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

by Richard Panek

How do you see something that is dark, if by “dark” you mean, as astronomers beginning in the 1970s and 1980s did, “impossible to see”? How do you do something that is, by your own definition, impossible to do? You don’t. You rethink the question. For thousands of years, astronomers had tried to apprehend the workings of the universe by looking at the lights in the sky. Then, starting with Galileo, they learned to look for more lights in the sky, those that they couldn’t see with their eyes alone but that they could see through a telescope. By the middle of the twentieth century, they were expanding their understanding of “light,” looking through telescopes that saw beyond the optical parts of the electromagnetic spectrum—radio waves, infrared radiation, x-rays, and so on. After the acceptance of evidence for dark matter, astronomers realized they would need to expand their understanding of “look.” Now, if they wanted to apprehend the workings of the universe, they would have to learn to look in a broader sense of the word: to seek, somehow. To come into some manner of contact with.