Cosmologists normally assume we live in a pretty average part of the universe, but there is growing evidence that this might not be the case. Some think that the Milky Way sits – like some kind of giant, space hillbilly – in a void, an immense region of near emptiness.
If true, this might help explain some gaps in our understanding of the cosmos.
The universe that emerged from the big bang was exceptionally smooth, but there were tiny ripples in the matter, imprinted by the rapid expansion known as inflation. Over billions of years, gravity drew matter out of the more tenuous regions, pooling it into the seeds of stars and galaxies. This has left the universe richly structured, with dense clusters of matter joined by a network of less dense sheets and filaments. Between these sit the cosmic voids.
While cosmologists know this structure exists, they generally ignore it in their calculations, assuming matter is smooth, rather than having to worry about clusters and voids. But is this assumption leading us astray?
Over the past few years, there has been growing observational evidence that our neck of the universe is not typical, and that our galaxy is in a large void, several hundred million light years across. What would be the effect of living in a whole lot of nothing? Benjamin Hoscheit and Amy Barger at the University of Wisconsin are the latest to try to answer this.
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