The Wilkinson Microwave Anisotropy Probe (WMAP) was launched in June of 2001. At the time, cosmologists hoped it would add to the knowledge gained by the Cosmic Background Explorer (COBE) that had been launched in November of 1989. Little did they know it would revolutionize the human idea of the universe and its origin. WMAP collected data for nine years before being decommissioned in October, 2010. The results of the probe have just been released.
It began with COBE, which revealed views of the universe as it looked 389,000 years ago. It was at that time that everything had cooled sufficiently for the first neutral atoms to be formed and light to move freely. COBE discovered evidence of the afterglow from the Big Bang, thereby supporting that theory of origins. Both COBE and WMAP examined what is known as the Cosmic Microwave Background (CMB). This is the background radiation that was left over from the Big Bang. The fluctuations within the CMB can be measured and they reveal much about how the universe was formed.
The difference between COBE and WMAP was the degree of sensitivity of the equipment. WMAP received better reception, producing much more detailed maps of the fluctuations. The goal was to describe the geometry of the universe and answer questions about its structure, composition and age. They hoped to learn how galaxies and galactic clusters were formed.
The results answered those questions and many more. It turns out that the universe is 13.7 billion years old, give or take 1 percent. WMAP demonstrated the irregularities that caused the stars and galaxies to group together. The modern universe is composed of 72 percent dark energy, 23 percent dark matter and only 4.6 percent atoms. Only 380,000 years ago, the universe had a very different composition. It was 63 percent dark matter, 15 percent photons, 12 percent atoms, and 10 percent neutrinos. Dark energy did not exist in any quantifiable amount at that time.
The first generation of stars ignited only 200 million years after the Big Bang. These stars took more than 500 million years to create cosmic fog. WMAP also found evidence that a sea of cosmic neutrinos permeates the universe and that the universe is flat with a cosmological constant. The first direct detection of pre-stellar helium, another important piece of evidence that supports the Big Bang theory, was also found.
Combined data from COBE and WMAP demonstrate that gravity in conjunction with the initial material from the Big Bang could have formed the structures of the universe, such as galaxies and galactic clusters. The implications of this for future research and understanding of the universe are immense. Although WMAP is now over, the research is being continued on the Planck mission.