A groundbreaking study from the Universities of Barcelona and Padua challenges the inflation theory, suggesting the universe began from a stable De Sitter space, driven by gravity and quantum mechanics alone. This model explains the formation of cosmic structures through quantum fluctuations evolving into gravitational waves, offering a simpler, testable alternative to the Big Bang’s fiery start.
Immediately after the Big Bang, which occurred around 13.8 billion years ago, the universe was dominated by unimaginably high temperatures and densities. However, after just a few seconds, it had cooled down enough for the first elements to form, primarily hydrogen and helium. These were still completely ionized at this point, as it took almost 380,000 years for the temperature in the universe to drop enough for neutral atoms to form through recombination with free electrons. This paved the way for the first chemical reactions.
The oldest molecule in existence is the helium hydride ion (HeH⁺), formed from a neutral helium atom and an ionized hydrogen nucleus. This marks the beginning of a chain reaction that leads to the formation of molecular hydrogen (H₂), which is by far the most common molecule in the universe.
Recombination was followed by the “dark age” of cosmology: although the universe was now transparent due to the binding of free electrons, there were still no light-emitting objects, such as stars. Several hundred million years passed before the first stars formed.
Quantum field theory (QFT) is a physics framework that describes how particles and forces behave based on principles rooted in quantum mechanics and Albert Einstein’s special relativity theory. This framework predicts the emergence of various remarkable effects in curved spacetimes, including Hawking radiation.
Hawking radiation is the thermal radiation theorized to be emitted by black holes close to the event horizon (i.e., the boundary around a black hole after which gravity becomes too strong for anything to escape). As ascertaining the existence of Hawking radiation and testing other QFT predictions in space is currently impossible, physicists have been trying to identify physical systems that could mimic aspects of curved spacetimes in experimental settings.
Researchers at Sorbonne University recently identified a new promising experimental platform for simulating QFT and testing its predictions. Their proposed QFT simulator, outlined in a paper published in Physical Review Letters, consists of a one-dimensional quantum fluid made of polaritons, quasiparticles that emerge from strong interactions between photons (i.e., light particles) and excitons (i.e., bound pairs of electrons and holes in semiconductors).
While the study is intriguing, additional observations will be essential to verify or challenge its findings.
A group of astronomers, led by researchers at Rhodes University, has analyzed 104 quasars through the MIGHTEE survey, a large-scale project using South Africa’s MeerKAT radio telescope.
Black holes played a critical role in the formation of the early universe. However, astronomers have been debating for a long time just how critical, as the information we had about early black holes, which exist at high red-shifts, was relatively limited.
A team of researchers, led by Raúl Jiménez, an ICREA scientist at the University of Barcelona’s Institute of Cosmos Sciences (ICCUB), and working in partnership with the University of Padua (Italy), has introduced a groundbreaking new theory about how the Universe began.
Published in Physical Review Research, their study offers a major shift in how scientists understand the earliest moments following the Big Bang.
The Big Bang is the leading cosmological model explaining how the universe as we know it began approximately 13.8 billion years ago.