The End of the World-The fate of the Universe

The End of the World

Remember the young Woody Allen's cosmic angst in the film Annie Hall? Having just read that the universe is expanding, the boy is so worried that he can't do his homework. "Someday it will break apart," he tells his shrink, "and that will be the end of everything." But, his mother snaps, "you're here in Brooklyn! Brooklyn is not expanding!"

Maybe not, but Woody was on to something. Long before the universe finally fades out, his nightmare will come true—though not as he imagined. Now about halfway through its estimated 10 billion-year lifetime, our sun is slowly brightening. In about 1 billion years, its energy output will have increased at least 10%, turning Earth into a Venusian hothouse where plants wither, carbon dioxide levels plummet and the oceans boil off.

Even so, we would still have to quit the sun's neighborhood before it begins its final death throes. With its nuclear fuel exhausted, the fiery orb will collapse upon itself like a giant soufflé, only to see its internal furnace briefly restoked in several last gasps. These will swell the sun's outer layers so they engulf all the inner planets, including Earth, turning it into what astrophysicist Neil de Grasse Tyson calls "a red-hot charred ember." The sun's red-giant phase will be brief, however. Shedding its heat and gases, it will become a cold, compact cadaver no bigger than Earth, a white dwarf lost in space.

Let's assume that humans—or some higher life-form—are still around to witness these cataclysms—an iffy supposition since we've been on Earth for only a fraction of the dinosaurs' time (2.5 million vs. 160 million years) yet already have the power to destroy ourselves. If we're still around, we will have to seek out homes on other planets orbiting other warming stars. That will take some giant leaps. Even the speediest galactic ark would have to travel hundreds of years, during which multiple generations would live and die on board, before reaching even a nearby star like Proxima Centauri, 4.3 light-years away. And in the end, not even such a sanctuary would save our descendants, or any other life-forms still inhabiting the universe, from its last, dying gasp.

By FREDERIC GOLDEN




THE FATE OF THE COSMOS

That means that the 100 billion or so galaxies we can now see though our telescopes will zip out of range, one by one. Tens of billions of years from now, the Milky Way will be the only galaxy we're directly aware of (other nearby galaxies, including the Large Magellanic Cloud and the Andromeda galaxy, will have drifted into, and merged with, the Milky Way).

By then the sun will have shrunk to a white dwarf, giving little light and even less heat to whatever is left of Earth, and entered a long, lingering death that could last 100 trillion years—or a thousand times longer than the cosmos has existed to date. The same will happen to most other stars, although a few will end their lives as blazing supernovas. Finally, though, all that will be left in the cosmos will be black holes, the burnt-out cinders of stars and the dead husks of planets. The universe will be cold and black.

But that's not the end, according to University of Michigan astrophysicist Fred Adams. An expert on the fate of the cosmos and co-author with Greg Laughlin of The Five Ages of the Universe (Touchstone Books; 2000), Adams predicts that all this dead matter will eventually collapse into black holes. By the time the universe is 1 trillion trillion trillion trillion trillion trillion years old, the black holes themselves will disintegrate into stray particles, which will bind loosely to form individual "atoms" larger than the size of today's universe. Eventually, even these will decay, leaving a featureless, infinitely large void.

BY MICHAEL D. LEMONICK



http://www.time.com/time/covers/1101010625/story.html