The Universe is not only expanding, but also doing this with acceleration, as has been proven by Hubble’s cosmological law. The law made most scientists assume that the expansion of the Universe will continue for a very long time, if not forever. However, three physicists from Princeton, led by Professor Paul Steinhardt, disputed this point of view. They presented a model of the Universe in which the expansion of space has almost come to an end. Scientists claim that the Universe will begin to contract, and this may happen surprisingly soon. According to cosmologists, “soon” is about 100 million years. This means that humanity is on the threshold of the beginning of the era of the Big Crunch. The physicists published their research in the Proceedings of the National Academy of Sciences.
Three models of the nature of dark energy
The authors use three models of the nature of dark energy to confirm their hypothesis. The first model assumes that the Universe will continue to expand faster and faster, while the second model assumes a slowdown in expansion in the very distant future. However, the article proposes to consider the third model, in which dark energy is a kind of quintessence, and the acceleration rate is already beginning to slow down a little.
The Universe in the third scenario is like a car whose driver started off with all his might, but now drops his foot off the accelerator pedal, not yet removing it completely. Consequently, the expansion is taking place at the highest rate that has ever been, but this acceleration is low compared to earlier times. Eventually, in this scenario, the acceleration will stop and then begin to gradually contract.
Early death of the Universe
Such models have been proposed before, in particular by Steinhardt. What is new here is an attempt to estimate how close we can be to the two critical points where acceleration first stops and then contract begins. In accordance with what the authors call the Quintesscence-Driven Slow Contraction CDM Model (QDSCCDM), they calculate that the end of expansion may come in less than 100 million years, which is less than 1% of the age of the Universe. The interval between the end of acceleration and the beginning of contraction can be the same. That is, the return to the singularity point will occur in about 13.9 billion years. We can say that humanity is now at the peak of the development of the Universe.
Steinhardt can fairly be called a man who has recently moved outside the cosmological mainstream. In 2017, a letter he wrote criticizing the widespread recognition of the “inflationary” period immediately after the Big Bang caused a scathing response from the scientific community, including Stephen Hawking. Meanwhile, the professor made a great contribution to astronomy and astrophysics. Not only did he help lay the foundations of inflationary cosmology, his work on the effect of gravitational waves on the cosmic background radiation and the recent discovery of quasicrystals have earned him immense respect in the field.
So his theory about the imminent era of a Big Crunch should be taken seriously.