View of Universe May Redefine Gravity

The universe appears to be clumpier than astronomers expected, according to the largest galaxy survey ever conducted ~ a finding that might lead to a new understanding of gravity.

“Maybe on very large scales, Einstein’s general relativity is slightly wrong,” says cosmologist Shaun Thomas of University College London. “This potentially could be one of the first signs that something peculiar is going on.”

According to DailyGalaxy.com:

When viewed close up, the matter in the universe bunches up into stars, galaxies and galaxy clusters. But as you zoom out, cosmologists expect the universe to look more and more smooth, sort of the way details in an earthly landscape blend together when viewed from an airplane.  

What clumpiness there is comes from tiny fluctuations in the density of matter in the early universe. As the universe expanded, spots with a little bit of extra matter gathered more and more matter through gravitational attraction. Based on the best model of how gravity works and what the universe is made of, cosmologists can extrapolate out from the Big Bang to get a pretty good idea of how lumpy the universe should be on every scale.  

Thomas and colleagues looked at the most zoomed-out view of the universe yet acquired, and found more lumpiness than models predict, using data from the Sloan Digital Sky Survey, which covers about a fifth of the entire sky, to make a rough 3-D map of 723,556 galaxies that are at least 4 billion light-years away. The researchers calculated how evenly distributed, or smooth, the galaxies appear on length scales of 2 billion light-years.

The findings could mean cosmologists need to reassess their understanding of dark energy, the mysterious force that drives the universe outward at an ever-increasing rate. Dark energy itself is supposed to be almost perfectly smooth, but clumps of dark energy could draw clumps of visible matter around them.

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