"Universe Is Most Likely Not Expanding"- New Research Claims

Accelerating expansion may not be real but instead be an apparent effect, according to new research published in the journal of Monthly Notices of the Royal Astronomical Society.

A new study by a group of researchers at the University of Canterbury in Christchurch, New Zealand, found the fit of Type Ia supernovae to a model of a universe devoid of all dark energy to be a better fit than to the model containing dark energy.

 

Dark energy, proposed in 1998, has been assumed to form an approximate 70% of the present material content of our Universe. This nebulous quantity is a popular, well known component of unknown physics.

Current models of the Universe require dark energy to explain the observed rate of acceleration in the expansion of our Universe. Such measures are based off of measurements in the distance of supernova explosions in distant galaxies that appear to be farther apart than they should be if the acceleration of expansion were not taking place. This brings a question to light... if dark energy is not the explaining factor for such a phenomenon... then what is? What if our approach has been incorrect this whole time?

In the past year, the statistical significance of this signature cosmic acceleration has been a common idea subjected towards heated debate. Previous debates have pitted the standard Lambda Cold Dark Matter (ΛCDM) cosmology against a universe that is empty, whose expansion neither decelerates nor accelerates. Both models take on the simplified 100 year old cosmic expansion law-- Friedmann’s equation.

Friedmann’s equation assumes an expansion identical to that of a featureless “coup” of a universe that has no complicating structure. However, the present day Universe is actually one that contains within it a complex cosmic web of breathtaking galaxy clusters in sheets and filaments surrounding empty and vast voids.

The chart below represents the difference in magnitudes of supernovae in the ΛCDM and Timescape cosmologies paired with the magnitudes in which the supernovae would appear to be in an empty universe (the horizontal, dashed line). Both models clearly represent the recent acceleration that was followed by a deceleration. However, in the Timescape model this is not a real effect and the curve is flatter than in the case of the ΛCDM model. (Lawrence Dam, Asta Heinesen, and David Wiltshire.)

David Wiltshire of the University of Canterbury in Christchurch New Zealand, the leader of the study said the following, potentially revolutionary words: “The past debate missed an essential point; if dark energy does not exist then a likely alternative is that the average expansion law does not follow Friedmann's equation."

Rather than comparing the ΛCDM cosmological model with an empty universe, this new study compares the fit of supernova data in the ΛCDM model to another model, Timescape cosmology. The model is devoid of all dark energy. Instead, clocks carried by observers in galaxies differ from the clock that best describes average expansion once the lumpiness of our Universal structure becomes significant. Figuring out an inferring acceleration is heavily dependent on the clock used.

Timescape cosmology turned out to be a slightly better fit to the supernova catalogue than ΛCDM cosmology. This reminds us of the words uttered during the OJ Simpson trial... “If it doesn’t fit then you must acquit.” However, not enough statistical data has been gathered in order to rule out one or the other and neither of the current evidence is strong enough to rule out one or the other either.

Thankfully, future missions such as the European Space Agency’s Euclid satellite will harness the power to discern which of the models is real and aid scientists in their adventure towards figuring out whether dark energy is real or not. Solving that cosmic puzzle not only requires more data, but also a more thorough understanding of the properties of the supernovae that currently limit the precision in which they can be used as a ruler to measure large, cosmic distances.

With all of that in mind, this new study shows significant, unexpected effects that are missed if only one expansion law is applied. This is rolling out the carpet for greater discoveries yet to come and sheds more light onto current questions physicists have today.