Cosmic Microwave Background

The slight variances in the temperature of the cosmic microwave background radiation as seen by the European Space Agency's Planck spacecraft. Leftover light from the Big Bang stretched into microwave wavelengths over cosmic history. (Image Credit: ESA/Planck)

The cosmic microwave background (CMB) is the oldest detectable light in the universe. This light fills the sky as a faint glow in the radio portion of the electromagnetic spectrum, peaking in the microwave frequency range. The CMB is thus invisible to the human eye, but scientists can study it using instruments sensitive to microwaves. The CMB is often referred to as the relic radiation, or afterglow, of the Big Bang, the event that began the universe 13.8 billion years ago. The CMB itself was generated about 378,000 years after the Big Bang during an epoch called "recombination." After the cosmos had cooled from its initially infernal temperatures to about 5,000 degrees Fahrenheit, the elementary particles of protons and electrons that were forged in the Big Bang joined to form hydrogen atoms. This recombination released photons, or particles of light, that now stream toward us from every direction. Analysis of the CMB has enabled researchers to estimate the universe's age as well as its composition of 68 percent dark energy, 27 percent dark matter and 5 percent "normal," everyday matter. Furthermore, the temperature variations and other detailed properties of the CMB speak to the universe's earliest development, including the possibility that it underwent a rapid period of expansion known as inflation.

Spotlight Live: Dark Energy – On the Brink of Discovery?

Aug 08, 2013

On August 22, three leading members of the new dark energy collaboration answered your questions about the dark energy and the expansion of the universe.

Revealing Dark Energy's Hold on the Universe

Aug 08, 2013
Artist's conception of dark energy, gravity

A new collaboration aims to learn how dark energy is driving the accelerated expansion of the universe.

A New Baby Picture of the Universe

Jul 31, 2013
Cosmic Microwave Background

On Wednesday July 31, three leading Planck scientists answered your questions about the new measurements of the cosmic microwave background.

Spotlight Live: A New Baby Picture of the Universe

Jul 23, 2013
Cosmic Microwave Background

On Wednesday July 31, three leading Planck scientists answered your questions about the new measurements of the cosmic microwave background.

The Inflating Universe (Sidebar)

Jul 18, 2013

One of the major tenants of the Big Bang model of how the universe began is an idea called inflation. 

Afterglow: Dispatches from the Birth of the Universe

Oct 31, 2012

Lawrence M. Krauss, John C. Mather, Amber Miller, Lyman Page and David Spergel discuss how the cosmic background radiation is poised to reveal a host of bold questions about the cosmos.

Primordial Portrait of the Universe

Jul 14, 2010
Planck space telescope

Central to the science of cosmology is the zeal to build better time machines. These are not designed literally to travel to the distant past, of course, but to get a better look at it. The latest of these is the Planck Surveyor satellite. 

Probing the Universe: Kavli Institute for Cosmology Cambridge

May 01, 2010

To help answer some of the most fundamental questions about the Universe, researchers at KICC are members of international collaborations that are making use of some the most advanced scientific instruments ever constructed.

Chao-Lin Kuo Heads South

Apr 01, 2009
Chao-Lin Kuo

To get to the South Pole, first take a commercial flight to Christchurch, New Zealand, then catch a special military flight to McMurdo Station, a large outpost on the Antarctic coast. From there it's a three-hour flight to Amundsen-Scott South Pole Station. 

Eyeing Dark Energy

Feb 29, 2008
South Pole Telescope

Frigid and bone-dry, with six straight months of night each year, the South Pole is a forbidding place to live or work. However, it’s one of the best spots on the planet for surveying the faint cosmic microwave background (CMB) radiation left over from the Big Bang. 


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