Evidence of universe's first instant
Findings announced Thursday affirm idea of hyperspeed expansion.
For a fleeting moment, the very fabric of the universe became a kind of hyperspeed spandex - stretching outward at perhaps 100 times the speed of light.
That concept, which describes the first trillionth of a second of the universe's beginnings, has gained wide acceptance among cosmologists. Now, scientists say they have discovered the first comprehensive, subtle signals from that cosmic growth spurt.
The discovery, announced Thursday, does not quite provide "smoking gun" confirmation of the concept, known as inflation. But scientists say they have detected wisps from the muzzle. With a few more years of data-gathering, they say they may be able to find the missing pieces that would clinch the case for a process widely held to have given the universe its initial "bang."
The new results represent a significant shift in efforts to uncover the origins and future of the universe, notes Lyman Page, a Princeton University physicist and member of the team reporting the discovery.
Cosmologists have long struggled to answer basic questions about the universe - its properties and composition, Dr. Page says. Now, scientists are adding an ability to "look back at these billionths of a billionth of a billionth of a billionth of a minute, ask detailed questions about the physics, and be able to answer them."
The new evidence comes from NASA's Wilkinson Microwave Anisotropy Probe (WMAP), a satellite designed to study the final whisper of the Big Bang - the primordial burst of energy widely held to have given birth to the universe. This whisper, actually low-level radiation, is known as the cosmic microwave background. The concept of inflation predicts that this whisper should leave behind signals from that event.
The WMAP team says it detected these signals from trends in relative brightness of bumps and dimples in the microwave background. These variations represent one of two kinds of polarized radiation - and the easiest type to spot - that inflation predicts. Ground-based and balloon-borne experiments have seen bits and pieces of this evidence. But WMAP has put a sky's worth together in one mosaic - an important milestone.
Launched in 2001, the WMAP satellite spent a year gathering data for a baby picture of the universe, which was built from subtle temperature differences in the microwave background. In 2003, the WMAP team decoded the information to yield the most precise estimates yet of the abundance of matter and energy, the universe's age, and its expansion speed. The variations also represent a cosmic blueprint for the large-scale distribution of galaxies astronomers see today.
These latest data come from an additional three years of observations, during which the scientists were working with a signal roughly 100 times weaker than the temperature information they gathered.
The new measurements are so precise that "we're now in position to be able to test specific models of inflation," some of which were first proposed "when I was in grad school. It's really cool to see it come to fruition," says Gary Hinshaw, a researcher at NASA's Goddard Space Flight Center in Greenbelt, Md., and a member of the team reporting the results.
Inflation holds that the observable universe blossomed from a tiny spot in space so minute that only quantum physics can describe it. Then, in a trillionth of a second, it expanded at almost unimaginable speed. The concept, first proposed nearly 30 years ago, erased difficult mismatches between the "standard" Big Bang theory at the time and the universe astronomers observed as they traced much of its 13.7-billion-year evolution through their telescopes. It also solved conundrums particle physicists faced as they probed the world of the very small.
So far, the team has been able to make some rough estimates of the upper limit on certain conditions during inflation. Dr. Hinshaw says that the inflationary period would have had less energy than 10 quadrillion billion electron-volts - still an enormous number that defies the comprehension of almost anyone but a physicist. By comparison, mankind's most powerful particle accelerator generates energies of only 1 billion electron-volts.
Team members say they hope to keep the experiment - already an "extended" mission in NASA's portfolio - running for several more years. This will allow them to increase the accuracy of their results, and perhaps yield evidence for the second kind of polarized signal cosmologists seek in the microwave background - from gravity waves the expansion would have triggered. Their imprint on the microwave background would provide the smoking gun for cosmic inflation, researchers say.
Meanwhile, the European Space Agency is slated to launch its own version of WMAP, dubbed the Planck mission, next year to give the field a dash of competition. Planck promises a more sensitive set of measurements than WMAP can provide.