Letter fro? Discover

Dec 3, 2003 6:00 AMNov 12, 2019 5:21 AM


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Photograph by Amy Eckert

The 100-inch Hooker telescope in California is now a curious antique, but it remains the most important optical instrument in the world because Edwin Hubble used it in the 1920s to determine that the universe is expanding.

The precision with which we can describe the universe has suddenly become nothing less than astounding. A little more than a year ago, you might have read that the universe is somewhere between 10 billion and 15 billion years old. Thanks to the WMAP satellite, launched in June 2001, we recently learned the universe’s precise age—13.7 billion years. That single piece of information has a cascading effect. It removes a variable from thousands of other research projects under way, making each and every one of them incredibly more valuable because their results will be incredibly more precise.

The satellite has made another remarkable contribution to science by helping us figure out with great precision what our universe is made of, and in what proportions. WMAP tells us that all the stuff we can see or even hope to see in the universe—stars, galaxies, gas, and dust—is just 4.4 percent of what is out there. Twenty-three percent of the universe, apparently, is composed of matter we cannot detect by any conventional means, whether X-ray satellites, radio dishes, or optical telescopes. Scientists call this invisible stuff dark matter. The other three-quarters of the universe is a form of energy we also cannot detect directly (but which by sophisticated means we can infer is actually there). Scientists call this dark energy. Just 25 years ago, astronomer Vera Rubin encountered thunderous skepticism when she announced she’d found evidence for abundant dark matter. In 1998 many researchers shook their heads in disbelief at claims that the universe is full of dark energy. Now both types of these dark entities have passed from strange speculation to accepted physics. The universe is not just strange but truly weird—weirder than even the boldest theorists would have guessed less than a decade ago.

We live in an age of discovery the likes of which people have never known. The only time that came close occurred about a hundred years ago when Albert Einstein, Max Planck, and other physicists came up with iconoclastic quantum theories to try to make sense of the physical world we can and cannot see. But they were theorists trying to catch up with what we had already observed. Our age is different because evidence and observation are pouring in at unprecedented speed, challenging the theorists to try to keep up. We can see only a tiny fraction of the world we live in, yet now we can retrace history back to the beginning of the universe and can reasonably predict its distant future. Even for the scientists who are making the discoveries, this is a time of true awe and wonder.

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