The Great Cosmic Map

Mercury, March/April 2003 Table of Contents

by Matthew Colless

The 2dF Galaxy Redshift Survey has given us a 3-D map of the local universe, which is helping to usher in an era of precision cosmology.

Maps tell us where we are and how to get to where we are going. But maps can also provide vivid insights into fundamental truths about the world we live in. A globe of Earth, for example, is the clearest illustration of the bald statement that "the world is round." Such revelations are not confined to geography: the depths of time are shockingly revealed by a geological map that peels back the rock strata, showing that a single location was once a mountain range, then beneath the sea, and then a mountain range once again.

Maps have also been fundamental to understanding our place in the universe beyond Earth. Cosmographies — maps of the universe — are as old as human civilization, and have gone hand in hand with cosmogonies describing the creation of the world. Such maps have been at the heart of scientific revolutions. How to draw the map of the solar system was the scientific issue at the heart of the Copernican revolution, fronting the deeper philosophical controversy over the anthropocentric world-view.

Until the 20th century, however, all such maps were, at least beyond the borders of the solar system, entirely speculative. Beyond the planets — far beyond — were the stars and the nebulae, but their arrangement and distances were essentially unknown.

The 2dF Galaxy Redshift Survey compiled these two maps of the North (left) and South Galactic Poles. The maps show the distribution of galaxies out to more than a billion light-years. Courtesy of the 2dFGRS team and Paul Bourke (Swinburne University Centre for Astrophysics and Supercomputing).

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