For those who live in a city or near one, the night sky isn't much to look at--just a few scattered stars in a smoggy, washed-out expanse. In rural Maine, though, or North Dakota, or the desert Southwest, the view is quite different. Even without a telescope, you can see thousands of stars twinkling in shades of blue, red and yellow-white, with the broad Milky Way cutting a ghostly swath from one horizon to the other. No wonder our ancient ancestors peered up into the heavens with awe and reverence; it's easy to imagine gods and mythical heroes inhabiting such a luminous realm.
Yet for all the magnificence of the visible stars, astronomers know they are only the first shimmering veil in a cosmos vast beyond imagination. Armed with ever more powerful telescopes, these explorers of time and space have learned that the Milky Way is a huge, whirling pinwheel made of 100 billion or more stars; that tens of billions of other galaxies lie beyond its edges; and, most astonishing of all, that these galaxies are rushing headlong away from one another in the aftermath of an explosive cataclysm known as the Big Bang.
That event--the literal birth of time and space some 15 billion years ago--has been understood, at least in its broadest outlines, since the 1960s. But in more than a third of a century, the best minds in astronomy have failed to solve the mystery of what happens at the other end of time. Will the galaxies continue to fly apart forever, their glow fading until the cosmos is cold and dark? Or will the expansion slow to a halt, reverse direction and send the stars crashing back together in a final, apocalyptic Big Crunch? Despite decades of observations with the most powerful telescopes at their disposal, astronomers simply haven't been able to decide.
But thanks to a series of remarkable discoveries--the most recent just two weeks ago--the question may now have been settled once and for all. Scientists who were betting on a Big Crunch liked to quote Robert Frost: "Some say the world will end in fire,/ some say in ice./ From what I've tasted of desire/ I hold with those who favor fire." Those in the other camp preferred T.S. Eliot: "This is the way the world ends/ Not with a bang but a whimper." The verdict seems to be in: T.S. Eliot wins.
Why do we care? For one thing, this is a question that has haunted humans for as long as we have walked the earth. A definitive answer--if that is indeed what we have--will force philosophers and religious leaders to rethink their assumptions and beliefs about eternity and how the world will end. For scientists, meanwhile, there are certain details in these discoveries that have profound--and bizarre--implications. For example, the new observations bolster the theory of inflation: the notion that the universe when it was still smaller than an atom went through a period of turbocharged expansion, flying apart (in apparent, but not actual, contradiction of Albert Einstein's theories of relativity) faster than the speed of light.