Is there a bulk flow of matter coursing through our universe? A new study bolsters the idea – and paints a new view of the process of inflation, the exponential expansion that occurred moments after the big bang.

The universe can be divided into two components: matter and radiation, which is seen as the cosmic microwave background (CMB). Much of the matter is in motion in a local sense – for example, our solar system is moving through the Milky Way. But according to the standard model of cosmology, the overall matter component should not be moving in any particular direction relative to the CMB.

Studies of the CMB show that Earth is moving in a particular direction with respect to the CMB. If this is all due to local movement, Earth should move with respect to distant cosmic objects at the same speed.

But when Yin-Zhe Ma of the University of Cambridge and colleagues analysed data from supernovae and about 4500 galaxies, they found that Earth’s motion with respect to these objects was different. This suggests that they too are moving relative to the CMB, and hints at a bulk flow of matter, says the team.


Unfinished expansion

One controversial explanation given for earlier evidence of this flow was the tug of a second, distant universe. Ma’s team says a more likely scenario is that the process of inflation, credited with smoothing out the distribution of matter and light in the early universe and causing the two components to move at the same rate, did not quite finish the job.

Team member Christopher Gordon of the University of Oxford cautions that this has yet to be confirmed by more precise data, such as from forthcoming instruments like the Square Kilometre Array and the Large Synoptic Survey Telescope, which will map more galaxies and supernovae, with far greater precision. “Actually seeing a signal from the pre-inflationary era would be a huge discovery,” he says.

Cosmologist Douglas Scott of the University of British Columbia in Vancouver, Canada, who was not involved in the study, calls it an “eminently sensible analysis”, but agrees with Gordon that more precise data is needed to claim discovery.

Journal Reference: http://www.arxiv.org/abs/1010.4276v1