The Big Bang theory states that matter, space, and time originated long ago from a hot, dense state. Atomic particles formed mere seconds after the Big Bang, yet it took hundreds of millions of years for stars and galaxies to appear. Well-tested physical laws describe the details of how the Universe evolved about one second after the Big Bang to the present. What happened in the first fraction of a second, however, remains a profound mystery.

Understanding the processes that occurred just after the Big Bang may allow us to answer the question of what caused the Big Bang. Compelling observational evidence indicates that there was a split-second period of rapid expansion, called inflation, when our infant Universe expanded so rapidly that some regions separated from others much faster than the speed of light.

But what propelled this inflation? Is it the same force that is accelerating the expansion of our Universe today? Wouldn't it be nice to look back in time to the moment of our Universe's origin to see what happened? We can study the Big Bang today by observing its afterglow, called the cosmic microwave background. This ancient, remnant radiation is all around us. In fact, in makes up a few percent of the snow seen on the "in-between" channels on broadcast television.

NASA's Cosmic Background Explorer (COBE) satellite and more recently other experiments, including balloon flights and NASA's Wilkinson Microwave Anisotropy Probe (WMAP), have made sky maps of this remnant light that display wrinkles imprinted on the Universe in its first moments. The wrinkles are slight temperature variations on the sky that point back to density differences within one second of the Big Bang. Regions with higher density attracted more matter, forming galaxies over the course of hundreds of millions of years.

Understanding what caused this initial lumpiness will point us toward the energy that powered the Big Bang itself. Modern theories predict that the wrinkles COBE discovered arose from the energy field that powered the Big Bang, and from gravitons, fundamental particles that transmit gravity. This is the point in time we plan to visit with an "inflation" space probe.

One proposed approach for the Beyond Einstein inflation probe would study the polarization of the cosmic microwave background, similar to how WMAP so carefully measures temperature patterns today. This CMBPol mission could reveal patterns in the polarization that will indicate how inflation stretched the early Universe.