At the heart of the primordial universe resided a delicate mosaic of tiny yet essential variations: the primordial density fluctuations. These minute disparities, invisible to the naked eye yet fundamental, served as seeds for the gigantic cosmic architecture observed today. It is not just a scientific curiosity, but rather the thread that connects the Big … Read more
Since the end of the 1990s, contemporary astronomy has revealed an unsuspected facet of our cosmos: a mysterious force, dubbed dark energy, which represents about 70% of the total energy density of the Universe and is responsible for the acceleration of its expansion. This phenomenon is intimately linked to the cosmological constant, a notion introduced … Read more
The cosmological horizon problem embodies one of the major challenges in modern cosmology, questioning the very foundations of our understanding of the observable universe. This conundrum raises a fascinating question: how can extremely distant regions of the universe, seemingly without any causal contact, exhibit such surprising homogeneity, particularly seen in the cosmic microwave background radiation? … Read more
In short: Contemporary cosmology, at the crossroads of theoretical advances and astrophysical observations, develops models where our universe, far from being unique, could coexist with a multitude of others. These cosmological theories of the multiverse, fueled by quantum physics and string theory, open a groundbreaking perspective: instead of an isolated Big Bang, the emergence of … Read more
In brief: The foundations of the cosmic inflation model in the primordial universe Cosmic inflation refers to a phase of accelerated expansion occurring very early in the history of the universe, precisely at the end of the Planck era, about 10-35 seconds after the birth of the cosmos. This cosmological model resolves major paradoxes that … Read more
In the darkness of the primitive cosmos, a few hundred million years after the Big Bang, the emergence of the first galaxies and their original stars played a decisive role in the structure and composition of the Universe as we know it. These primordial galaxies, often small and dense, housed Population III stars, the very … Read more
The reionization of the primordial universe is a crucial step in cosmic evolution that occurs after the Dark Age, a period during which the cosmic atmosphere was dominated by opaque neutral hydrogen. This phenomenon reflects the gradual transition of this dark universe to a lit and ionized environment through the emergence of the first stars … Read more
Baryonic acoustic oscillations (BAO) represent a fundamental phenomenon in cosmology, marking a crucial sequence in the history of the Universe. These primordial sound waves, which occurred in the hot plasma composed of baryons and photons, have left indelible traces visible in the large-scale structure of the Universe. By studying these oscillations, astrophysicists gain access to … Read more
Observations of the cosmos reveal mysteries that are intricately woven into the delicate fabric of the primordial universe. Among these invisible footprints, the Sachs-Wolfe effect holds a prominent place. It traces the memory of gravitational evolution through the anisotropies of the cosmic microwave background, this ancient breath imbuing every photon of the cosmic background radiation. … Read more
Black holes embody one of the deepest mysteries of the universe, revealing both the extreme power of gravity and the limits of current physics. These celestial objects, formed from the collapse of massive stars, concentrate an incredible mass into an infinitely small space. As a result, they become natural laboratories where quantum gravity and quantum … Read more