A Fizzle or a Crunch?

It seemed last week that a question as big as the universe had been settled. Two long-rival teams of astronomers announced they had “decisively” concluded that the universe will not end in a Big Crunch, as previously theorized. Rather, the universe will continue its expansion from the original Big Bang forever, growing colder and dimmer and gradually petering out as stars die and galaxies dissipate. These conclusions were presented with such assurance that many observers thought the contentious field of cosmology had finally reached certain agreement. Not a chance.

Cosmologists, those who study the cosmos, are famous for making confident declarations about highly speculative matters. Thus the quip, “cosmologists are often in error but seldom in doubt.” And despite the two teams’ cocky declarations, the fate of the universe continues to inspire spirited debate.

Until recently, some astronomers in the two teams had concluded that the universe would end in a Big Crunch, falling inward on itself, because it held enough concentrated matter to slow the outward expansion caused by the Big Bang. The total mass, they theorized, would eventually exert enough gravity to pull distant stars and galaxies back to the center, much as the gravitational power of the Earth keeps the moon in orbit.

These theories, based on abstract mathematical calculations, proved less probable last year when the two teams were granted observation time on the Hubble Space Telescope. Hubble allowed them to gaze at images of star systems 7 billion light years away, revealing what the universe looked like only 300,000 years after the Big Bang. From the images, the two teams concluded that the universe has less than 80% of the matter needed to make it contract.

However, many respected cosmologists, those not in the inner circle of astronomers represented at the news conference, continue to insist that the universe has far more matter than we think. The undiscovered matter, some theorize, is hidden in black holes that we can’t easily detect, and its behavior is determined by forces like anti-gravity (which repels rather than attracts) that we have yet to understand.

Such challenges are typical of those posed by independent-minded scientists throughout cosmology’s history. They are inspired by a kind of social anti-gravity that seems to motivate cosmologists in particular to question, rather than blindly orbit around, the established ideas of the inner circle. And by setting off a new scramble for data, they are essential to the field’s advancement.