One of the biggest puzzles in astronomy is the nature of dark matter and dark energy. These two components were proposed at different times to explain what we see in the cosmos, but even after decades of research, we still aren't close to understanding what they are and whether they truly exist.
Now, a new study suggests a way to get rid of both of them. André Maeder, an honorary professor at the University of Geneva, Switzerland, has proposed going back to the fundamental equations of relativity and Newtonian gravity to find a way to abandon the Dark Universe model. His idea is reported in the Astrophysical Journal.
Using this hypothesis, the physicist was able to reproduce the accelerated expansion of the universe without using dark energy. This explains the movement of galaxies within the large galaxy cluster without claiming that dark matter exists.
“In this model, there is a starting hypothesis that hasn’t been taken into account, in my opinion,” Maeder said in a statement. “By that I mean the scale invariance of the empty space; in other words, the empty space and its properties do not change following a dilatation or contraction.”
This tweak creates a small acceleration term that can be used to understand features currently explained by dark matter and dark energy. For example, it explains the velocities of cluster galaxies based on visible matter alone. It also explains how stars move within galaxies, without the need for dark matter. This was actually why Vera Rubin proposed the existence of such a substance in the first place.
The introduction of scale invariance clearly can explain features we witness in the universe, but is it really a nail in the coffin for dark matter and dark energy? It’s not that simple. The hypothesis only works for the wide and big features since scale invariance can only be found in general relativity. That’s because, for Einstein’s theory, empty space is empty. But empty space is not empty according to quantum mechanics.
In the quantum world, every bit of space-time changes when it's dilated or compressed. Actually, from quantum mechanics, there’s something called vacuum energy that has been linked to dark energy, although the expected values from astronomical observations are different from the theoretical quantum ones.
While we still don’t know what dark matter and dark energy are, they continue to be the best theory to explain the cosmos. But more research might tell us if scale invariance could be a serious contender for the crown.