The beginning of the universe, for beginners – Tom Whyntie



Planck reveals almost perfect universe –

Planck reveals almost perfect universe –

The results revise downwards the proportion of the universe made up by dark energy from 74% to 68.3%, while dark matter accounts for 26.8% of the total (up from 22%) and ordinary matter 4.9% (up from 4%). Planck also reveals that the universe is some 80 million years older than thought, to put the age of the universe at 13.8 billion years old.

Launched by ESA in 2009, Planck uses two instruments to measure the CMB at frequencies between 27 GHz and 1 THz. It takes these measurements at a point in space that is some 1.5 million km further out from the Sun than the Earth. Known as Lagrange point L2, Planck hovers there, barely disturbed by stray signals from Earth and without needing to use much fuel to stay in position.

There are, however, some hints of physics beyond the standard model of cosmology in the new Planck data. Efstathiou showed that fluctuations in the CMB temperatures at large angular scales do not match those predicted by the standard model, in addition to an asymmetry in the average temperatures on opposite hemispheres of the sky. Such deviations were hinted at by WMAP but were largely ignored because of doubts over their origin.

“Such features are not caused by galactic emission or instrumentation,” says Efstathiou. “This is exotic physics – there seems to be some memory that has been retained on the largest scales from previous phases of the universe.” One possible explanation for this is that the universe is not the same in all directions on a larger scale than we can observe.

Another big aim of the Planck mission is to detect a so-far-unobserved type of polarization known as “B-modes”, which date back to the period of inflation and are determined by the density of primordial gravitational waves. If such waves could be detected, they might tell us what mechanism generated them in the universe’s first moments, what caused inflation, and even if there was something before the Big Bang. However, Efstathiou says that the Planck team has not yet exploited those data.

In 2006, after three years of data-taking, the WMAP team measured the incredibly weak polarization signal of the photons, allowing cosmologists to infer how much the fluctuations are cuased by the distorting effects of matter and how much they are down to gravity waves in the infant universe. WMAP placed strong constraints on models of inflation, showing that the first stars formed when the universe was 400 million years old.