The Canon (43 page)

Beyond revealing its roots, each light beam speaks of the journey it had en route to its telescopic rendezvous: the relative desolation, dustiness, violence, or sedateness of the terrain it traversed, the masses it passed, the time it has been in transit, the likely fate of the radiant body that gave birth to it so very long ago. Another extraordinary ordinary truth of astronomy is that a look outward into space is also a look backward in time. Light is mighty light on its feet, and nothing in the universe is known to outrun it; but light is not infinitely fast, which means it needs time to get from point
a
to point
b.
And because space is so expansive, and the gaps between any two items so chasmic, the light we detect from the stars is old news. Even the light leaping off the surface of our nearest star, the sun, needs eight minutes to stream across 93 million vacuum-packed miles before it can strike your sensibly sunscreened skin. The image of Jupiter you see in your backyard telescope is how the planet looked half an hour ago, while that of Saturn is some seventy minutes old. Peer beyond our solar system, and you start digging into the lumen archives. In the constellation of Canis Major, for example, you'll find Sirius, the Dog Star, gleaming twice as brightly as any other star in the sky; those sequins left home nearly nine years ago. Or skip to the Little Dipper and mark the showpiece spot at the handle's tip; that light belongs to Polaris, the North Star, as it was back when Will Shakespeare was still wearing shorts.

Granted, nearly everything that you can perceive in the nighttime sky with the unaided eye very likely hasn't changed much between the time the radiant energy was dispensed and the time it reached Earth. On a really excellent night of stargazing, you can distinguish maybe 2,500 stars from any single location, and all of those stars, nearly all of the dots that the ancients connected on their charts into the named constellations, are located in our galaxy, most of them quite close, within a few hundred light-years of the sun. If it is dark enough and the right time of year, you can also see the fuzzy band of light that is colloquially
referred to as the Milky Way, as though it had nothing to do with us, or the major and minor Dogs, or the double Dippers, or any of the other standbys of the night sky. Of course, once again you are navel-gazing, looking right at our home galaxy, this time toward the bulging central disk where most of the Milky Way's 300 billion stars reside. Thick plumes of interstellar gas and dust lying between the sun and the bulge obscure the view, but even if you could stare straight into the galactic heart, you wouldn't be looking terribly far: from our earthly perch, located about two-thirds of the way down one of the four major spiral arms of our pinwheeling Milky Way, it's only a distance of 26,000 light-years to the hub. There are a couple of other galaxies right at the edge of the bare eyeball's ability, most notably the Andromeda galaxy, located just to the south of Cassiopeia. Andromeda is much farther away than any of the visible stars, but still, it is the nearest big neighbor to the Milky Way, a mere 2.5 million light-years away. On a cosmic scale, where the average star manages to radiate more or less stably for several billion years, 2.5 million years is but a twink of an eye. So, yes, the star light you see tonight may be hundreds, thousands, a million years old, but with few exceptions the stars themselves are still out there, burning bright.

Spend some time with a serious telescope, however, and all bets are off, and so, too, are many of the lights. The stronger the telescope, the more distant the objects that astronomers can view. They can see far beyond the Milky Way, Andromeda, and the other members of our so-called Local Group of galaxies, to millions of other galaxies, tens of millions, hundreds of millions, billions of light-years away. They can see flocks and flocks of spiral galaxies shaped much like our own, whirls of cream aswirl in the black coffee of space; and elliptical galaxies that look like giant scoops of rice, with stars for grains; and riffs on the basic ellipse and spiral themes, along with rumpled deviants called irregulars—galaxies shaped like cartwheels, beer barrels, pork chops, and pencils, or those flat plastic monkeys that you hook into chains. Astronomers can also peer inside those distant galaxies and descry and tally their parts—their stars, their nebulae of dust and gas, even some evidence of planets and comets. They have found elfin galaxies of 100,000 stars, and colossi of 3 trillion. Whatever their shape and census, galaxies display an unmistakable coherence, their components clearly bound together by gravity into distinct communities, shining states of shared stellar fates. The word "galaxy"
means
"Milky Way," and fittingly so, for every one of the 100 billion known galaxies is, like ours, a place that stars call home—or used to. Remember that the more distant the galaxy glimpsed, the more archaic the image, and the more mind-teasing the implications. If you go to a good science museum or planetarium, you'll likely find some of the gorgeous "ultradeep field" surveys captured by the Hubble Space Telescope, of hundreds of extremely distant galaxies. With few exceptions, the stars in those galaxies pictured have long since died—sputtered and collapsed into dull brown dwarves, or spattered their outer sheaths into their surroundings, as supernovas. In some cases, hot new stars have taken the place of the ancestral lights captured by our telescopes. In others, the galaxies are likely cooler and darker and more sedate than they appear to our necessarily time-lagged eyes. Some of the galaxies are thought to have been swallowed up by surrounding galaxies, or by a giant black hole that lurks at their core, as black holes are thought to exist in the center of many galaxies, including our own.

In so many ways, deep-space scans can outspook a'séance. For example, astronomers perpetually monitor the skies in search of supernovas and the abundance of data that such big light shows can offer. On average, a star explodes somewhere in a galaxy about once a century. To find these rare events, astronomers take weekly pictures of the same 8,000 or so galaxies, over and over again, Tuesday in, Marsday out. "We look for what's different," said Alex Filippenko. "Usually there's nothing, but every so often, we find a new, exploding star. Last year, we found eighty-two." One week, it's the same old barred spiral, with all the pizzazz of a Boise potato. The next, a blinding bombshell shatters the calm, swamping the rest of the galaxy's photonic sum. Can anything seem more instantaneous, more here and now and in your face, than a mammoth sun that goes kablooey? Yet once again, time bides its time and abides by the lawful, awful limits of light. The cataclysmic event that "suddenly" appeared on an astronomer's scan occurred, oh, half a billion years ago, and the "new" exploding star has long since dispersed into the void, and who knows that it didn't, in dying, seed the birth of another sun, with satellite Saturns and Jupiters and gazing Gaias of its own. On a cosmic scale, at least, there is always new hope from the dead.

The universe that we live in and are inextricably of was born nearly 14 billion years ago—13.7 billion years ago, to be a bit more exact about it, and scientists are confident that this figure fits well with a welter of findings. The universe and everything it enfolds—all known and suspected matter and energy, all space and time, all broken dreams, lost loves, and inside-out umbrellas—began in the momentous moment we call the Big Bang. If the name sounds both a little smutty and a little
Barney, it should. When the great Sir Fred Hoyle coined the term during a radio interview some sixty years ago, he meant it as a glib put-down. An adamant atheist as well as a prominent cosmologist, Sir Fred disliked the idea then gaining currency of a universe with a defined origin, viewing it as the equivalent of a cosmic nativity scene open to any number of religious tie-ins; he and his like-minded peers favored a "steady-state" model of a static universe that had always existed in pretty much its current contours. Hoyle's heckle proved so catchy, however, that soon proponents as well as critics were referring to the hypothesized birth of the universe as the Big Bang. Even as an ever accreting body of evidence has transformed a plausible conjecture into a bedrock premise of contemporary space science, still the lighthearted tag line holds. True, there wasn't really a bang. A bang is a sound, and sound waves need air molecules to propagate, and in the beginning not only was there no air there, there were no molecules, either, or atoms, just pure energy.

And "big"? In the beginning, there was really the smallest small of all, the entire universe contained in something less than a billionth of a trillionth the size of an atomic nucleus. But let's be serious. An event like the birth of the universe is a very big deal, and it was a bang in the sense of being an explosion. A tremendous amount of stuff, of energy, the beginnings of matter and, importantly, of space itself, of somethingness rather than the unnerving utter nothingness that might have been, or not have been, broke free of its confinement, of an infinitesimally small and circumscribed borderline called a singularity, and began ballooning outward in all directions with unthinkable force and at relativistic speed—that is, close to the speed of light. So, yes, it
was
a Big Bang, and we can be glad that Hoyle chose to poke fun at the concept long enough to capture its dispositional humor in a phrase.

We don't know why there was a Big Bang—what preceded it, what triggered it, or what was going on at the moment of truth, moment oh-point ... whoa. Using mathematical models, scientists have chased the universe back to a point hootingly close to the Big Bang—"to 10
^-35
seconds after time zero," according to Alan Guth, a physicist at MIT. But filling in that last little tittle, that niggling hundred-billionth of a yoctosecond, now that's tough. To resolve that, scientists will have to settle some difficult questions, like whether the laws of physics were born with the Big Bang and therefore collapse into meaninglessness when you metaphorically enter the singularity of the Big Bang; or whether the laws predated the Bang and perhaps gave rise to it. Whatever the cause, we know the consequences. Our universe began with the
Big Bang, and it has been expanding, and cooling, ever since; and everything about the structure, shape, and makeup of the cosmos—its silky homogeneity on a large scale, its lumpy clotting into stars and galaxies when you take a closer look—traces back to that moment of infinitesimally huge and splendidly, blessedly adulterated unity. Simon Singh, a physicist and science writer, has described the detection of the Big Bang as "the most important discovery of all time," and he may be right. But whereas other important advances like sliced bread and Teflon prove their case with French toast, what are we to make of this contender for science's ultimate laurel? We can't touch it, taste it, see it, or butter it. Why should we believe that the Big Bang is true?

The formulation of the Big Bang model of the universe was an exercise in reverse psychology. First, astronomers realized that the universe was expanding outward in all directions, like an inflating balloon, or a loaf of yeasty bread baking, or one of those Japanese paper flowers that unfurls in water; then they began working backward. Run a movie of those everyday analogies in reverse, and what would you see? A buoyant, globular party favor collapsing into a flat cat-tongue of rubber, or a hydrangea-sized blossom being sucked back into a slight, suspect pill. So, too, it seemed, would a backward film of the universe bring the scattered cosmic characters ever closer, until everything condensed into a very small speck of starter dough—if not quite as small as a single point, then at least a single point of view.

The man generally credited with discovering the expansion of the universe was Edwin P. Hubble, a legendary Missouri-born, pipe-smoking astronomer considered as comely as he was brilliant. He was "an Olympian," his wife declared, "tall, strong, and beautiful, with the shoulders of Hermes of Praxiteles." Hubble also managed the impressive trick of luxuriating in his considerable celebrity and hobnobbing with such nonastronomical luminaries as Douglas Fairbanks, Cole Porter, and Igor Stravinsky, all the while retaining his lofty scientific reputation. Fifty years after his death, Hubble's crossover appeal lives on, for not only do astronomers still apply "Hubble's law" and the "Hubble constant" to their workaday investigations, but NASA's decision to christen its multibillion-dollar space-based telescope the Hubble has helped to keep his name alive in the wider public eye, at least until the slowly decaying instrument itself winks off for good.

Hubble first won renown for his persuasive demonstration that our galaxy was not the be-all and after-all of the universe, and that many of the mysterious splotches on astronomers' photographic plates that had
been dubbed nebulae, for their cloudlike appearance, were not constituents of the Milky Way, as the mainstream view had it, but were independent celestial bodies lying at staggering distances from our galaxy—bodies that were soon determined to be whole other galaxies. On characterizing these autonomous, shimmering star prefectures in greater detail, Hubble found evidence that not only were they really far away, but they were getting farther away all the time. Whichever galaxies in whatever quadrant of the cosmic landscape he examined, they all appeared to be fleeing from our poor little galaxy, as though the Milky Way had broken out in buboes, or asked for help with the dishes. Moreover, the farther the galaxy, the faster it seemed to be beating its retreat. This could be seen because in sprinting away each galaxy turned a bit red in the face, and the greater the distance, the deeper the beet.

Here we have one of astronomy's fundamentals, an essential food group of the field and a powerful piece of evidence in favor of the Big Bang model of the birth and evolution of the universe: the light waves coming from galaxies undergo what is called a redshift before presenting themselves at our door. If you compare telltale atomic fingerprints, or spectra, of the light from a distant galaxy with equivalent spectra of known light sources here on Earth, you'll see that the patterns of dark and bright lines on both sets of spectra are identical bar for bar, indicating that the same mix of atomic elements must be generating the radiation both out there and down here. On the galactic spectra, however, the entire array of lines looks as though it had been shoved over toward the redder, longer-wavelength end of the electromagnetic spectrum and away from the bluer, shorter-wavelength side, compared to the terrestrial benchmark lights. What does this redshifting mean? It means that the pulsating waves of star light, as they traverse the gulf between their natal galaxies and our vigilant scopes, are being stretched and pulled and lengthened, the distances between the crest and trough of each light wave gradually widened, the peaks softened, the pique assuaged.