National Geographic : 2005 May
"primeval atom," as he put it. "The evolution of the world can be compared to a display of fire works that has just ended: some few red wisps, ashes and smoke," wrote Lemaitre. From this poetic scenario arose today's big bang. Many were appalled by this concept. "The notion of a beginning ... is repugnant to me," said British astrophysicist Arthur Eddington in 1931. But evidence in its favor slowly gathered, climaxing in 1964, when scientists at Bell Tele phone Laboratories discovered that the cosmos is awash in a sea of microwave radiation, the remnant glow of the universe's thunderous launch. Ever since then the image of the big bang has shaped and directed the work of cosmolo gists as strongly as Ptolemy's celestial spheres influenced astronomers in the Middle Ages. Freedman and others confidently peg the uni verse's current rate of expansion, as well as its age. A birthday cake for the universe would require some 14 billion candles. Astronomers havefound some strange objects in this expanding universe-and these too are Einstein's children. In the 1930s a young Indian physicist, Subrahmanyan Chandra sekhar, applied special relativity and the new theory of quantum mechanics to a star. He warned that if it surpassed a certain mass, it would not settle down as a white dwarf at the end of its life (as our sun will). Instead gravity would squeeze it down much further, perhaps even to a singular point. Horrified, Eddington declared that "there should be a law of Nature to Now Einstein's "biggestblunder"isstarting In 1980 Alan Guth, now at the Massachusetts Institute of Technology, gave the big bang a boost, adding new particle physics to Einstein's flexible space-time. He realized that for its first trillionth of a trillionth of a trillionth of a second, the infant cosmos could have undergone a super charged expansion-an instant of "inflation" -before settling into more measured growth. Inflation would have helped smooth out the matter and energy in the universe and flattened its overall space-time curvature, just as satellites have found by making precise measurements of the cosmic microwaves. And these days some theorists believe inflation wasn't a flash in the pan. In an ongoing process of creation, space time could be inflating into new universes every where and all the time-an infinity of big bangs. Within our own universe, the high priests of astronomy have continued the cosmological quest initiated by Einstein and Hubble, first at Mount Wilson, then at the 200-inch telescope on California's Palomar Mountain, 90 miles to the south. How fast is the universe ballooning outward? they asked. How old is it? "Answering those questions," says Wendy Freedman, direc tor of the Carnegie Observatories, "turned out to be more difficult than anyone anticipated." Only at the turn of this century, with the help of a space telescope aptly named Hubble, did 120 NATIONAL GEOGRAPHIC * MAY 2005 prevent a star from behaving in this absurd way!" There was no such law. Chandrasekhar had opened the door for others to contemplate the existence of the most bizarre stars imaginable. First there was a naked sphere of neutrons just a dozen miles wide born in the throes of a supernova, the explosion of a massive star. A neutron star's density would be equivalent to packing all the cars in the world into a thimble. Then there was the peculiar object formed from the collapse of an even bigger star or a cluster of stars-enough mass to dig a pit in space-time so deep nothing can ever climb out. Einstein himself tried to prove that such an object-a black hole, it was later christened could not exist. Like Eddington, he loathed what would be found at a black hole's center: a point of zero volume and infinite density, where the laws of physics break down. The discoveries that might have forced him to acknowledge his the ory's strange offspring came after his death in 1955. Astronomers identified the first quasar, a remote young galaxy disgorging the energy of a trillion suns from its center, in 1963. Four years later, much closer to home, observers stumbled on the first pulsar, a rapidly spinning beacon emit ting staccato radio beeps. Meanwhile spaceborne sensors spotted powerful x-rays and gamma rays streaming from points around the sky.