Ellipsoidal Universe

A new theoretical assessment of data taken by the Wilkinson Microwave Anisotropy Probe (WMAP) suggests that the universe -- at least that part of it that can be observed -- is not spherically symmetric, but more like an ellipsoid.

The WMAP data has served to nail down some of the most important parameters in all of science, such as the age of the universe since the big bang (13.7 billion years), the time when the first atoms formed (380,000 years after the big bang), and the fractions of all available energy vested in the form of ordinary matter, dark matter, and dark energy. One remaining oddity about the WMAP results, however, concerns the way in which portions of the sky contribute to the overall map of cosmic microwaves; samples of the sky smaller than one degree across, or at the degree level, or tens of degrees seem to be contributing radiation at expected levels. Only the largest possible scale, that on the order of the whole sky itself (the technical term is quadrupole moment), seems to be under-represented.

Now Leonardo Campanelli of the University of Ferrara and his colleagues Paolo Cea and Luigi Tedesco at the University of Bari (all in Italy) have studied what happens to the quadrupole anomaly if one supposes that the shell from which the cosmic microwaves come toward earth is an ellipsoid and not a sphere. This shell is called surface of last scattering since it corresponds to that moment in history when photons largely stopped scattering from charged particles when it became cool enough for many of the particles to bundle themselves into neutral atoms. If the microwave shell is an ellipsoid with an eccentricity (non-sphericity) of about 1 percent, then the WMAP quadrupole is exactly what it should be.

This is not the first time a non-spherical universe has been suggested, but it is the first time the idea has been applied to the state-of-the-art WMAP data. Historically an ellipsoidal universe would nicely parallel Johannes Kepler's discovery that the planetary orbits were ellipses and not circles. This adjustment in astronomical thinking was just as revolutionary as Copernicus' helio-centric model, and it helped Newton and others arrive at the idea of an inverse-square law for gravitational attraction.

What could have caused the universe as a whole to be ellipsoidal? Campanelli (campanelli@fe.infn.it), Cea and Tedesco say that a uniform magnetic field pervading the cosmos, or a defect in the fabric of spacetime, could bring about a non-zero eccentricity.

Campanelli, Cea, and Tedesco, Physical Review Letters, 29 September 2006
Contact Leonardo Campanelli
University of Ferrara
campanelli@fe.infn.it