What are the best current estimates of the age of the Universe and what makes up the Universe?

The exciting results from the Wilkinson Microwave Anisotropy Probe (WMAP) have recently provided answers to these questions with unprecedented confidence. The age of the Universe is 13,700,000,000 years, give or take 200,000,000 years. WMAP measures the oldest light in the Universe, formed about 380,000 years after the Big Bang, at the time when atoms first formed (before that the Universe was so hot that atoms were not stable). This light started as ultra high energy gamma rays, but as the Universe has expanded, the light has “cooled” until now it is seen as the Cosmic Microwave Background.

By itself, WMAP does not measure the constituents of the Universe. When combined with other observations, the WMAP data can be used to search for what the WMAP team calls the “fingerprint” of what the Universe is like. By looking at predictions of many theories and variations of theories, the WMAP Science Team found a best fit to all the available data. Dr. Charles Bennett, Principal Investigator for WMAP, notes that the pieces of the puzzle all fit together in what he calls “cosmic consistency.” Having multiple measurements that all point toward the same answer helps add confidence to the picture. What they find is:

Only 4% of the Universe is ordinary matter, the stuff we are all made of.

23% of the Universe is “dark matter.” Dark matter, as its name implies, does not glow but can be detected by its gravitational influence on things around it. Knowing that dark matter is there, however, does not tell us what it is. That remains a mystery.

A whopping 73% of the Universe is made of “dark energy, “ something even more mysterious than dark matter. Whatever it is, dark energy has the effect of speeding up the expansion of the Universe. Because dark energy is dominant, the Universe will expand forever.

WMAP is a NASA project, with major contributions by Goddard Space Flight Center and Princeton University. You can find more information and images at the links given below.

Additional information:

Description and pictures from the WMAP early results

The home page of the WMAP Project

Our thanks this week to Dr. Dave Thompson. Dr. Thompson is an astrophysicist who studies gamma rays in the Laboratory for High Energy Astrophysics. He helped build, test, and analyze data from EGRET on the Compton Gamma Ray Observatory, and he is now helping build part of the Gamma Ray Large Area Space Telescope (GLAST), scheduled for launch in 2006. His particular scientific interest is gamma-ray pulsars.