Dark matter ‘smoother’ than first thought, study discovers

Dark matter, the mysterious substance believed to comprise a quarter of our universe, is spread out more smoothly than previously thought, said a study on Wednesday that may challenge some tenets of physics.

The finding may throw into question what little we know about the birth and growth of the cosmos, astronomers said.

“All we can say for now is that something appears to be not quite right,” study co-author Konrad Kuijken of the Leiden Observatory in the Netherlands told AFP.

Studying the light of some 15 million distant galaxies with Europe’s Very Large Tele- scope in Chile, Kuijken and a team found dark matter to be significantly “less clumpy” than previously shown by the European Space Agency’s Planck satellite.

Dark matter is a mysterious substance not visible to telescopes and perceived only through its gravitational pull on other objects in the universe.

Planck studied radiation remnants from the Big Bang that created the universe about 14 billion years ago.

The new study, in turn, examined how the light from distant galaxies is bent through the gravitational influence of matter.

“The surprise result ... has implications for our understanding of the universe, and how it has evolved during its almost 14-billion-year history,” the Royal Astronomical Socie- ty and the European Southern Observatory, which hosts the VLT, said in a statement.

This could mean rethinking the very essence of dark energy — an unexplained force thought responsible for accelerating the expansion of the universe.

Instead of the single “cosmological constant” suggested by Albert Einstein, there could be several different forms of dark energy, said Kuijken.

“Another exciting possibility is that this is a sign that the laws of gravity on the scale of the universe are different from general relativity” — Einstein’s gravity theory which underpins much of physics today.

The Planck satellite found that “normal matter” — which makes up humans, planets, stars and galaxies — comprises 4.9 percent of the universe.

Dark matter makes up significantly more than thought — 26.8 percent of the universe in total. Dark energy accounts for the rest at 68.3 percent.

Another exciting possibility is that this is a sign that the laws of gravity on the scale of the universe are different from general relativity.” Konrad Kuijken, of the Leiden Observatory in the Netherlands