The cosmos is not only expanding, but it is expanding faster than ever before, leading most scientists to believe it will continue to expand indefinitely. A trio of Princeton scientists, on the other hand, have disputed this notion, providing a model of the cosmos in which the expansion is virtually complete. They say that the cosmos will begin to contract in on itself and that this might happen shockingly soon.
However, this is a cosmologist’s “soon,” on the order of 100 million years, which most humans would not consider near. Perhaps more than anything else this century, the finding of acceleration in the expansion of the universe has rocked cosmology.
Prior to this, the main dispute was whether the universe would continue to expand indefinitely, although more slowly, or if it would be drawn back into a “great crunch” when gravity overcame the movement apart. Acceleration and the Dark Energy theory used to explain it seemed to rule out the chance of the universe ever contracting again, but a small group of scientists aren’t ready to give up the concept. Professor Paul Steinhardt has proposed “bouncing” theories of the universe in particular. Now, in Proceedings of the National Academy of Sciences, Steinhardt and co-authors believe that the transition from expansion to contraction may be approaching without our knowledge.
The authors make no guarantees. They relate to three different types of Dark Energy models. One would see the cosmos continue to grow at an uncontrollable rate indefinitely, while the other would see it slow at an unknown moment in the future. However, the research suggests that we explore a third scenario in which Dark Energy is a form of quintessence and the pace of acceleration is slowing. In this situation, the universe is like a car whose driver accelerated from the lights with all the strength they could summon, but is now relaxing their foot off the accelerator without completely removing it.
As a result, growth is occurring at its quickest rate ever, while the acceleration is minor in comparison to previous periods. Acceleration will eventually stop in this circumstance. After reaching a point where the universe’s expansion is steady, it will begin to decelerate until finally ceasing to grow and contracting.
Such models have already been proposed, most notably by Steinhardt. What’s new here is an attempt to estimate how near we are to the two critical points where acceleration stops and contraction begins. The authors estimated that the end of expansion might be less than 100 million years away, or less than 1% of the universe’s age, using the Quintessence-Driven Slow Contraction CDM Model (QDSCCDM).
The distance between the end of acceleration and the start of contraction might be comparable. Even if the QDSCCDM is correct, this is a bottom bound – timeframes are dependent on elements that are beyond our present ability to quantify, so these events might occur much later. However, if the model offered is thought to be feasible, it may inspire efforts to build our capacities to the point where we can assess if the turning moment is approaching.
Steinhardt may be considered as having lately ventured beyond the cosmological mainstream. In 2017, a letter he co-wrote challenging the popular acceptance of an “inflationary” phase following the Big Bang drew harsh criticism from celebrities such as Stephen Hawking. On the other hand, he is not someone who should be disregarded lightly. Not only did he contribute to the development of inflationary cosmology, but his research on the influence of gravitational waves on cosmic background radiation and the more recent finding of quasicrystals have garnered him widespread acclaim.
