Ceilidh

Michael Zey
futurist3000@aol.com

Tue Jan 11, 5:36 PM ET

By Deborah Zabarenko

SAN DIEGO (Reuters) - By looking at a vast swath of sky, astronomers said on Tuesday they have figured out a way to measure the universe -- using a kind of "cosmological ruler."

They found that the universe is flat, with ripples that began as the tiniest variations in radiation left over from the Big Bang, which many cosmologists believe gave birth to the universe.

As it cooled after the mega-explosion some 13.7 billion years ago, the infant universe was actually making a sound and those waves produced the ripples, said Daniel Eisenstein, an astronomer at the University of Arizona.

The way galaxies are scattered across the sky now corresponds to the sound waves in the early times of the cosmos, Eisenstein told reporters at a meeting of the American Astronomical Society.

"We regard this as smoking-gun evidence that gravity has played the major role in growing from the initial seeds in the microwave background (left over from the Big Bang) into the galaxies and clusters of galaxies that we see around us," he said.

"The most exciting thing from my point of view is the signature of these wiggles in the galaxy distribution ... may be very useful as a cosmological ruler," said Richard Ellis of Caltech Optical Observatories.

Astronomers had guessed that the distance between these primordial ripples was related to how galaxies are distributed around the cosmos, but they didn't know for sure. Now the relationship is more clear, and the space between the ripples can be used as a measuring tool for the universe.


MAPPING THE GALAXIES


Researchers from the United States, Britain and Australia worked in two teams to determine this relationship, which showed that galaxies tend to form in clumps roughly 500 million light-years apart -- exactly the distance predicted by the sound-wave ripples in the early universe.

A light-year is about 6 trillion miles, the distance light travels in a year.

Astronomers had also theorized that the universe was flat -- rather than a round ball or an open shape like a curved sheet of paper -- and the current research confirms this, Eisenstein said.

A flat universe gives support to the widely held theory of inflation, the idea that the universe grew explosively in its earliest times. It also supports the notion that normal matter -- everything we can see, feel and know on Earth -- makes up a small fraction of the universe. The rest is dark matter and a mysterious dark energy.

Finding the cosmic ruler required two teams of scientists to map more than 260,000 galaxies. One team was made up of astronomers working on the Sloan Digital Sky Survey, which aims to map one-quarter of the sky. The other was part of a group of astronomers known as the 2-degree Field Galaxy Redshift Survey.