THE HOMOCENTRIC UNIVERSE:

SPACE IS VAST AND ALIEN. That's one basis of its romance, but it's also a cognitive hurdle for anyone trying to wrap their head around its reaches. "The trouble we normally have with space is, if we try to understand something, we only have one example--our own planet," says Colin Stuart, a fellow of the Royal Astronomical Society and the author of the forthcoming How to Live in Space: Everything You Need to Know for the Not-So-Distant Future.

A solipsistic view isn't necessarily a bad thing, he says: Using Earth as a data point is often helpful--especially for science educators trying to connect with enthusiasts who aren't fluent in astronomical jargon. "We always try to compare things to Earth when we can," Stuart says. "If you're starting with something they know about, you're not starting from the beginning." He stacks up volcanoes, valleys, and trenches in space against the Grand Canyon or Everest, "because people have that frame of reference," even if the features are on vastly different scales. (Olympus Mons, the highest of Mars's volcanic peaks, is 2.5 times taller than Everest, and roughly the width of France.)

"Unless you're embedded in the science speak, I could be saying any kind of gobbledygook, but that might not make any sense to anyone," says Michelle Nichols, the director of public observing at Chicago's Adler Planetarium. Nichols often translates features of space that might otherwise be somewhat inscrutable into familiar scenarios or childhood games. She compares sun spots, as glimpsed through a telescope, to iron filings dancing under a magnet's sway. "People remember doing that," she says. "They go, 'Right, now I see it.'"

To some extent, scientists lean on analogues in peer-reviewed papers, too. In a recent paper in Science, a team of researchers including Jani Radebaugh, a planetary scientist at Brigham Young University, and her collaborator Matt Telfer, a physical geographer at the University of Plymouth, reported on Pluto's dunes, which look something like the ones on Earth's deserts or beaches. A lay viewer glancing at the images captured by the New Horizons spacecraft might not have made the connection, but an analogue can turn on a lightbulb. "They may only see a whitish background with some squiggles," Nichols says. "As soon as you say, 'It's like a sand dune,' they say, 'Oh, wait a minute! I've been to the Indiana dunes, I've seen pictures of the Sahara.'" Pluto's drifts aren't sand--they're slopes of frozen methane--but the wind has sculpted them into similar shapes, and that knowledge may give laypeople a foothold.

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