The Washington Post asked me to review The 4 Percent Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality. Back in my green days as a science writer and editor, I kept up fairly well with things cosmological, but the seductions of biology have distracted me from the sky for some time now. So it was a pleasure to get back up to speed--and to discover just how weird things have gotten in the universe--with Panek's book:
In 1969, an astronomer named Jeremiah Ostriker realized that the Milky Way was spinning too fast. That may sound odd, given that it takes the sun 230 million years to make a full orbit. But when Ostriker tried to simulate the Milky Way on a computer, he found that it was spinning so quickly that it should have ripped itself apart long ago. There weren't enough stars to hold it together.
Ostriker went to his fellow Princeton scientist James Peebles to share his puzzle. "There's something wrong here," Ostriker said to Peebles. The two scientists decided there could only be one solution: The stars we can see in the Milky Way are just a small fraction of the actual galaxy. They are embedded in a vast, unseen halo, made of an unknown stuff that has come to be known as dark matter. When Ostriker and Peebles looked to other galaxies, they found hints of dark matter there as well.
Other astronomers didn't want to believe it. After all, they had spent the past four centuries learning about the universe by collecting the light of the universe in their telescopes. Now it seemed they were missing most of the cosmic show. But as Richard Panek chronicles in his fascinating new book, "The 4 Percent Universe," it turned out that there was a lot more wrong with the universe than even Ostriker had realized and that his and Peebles's work was only the beginning of an enormous undertaking by many scientists.
The latest surveys of the universe indicate that only 4 percent of it is made of ordinary matter. Nearly 23 percent is made up of dark matter, which some physicists suspect consists of wispy subatomic particles that may someday be caught in a detector. And the remaining 73 percent is made up of something far more baffling: an energy that is causing the universe to expand at an ever-increasing rate. Scientists call it "dark energy," and they have no idea what it is. "Get rid of us and of everything else we've ever thought of as the universe," writes Panek, "and very little would change"...
You can read the rest of the review here