Towards A Better Understanding of the Very Early Universe

Using a British radio telescope called the Very Small Array (VSA), located on
the flanks of Mount Teide in Tenerife, astronomers from the Universities of
Manchester and Cambridge and the Instituto de Astrofisica de Canarias (IAC)
have made measurements of the Cosmic Microwave Background (CMB) – radiation
left over from the Big Bang – which shed new light on events in the first
minute fraction of the Universe’s existence.

By combining their results with those of NASA’s Wilkinson Microwave
Anisotropy Probe (WMAP) satellite, they have been able to constrain the
behaviour of the Universe during the ‘inflationary’ phase believed to have
taken place when it was only 10(-35) seconds old. If confirmed, these
results will significantly challenge our current views of inflation and
the first moments of creation.

Dr. Richard Davis of Jodrell Bank Observatory, University of Manchester, who
was involved in the design and building of the VSA and leads the Jodrell Bank
team, said, “From the holiday island of Tenerife we have probed the first
moment of creation, when the Universe was a million-million-millionth of the
size of the atom. Using this British-funded instrument, we see echoes of the
crazy expansion which took place in the early Universe; it is quite
incredible!”

The idea of inflation is that the Universe expanded extremely quickly during
its very early existence, creating a Universe whose properties are very
uniform on the largest scales. However Quantum Mechanics, the theory of the
sub-atomic world, would have created minute fluctuations in the density of
the early Universe which eventually led to the formation of galaxies such
as our own Milky Way. These fluctuations also imprinted minute temperature
variations on the observed CMB, so allowing them to be studied by extremely
sensitive instruments such as the VSA.

The Quantum Mechanical fluctuations produced variations in density and
temperature over a very wide range of scale sizes. The finer detail of the VSA
observations, as compared with those of WMAP, has enabled a better
understanding of how the distribution of these fluctuations varies as a
function of size.

Previous ideas had suggested that, once the subsequent history of the
Universe is accounted for, the distribution of fluctuations would be
independent of scale. However, the current results show that the
fluctuations are most apparent at an angular scale of about 1/2 degree, the
size of the Moon in the night sky. On both larger (the size of the
Universe) and smaller (the size of a cluster of galaxies) scales, these
variations in density and temperature are much less.

“The most popular inflation models predict much smaller variations than those
seen in the new observations,” said Dr. Richard Battye (Jodrell Bank
Observatory), who was involved in the analysis and interpretation of the
data. “The increasing sensitivity of instruments such as the VSA is
enabling us to test these inflation models. The results are not totally
conclusive at this stage, but if true they will require a complete re-think
of the prevailing view of the first moments of creation.”

The results from the VSA have been confirmed by a concurrent experiment, the
Cosmic Background Imager (CBI), which is located high in the Chilean Andes and
operated by the California Institute of Technology. The results at this stage
are highly suggestive, but it is hoped that further measurements by the VSA,
CBI and eventually the PLANCK satellite, will allow more definitive
conclusions to be drawn. PLANCK, which is due to be launched by the European
Space Agency in 2007, will employ highly sensitive receivers built by
engineers at the Jodrell Bank Observatory.

Two papers detailing these results have been submitted to the Monthly Notices
of the Royal Astronomical Society.

Supporting images and publication details can be found at:
http://www.jb.man.ac.uk/news/vsa2/