Calculations find that many universes could sustain stars
Fred Adams sees stars in the most unlikely places.
His calculations suggest that, contrary to some previous claims, stars are not only common in our cosmos but are also ablaze in myriad other universes, where the laws of physics may be drastically different. Even in a cosmos where balls of gas and dust never collapse and ignite to make conventional stars, radiation produced by black holes and clumps of invisible material called dark matter may play the same role as stars, says Adams, a theorist at the University of Michigan in Ann Arbor.
“In fact, all universes can support the existence of stars,
provided that the definition of star is interpreted broadly,” notes
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,
Other researchers, he notes, have considered a broader class of questions in exploring the multiverse, including not only the possibility of star formation and stellar structure, but also that of galaxy formation and the existence of life.
“I did a specific
approach that is much more detailed on the particular topic of ‘can there be stars?’ ”
By allowing all three of the parameters, rather than a
single parameter, to vary,
He cautions, however, that his calculations assume that all
possible values of the each parameter are equally likely. For instance, it may
be more likely for a universe to have a smaller nuclear reaction rate than a
larger one. “We simply do not know,”
The results are not “particularly surprising, as stars are
both fairly simple and fairly robust objects that essentially require [only] a
heat source and gravity,” says Anthony Aguirre of the
The findings have several intriguing implications, he adds. Had
“The paper nicely points out that when considering whether other, different universes can sustain life, it is very important to carefully consider how the known universe could change, but also to consider all sorts of things that don't really exist here, such as black-hole-powered solar systems, or dark-matter stars,” Aguirre says. “This open-minded approach can serve, in some cases, as a counter-argument to claims that our universe is fine-tuned for life.”
Adams, F.C. In press. Stars in other universes: Stellar structure with different fundamental constants. Journal of Cosmology and Astroparticle Physics. doi: 10.1088/1475-7516/2008/08/010