Some works of popular science, trying to impress the reader with the scale of the universe and the insignificance of humans on the cosmic scale, argue that there’s nothing special about our place in the universe: “an ordinary planet orbiting an ordinary star, in a typical orbit within an ordinary galaxy,” or something like that. But this is wrong! Surfaces of planets make up a vanishingly small fraction of the volume of the universe, and habitable planets, where beings like ourselves are neither frozen nor fried by extremes of temperature, nor suffocated or poisoned by a toxic atmosphere, are rarer still. The Sun is far from an ordinary star: it is brighter than 85% of the stars in the galaxy, and only 7.8% of stars in the Milky Way share its spectral class. Fully 76% of stars are dim red dwarves, the heavens’ own 25 watt bulbs.
What does a typical place in the universe look like? What would you see if you were there? Well, first of all, you’d need a space suit and air supply, since the universe is mostly empty. And you’d see nothing. Most of the volume of the universe consists of great voids with few galaxies. If you were at a typical place in the universe, you’d be in one of these voids, probably far enough from the nearest galaxy that it wouldn’t be visible to the unaided eye. There would be no stars in the sky, since stars are only formed within galaxies. There would only be darkness. Now look out the window: you are in a pretty special place after all.
One of the great intellectual adventures of the last century is learning our place in the universe and coming to understand its large scale structure. The Cosmic Web written by J. Richard Gott, an astrophysicist who has played an important role in discovering that structure, explains how we pieced together the evidence and came to learn the details of the universe we inhabit. It provides an insider’s look at how astronomers tease insight out of the messy and often confusing data obtained from observation.
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