To evaluate new information, to see how it fits with the big bang, cosmologists increasingly turn to supercomputers.

A Universe in Ferment

Cosmology. The branch of science that takes as its subject, well, everything -- the universe. The seemingly infinite reaches of space, the expanse of time -- past, present, future. Cosmology asks how and when did all this come into being? What structure does it have? How is it evolving?

Cosmologists have plenty to think about lately. Although understanding of the visible universe has progressed by leaps and bounds in the last 20 to 30 years, the pace of new information -- from sensitive electronics harnessed to Earth telescopes, sophisticated satellites and, most recently, the Hubble Space Telescope -- shows no sign of slowing down. Cosmology is in the news, with theorists and observers contending to make sense of it all.

To evaluate the new information, to see how it fits into the general framework of the "big bang" model of cosmic origin, cosmologists increasingly turn to supercomputers. Edmund Bertschinger, a theoretical astrophysicist at MIT, is one among a group of physicists and computer scientists who in 1993 formed a nationwide collaboration, the Pittsburgh Supercomputing Center.

Bertschinger has focused on one of the most fundamental questions: the origin of large-scale structure in the universe. Detailed observations since the late 1980s show that galaxies are not evenly distributed in space, as previously believed, but clustered, with areas of high and low density. Through a two-pronged approach, modeling microwave radiation from space and modeling the evolution of matter itself, Bertschinger looks at how small irregularities at the start of the big bang could have led to the universe we see around us now. "Somehow the universe started with this tremendous hot fireball," says Bertschinger. "The early universe was quite smooth. How did it get to be so lumpy today?"

No, they're not Easter Eggs. They're the infant universe hatching from its structureless shell. The COBE science working group produced the blue and pink all-sky map from data collected by the Cosmic Background Explorer (COBE) satellite. It depicts minute temperature fluctuations, ranging from 0.00015 degrees Kelvin colder (blue) than the background to 0.00015 degrees K. warmer (pink). The second map represents Edmund Bertschinger's simulations on the CRAY T3D at Pittsburgh. This map, at higher angular resolution (0.5 degrees) than COBE could detect (7 degrees), shows negative (blue) and positive (red) fluctuations of 0.0002 degrees K. The simulation assumed a mixed hot and cold dark matter model with 5 eV neutrino mass.

Researchers: Edmund Bertschinger, Massachusetts Institute of Technology.
Hardware: CRAY C90, CRAY T3D
Software: LINGER
Keywords: Cosmology, astrophysics, physics, cosmic origin, big bang, galaxy clusters, density, cosmic microwave background, thermal radiation, Cosmic Background Explorer satellite, dark matter, particle dynamics, COBE.

Related Material on the Web:
The Grand Challenge Cosmology Consortium (GC3) Home Page
The GC3 at MIT Home Page, research of Edmund Bertschinger and others.
The GC3 at Pittsburgh Supercomputing Center.
Projects in Scientific Computing, PSC's annual research report.

References, Acknowledgements & Credits