Physics Nobel 2006: Mather & Smoot

George F Smoot

John C Mather and George F Smoot have been jointly awarded the 2006 Nobel Prize in physics for their discovery of the blackbody form and anisotropy of the cosmic microwave background radiation. John C. Mather is a Senior Astrophysicist at NASA's Goddard Space Flight Center and George F Smoot is Physics Professor at University of California at Berkeley.

Their work looks back into the infancy of the Universe and attempts to gain some understanding of the origin of galaxies and stars. Their work is based on measurements made with the help of the COBE satellite launched by the NASA on November 18, 1989. The COBE results provided increased support for the Big Bang scenario for the origin of the Universe. The measurements also marked the inception of cosmology as a precise science. It was not long before it was followed up, for instance by the WMAP satellite, which yielded even clearer images of the background radiation. Soon, the European Planck satellite will be launched in order to study the radiation in even greater detail.

John C Mather

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, 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 background radiation was first measured in 1965 by Arno Penzias and Robert Woodrow Wilson with their radio antenna at Bell Telephone Laboratories. They received Nobel Prize for their work in 1978. Smooth and Mather's work led to more precise measurements of various characteristics of this radiation with COBE satellite.

WMAP has produced a detailed picture of the infant universe. Colors indicate "warmer" (red) and "cooler" (blue) spots. The white bars show the "polarization" direction of the oldest light [Photo credit: NASA/WMAP Science Team]

COBE also had the task of seeking small variations of temperature in different directions (anisotropy). 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.

Further Study:
WMAP's introductory page on Cosmic Microwave background
Wikipedia page on Cosmic Microwave Background

Searching CPT Violation

At a fundamental level the nature is ruled by a law of symmetry called the CPT invariance. C stands for charge, P for parity and T for time. So, if we start with a collection of interacting elementary particles and create a mirror-image version (Parity reversal), change the signs on all electrical charges (C) of those particles, and let time run backward, the interactions among the particles would still remain identical to what it was before this CPT transformation.

Since CPT involves space and time operations, any evidence of violation of CPT invariance would mean disruption of he spacetime symmetries embodied in relativity theory and would have far-fetching effect on basic Physics and cosmology. In effect, it would mean that space is not 'isotropic' or that not all directions in space are equivalent. There would be one special direction in space, and the propagation of electromagnetic radiation would be different in different directions depending on its orientation relative to this special direction.


Photo credit: NASA/WMAP Science Team.
WMAP has produced a detailed picture of the infant universe. Colors indicate "warmer" (red) and "cooler" (blue) spots. The white bars show the "polarization" direction of the oldest light.



To look for this effect, scientists at the National Astronomical Observatories in Beijing carefully studied recent measurements of the cosmic microwave background radiation, the remnant of the energy that originated from the big bang and now surrounds the space around us in all directions at approximately 2.9 degree Kelvin. They used data from the satellite-borne Wilkinson Microwave Anisotropy Probe (WMAP) and the BOOMERANG instrument, flown by balloon over Antarctica. These data sets include detailed measurements across the sky of the direction of the electric field, or polarization, of the Cosmic Microwave Background. If CPT symmetry is violated, then all polarizations will rotate with respect to the special space direction as the radiation travels through the universe. In that case the distribution of polarization of all spatial points would not be just random but there would be a specific type of correlation between two points influenced by the existence of such a special direction.

The Chinese team has found signs of this correlation in their analysis, but statistically speaking, it is not yet significant enough and could have arisen from random chance. More detailed investigation would be needed but it's certainly a good brave step in the direction of that more detailed exploration.

Here is the paper: "Searching for CPT Violation With Cosmic Microwave Background Data From WMAP and BOOMERANG", B. Feng, M. Li, J. Q. Xia, X. Chen, and X. Zhang, Phys. Rev. Lett. 96, 221302 (issue of 9 June 2006)

Further Study:
WMAP's introductory page on Cosmic Microwave background
Wikipedia page on Cosmic Microwave Background