In 1998, scientists made a discovery that shook the foundations of astrophysics – the Universe is not only expanding, but is doing so faster and faster. The explanation for this phenomenon was attributed to dark energy, which was supposed to be responsible for this unusual effect. New research suggests that what we see may just be an illusion. Isn’t dark energy necessary to explain the expansion of the Universe?
Since the discovery of the accelerating expansion of the Universe, dark energy has become one of the most important issues in astrophysics. According to the dominant Lambda-CDM model, dark energy constitutes as much as 70% of the “energy budget” of the Universe. It is described as a unified force that acts in every part of space, opposing gravity and “pushing” galaxies apart.
There are various theories about the nature of dark energy – from connections with vacuum energy to more advanced models assuming its dynamic evolution. The problem, however, is that its existence has never been directly confirmed. It is therefore not surprising that alternative theories are being sought.
Model Timescape
One of the most interesting challenges to the Lambda-CDM theory is model Timescapewhich takes into account the uneven distribution of matter in space. Instead of assuming that the universe is homogeneous and isotropic (that is, it looks the same in all directions), Timescape considers that denser regions – galaxies and star clusters – and the vast voids between them can influence the perception of expansion.
According to this model, the rate of expansion of space varies depending on the density of a given region. Empty spaces expand faster because they lack massive material to slow down the process. The average effect of this unevenness may mimic the accelerated expansion of the universe, which has previously been attributed to the action of dark energy.
What does the research show?
A team of scientists, analyzing data from type Ia supernovae (especially from the Pantheon+ set), compared two models: the classic Lambda-CDM and Timescape. It turned out that in the case of the “closer” Universe, the Timescape model explained the observed phenomena better. Even when analyzing more distant supernovae, Timescape performed as well or better than the Lambda-CDM model.
The uneven distribution of matter that creates “lumps” of galaxies and cosmic voids can significantly influence our perception of the expansion of the Universe.
Objections and open questions
Everything looks beautiful. But the Timescape model also relies on certain things. The analysis did not take into account, for example, singular velocities – local movements of galaxies that may distort the measurements. Additionally, the Pantheon+ dataset used is not as precise as newer databases, including: DES5yr.
Additionally, the Lambda-CDM model has other powerful support – baryonic acoustic oscillations and gravitational lensing, which unanimously point to the existence of dark energy. Future research will need to incorporate these elements into Timescape analyzes to further determine which model better describes our Universe.
Read also: Researchers look for dark energy in black holes. How are they doing?
A battle of two theories
If the Timescape model proves correct, we will be in for a major paradigm shift. The accelerated expansion of the Universe may only be an illusion resulting from the uneven distribution of matter. And not only does it question the need for dark energy, it also forces us to rethink the basic assumptions of cosmology. I wonder how the issue of a real war between two models describing our Universe will develop.
Source: antyweb.pl
