadore are battering the parking lot outside. I ask the two students how they explain to people that they go to a brewery each day when they’re supposedly working on their PhDs. “I’ve had a lot of interesting comments,” MacTavish admits. And what happens when her friends discover that she’s building a high-tech telescope rather than perfecting a new kind of beer? Then, she says, they’re even more intrigued. “Telescopes and beer,” she reflects with a grin. “Does it get any better than this? I don’t think so.”
Dan Falk’s first book, Universe on a T-Shirt: The Quest for the Theory of Everything, was published this fall by Viking (Penguin) Canada.