Ever being the scientific generalist and novice that I am, I have never heard of the “Fractal Universe”. But after reading about the big, gaping void a billion light-years across a couple of weeks back, and this blog posting in this week’s New Scientist, I got curious:
There is, however, a group of rebel physicists who did predict the existence of such a mind-bogglingly enormous structure. Back in March, I wrote an article entitled, Is the Universe a Fractal?, detailing the ongoing debate between mainstream cosmologists, who assume that the large-scale universe is homogeneous, and a band of physicists led by Luciano Pietronero, who claim that the structure of the universe is fractal.
The standard model of cosmology – that is, the big bang, cold dark matter universe – is founded on the assumption that the distribution of matter (both normal and dark) becomes evenly spread at sufficiently large scales. Look in one spot in the sky and then another and they should appear nearly the same, they say. There shouldn’t be a big hole in one spot and a giant cluster of matter in another.
The fractal guys argue that, on the contrary, matter continues to clump into ever-bigger structures even at the largest scales. It’s like this: imagine you could have a bird’s eye view of the universe (obviously impossible, but play along) and you zoom in to look at a single star. Then you begin to zoom out and you discover that the star is part of a galaxy. Keep zooming out and you see that the galaxy is part of a cluster of galaxies and the cluster of galaxies is part of a supercluster of galaxies and and the supercluster of galaxies is … This is where the debate begins.
According to the standard model, there’s nothing bigger than a supercluster. When I interviewed mainstream physicists David Hogg and Daniel Eisenstein for my article, they were claiming that the pattern should start to smooth out at about 200 million light years. According to the fractal guys, it just keeps getting bigger.
So in other words, since there could be more large empty voids out there, there should be even larger groupings of super clusters of galaxies, like super-duper deluxe gigantic groupings of galactis clusters and super clusters!
Like I said, cosmology is a new study for me, so I can’t lay out any theories of my own, but I did find an interesting slide show, http://www.fractaluniverse.org/ which is informative and asks some hard questions on it’s own.
And I do so love asking the hard questions! 😉