A trio of recent findings on cosmic microwave background radiation lends strong support to the idea that the entire observable universe was once smaller than an atom and underwent a "super-charged" Big Bang. In an infinitesimal fraction of a second the entire universe experienced a mind-bogglingly vast expansion or "inflation." The findings are consistent with the way we see galaxies distributed across the cosmos. They are also consistent with the idea that everything we can see with telescopes—up to 14 billion light years away—is the tiniest fraction of a universe so large that it may in fact be infinite.

The CMB sky over Mt. Erebus. In this fanciful picture, the CMB sky looms behind the prelaunch preparations of BOOMERANG. The BOOMERANG images of the early universe have been overlaid onto the sky to indicate what size that the fluctuations would appear if a standard 35mm camera were sensitive to microwave light. The color map of the CMB images has been changed here to aesthetically match the rest of the picture. The CMB images and the prelaunch picture are available separately. Image courtesy of the BOOMERANG collaboration.

The Big Bang Theory is the well established idea that the universe originated about 14 billion years ago in an "explosion" from a single point of nearly infinite temperature and density. All the matter and energy that we can detect— from the tree you see outside your window to the furthest galaxy—was once compacted almost into a single point. Scientists first arrived at this theory when they observed that galaxies are flying apart from each other and that the farther the galaxy is from us, the faster it is moving away. They are flying apart because space itself is expanding. Running the clock backwards yields an age of about 14 billion years.

While this means the observable universe—that is, the part we can see through telescopes—extends 14 billion light years in every direction, it doesn't mean this is the total scope of the universe. The cosmic microwave background findings support the idea that the universe, in its entirety, is vastly larger. We just don't see it because the light from those objects further out has not had enough time to reach us yet. What happened, cosmologists now believe, is that in the first instant of its existence, the universe underwent "inflation" whereby space itself expanded so quickly and vastly that most of it was pushed beyond what we can see even today 14 billion years later.

The early universe was very hot and very dense with exotic particles—the predecessor to atoms and energy. As it expanded, it cooled. When the universe was about 400,000 years old, the temperature had cooled enough to allow ordinary atoms (chiefly hydrogen) to exist. It was then that there was hardly any interaction between the cosmic background radiation and matter. This radiation could then cool from about 4000 kelvins to its present temperature of only 2.74 kelvins (i.e. 2.74K above absolute zero). In terms of energy, this corresponds to a reduction from the visible light region to weak microwaves.

Here are a few milestones in the history of the universe: