An interesting study looks at alternate universes with different physics to determine how frequently you get an environment where stars will form. It turns out about 25% of the time; more often than you’d guess.
Science News / Stars Ablaze In Other Skies
According to inflation, a leading theory of the birth of the universe, the cosmos underwent a tremendous growth spurt in its first tiny fraction of a second, enlarging from subatomic scale to the size of a grapefruit. This rapid expansion may also have occurred in other patches of space remote from our cosmos, creating a multitude of pocket universes, or multiverses, with different physical laws.
In his analysis, Adams simulated conditions in other universes by simultaneously varying three parameters: the gravitational constant, which determines the strength of gravity; the fine structure constant, which sets the strength of the electromagnetic force; and a composite number that determines the rate of nuclear reactions, which keep stars shining.
By allowing all three of the parameters, rather than a single parameter, to vary, Adams created a simulation that may embrace a larger number of possible universes, he says. He finds that stars are stable entities in roughly one-fourth of the universes he considered. “That’s a sizable amount of real estate.”