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Surveying the whole panoply of physics, from quasars imaged by Hubble near the edge of the observable universe to the subatomic realms probed by particle accelerators, one increasingly gets the sense that science has as yet detected only the tip of an iceberg. Consider the question of dimensionality: On how many dimensions is the universe built? Newton got by with just the three dimensions of familiar, everyday space. Einstein improved on Newton's accuracy by adding time as a fourth dimension: His gravitational fields bend space within four-dimensional space-time. But gravitation is only one of the many fields that, as Weinberg notes, pervade the vacuum of space. If you're trying to write a unified theory of all the known particles and fields, you may find yourself working in a dozen or more dimensions. And for all we know there are multitudes of as yet undetected particles, each with its own field, implying still more dimensions.

Are these dimensions real, or—as philosophers came to consider Ptolemy's Earth-centered model of the universe—just a handy way of calculating? Increasingly, physicists suspect that they are real. If so, the perceived universe is but a glimmer on the surface of something much larger and more complex, and the known laws of nature are not bedrock but a kind of weather, like the clouds that form over mountain peaks. Dark energy may offer a glimpse of the mountain—or iceberg—beneath. So the next time someone wonders aloud what use it is to spend billions on Hubble and the other space telescopes when we have "problems here at home," the answer may be that their use is to help us understand just what home is, and where it abides in the wider and wilder landscape.

Hubble is getting old. The next shuttle service mission to upgrade and repair it—scheduled for late next year—may be the last. Fortunately it's not alone up there. Its peers include the Spitzer Space Telescope, which detects long-wavelength infrared light invisible from the surface of Earth; the Chandra X-ray Observatory, which probes the short-wavelength part of the spectrum; and little Swift, a satellite that pinpoints short-duration, high-energy gamma-ray bursts and instantly emails word of them to professional and amateur astronomers around the world. None can do all that Hubble does, but coming up is the genuinely gigantic James Webb Space Telescope: Scheduled for launch in 2013 into an orbit a million miles (1.6 million kilometers) high, Webb will gather infrared light with a mirror over 21 feet (6.4 meters) in diameter, stylishly screened from sunlight by an umbrella the size of a tennis court. Together with a growing network of ground-based telescopes and detectors, the space observatories are producing floods of astronomical data, at a constantly increasing rate. They promise, as Lyman Spitzer noted back in 1946, to alter not only what we know, but how we learn.

Timothy Ferris is the author of Coming of Age in the Milky Way, The Whole Shebang, and other works. A film based on his latest book, Seeing in the Dark, premiered in September on PBS.
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