But, with great simulations come great, intricate, daunting catalogues of information to formulate and keep track of.

Inside the simulation's hypothetical section of the universe are all of the ingredients that go into creating a star, such as the fundamental chemical properties of the gases present, the expansion of the universe, and gravity. The code also calculates the rate at which molecular hydrogen cools the cloud as it forms.

Finally, it takes into consideration Cold Dark Matter, a cosmic material that researchers know exists but haven't been able to observe. They have, however, been able to figure out the amount that exists, how it behaves, and what impact it has on other, observable cosmic material.


All of these properties set the rules of the experiment. But a simulation also requires something for those rules to act on. Otherwise, you've decorated the gym, but no one's on the dance floor.

Norman and his collaborators used what is known as a Gaussian random field to populate their hypothetical universe and start the party. Gaussian random fields set the initial conditions in many cosmological experiments. They mimic the conditions of the universe at a given time and create a random interpretation of it. For example, there is a range of the amount of matter allowed in the simulation, but the precise amount of matter in a given run is established randomly.

In the first star simulations, the Gaussian random field provides a section of universe that is full of the minute density fluctuations that are necessary for star-forming clouds. These density fluctuations are random in their location. Their size and number, however, follow a very specific spectrum that is highly constrained by researcher's observations.

Think back to the dances of your youth. Everyone is sitting in the bleachers of some junior high school gym, but nobody is willing to be the first out on the floor. A Gaussian random field provides those first few intrepid souls, the Devil-may-care dancers that everyone else can join.

"There were a lot of ingredients, but that's what makes this such a rich, important simulation," Norman says.

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