Despite repeated challenges from renegade theories, the big bang model of our cosmic origins remains the most convincing: it posits that the universe began in a violent explosion, creating a world filled with hot, fluidlike plasma that only later cooled as it expanded. For decades scientists have expected to be able to detect acoustic oscillations, or "waves," that pulsed through this plasma some 10 billion years ago. Last month, a group discovered evidence of these oscillations in the cosmic microwave background radiation (CMB)in essence the afterglow from the big bang. And now new results from astrophysicists at Carnegie Mellon University and the University of Maine reveal acoustic oscillations in the distribution of matter in the universe as well.

"Not only do these results provide support for the hot big bang inflationary model, but they also show we understand the physics of the early universe," Carnegie Mellon postdoctoral researcher Christopher Miller says. "This physics can take us forward in time, predicting the matter-density distribution from the CMB, or backward in time, predicting the CMB using the distribution of galaxies and clusters of our local unverse." Drawing on a wealth of data, the team created and compared snapshots of part of the universe both as it is now and as it was 300,000 years after the big bang, when the CMB emerged.

"Now that we understand this framework, we can decouple the evolution of the universe from the evolution of galaxies and start attacking other fundamental questions like, How did galaxies form and why?" Carnegie Mellon professor Robert Nichol remarks. "It's a great time to be a cosmologist!"