OCTOBER 2007

Cosmologists are shocked by the recent discovery of a monstrous void of empty space spanning nearly a billion light years in diameter. The void – the biggest ever observed – challenges the standard picture of how structure has formed throughout the universe's history. No one's sure how big of a problem the void is for standard cosmology, but it certainly flies in the face of generic predictions.

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.
As is, mainstream cosmologists have a hard time explaining the existence of structures as big as superclusters, but they make it work by invoking something called a bias parameter. The bias parameter is there to make up for the difference between the distribution of normal luminous matter and the distribution of mysterious dark matter. The bias is declared to be 2 – which means they are assuming that the dark matter distribution is twice as smooth as what we see with our eyes (and telescopes).
A deciding factor between the two models, then, is the distribution of dark matter; in particular, whether or not there is dark matter lurking in the voids. If the mainstream guys are right, the voids should be full of evenly spread dark matter. If the fractal guys are right, the voids should be truly empty … and huge. "If the cold dark matter model is correct, then there should be dark matter in the voids," Hogg told me.
So here we are, with a void nearly a billion light-years across that is truly empty – no stars, no dark matter. Does that mean that the universe is fractal? One observation isn't enough to support a definitive conclusion – but it seems the fractal guys, who have long been shunned by the mainstream, deserve to be heard. The reason their ideas have been considered dangerous is that if the universe is fractal, it's back to the drawing board for all of cosmology. But as I wrote back in March, "If the voids are full of dark matter, then the apparent fractal distribution of luminous matter becomes rather insignificant. But if the voids are truly empty, the fractal claim requires a closer look." http://www.newscientist.com/blog/space/
Amanda Gefter, opinion editor (Illustration: Greg Bryan et al.)

'We have broken speed of light'

By Nic Fleming, Science Correspondent
Last Updated: 12:01am BST 16/08/2007

A pair of German physicists claim to have broken the speed of light - an achievement that would undermine our entire understanding of space and time.

According to Einstein's special theory of relativity, it would require an infinite amount of energy to propel an object at more than 186,000 miles per second.

However, Dr Gunter Nimtz and Dr Alfons Stahlhofen, of the University of Koblenz, say they may have breached a key tenet of that theory.

The pair say they have conducted an experiment in which microwave photons - energetic packets of light - travelled "instantaneously" between a pair of prisms that had been moved up to 3ft apart.

Being able to travel faster than the speed of light would lead to a wide variety of bizarre consequences.

For instance, an astronaut moving faster than it would theoretically arrive at a destination before leaving.

The scientists were investigating a phenomenon called quantum tunnelling, which allows sub-atomic particles to break apparently unbreakable laws.

Dr Nimtz told New Scientist magazine: "For the time being, this is the only violation of special relativity that I know of."