What Is Cosmic Microwave Background? Top Science Prize Awarded to Researchers Who Determined the Age of the Universe

The Cosmic Microwave Background, nicknamed the "baby photo" of the universe. NASA/WMAP Science Team

On Sunday evening at a star-studded ceremony in Palo Alto, a team of scientists was awarded a $3 million Breakthrough Prize in Fundamental Physics designed to recognize physicists "working on the deepest mysteries of the Universe." The top prize went to the team behind a project called the Wilkinson Microwave Anisotropy Probe. That spacecraft measured what's called the Cosmic Microwave Background, cementing what scientists know about the age of the universe and the stuff that makes it up. But what on earth does all that mean?

The Wilkinson Microwave Anisotropy Probe, nicknamed WMAP, is a spacecraft that launched in 2001. It headed away from the sun, to the opposite side of Earth's orbit, and spent about nine years looking for tiny changes in temperature across the universe. "Across the universe" here isn't poetry: WMAP looked to the very oldest light, as far away as human instruments can see.

"The universe is expanding into the future," David Spergel, one of the scientists behind the project, told Scientific American in a video explaining WMAP's work.

The result is the photograph nicknamed the universe's "baby picture," published just a year after the satellite began taking measurements. Darker colors like blue represent colder spots, brighter colors like red represent warmer spots—although there's just a fraction of a degree of difference between the two.

Scientists can use these measurements to understand deeply engrained characteristics of the universe. That's because as the universe expands, it cools from the intense heat that marked the Big Bang. That means, where the universe is a teeny tiny bit warmer, it's expanded just a hair less and has more photons (light particles). Spergel nicknames this "fossil light."

Where it's a tiny bit colder, the universe contains more dark matter and dark energy. Scientists still don't understand what either dark energy or dark matter are, but they now know—thanks to the WMAP measurements—that normal matter makes up just a tiny portion, less than 5 percent, of the universe. Seeing how dark matter and dark energy warp the expansion of the universe, they're our best bet for understanding it.

"So I think the great surprise to me with the microwave background data is twofold: One, the universe is simple, the other that the universe is strange," Spergel told Scientific American.

WMAP's measurements have been followed up on by a European satellite called Planck, which has both honed some of the measurements and spotted a few discrepancies in scientists' theories about the early universe.

And the scientists behind WMAP honored at the ceremony are working on other instruments that will keep tackling the universe's mysteries. Charles Bennett, a physicist at Johns Hopkins University, is working on a new telescope called the Cosmology Large Angular Scale Surveyor to push our timeline of the universe even further back in time. Gary Hinshaw, a physicist at the University of British Columbia, is working on building new radio telescopes to tackle some of the same questions. A third collaborator, physicist Lyman Page, Jr., of Princeton University, is working on still another new instrument, called the Atacama Cosmology Telescope, to take even more high-res measurements of the same discrepancies WMAP measured.