How Old Is the Universe?

It's all very well for astronomers to say that the universe is 13.7 billion years old, but you have to wonder just how they figured that out. Vanderbilt University astronomer Weintraub (Is Pluto a Planet?) explains it all for astronomy buffs in an enthusiastic way. He starts with how scientists first determined the age of the solar system—about 4.5 billion years —by isotope dating the oldest known rocks: lunar rocks brought back by astronauts, and meteorites that have collided with Earth. He then shows how stellar life cycles indicate an age of about 13 billion years. Astronomer Edwin Hubble's discoveries—that fuzzy spiral nebulae were really distinct and very distant galaxies, and that those galaxies are moving away from us—offered a new measure and new result: 13.5 billion years. Refining that number requires measuring things we can't even see: dark energy and dark matter, including exotics like wimps (weakly interacting massive particles) and machos (massive compact halo objects). Weintraub guides readers on a winding journey through history, explaining various dating approaches and illustrating the determination of astronomers to find the answer to one of the most basic questions about our universe. 46 b&w photos; 76 line illus. (Jan.)