Ringside Seat to the Universe's First Split Second
You don't get much closer to the big bang than this.
Scientists peering back to the oldest light in the universe have
evidence to support the concept of inflation, which poses that the
universe expanded many trillion times its size faster than a snap of
the fingers at the outset of the big bang.
We're talking about when the universe was less than a trillionth of a trillionth of a second old. In that crucial split second, changes occurred that allowed for the creation of stars and galaxies hundreds of millions of years later.
The new finding was made with NASA's Wilkinson Microwave Anisotropy
Probe (WMAP) and is based on three years of continuous observations of
the cosmic microwave background, the afterglow light from the first
moments of the universe.
Time Line of the Universe -- The expansion of the universe over most of it's history has been relatively gradual. The notion that a rapid period "inflation" preceded the Big Bang expansion was first put forth 25 years ago. The new WMAP observations favor specific inflation scenarios over other long held ideas. Click image to enlarge. (Credit: NASA)
It's admittedly mind-boggling. Inflation poses that the universe
expanded far faster than the speed of light and grew from a subatomic
size to a golf-ball size almost instantaneously. This concept,
however, was a mere product of calculations done with pencil and paper
around 1980. The idea stands on much firmer ground today.
"Inflation was an amazing concept when it was first proposed 25 years
ago, and now we can support it with real observations," said WMAP team
member Dr. Gary Hinshaw of NASA Goddard Space Flight Center in
Greenbelt, Md., a lead author on one of the scientific papers
submitted for publication.
How do we gaze back to the infant universe? The cosmic microwave
background is a fossilized record of what occurred way back
when. Embedded in this light are subtle patterns that point to very
specific conditions about the early universe.
Previous observations have focused on the temperature patterns of this
light, which have provided an accurate age of the universe and
insights into its geometry and composition. The temperature
differences, varying by about a millionth of a degree, point to
density differences- a little more matter here, a little less matter
there. Over the course of millions of years, gravity exploited the
density differences to create the structure of the universe stars and
galaxies separated by vast voids.
The new WMAP observations give not only a more detailed temperature
map, but also the first full-sky map of the polarization of the
microwave background. The polarization signal is at
least 100 times fainter than the temperature signal.
This major breakthrough enables scientists to obtain much deeper
insight into what happened within the first trillionth of a second,
when cosmic inflation perhaps occurred.
WMAP has produced a new, more detailed picture of the infant universe. Colors indicate "warmer" (red) and "cooler" (blue) spots. The white bars show the "polarization" direction of the oldest light. This new information helps to pinpoint when the first stars formed and provides new clues about events that transpired in the first trillionth of a second of the universe. (Credit: NASA)
The WMAP team is announcing two major results: evidence for cosmic
inflation, and confirmation of when stars first turned on. Both
results depended on a combination of temperature and polarization
WMAP finds that the first stars - the forebears of all subsequent
generations of stars and of life itself - were fully formed remarkably
early, only about 400 million years
after inflation. This is called the era
of reionization, the point when the
light from the first stars ionized
hydrogen atoms, liberating electrons
from the protons.
Polarization is affected by the environment through which the light
passes, such as the polarized glare of sunlight produced when it
reflects off of a shiny object. Scientists are hunting for two kinds
of polarization signals in the microwave background. One, called the
E-mode, points to the era of reionization. This is the polarization
caused by the microwave background scattering off of the ionized
hydrogen. The other is called B-mode, which points directly to
WMAP detected E-mode polarization but not B-mode yet. B-mode detection
could provide smoking-gun evidence for inflation. But with the
temperature map plus the E-mode polarization map, the WMAP team can
say several things about inflation.
For example, scientists now have an upper limit on the energy of
inflation. Also, WMAP data support basic predictions of inflation
about the size and strength of spacetime fluctuations and how they get
weaker on smaller length scales.
"It blows my mind that we can now distinguish between different
versions of what happened within the first trillionth of a second of
the universe," said Dr. Charles Bennett of the Johns Hopkins
University in Baltimore, WMAP principal investigator.
And it's only going to get better as WMAP continues to soak up
light. The polarization detection will grow stronger. "The longer WMAP
observes, the more it reveals about how our universe grew from
microscopic quantum fluctuations to the vast expanses of stars and
galaxies we see today," Bennett said.
The European Space Agency plans to launch a mission called Planck by
2008 that will study microwave background polarization. A proposed
NASA Beyond Einstein inflation probe would search for B-mode signals,
the calling card of the big bang.
WMAP, a partnership between NASA/Goddard and Princeton, was launched
on June 30, 2001, and is now a million miles from Earth in the
direction opposite the Sun. The WMAP team includes researchers in
U.S. and Canadian universities and institutes.