Dark energy is another one of them mysteries that astronomers love. Turns out there are a whole loada observations suggesting that the universe ain’t just expanding, but acceleratin’ away from us. Something has gotta be providing the oomph for this cosmological acceleration and for want of a better term, theorists have nick-named it dark energy (cos we can’t see it…geddit?).
There ain’t no shortage of suggestions for where this dark energy comes from. One of the favorites is that the cosmological constant ain’t zero but has some value that explains the acceleration away. But do the sums and astrobods come up with a value that looks so arbitrary that none of them can bring themselves to believe it.
Enter Golam “Precious” Hossain at Penn State who has his own ideas. He reckons that if the early universe fragmented into island universes surrounded by a vacuum, that could make the expansion accelerate in the way we see it but without any special energy or hidden mass providing a secret push. It also leaves the cosmological constant as zero. So we happen to be living in one of these islands (the others are beyond the edge of the visible universe, presumably)
There are one or two holes in this idea. Surely the visible universe stretches far enough to see these other islands or atleast the edge of our own. And if if it don’t, why wouldn’t these island universes show up in the cosmic background radiation? Somehow, I don’t think Precious has cracked it yet.
Ref: arxiv.org/abs/0709.3490: Structure Formation and the Origin of Dark Energy