Scientists have long proposed a model in which the universe could stop expanding, ending in a Big Crunch that would reset space and time as we know it. However, a pair of theoretical physicists has proposed a third way. The universe will never end, and in a study attempting to define the nature of dark energy, the physicists propose that cosmic expansion is not always constant. Dark energy can periodically turn on and off, sometimes causing the cosmos to expand, and other times reducing it until the right conditions for a new Big Bang and the birth of a new universe occur.
Dark Energy and the Growth of the Universe
Our universe is currently experiencing an uncontrolled expansion phase. The cosmos is growing faster every passing moment. Cosmologists do not understand the cause of this acceleration and hypothesize that dark energy is the cause. If this acceleration persists, our universe will eventually expand into oblivion, with all matter and radiation too far apart from each other.
But this would not be the first phase of uncontrolled growth. In the early moments of the Big Bang, energies and densities were so extreme that the physics we know would not be valid. For this reason, we speak of singularity, a point of infinite density where our mathematical and physical knowledge has no value.
Subsequently, the universe underwent an incredibly rapid expansion period known as inflation, also currently poorly understood. Theoretical physicists have long wondered if these two phases of accelerated expansion, one in the early moments of the Big Bang and one in the current era, are connected. Is it also possible that there is an entity that guides both?
An infinite cycle
To answer this question, a pair of theoretical physicists published a study (ref.) on February 7th on arXiv that examined a model of the cosmos in which dark energy has always played a key role. Past research had hypothesized that dark energy turns on at various times to drive cosmic expansion. But the new research proposes a more realistic model that includes matter and radiation.
The main purpose of the study is to see if dark energy can avoid the singularity of the Big Bang, guide inflation, and accelerate the contemporary universe. To avoid the initial singularity, the universe would not have started from a point of infinite density. While the universe we live in would be the result of an infinite series of repeated “big bounces”.
In this scenario, dark energy guides the universe until it reaches a certain size. But then this energy transforms, forcing the universe to contract. The cosmos then undergoes a great crisis, but just before reaching a state of infinite density (the singularity), dark energy generates a new period of incredibly rapid inflation and restarts the cycle.
The mathematical correction
Despite the initial success, the researchers were unable to find a generic class of dark energy models that could always lead to the same results. To overcome this mathematical problem, they had to artificially insert a lower value for the current accelerated expansion than predicted by quantum mechanics to obtain the exact result.
However, this new research points in a promising direction, providing a valid platform for exploring other models like this one. Humanity is probably not destined to live in a cold and empty cosmos, because dark energy could behave differently than we think today in a distant future. Only continued research will reveal our destiny.