Final answer:
Georges Lemaître, a Belgian cosmologist, proposed the initial concept of the Big Bang, predicting the universe's expansion and Hubble's Law before they were empirically observed. His ideas on the universe starting from a 'primeval atom' and his work on particle interactions in the early universe laid the foundations of modern cosmology.
Step-by-step explanation:
Georges Lemaître was a Belgian priest and cosmologist who made significant contributions to the Big Bang theory. Born in 1894, Lemaître studied theology as well as mathematics and physics. He was instrumental in exploring the concept of the expanding universe and was the first to propose a concrete model of the Big Bang. This model suggested that the universe started as a single 'primeval atom', which eventually fragmented into smaller pieces, leading to the formation of the current atoms in the universe through a process akin to nuclear fission. Lemaître's work predated and anticipated the empirical findings that became known as Hubble's Law, which observed that galaxies are moving away from each other, implying that the universe is expanding. His insights laid the groundwork for the understanding of the universe's beginnings and its initial hot, dense state.
Additionally, Lemaître, alongside collaborators such as George Gamow, further developed the Big Bang theory. They predicted that as the universe expands and cools, the interactions among particles would lead to the formation of protons, neutrons, and eventually the nuclei of light elements such as deuterium, helium, and lithium. This theoretical framework is bolstered by measurements such as the cosmic microwave background radiation and the abundance of deuterium, supporting the Big Bang theory as a robust model of the universe's inception.