Cosmic Times

Cosmic Times

Age of the universe:
12-20 billion years
Size of the universe:
30 billion light years

Baby Universe's 1st Picture

What did the newborn universe look like? In 1965, scientists used a radio telescope and found the answer. They discovered a background of microwave radiation that was very plain. Today's technology shows a more detailed picture of this cosmic microwave background (CMB), and it tells us there's a lot more to the story. The detail also provides further evidence of the Big Bang.

"If you're religious, it's like looking at God," said George Smoot, a scientist at the University of California. Dr. Smoot is the leader of the research team that made the discovery. He was addressing a room packed with scientists at a meeting of the American Physical Society.

COBE's map of the cosmic microwave background across the entire sky

Image credit: NASA/COBE DRM Team

COBE's map of the sky, showing minute fluctuations in the cosmic microwave background. Astronomers estimate this map shows the background radiation 300,000 years after the Big Bang.

According to the Big Bang theory, the universe expanded from an unthinkably small and dense ball of energy. An "explosion" caused this dense ball of energy to expand. This sent very hot radiation, and space itself, moving outward in all directions. As the universe expanded and cooled, this ball of energy produced particles of matter in the form of quarks and electrons, and then protons and neutrons. Protons and neutrons combined to make the nuclei of the gases hydrogen and helium. This hot gas also gave off radiation in all directions that gradually cooled down to the microwave energy range. Today, we detect the radiation as a cosmic microwave background (CMB). Over time, gravity gathered the denser clumps of gas into the familiar galaxies, stars, and planets of today's universe.

Data from the 1960s showed the CMB energy was the same across the entire sky. But in 1967, astrophysicists Martin Rees and Dennis Sciama predicted the CMB should not be the same everywhere. However, the very slight differences in temperature were extremely hard to detect until NASA's Cosmic Background Explorer satellite (COBE) was launched in 1989.

Scientists have now confirmed the existence of very slight – but measurable – energy differences. Dr. Smoot and histeam created an all-sky map of these microwave variations. This map shows these "lumps" in the oldest light in the universe. The COBE data shows the light from the very early universe, only 300,000 years after the Big Bang. The current age of the universe is estimated at 12 to 20 billion years.

Three years ago, COBE excited scientists with data that exactly matched predictions about the spectrum of light in a universe that began with a Big Bang. These data were collected by COBE on an instrument designed by John Mather of NASA's Goddard Space Flight Center. With the addition of the latest findings of "lumps" in the oldest light, the Big Bang theory, is now firmly the lead model for how the universe began. Other models either cannot account for COBE's results or require very awkward and unlikely explanations.

The lumps in the map do not match up with anything in the night sky today, but they are very important, say the researchers. If the CMB was perfectly smooth, according to theory, we could not exist! Although the greatest variations (lumps) in the CMB are only at a level of one part in 100,000, they are big enough to lead to the current structures in the universe (galaxies, stars, etc).

Princeton astrophysicist David Spergel observed at the meeting, "It's the most important discovery in cosmology in the past 20 years." •

A service of the High Energy Astrophysics Science Archive Research Center (HEASARC), Dr. Andy Ptak (Director), within the Astrophysics Science Division (ASD) at NASA/GSFC