From the romantic image of the astronomer gazing at the heavens to the spectacular snapshots captured by the intricately crafted lenses of the Galileo and Hubble telescopes, telescopic technologies have garnered the most notice among the public as the way to study the universe. But these methods - called direct observation - are limited because Earth-bound star gazers see events often billions of years after they have occurred, due to the incredible distances separating Earth's galaxy, the Milky Way, from others.

The coming weeks will bring a new development in the field of theoretical astronomy, as a team of researchers at the Cornell Theory Center debuts a new algorithm that will allow them to simulate how the universe formed after the Big Bang.

"After the Big Bang, we have to ask what the universe is made of. Most of it is seen as exotic particles, or baryons, but different models show different rates at which the universe is expanding," said Dr. Renyue Cen, a Princeton University researcher working on the project. "We're trying to find the correct model of the universe. But the only way to test it is by putting them into the computer and evolve it, given the physical laws they must follow."

Theoretical astronomy helps fill in the billion-year holes left by direct observation by using supercomputers to model different researchers' theories. "Since we can't do actual experiments on stars, planets, galaxies, or even the whole universe, we must do the experiments numerically," said Terry Oswalt, a professor of physics and space sciences at the Florida Institute of Technology.

Scientists working on the Cornell project are busily examining galaxy clusters and simulating their evolution on an IBM RS/6000 Scaleable POWERparallel system. The new algorithm will enable them to more accurately simulate the "particles of matter" that are between the clusters of galaxies, and can provide crucial data from about 51 million years after the Big Bang up to today - a period of time spanning 13 billion years - says Cen.

The previous simulation used by the team followed only dark matter and interacted only with gravity. It supplemented the simulation with the Particle Mesh method, which enabled it to more closely measure gas pressure in the space between the galaxies.

Cen said the new algorithm is an Adaptive Mesh model, which enables researchers to compact their model of the universe patterned along a uniform grid in the simulation. By compacting the grid the way a recycler would crush an aluminum can, the researchers bring the simulation of the widespread galaxy clusters closer together. This gives astrophysicists a better chance of determining what happened, because they can look at a larger number of galaxy clusters together.

"The primary difficulty is that you need to have a big volume of galaxy clusters to have a fair sample. The typical separation is about 50 megaparsecs, or 150 million light years," Cen said. "Right now, we can only have one cluster in a simulation box. It is not representative of the whole universe. With the new algorithm, we will be able to increase the volume to 10 galaxy clusters or more in one field of view."

It will bring the matter between the galaxies nearer as well.

The new algorithm will allow the "big step forward by deforming the grid," said Cen. "The trick is to move the mesh, the grid points, to where the clusters are. The algorithm tells the program how and when to deform the grid. It is a dynamic process. The grid of the universe is normally quite uniform. At the end of the simulation, though, it will be quite irregular."

The project, which has received funding from the Advanced Research Projects Administration, the National Science Foundation, and IBM, is just about to begin. Cen says simulations could last as long as six days or even longer.

But that time span is nothing compared to the eons that are being compacted in the simulation. Oswalt, who is not involved in this particular project, said the time scales involved in the study of galaxy clusters is so long - millions of years and more - that their "motions can only be simulated numerically. These simulations can predict what the positions and velocities and masses of cluster members should look like now, and such comparisons with the Hubble and ground-based data are used to decide among the competing computed models which is most likely correct."