The release on Thursday of a stunning map of the oldest light in the universe will almost certainly be the event of the year for cosmologists.
The European Space Agency’s “cosmic microwave background” image, compiled from Planck satellite observations, will remind people that there are two complementary ways of gathering evidence to help scientists understand the universe at the most fundamental level.
One is to create extreme conditions – ultra-small versions of the Big Bang that created the universe 13.8bn years ago – on Earth, by smashing together subatomic particles at almost the speed of light. That’s how physicists used the Large Hadron Collider at Cern last year to discover the Higgs boson.
The second approach is to observe the aftermath of the Big Bang in the universe itself, through astronomy. The €700m Planck is the third and most sensitive observatory designed to map the radiation released 380,000 years after the Big Bang, when the young universe had cooled enough for light to pass through it for the first time, following Nasa’s pioneering COBE and W-MAP spacecraft.
There are two contrasting reactions to the Planck results. Some scientists have emphasised how well the findings fit today’s “standard model” of cosmology: Big Bang followed instantly by a very brief period of unimaginably fast expansion – “cosmic inflation” – and then slower expansion for ever after, driven by mysterious “dark energy” driving the universe apart.
Or, more interestingly, you can look for the “anomalies” in the Planck picture that the standard model cannot explain. These include the fact that half the sky appears to be slightly but significantly cooler than the other half – existing physics cannot explain irregularity on such a vast scale.
Maybe the Big Bang was not the beginning, says Planck astrophysicist George Efstathiou of Cambridge University: “It’s perfectly possible that there was some phase of the universe before the Big Bang actually happened where you can track the history of the universe to a pre-Big Bang period.”
That is pure speculation at this stage but scientists will be looking for more clues to exciting “new physics” next year when the European Space Agency will publish more detailed analysis of Planck data.