An international team of astronomers has used the CSIRO-run Australia Telescope Compact Array in NSW to measure the cooling of the universe since the Big Bang.
Update: This story originally missed a "-" when talking about the current temperature of the universe. It's -270.27 degrees Celsius, not 270.27 degrees Celsius. Otherwise things would be a great deal hotter...
The ATCA comprises six 22-metre antennas and is located 500 kilometres north-west of Sydney, near Narrabri.
"This is the most precise measurement ever made of how the universe has cooled down during its 13.77 billion year history," said Robert Braun, chief scientist at CSIRO's Astronomy and Space Science division, in a statement.
The team studied the effect that gas in an unnamed galaxy 7.2 billion light years from Earth had on the radio waves emitted by a more distant quasar galaxy. Because of the time light takes to travel such vast distances, the scientists' readings gave an indication of the temperature of the universe when it was half its current age.
Gas in the unnamed galaxy affected the radio waves emitted by the quasar galaxy, absorbing some of the radio waves' energy and leaving a distinctive fingerprint which allowed scientists to calculate the temperature of the gas, which is warmed only by the cosmic background radiation left by the Big Bang.
The team measured the temperature at -267.92 degrees Celsius (5.08 Kelvin), which is warmer than today's universe (-270.27 degrees Celsius; 2.73 Kelvin). This is in line with the Big Bang Theory, which predicts cooling of the universe as it expands over time.
"According to the Big Bang theory and as a consequence of adiabatic expansion of the Universe, the temperature of the cosmic microwave background (CMB) increases linearly with redshift," states the paper produced by the team, A precise and accurate determination of the cosmic microwave background temperature at z=0.89.
"This relation is, however, poorly explored, and detection of any deviation would directly lead to (astro-)physics beyond the standard model."
The work of the team, which had participants Sweden, France, Germany and Australia, has been accepted for publication by Astronomy & Astrophysics and is available online at Arxiv.org.