The study suggests the Universe may not have begun with a single explosive origin but may instead align with cosmic bounce models, in which the Universe emerged from an earlier contraction and left behind relic black holes that could survive into the present day. If correct, these primordial objects could help explain several long-standing mysteries in cosmology, including the nature of dark matter and the processes that seeded galaxy formation.
Professor Enrique Gaztanaga, lead author from the University of Portsmouth's Institute of Cosmology and Gravitation and the Institute of Space Sciences in Barcelona, said that while the standard Big Bang model has been remarkably successful - explaining the Cosmic Microwave Background and accurately predicting galaxy distribution - some of the deepest mysteries in physics remain unresolved. These include what triggered the Big Bang, what caused rapid early inflation, and what dark matter actually is.
"Our research explores a possibility that could connect several of these puzzles: the Universe may not have begun with a singular bang at all, but instead emerged from a cosmic bounce mimicking inflation, with some of the oldest objects in the Universe potentially surviving as relics from before it," Gaztanaga said.
In Einstein's theory of general relativity, the Big Bang corresponds to a singularity - a point where density becomes infinite and the known laws of physics break down. Many physicists interpret this as a sign that the description of the earliest moments of the Universe is incomplete. Bouncing cosmology offers an alternative, in which the Universe originates from a large contracting cloud that rebounds into expansion, reaching a very high but finite density before reversing.
The researchers suggest this bounce could arise naturally from quantum physics. At extremely high densities, quantum effects create a powerful pressure that prevents matter from being compressed indefinitely - a phenomenon that already stabilises dense objects such as white dwarfs and neutron stars. A similar effect on cosmic scales could halt the collapse and trigger a rebound.
Some black holes could have formed during the earlier cosmic phase and survived the bounce, leaving behind relic objects that may still influence galaxy structure billions of years later. Others could form shortly after the bounce from amplified density fluctuations, where matter in the early Universe was unevenly distributed in stronger, more pronounced clumps. These enhanced clumps would collapse more easily under gravity, making it more likely for large cosmic structures and black holes to form early.
The bounce, the researchers suggest, could also account for why the early Universe expanded so rapidly and evenly - the phenomenon known as inflation - and may shed light on the accelerating expansion of the Universe today, currently attributed to dark energy.
One striking implication is that structures formed during the collapsing phase may have survived the bounce. The team's calculations suggest that compact objects larger than roughly 90 metres could pass through the transition and reappear in the expanding Universe as fossils from before. Possible relics include gravitational waves, density fluctuations, and ancient black holes.
These relic black holes could help explain dark matter - the invisible substance that shapes galaxies and the large-scale structure of the Universe. If large numbers formed during the bounce, they could account for a significant fraction, potentially all, of dark matter.
The idea may also help explain recent discoveries by the James Webb Space Telescope of unexpectedly massive objects in the early Universe. Many astronomers suspect these sources are linked to rapidly growing black holes that appeared surprisingly soon after the Big Bang. "If massive black holes already existed immediately after the bounce, the early Universe would not need to start from scratch when building the first galaxies," Gaztanaga said.
The theory makes predictions testable with future observations, including searches for relic gravitational waves from a previous cosmic phase or subtle patterns in the cosmic microwave background that preserve traces of the Universe before the Big Bang.
"Much work remains to test these ideas," Gaztanaga added. "But if the Universe did experience a bounce, the dark structures shaping galaxies today could be remnants from a cosmic epoch that preceded the Big Bang."
Research Report:Cosmological bounce relics: Black holes, gravitational waves, and dark matter
Related Links
University of Portsmouth
Understanding Time and Space
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