A new study led by the University of Portsmouth in the United Kingdom proposes that the Big Bang was not the absolute beginning of the history of the universe. Some black holes may have formed long before the birth of the universe as we know it and survived a "cosmic rebound" event. The research team calls these hypothetical objects "cosmic fossils" and believes that they may still be scattered throughout the universe and are expected to help solve dark matter, one of the most profound mysteries of contemporary astronomy.
Traditional cosmology believes that about 13.8 billion years ago, the universe exploded from an extremely hot and dense initial state, the so-called "Big Bang", and then gradually formed galaxies and large-scale structures. This standard model has been extremely successful in explaining the cosmic microwave background radiation and the distribution of galaxies on large scales, but it still leaves many unsolved mysteries, such as: why the big bang occurred, why the universe was in such a "special" state in the first place, what the physical mechanism was that drove early inflation, and the true identities of dark matter and dark energy.
The lead author of the new study, Professor Enrique Gaztañaga of the Institute of Cosmology and Gravitation at the University of Portsmouth and the Institute of Space Sciences in Barcelona, Spain, pointed out that this work explores the possibility of connecting multiple difficult problems at the same time. In this picture, the universe did not originate from a single "explosion" singularity, but experienced a "cosmic bounce" from contraction to expansion, and in the process produced a rapid expansion effect similar to inflation. Some of the oldest cosmic structures may have existed before the bounce and passed through the bounce phase as "relics", retaining information from earlier cosmic epochs.
Within the framework of Einstein's general theory of relativity, the traditional Big Bang is usually associated with a "singularity": In this idealized state, the density of matter approaches infinity and existing physical laws fail. Many theoretical physicists view singularities as a sign that current theories have reached their applicable limits, rather than as the true metaphysical starting point of the universe. In contrast, "rebound cosmology" imagines that the universe began as a huge cloud of matter, first experienced slow contraction, and then reversed when the density reached an extremely high but still finite state, thereby switching from contraction to expansion and avoiding a mathematical infinite singularity.
The research team believes that this cosmic rebound can be produced by the natural effects of quantum physics. When the density of matter is extremely high, quantum effects produce a pressure-like effect that prevents matter from being compressed to infinitesimal sizes. This mechanism has precedents in dense objects such as white dwarfs and neutron stars. In the new model, this type of quantum pressure is extended to the scale of the entire universe: as the universe contracts as a whole, quantum effects will prevent further collapse at a certain critical density and trigger a new round of expansion, while reproducing a rapid expansion phase similar to early inflation.
This mechanism may not only provide a natural explanation for inflation, but may also be linked to the accelerated expansion of the universe observed today - often attributed to "dark energy". The study proposes that the quantum effects and dense structures produced during early contraction and rebound may manifest as additional gravity or "effective energy components" on large scales, thereby affecting the later evolution of the universe.
In this narrative of cosmic history, black holes play a key role. Research points out that some black holes may have formed when the universe was still in the contracting stage, and remained intact during the rebound process, traveling to the expanding universe we live in today. Another part of the black holes may have formed shortly after rebounding: Abnormally large density fluctuations in the early universe would have formed high-density regions, making it easier for matter to collapse under the influence of gravity, creating black holes and other large cosmic structures.
According to the calculations of the research team, if there are compact celestial bodies that are dense enough and have a size larger than about 90 meters, they will have the ability to survive the rebound process and appear as "relics" in the new round of expansion of the universe. These potential relics include density disturbances, compact objects, and ancient black holes. Black holes are of particular concern because they not only record physical information about extreme gravitational environments, but may also have a long-term impact on the formation and evolution of subsequent galaxies.
Notably, there may be a direct connection between these surviving ancient black holes and dark matter. If a large enough number of black holes were formed and preserved during the rebound phase of the universe, they are expected to constitute a large part of the universe's dark matter, and may even become the entire source of dark matter. This provides a different interpretation path from the new particle hypothesis for the dark matter problem that has long troubled the astronomical community.
The model may also provide clues to some anomalies in recent astronomical observations. For example, astronomers have discovered a group of mysterious objects called "little red dots" in the early universe. They appear to be related to the supermassive black holes that grew rapidly in the early universe, and are in tension with the traditional timeline of structure formation. New research points out that if some massive black holes "pre-existed" after the universe bounced, then the universe did not need to start from scratch when building the first galaxies, which helps explain why "unexpectedly mature" dense objects and structures appeared very early in the history of the universe.
In order to test this theoretical framework of cosmic rebound and ancient black hole remnants, the research team proposed a variety of potential observation approaches. One is to look for "relic gravitational waves" from earlier cosmic epochs. These ripples in space-time, produced by large-scale collapse and rebound, may remain to this day with specific spectral characteristics. The second is to look for subtle imprints in the cosmic microwave background radiation, detecting residual signals that may come from conditions before the Big Bang.
Professor Gastaniaga emphasized that this theory is still in the development stage, and a lot of work is needed to refine the model and compare it with the accumulating accurate observation data. However, if the universe did undergo a rebound, then the "dark" components that shape galaxies and large-scale structures today - including possible manifestations of dark matter and even dark energy - are likely to be deep structures left over from a cosmic epoch that predates the Big Bang.
The study, titled "Cosmic Rebound Relics: Black Holes, Gravitational Waves and Dark Matter," was published on February 24, 2026, further promoting cutting-edge discussions on the origin of the universe, the nature of dark matter, and quantum effects in extreme gravitational environments.