Calculating the Cosmos
By Kathy Sawyer Washington Post Staff Writer Monday, April 30, 2001; Page A01
Three independent teams of astronomers yesterday presented the most precise measurements to date of the infant universe as it existed approximately 14 billion years ago, exposing telltale reverberations they called "the music of creation."
The results represent a significant advance in scientists' efforts to understand what happened in the initial split second of cosmic creation and how the universe has evolved since, researchers said.
The observations provide a new basis for calculating the contents of the universe, confirming mounting evidence that ordinary matter - all the shining stars and galaxies, plus people, computers, cats and so on - account for less than 5 percent of it all. The rest takes the form of mysterious "dark matter" (30 percent) and an even more enigmatic "dark energy" in space (65 percent) that is causing galaxies to rush apart from each other at an accelerating rate with unknown consequences for the cosmic future.
The agreement among the various groups and approaches "is both stunning and humbling," said astrophysicist Michael Turner of the University of Chicago. He helped predict these proportions years ago using a different method. He added that these latest results put Albert Einstein's theories of gravity, as well as the Big Bang theory and other key pillars of modern cosmology, "all on a much firmer footing."
Paul Richards of the University of California at Berkeley is leader of the MAXIMA high-altitude balloon project - Millimeter Anisotropy Experiment Imaging Array. He said, "This study provides strong confirmation that, overall, we're using the right model to describe the universe." His was one of the groups presenting results yesterday at a meeting of the American Physical Society here.
In observations that were technically impossible until recent years and are still extremely difficult, the research teams reached back across time and space to take precise readings of light emitted about 400,000 years after the Big Bang explosion that gave birth to the universe. Their maps of this light constitute a snapshot of a time when atoms had begun to form in the primordial soup of hot, charged particles, or plasma, so that light was finally able to move through it. But the first stars and galaxies were still far in the future.
"We're looking back as far as you can go with light - 14 billion years, or roughly the age of the universe," said John Carlstrom of the University of Chicago. He presented yesterday the first data from the Degree Angular Scale Interferometer instrument at the South Pole. "In a sense, [the ancient light] allows us to 'see' sound in the early universe."
The light, known as the cosmic microwave background, is the cold echo of the hot Big Bang fireball. Reaching Earth from all directions, it is enfeebled and stretched into the microwave range by the expansion of the cosmos. Scientists say that 1 percent of the static picked up on a home TV antenna is the echo of the Big Bang approximately 15 billion years ago.
Astronomers first detected this background glow in 1965, using a ground-based radio telescope. But the radiation appeared bafflingly uniform and featureless in contrast to the present-day universe - all lumpy with stars and galaxies. Russian and American theorists soon predicted that the seeds of this lumpiness should show up in what mathematicians call a "harmonic series" of fluctuations imprinted on the embryonic glow.
The primordial cosmic soup "is full of sound waves compressing and rarefying matter and light, much like sound waves compress and rarefy air inside a flute or trumpet," said Paolo deBernardis, Italian leader of the international collaboration known as BOOMERANG, or Balloon Observations of Millimetric Extragalactic Radiation and Geophysics, another high-altitude balloon project presenting new analysis.
In 1991, NASA's Cosmic Background Explorer spacecraft detected the first evidence of any irregularity in the glow. The findings announced yesterday reveal far more detail at much smaller scales. The work is funded primarily by the National Science Foundation and NASA.
The DASI, BOOMERANG and MAXIMA teams measured variations as fine as 50 millionths to 100 millionths of a degree of temperature (or brightness) in the background radiation. These ripples signal the tiny peaks and valleys of over-density and under-density, which gravity gradually has built into the universe we see today, researchers said.
The results support the leading theory about what happened in the first billionth of a trillionth of a trillionth of the Big Bang explosion, which set the conditions for everything that followed. Known as cosmic inflation, the theory calls for a cosmos that started much smaller than an atom and suddenly underwent a violent, exponential growth spurt.
Inflation theory requires a "flat," or ordinary, cosmic geometry. This means that light rays traveling parallel will stay parallel forever, neither converging nor diverging. This scheme is controlled by the density of matter and energy in the universe and the accompanying gravitational influence. BOOMERANG and MAXIMA last year had reported evidence of that flatness - in the form of a single acoustic ripple, or "peak" - and the new DASI results further support it.
Scientists yesterday expressed particular excitement about being able to refine their observations enough to find two additional acoustic peaks following the first. All three teams presented graphs showing the soaring first peak followed by two lower ones.
"Now we see . . . three of these peaks and can tell not only which note is being played, but also which instrument is playing it," said Andrew Lange of the California Institute of Technology, U.S. leader for BOOMERANG, whose telescope took the measurements while flying 120,000 feet above Antarctica.
It was their ability to compare the heights of the peaks that enabled the researchers to calculate the composition of the universe and show that ordinary matter (4.5 percent) is a mere spice in a cosmos dominated by unknown types of matter and energy.
With even more advanced instruments coming on line, researchers said, they expect to learn how that initial cosmic growth spurt was triggered.
Although the cosmic acoustics theoretically could be translated onto a CD, based on the observed frequency and amplitude, the scientists said, it is unlikely to be a hit. "It would be a very low tone," Turner said. "The frequency is one cycle per 400,000 years. Not even whales could hear it."