Scientists peering back to the oldest light in the universe have new evidence for what happened within its first trillionth of a second, when the universe suddenly grew from submicroscopic to astronomical size in far less than a wink of the eye.
Timeline 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. Credit: NASA
Using new data from a NASA satellite, scientists have the best evidence yet to support this scenario, known as "inflation." The evidence, from the Wilkinson Microwave Anisotropy Probe (WMAP) satellite, was gathered during three years of continuous observations of remnant afterglow light -- cosmic background radiation that lingers, much cooled, from the universe's energetic beginnings 13.7 billion years ago.
In 2003, NASA announced that the WMAP satellite had produced a detailed picture of the infant universe by measuring fluctuations in temperature of the afterglow -- answering many longstanding questions about the universe's age, composition and development. The WMAP team has built upon those results with a new measurement of the faint glare from the afterglow to obtain clues about the universe's first moments, when the seeds were sown for the formation of the first stars 400 million years later.
"It amazes me that we can say anything about what transpired within the first trillionth of a second of the universe, but we can," said Charles L. Bennett, WMAP principal investigator and a professor in the Henry A. Rowland Department of Physics and Astronomy at The Johns Hopkins University. "We have never before been able to understand the infant universe with such precision. It appears that the infant universe had the kind of growth spurt that would alarm any mom or dad."
The newly detected pattern, or polarization signal, in the glare of the afterglow is the weakest cosmological signal ever detected -- less than a hundredth of the strength of the temperature signal reported three years ago.
"This is brand new territory," said Princeton University physicist Lyman Page, a WMAP team member. "We are quantifying the cosmos in a different way to open up a new window for understanding the universe in its earliest times."
Comparing the brightness of broad features to compact features in the afterglow light (like comparing the heights of short-distance ripples versus long-distance waves on a lake) helps tell the story of the infant universe. One long-held prediction was that the brightness would be the same for features of all sizes. In contrast, the simplest versions of inflation predict that the relative brightness decreases as the features get smaller. WMAP data are new evidence for the inflation prediction.
The new WMAP data, combined with other cosmology data, also support established theories on what has happened to matter and energy over the past 13.7 billion years since its inflation, according to the WMAP researchers. The result is a tightly constrained and consistent picture of how our universe grew from microscopic quantum fluctuations to enable the formation of stars, planets and life.
According to this picture, researchers say, only 4 percent of the universe is ordinary familiar atoms; another 22 percent is an as-yet unidentified dark matter, and 74 percent is a mysterious dark energy. That dark energy is now causing another growth spurt for the universe, fortunately, they say, more gentle than the one 13.7 billion years ago.
WMAP was launched on June 30, 2001, and is now a million miles from Earth in the direction opposite the sun. It is able to track temperature fluctuations at levels finer than a millionth of a degree.
The WMAP team includes researchers at the Goddard Space Flight Center in Greenbelt, Md.; The Johns Hopkins University; Princeton University; the Canadian Institute of Theoretical Astrophysics in Toronto; the University of Texas at Austin; Cornell University; the University of Chicago; Brown University; the University of British Columbia; the University of Pennsylvania; and the University of California, Los Angeles.
Astronomers Detect First Split-Second of the Universe
Scientists announced new evidence supporting the theory that the infant universe expanded from subatomic to astronomical size in a fraction of a second after its birth.
The finding is based on new results from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) satellite, launched in 2001 to measure the temperature of radiant heat left over from the Big Bang, which is the theoretical beginning to the universe.
This radiation is known as the Cosmic Microwave Background (CMB), and it is the oldest light in the universe.
Using WMAP data, researchers announced in 2003 that they had pieced together a very detailed snapshot of the universe as it was about 400,000 years after the Big Bang, and that they had determined things like its age, composition and development.
The previous data showed that the universe was about 13.7 billion years old. It also revealed that it wasn't until about 200 million years after the Big Bang that conditions were cool enough for the first stars to form. Scientists were also able to conclude that the universe is composed of about 4 percent real matter, about 23 percent dark matter, and about 73 percent dark energy. Nobody actually knows what dark matter or dark energy are, however.
The new WMAP observations, announced at a NASA press conference today, reveal what the universe was like in the first trillionth of a second after the Big Bang. From the microwave background, researchers teased out a new signal called the "polarization signal."
"This new signal is roughly 100 times weaker than the signal we analyzed three years ago and about a billion times less than the radiant warmth we feel from the Sun," said Lyman Page, a WMAP team member from Princeton University.
The researchers collected observations of this polarization signal to create a map of the early universe, allowing them to test a sub-theory within the Big Bang theory, called "inflation."
Inflation theory states that the universe underwent a rapid expansion immediately following the Big Bang.
"During this growth spurt, a tiny region, likely no larger than a marble, grew in a trillionth of a second to become larger than the visible universe," said WMAP researcher David Spergel, also from Princeton University.
The new observations reveal that the early expansion wasn't smooth, with some regions expanding faster than others.
"We find that density fluctuations on the 1- to 10-billion-light-year scale are larger than density fluctuations on the hundred-million-light-year scale," Spergel said. "That is just what inflation theory predicts."
These fluctuations are thought to have led to clumping of matter that allowed the formation of galaxies.
Brian Greene, a physicist from Columbia University who wasn't involved in the research, called the new findings "spectacular" and "stunning."
"A major question that people have asked for decades is where do stars and galaxies come from? The answer coming from WMAP data supports the idea that quantum fluctuations are the answer," Greene said. "WMAP's data supports the notion that galaxies are nothing but quantum mechanism writ large across the sky."
The new findings brings humanity closer to answering one of its oldest questions, that of where we come from, Greene said.
"WMAP certainly doesn't answer this question, but its data is taking us one giant step closer to the answer by giving us a precise quantitative look at the universe's earliest fraction of a second," Greene said. "It's a tiny window of time, but it's a critical one in our quest to learn what happened at time zero itself."