The discovery that our Universe is expanding at an accelerated rate made huge news. It won the researchers several prestigious prizes including the Nobel prize. But what if they were wrong?
In the late 1990’s, studies of Type 1a supernovae showed that the expansion rate of the universe appears to be accelerating. This impacted the acceptance of the idea that the universe is dominated by ‘dark energy‘ which drives this accelerating expansion. This theory has become a part of the ‘standard’ model of cosmology.
But a journal paper published in Nature on 21 October 2016 may challenge the theory.
A team of scientists led by Professor Subir Sarkar of Oxford University’s Department of Physics were able to study 740 Type 1a supernovae, ten times more than the original researchers had access to, and the results were not quite what they were expecting. It appears that their results are much more consistent with a uniform rate of expansion.
Professor Subir Sarkar said:
“The discovery of the accelerating expansion of the universe won the Nobel Prize, the Gruber Cosmology Prize, and the Breakthrough Prize in Fundamental Physics. It led to the widespread acceptance of the idea that the universe is dominated by “dark energy” that behaves like a cosmological constant – this is now the “standard model” of cosmology.”
“However, there now exists a much bigger database of supernovae on which to perform rigorous and detailed statistical analyses. We analysed the latest catalogue of 740 Type 1a supernovae – over ten times bigger than the original samples on which the discovery claim was based – and found that the evidence for accelerated expansion is, at most, what physicists call “3 sigma”. This is far short of the “5 sigma” standard required to claim a discovery of fundamental significance.”
But this isn’t quite the end of the theory that our Universe is expanding at an accelerated rate, there is other data available that seems to support the idea. This includes information on the cosmic microwave background but Professor Subir Sarkar says:
“All of these tests are indirect, carried out in the framework of an assumed model, and the cosmic microwave background is not directly affected by dark energy. Actually, there is indeed a subtle effect, the late-integrated Sachs-Wolfe effect, but this has not been convincingly detected.”
There are plans for more research using the European Extremely Large Telescope which aims to take part over a 10–15 year period to determine whether the expansion rate is really accelerating.
Understanding our universe and how it all works is a difficult task, almost impossible. There are always more questions than answers. Who knows what scientists will learn over the next 10-15 years of research.