News & Views item - October 2006

 

 

Physics Nobel Prize Awarded for Demonstration of the Properties of the Cosmic Microwave Background. (October 4, 2006)

  George Smoot (left) and John Mather
  Credit: LBNL/NASA

    Through the use of NASA's COBE (Cosmic Background Explorer) satellite launched in 1989 John C. Mather of NASA's Goddard Space Flight Center, Greenbelt, MD, USA, and George F. Smoot of the University of California, Berkeley, CA, USA discovered "the blackbody form and anisotropy of the cosmic microwave background radiation" and have today been awarded the Nobel Prize in Physics for their work.

 

The CMB was first predicted in 1948, was accidentally discovered in 1965, but key properties remained uncertain when NASA launched COBE in 1989.

 

Mather's and Smoot's results provided increased support for the Big Bang theory for the origin of the Universe, as this is the only scenario developed so far that predicts the kind of cosmic microwave background radiation measured by COBE and in the view of The Royal Swedish Academy of Sciences, "These measurements also marked the inception of cosmology as a precise science."

 

The Academy's announcement explains that:

According to the Big Bang scenario, the cosmic microwave background radiation is a relic of the earliest phase of the Universe. Immediately after the big bang itself, the Universe can be compared to a glowing "body emitting radiation in which the distribution across different wavelengths depends solely on its temperature. The shape of the spectrum of this kind of radiation has a special form known as blackbody radiation. When it was emitted the temperature of the Universe was almost 3,000 degrees Centigrade. Since then, according to the Big Bang scenario, the radiation has gradually cooled as the Universe has expanded. The background radiation we can measure today corresponds to a temperature that is barely 2.7 degrees above absolute zero. The Laureates were able to calculate this temperature thanks to the blackbody spectrum revealed by the COBE measurements.

 

COBE also had the task of seeking small variations of temperature in different directions (which is what the term 'anisotropy' refers to). Extremely small differences of this kind in the temperature of the cosmic background radiation – in the range of a hundred-thousandth of a degree – offer an important clue to how the galaxies came into being. The variations in temperature show us how the matter in the Universe began to "aggregate". This was necessary if the galaxies, stars and ultimately life like us were to be able to develop. Without this mechanism matter would have taken a completely different form, spread evenly throughout the Universe.

A detailed description of the methodology and the science can be found at http://nobelprize.org/nobel_prizes/physics/laureates/2006/phyadv06.pdf