Countless observations have shown that our Universe has been expanding for billions of years. If we could play the cosmic movie backwards, at some point in the distant past all the matter and energy we see today must have been crammed together in a tiny region of unimaginably high density and temperature. Cosmologists call that moment the Big Bang.

In the mid-1960s, Bell Labs astronomers Arno Penzias and Robert Wilson serendipitously discovered that microwaves are coming from all directions in the sky with equal intensity. The Big Bang model for the beginning of the Universe actually predicted that we should see an afterglow radiation that fills the Universe. Penzias' and Wilson's discovery of this afterglow, now known as the cosmic microwave background, was a turning point in cosmology since it convinced most scientists to embrace the Big Bang model for the origin of our Universe.

NASA Scientist Dr. John C. Mather shows some of the earliest data from the NASA Cosmic Background Explorer (COBE) Satellite during a press conference held at NASA Headquarters in Washington, DC. Dr. Mather was co-recipient of the 2006 Nobel Prize for Physics today October 3, 2006. Photo Credit: NASA/Bill Ingalls

To study the cosmic microwave background in more detail, scientists launched NASA's Cosmic Background Explorer (COBE) satellite in 1989. Led by John Mather of NASA's Goddard Space Flight Center, the COBE team found a perfect match between the measured spectrum of the background and the spectrum predicted by the Big Bang theory. The exquisite correlation between theory and observation—a rarity in science—offered powerful support to the idea that our Universe did in fact originate in a Big Bang.

Another COBE group, led by George Smoot, discovered slight temperature fluctuations embedded in this afterglow that point back to slight density differences in the infant Universe. These fluctuations were the primordial seeds that evolved into all the large-scale structure we see today as gravity turned these small deviations into clusters of galaxies and the humongous voids between clusters. Mather and Smoot shared the 2006 Nobel Prize in Physics for their groundbreaking measurements.

Scientists working with data from NASA's Wilkinson Microwave Anisotropy Probe (WMAP) refined these results in 2003 and again in 2006 by resolving the temperature fluctuations down to smaller angular scales. Working with theory and other astronomical data, the WMAP results pin down the age of our Universe (13.7 billion years), the era of first starlight (about 400 million years after the Big Bang), and the cosmic recipe (74% dark energy, 22% dark matter, and 4% familiar "atomic" matter). WMAP's precise measurements are beautifully consistent with the theory that the infant universe experienced a brief moment of hyperexpansion—inflation.

Even though we now know the age and recipe of our Universe, we don't know what started it all. What was the energy that powered the Big Bang? What came “before” the Big Bang? What process planted the primordial seeds? We will go Beyond Einstein as we study these profound questions and attempt to understand our origins.