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A Picture Worth a Thousand Answers


Scientists Capture Best Image Ever of Universe's Beginning

By Rob Stein
Washington Post Staff Writer
Wednesday, February 12, 2003

A powerful satellite has captured the best picture ever taken of the infant universe, an image so detailed that scientists said it answers some of the most important questions about the cosmos, including when it was born and how it will probably die. 

The image, created from a year's worth of data collected by a NASA probe 1 million miles from Earth, has solved long-standing puzzles, such as what the universe looked like right after it was forged in the violent inferno of the big bang, when the first stars blinked on in the coalescing heavens and what kind of matter makes up the expanding universe that exists today.

Astronomers calculated that the universe is 13.7 billion years old, that the first stars lighted up just 200 million years after the cosmos was born, and that it will expand forever, thinning and cooling until it eventually reaches nothingness.

"These results are truly profound, and give us insights into some of the most fundamental questions that humans ever posed," said Edward J. Weiler, NASA's associate administrator for space science.

The image was created from the most sensitive temperature measurements ever made of a faint glow that is dissipating through space, the last remaining light from the blinding flare of the big bang. By detecting subtle variations in the glow's warmth, scientists were able to discern the primordial structure of the universe a mere 380,000 years after its birth.

From that, scientists calculated even further back in time to determine the conditions that must have existed at the moment of cosmological conception. They also extrapolated forward to measure the matter that makes up the universe today and, from that, predict what it will do in the future.

"I think every astronomer will remember where they were when they heard these results," said John Bahcall, a leading astrophysicist from Princeton University. "I certainly will. This announcement represents a rite of passage for cosmology from speculation to precision science. I personally am thrilled by the results."

Because of the time it takes light to travel, the new data show the universe almost immediately after the big bang, the furthest back astronomers have ever been able to see. It shows clumps of matter just beginning to cool and congeal from the fireball of the big bang into what would eventually become all the galaxies in the universe.

From that, astrophysicists were able to calculate the age of the universe with unprecedented precision. Earlier estimates had ranged from 8 billion to 20 billion years, but in recent years they narrowed to somewhere between 12 billion and 15 billion years. The new estimate of 13.7 billion years has a margin of error of only 1 percent, compared with about 30 percent for the best previous estimates.

The data strongly confirm the prevailing big-bang theory and allow researchers to test various versions of the "inflation theory," which holds that even before the universe was one second old it had expanded dramatically.

"We've now laid the cornerstone of a unified cosmic theory, by having a new set of very accurate numbers that describe a wide range of cosmic measurements," said Charles Bennett of NASA's Goddard Space Flight Center in Greenbelt, who led the project. "We have not answered all the questions. But we've certainly turned a corner." He announced the findings at a briefing at NASA headquarters.

The data also have enabled scientists to produce the most exact calculation ever of what the cosmos is made of today. It turns out that only 4 percent of the universe is made up of atoms with known forces such as electromagnetism and gravity, the ordinary stuff that makes people, potatoes, porcelain and everything else that humans know. Twenty-three percent of the universe is made from mysterious unseen material dubbed "dark matter" because scientists know so little about it. The remainder -- 73 percent -- is made up of yet another poorly understood force called "dark energy."

"I was very skeptical of this concoction," Bahcall said. "But the results have really convinced me. This is the only conclusion one can come to, strange as it is. It's fantasy, but you know it's fantasy turned real. It's unbelievable but true."

One possible explanation for dark energy is the "cosmological constant," an energy in empty space that would oppose gravity and was originally predicted by Albert Einstein, who later discarded it as his biggest blunder.

This dark energy, astronomers said, is the reason why the universe seems to be expanding at an accelerating rate. There is not enough normal matter to counteract the effects of dark energy, which is also known as anti-gravity. As a result, the astronomers said, they can now predict confidently that the universe will continue to expand forever instead of eventually collapsing back in on itself in a "big crunch," as some had predicted.

"The universe is expanding and cooling. That will continue happening. The universe will get colder, the temperature will drop and things will move apart. The density will go towards zero," Bennett said in an interview.

"It will dissipate and peter out, as opposed to the alternative of having the universe close back in on itself. If you had to choose how the universe would end, by fire or ice, this is the ice answer."

One of the biggest surprises from the new data is that the first generation of stars to shine in the blackness of space ignited just 200 million years after the big bang. Previous estimates were that the first stars were born perhaps as many as 1 billion years after, but no sooner than about 500 million years.

The new picture of the universe comes from the first data collected by the Wilkinson Microwave Anisotrophy Probe (WMAP), a small $145 million satellite launched on a Delta 2 rocket June 30, 2001. The craft is equipped with a suite of instruments designed to gather the most precise measurements of cosmic microwave background radiation, the technical term for the light left over from the big bang.

Scientists have likened the light to an archaeological artifact, something they can examine to validate theories about the universe and gain fundamental insights into its creation, composition, geometry and fate.

"It's a direct remnant of the big bang," Bennett said.

Scientists are highly confident in the new measurements because every one fits perfectly into what would have been expected based on existing theories, and matches precisely complementary measurements gathered independently by other instruments, including the powerful Hubble Space Telescope.

"What we find when we do this is remarkable -- it all fits," said David Spergel, a Princeton scientist involved in the project. "It's a lot like matching fingerprints."

The average temperature of the light is 4.9 degrees Fahrenheit above absolute zero. WMAP can detect the most subtle variations in light's temperature, which varies only by millionths of a degree.

The researchers compared the map of the sky they created from the WMAP measurements to a variety of simulations of what physics would predict based on competing theories about the universe.

"We are now for the first time in a position to sort through specific inflation theories," Bennett said.


© 2003 The Washington Post Company


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