Watkins’ research presents a challenge for current cosmological model
According to Richard Watkins' latest research, nearby galaxies have an enigmatic "flow," like billiard balls rolling on a slightly tilted table - motion that challenges the current cosmological model.
Watkins, a physics professor at Willamette University in Salem, Ore., is at the leading edge of research into the movement of galaxies. He works with Hume Feldman from the University of Kansas and Michael Hudson from the University of Waterloo to use satellite data to draw conclusions about how galaxies flow.
In 2001, NASA launched the Wilkinson Microwave Anisotropy Probe (WMAP), which measures remnant light from the Big Bang. This light loses energy as the universe itself expands. By measuring tiny differences in the resultant low-frequency microwave radiation, WMAP's precise scans define parameters of mathematical models of the universe.
According to the prevailing model, the expansion of space causes all galaxies to recede from each other. Galaxies also flow towards areas of higher concentrations of mass because of gravity. The model makes very specific predictions about how galaxies should move based on expansion and gravity. Scientists refer to any additional movement as "peculiar velocity."
In Monthly Notices of the Royal Astronomical Society, Watkins' team measures this peculiar velocity by directly comparing previous surveys of differing volumes of space from "nearby" galaxies - within 163 million light-years of Earth.
His team calculated that nearby galaxies are flowing quickly, at the very edge of consistency with the prevailing model. "What's the likelihood that a universe with the WMAP parameters could give us this big of flow?" Watkins asked. "It's less than 2 percent."
The simplest explanation for the flow found by Watkins' team is that we live in a statistically unlikely volume of space. "If you had a hundred volumes, you'd expect one or two out of a hundred to be moving with this velocity," Watkins said.
A researcher from NASA's Goddard Space Flight Center, Alexander Kashlinsky, takes Watkins' results much further. Kashinlisky cites Watkins' work in a recent article as potential support for Kashlinsky's notion of "dark flow."
Kashlinsky's team uses a different technique to look much further away on a much larger scale. In their latest paper, the team claims to have found evidence of a large flow of galaxies that is in roughly the same direction as the much smaller flow measured by Watkins' team in nearby space.
While Watkins' measured flow is improbable but within the bounds of the prevailing model, Kashlinsky's results would require a major revision. Kashlinsky suggests the flow "might provide an indirect probe of the Multiverse," a theory that suggests that our universe may be part of a higher dimensional space in which there are many - or even and infinite number of - other universes, potentially with different physical laws.
His results have met with some skepticism in the scientific community. Several physicists have taken aim at Kashlinksy's conclusions, specifically the way he computes the level of uncertainty in his calculations.
According to Watkins, figuring out uncertainty on such extreme scales is difficult, and his next step is to use computer simulations to test his team's assumptions. Watkins also expresses some reservations about tying his team's results to Kashlinksy's conclusions.
"There may be some process that we don't understand. Perhaps something that occurred between the Big Bang and now to cause this peculiar velocity, but you don't need something radical to explain our flow."
Scientists remain conflicted about the extent, direction and cause of the flow. "We need more data," Watkins said. "This is an indication that something is not quite right. Right now, it's just a hint."