Within cosmology there are questions about the end of the universe and many theories about how it will end. So far the Lambda-CDM, based on a cosmological constant, has been the main theory on which the expansion of the universe has been based. On the other hand, the Big Freez is the immediate effect of what would be the end of the universe, but recent research by Princeton University is raising new questions to this cosmological question. The point of part of the new hypothesis is the axion that would make dark energy behave in a different way than hitherto conceived. This would result in the Big Crunch and an end of cosmological time. Read on to learn about new perspectives in theoretical physics to get to the bottom of questions about the cosmos.
Will the universe really expand forever?
Will the universe expand forever or is there a limit to its growth? This question, which has plagued modern cosmology for decades, has been given new life by recent studies that challenge the standard model. Previous research has suggested that the expansion of the universe may have undergone an abrupt transition in the past, opening the door to new ways of interpreting its growth rates. Now, a new cosmological model takes that idea further: not only does it propose that dark energy changes over time, but it predicts a specific end to the universe in about 20 billion years.
A new scientific study suggests that the life of the universe is not infinite and that it could culminate in a massive collapse in about 20 billion years. This work, developed by researchers from universities such as Cornell and Shanghai Jiao Tong, offers a cosmological model in which dark energy does not behave as we thought and suggests that the universe could stop expanding and begin to contract, giving rise to a phenomenon known as Big Crunch.
A new view of cosmic destiny
Until recently, the dominant idea among cosmologists was that the expansion of the universe would continue forever. This accelerated expansion was attributed to a mysterious force called dark energy, which would account for about 70% of the energy content of the universe. This energy was assumed to have a constant pressure over time, acting as a cosmological constant, and would drive the expansion of space indefinitely.
But the latest measurements from the Dark Energy Survey (DES) and the Dark Energy Spectroscopic Instrument (DESI) challenge that assumption. According to the new model proposed by the study’s authors, dark energy is not constant, but changes over time. This dynamical behavior can be explained by the inclusion of a hypothetical particle: the ultralight axion.
This axion, together with a negative cosmological constant, allows the construction of a model that not only fits the current data, but also predicts a different end for the universe: not an infinite expansion, but a cosmic collapse.
A prediction with fundamentals, but also uncertainties
The aDE model fits the most recent data well, but it is not without uncertainty. As the authors themselves point out, there is significant degeneracy in the model parameters. This means that different combinations of values could explain the current data equally well. For example, there are possible solutions where Λ is zero, which would imply an indefinite expansion.
Still, the best fit to the current data suggests that Λ is negative, with a value of approximately -1.61. In the words of the authors, “with the best fit parameters of the model, we find that the lifetime of the universe is 33.3 billion years.”
Another interesting point is that the proposed axion has an extremely small mass, on the order of 10-³³ electron volts, which makes it very difficult to detect directly. However, its influence on a cosmic scale is significant, since it modulates the rate at which dark energy changes over time.
Beyond the Big Crunch: cosmological and theoretical implications
The study also opens doors to deeper questions. For example, the negative cosmological constant is not an isolated concept: in the context of theoretical physics, anti-de Sitter space (AdS) – where Λ is negative – is common in theories derived from string theory. In fact, some authors suggest that universes with negative Λ would be more natural within the string theoretical framework than those with positive Λ.
Also of interest is the role of the axion, a particle predicted in several models of physics beyond the standard model. In this work, it not only appears as a candidate for dynamical dark energy, but also contributes to shaping the fate of the universe. This connection between cosmology and fundamental particles gives new clues on how to understand reality beyond the observable.
Finally, the authors mention that if other, even lighter axions exist, their presence could further shorten the lifetime of the universe. This implies that the Big Crunch scenario is not only possible, but could be advanced if the existence of more dynamical components in dark energy is confirmed.