The 4% Universe: Dark Matter, Dark Energy, and the Race to Discover the Rest of Reality

by Richard Panek

Just as our eyes didn’t need to evolve to see radio waves in order for us to survive, maybe our minds didn’t need to evolve to understand the numbers that astronomers were now trying to incorporate into their thinking. Like cultures that count “One, two, three, more,” we tend to regard the scale of the universe—to the extent that we regard it at all—as “Earth, planets, Sun, far.” Consider: How long would it take you to count to a million at the “one Mississippi” rate of one second per number? Eleven days—or, to be exact, 11 days, 13 hours, 46 minutes, and 40 seconds. How long would it take you to count to a billion at the same rate? A billion is a thousand million—that is, a million one thousand times over. So you would have to count a million Mississippis—eleven days of counting—a thousand times. That’s 31 years, 8% months. To reach a trillion, you’d have to count to a billion a thousand times—31 years a thousand times, or 31,000 years. A light-year—the distance light travels in a year—is about six trillion miles. To count to six trillion, you would need six sets of 31,000 years, or 186,000 years. Earlier generations of astronomers had to learn to adjust their thinking to accommodate successive discoveries about new scales of the universe: that the Sun is 93 million miles distant; that the nearest star after the Sun is 4.3 light-years, or 25 trillion miles, away (that’s 186,000 years of Mississippis 4.3 times, or about 800,000 years); that our “island universe” consists o...