Cyclic Universe

A few years ago I wrote in the blog how the universe may have have originated. Many scientists believe there was no singularity in the beginning in the form of infinite density. CMB and gravitational wave observations indicate that the hottest phase of the hot Big Bang, was not more than about ~10²⁸  K or ~10¹⁵ GeV in terms of energy. That places a cutoff on how far you can extrapolate the hot Big Bang backwards: to a time of ~10^-35 seconds and a size of ~1.5 meter for the observable universe. The inflation theory states that before that there were no particles (and thus no such heat), but all energy was embedded in the inflation field. Einstein was considering that singularities derived from the general relativity were more like mathematical artefacts, not presenting a realistic nature such as the center of the black hole. He tried to augment quantum effects into the theory and proposed that an Einstein–Rosen bridge arises from the center of a black hole, which bounces in the other end into a white hole. This bridge also called as a "worm hole" can shortcut distant locations in the universe or even connect to another universe. Possibly our universe was born from a massive collapse of a black hole. The idea that the universe was born from a white hole is a theoretical concept, not a widely accepted scientific fact.  

Black hole cosmology proposed originally proposed in 1972 by Raj Pathria, postulates that our observable universe is the interior of a black hole, a concept rooted in theoretical models. In contrast, the Lambda-CDM model, the standard cosmological model, describes the universe as expanding from a hot, dense state (the Big Bang), driven by dark energy and containing dark matter and ordinary matter. Black hole cosmology suggests that the event horizon, the boundary from within which nothing can escape a black hole, is also the horizon of the visible universe. The theory is supported by the observations that the observable universe has radius, Hubble radius, that seems to equal to the Schwarzschild radius of the universe, which however may be coincident as published by Landsberg in 1984. According to the blackhole cosmology our universe in a black hole is closed: finite but without boundaries. It can be thought of as a three-dimensional analogue of the two-dimensional surface of a sphere. Hence, moving away in any direction would eventually lead to coming back from the opposite direction

Polish theoretical physicist Nikodem Poplawski of the University of New Haven, proposed in 2010 the first physically grounded mechanism for the theory that all black holes act as doorways to other universes. He describes a collapse of a black hole avoiding a singularity with the concept of spacetime torsion: "The matter instead reaches a state of finite, extremely large density, stops collapsing, undergoes a bounce like a compressed spring, and starts rapidly expanding. Extremely strong gravitational forces near this state cause an intense particle production, increasing the mass inside a black hole by many orders of magnitude and strengthening gravitational repulsion that powers the bounce. It produces a finite period of cosmic inflation, which explains why the universe that we observe today appears at largest scales flat, homogeneous, and isotropic." The inflation period of the early universe spread the horizon out of causality and our visibility. Thus we cannot ever detect any evidence from the parent or any child universe. However,  Desai and Popławski published in 2016 that inflation generated by spin and torsion is consistent with the cosmic microwave background data from the Planck satellite.

The recent observations made by the James-Webb telescope, published by Shamir in 2025, hints that the rotation of the galaxies is not random, and while around two-thirds of nearly 300 galaxies spin clockwise, the other third rotates counter-clockwise. One explanation is that the entire universe was born rotating. Because all known black holes are rotating objects, the universe born in a rotating black hole inherits the axis of rotation of the black hole as its preferred axis. That explanation supports black hole cosmology. Popławski also highlighted on the discovery: "If the universe is rotating, it must rotate relative to some frame of reference corresponding to something bigger, and therefore, the universe is not the only one; it is a part of a multiverse."

In April 2014, the DESI scientists shared the results of their first year of observations (related blog). Data from six million galaxies measured dark energy between roughly 2 and 12 billion years ago. The data yielded signs that dark energy may have been weakening over the last few billion years. This challenges the standard Lambda-CDM model where dark energy is cosmological constant, and the energy of the vacuum of space itself. Dark Energy Survey (DES) team published the results in March 2025 with stronger evidence of evolving dark energy. The findings challenge the fate of the universe, which has been thought to be ever expanding cooling cosmos. Researchers from Cornel University have developed recently a model that predicts our universe will end in a "Big Crunch" after approximately 20 billion years. Poplawski's recently revised theory is that a spinning universe can also account for dark energy: "Dark energy would emerge from the centrifugal force in the rotating universe on large scales and the cosmological constant is proportional to the square of the angular velocity of the universe." Because in black hole cosmology, the universe created by a black hole is closed, that would mean the centrifugal force arising from a spinning universe becomes a force acting in all directions away from the universe's parent primordial white hole. Furthermore the angular velocity of the universe decreases as the universe expands, which is a consequence of the conservation of the angular momentum of the universe. The centrifugal force in a rotating universe, which also decreases, may be the origin of dark energy, in accordance with recent DES observations showing that dark energy becomes weaker with time. 

Poplawski's explanation for dark energy sounds very logical for me, in contrast to ever growing energy and negative pressure associated to the cosmological constant. My hypothesis is that dark energy was extreme during the inflation epoch when the universe had a maximum free spin, and it weakened when the inflation field decayed into the particles, causing some inertia. Later the matter dominated era brake dark energy by gravitation until it lost a grip and dark energy started domination leading to accelerated expansion about 4-5 billion years ago. Recently weakened dark energy may still permit gravitation to pull back a "Big Crunch", another black hole that drains the universe through the vortex to the birth of a new universe. One question is whether all entropy from this universe gets inherited to the new one...