Nobel Prize in Physics 2006

The Nobel Prize in Physics 2006 has been awarded to:

John Mather
George Smoot

“…for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation.”

Dr Mather is a senior staff scientist based at the NASA Goddard Spaceflight Center in Greenbelt, Maryland, and Dr Smoot a professor of physics at the University of California, Berkeley.

Mather and Smoot were awarded the Nobel Prize for showing that the universe began some 14 billion years ago in a hot and highly compressed state, and expanded in a rapid process that is commonly referred to as the “Big Bang”. The evidence of that explosion is seen today in a background of microwave radiation present throughout the visible universe.

At first glance the Cosmic Microwave Background (CMB) radiation appears completely uniform, with a constant temperature of 3K (-270 degrees Celsius, or 3 degrees above absolute zero), but studied in detail, tiny variations in the temperature of the radiation reveal a clumpiness in the early universe that led to the formation of stars and galaxies. The CMB is effectively the very oldest light in the universe, the wavelength of which has – through expansion – stetched out over time from the very high energy and temperature of the infant cosmos, to the cold space of today. The CMB comes from a time 380,000 years after the Big Bang.

The CMB was predicted by Ralph Alpher and Robert Herman in 1948, and discovered serendipitously in 1965 by two communications engineers – Arno Penzias and Robert Woodrow Wilson of Bell Telephone Laboratories in New Jersey. Penzias and Wilson at first thought that the radio noise they detected was due to bird shit coating their antenna. This was jokingly referred to in technical papers as a “white dielectric material”. Penzias and Wilson won the 1978 Nobel Prize for their achievement.

Since the discovery of the CMB, there have been a number of ground and space-based experiments to study the CMB. Mather and Smoot’s prize-winning work is based on data from the NASA Cosmic Background Explorer (COBE) satellite that operated from 1989-1996. Mather’s team of scientists showed showed that the CMB temperature profile has a very well-defined form called the blackbody spectrum, and this discovery confirmed a major prediction of Big Bang theory. The spatial distribution of the radiation – the clumpiness, or to be more technical, anisotropy – was discovered and measured by Smoot and his co-workers.

The CMB is akin to an archaeological relic, and contains a wealth of information about the origin and evolution of the universe. It could also tell us something about the eventual fate of the cosmos: whether it will go on expanding forever, or stop expanding and contract.

Since the COBE mission, there have been other high resolution studies of the CMB. In 1991, NASA launched the Wilkinson Microwave Anisotropy Probe (WMAP) to study in more detail than COBE the clumpiness of the CMB, and the data from this satellite have shed much light on the formation of matter in the early universe. The European Space Agency intends next year to build on this success and launch its own CMB mission – the Planck Surveyor, which will study CMB variations in even finer detail than WMAP.

While the Nobel Prize is generally awarded to individuals or small groups, it should be remembered that science these days is a collaborative effort, and not just in experimental work such as the COBE mission. As Mather and Smoot themselves acknowledge, the work with COBE that led to the discoveries about the nature of the CMB was carried out by many scientists and engineers, and they all deserve credit. According to Mathers:

“In total there were 1,500 people, so it’s a huge team effort that we’re recognising today.”

Congratulations to Drs Mather and Smoot!

Keywords: science astronomy physics