An astrophysicist looks a few trillion years down the road

You might call Fred Adams and Greg Laughlin the ultimate futurists.

In their new book, "The Five Ages of the Universe: Inside the Physics of Eternity" (The Free Press), the astrophysicists marshal what generations of scientists have learned about the nature of matter and the cosmos since the Copernican revolution to craft an unauthorized biography of the universe - complete with obituary.

What a long, strange story it is. Their tale is measured in years whose number starts with a 1 and, for the purposes of this telling, stops at 100 zeros.

As the universe evolves, galaxies run out of hydrogen. Star formation stops. Much later, an ever-shrinking population of now-exhausted stars glow with the light and warmth of four 100-watt light bulbs. They derive their feeble energy from proton decay. As protons and neutrons decay, the large structures they comprise slowly disappear.

Black holes, the tortoises of a once-rich astronomical menagerie, are the last to vanish, slowly evaporating until they end in a brief flash of radiation. What's left is a tenuous assortment of electrons, positrons, neutrinos, and radiation of vast wavelengths inhabiting the still-expanding fabric of space-time.

To human eyes, the cosmos as we know it may end in darkness, but the trip is never dull. And out in the vast darkness lies the possibility that a new universe could emerge.

All of which leaves Dr. Adams in fine humor, despite his story's dark end.

"People have accused me of being too cheerful," says the University of Michigan professor in an interview prior to a lecture and book-signing at Boston's Museum of Science. "But this is the ultimate 'big picture.' It provides a valuable perspective on our time and suggests that while our time is a good time, it may not be the only good time."

Life as we know it on Earth, he explains, could emerge and evolve several times over during the next few trillion years, should Earth-like planets ever orbit low-mass red-dwarf stars, the most common form of stars in the observable universe. After the current "stelliferous era" ends, giant balls of hydrogen known as brown dwarfs, which never grew large enough or dense enough to become stars, could merge and ignite, forming stars capable of warming any world they might capture as they wander.

The notion of tracking the universe's future emerged from his interest in how stars evolve, Adams says. In 1995, he teamed up with Dr. Laughlin, from the University of California at Berkeley, to take the very long view on the universe. Meanwhile, the University of Michigan developed a "theme semester" centered on the idea of death, extinction, and the future of humanity. Adams's contribution to the course became clear - the death of the universe.

But, he says, he and Laughlin ultimately were driven by the paucity of research done on the subject since a few seminal papers appeared in the 1960s and '70s, and by the advances in physics and astronomy since then. Those advances, he says, greatly expand the range of informed projections one could make about how the universe might evolve. The work resulted in a 1997 paper that earned Adams a prestigious award from the American Astronomical Society.

Even as the two worked on the book, Adams says, the questions they asked of themselves continued to demand calculations that broke ground. For example, he continues, "no one had calculated the long-term evolution of low-mass stars before we did," leading to the conclusion that red dwarfs can burn - and hence nurture life - for trillions of years.

Still, he acknowledges that many of the book's predictions leave him and Laughlin open to criticism, which he says typically comes as: "Science is in the business of making predictions, but what good are they if you can't test them?"

"Predictions can be useful even if you can't realize them immediately," he replies, since they help frame the ideas that observational physicists, astrono-mers, and astrophysicists will test with telescopes and particle accelerators. Indeed, he says, two kinds of experiments could provide significant reality checks on much of what the book offers.

One would be to measure Hawking radiation, the extremely slow mechanism by which black holes are believed to lose mass and so evaporate.

A second, currently being conducted in large underground water tanks at labs around the world, is the search for proton decay. So far, experiments haven't seen it yet, which only allows scientists to set a lower limit on the amount of time it takes for a proton to decay.

(c) Copyright 1999. The Christian Science Publishing Society